Patent Application
20130095480
Tumor-associated glycans play a significant role in promoting aggressive and metastatic behavior of malignant cells [1-5], participating in cell-cell and cell-extracellular matrix interactions that promote tumor cell adhesion and migration. Among glycans that play a critical role in stromal tumor cell interactions are glycosaminoglycans (GAGs) attached to proteoglycans (PGs). Altered production levels of PGs and structural changes in their GAGs are reported in many neoplastic tissues [6-10]. GAGs are polysaccharide chains covalently attached to protein cores that together comprise PGs [6, 11] and based on the prevalence of GAG chains, chondroitin sulfate (CS)/dermatan sulfate (DS) PGs (CS/DS-PGs), heparan sulfate PGs and keratan sulfate PGs have been described [12]. Increased production of CS/DS-GAGs is found in transformed fibroblasts and mammary carcinoma cells [8, 13, 14] and it has been shown that these polysaccharides contribute to fibrosarcoma cell proliferation, adhesion and migration [15].
Several studies have disclosed the critical involvement of P-selectin in the facilitation of blood borne metastases [16-18]. P-selectin/ligand interaction often requires sialylated and fucosylated carbohydrate such as sialyl Lewis X and sialyl Lewis A [19]; however, P-selectin also binds to heparan sulfate, certain sulfated glycolipids and CS/DS-GAGs [20-23]. In previous studies we found that CS/DS-GAGs are expressed on the cell surface of murine and human breast cancer cell lines with high metastatic capacity and that they play a major role in P-selectin binding and P-selectin-mediated adhesion of cancer cells to platelets and endothelial cells [24]. However, variation in the abundance and function of CS/DS relative to tumor cell phenotypic properties and P-selectin binding are not well defined. It is likely that P-selectin binding to tumor cells and the functional consequences of such binding are dependent on which sulfotransferases define the relevant CS/DS and which core proteins carry the CS polysaccharide.
CS/DS expression is controlled by many enzymes in a complex biosynthetic pathway and this leads to considerable variation in structure and function. The chondroitin backbone of CS/DS-GAGs consists of repetitive disaccharide units containing D-glucuronic acid (GlcA) and N-acetyl-D-galactosamine (GalNAc) residues, or varying proportions of L-iduronic acid (IdoA) in place of GlcA [25, 26]. Major structural variability of the CS/DS chains is due to the sulfation positions in repeating disaccharide units by the site-specific activities of sulfotransferases that produce the variants CS-A, CS-B (dermatan sulfate, DS), CS-C, CS-D and CS-E [26, 27]. CHST3, CHST7, CHST11, CHST12, CHST13, CHST14 and CHST15 are the enzymes that sulfate the GalNAc residues of chondroitin polymers.
The variation, abundance and function of CS/DS-GAGs are also affected by the expression of the PG core protein presenting them. Syndecan-1 (SDC-1), syndecan-4 (SDC-4), neuropilin-1 (NRP-1) and CSPG4 are membrane proteins capable of carrying CS chains [35-39]. Among these PGs, CSPG4 exclusively carries CS chains [40, 41].
We and others have previously shown that glycosaminoglycans on tumor cells are involved in binding to P-selectins, and that this interaction is involved in metastasis.
There is a need for cancer markers to better indicate cancer prognosis. This can help guide treatment plans as well as help patients plan their lives and make treatment decisions.
Here we have investigated the utility of structural genes for glycosaminoglycans and genes encoding synthetases involve in glycosaminoglycan synthesis for possible utility as prognostic markers in cancer treatment.
It is shown here that the Carbohydrate (Chondroitin 4) Sulfotransferase 11 (CHST11) gene is highly expressed in aggressive breast cancer cells but significantly less so in less aggressive breast cancer cell lines. Furthermore, a positive correlation was observed between the expression levels of CHST11 and in vitro indicators of metastasis.
The same observations were made concerning the carrier proteoglycan Chondroitin Sulfate Proteoglycan 4 (CSPG4): It is highly expressed on aggressive breast cancer cell lines, and less so on less aggressive breast cancer cell lines; and its overexpression contributes to in vitro indicators of metastasis.
In addition, CSPG4 and CHST11 were over-expressed in tumor-containing clinical tissue specimens compared with normal tissues.
Thus, overexpression of either or both of CHST11 and CSPG4 genes is predictive of more aggressive tumors and indicates a worse prognosis.
We have also found that expression level in tumor samples of both the CHST11 and CSPG4 genes is dependent on the methylation state of these genes. Specifically, both the CHST11 and CSPG4 genes are overexpressed in tumors when the CHST11 and CSPG4 genes are hypomethylated in the tumor tissue. Thus, hypomethyation of these genes can be used as a surrogate indicator of overexpression of the two genes. This means that overexpression of the CHST11 and CSPG4 genes can be inferred in a tumor when the tumor tissue has these genes hypomethylated. Direct measurement of gene expression requires living tumor cells or well prepared frozen samples, but paraffin-embedded sections and catalogued stained tissues, can be used for DNA samples that will show whether these genes are hypomethylated or hypermethylated. Thus, in some cases it is easier to determine methylation state of these genes than to directly measure overexpression, and many tissue samples can be used to determine methylation status that cannot be used for measurement of gene overexpression.
One embodiment of the invention provides a method of determining a prognosis of a cancer in a human comprising: determining expression level of CHST11 in a cancer tissue sample or determining methylation status of CHST11 gene in a cancer tissue sample. High expression indicates a more aggressive tumor and a tumor more likely to metastasize.
Another embodiment of the invention provides a method of determining a prognosis of a cancer in a human comprising: determining expression level of CSPG4 in a cancer tissue sample or determining methylation status of CSPG4 gene in a cancer tissue sample. High expression indicates a more aggressive tumor and a tumor more likely to metastasize.
Another embodiment provides a method of determining a prognosis of a cancer in a human comprising: (a) determining expression level of CHST11 in a cancer tissue sample or determining methylation status of CHST11 gene in a cancer tissue sample and (b) determining expression level of CSPG4 in a cancer tissue sample or determining methylation status of CSPG4 gene in a cancer tissue sample.
The expression of CHST3, CHST7, CHST11, CHST12, CHST13, CHST14, CHST15 was measured by qRT-PCR and normalized using 18S. Data were analyzed by one-way ANOVA and post hoc analysis using data from three (CHST7, CHST12, CHST13, CHST14) and four (CHST3, CHST11, CHST15) independent experiments. Means and standard deviations are shown. Statistically significant differences and P values are shown.
A) Flow cytometry analysis of CS-A expression using anti-CS-A 2H6 mAb (15 μg/ml). B) P-selectin binding to cells using recombinant P-selectin (15 μg/ml). Open histograms show binding of the secondary antibody only (control), while filled histograms show anti-CS-A and P-selectin binding. One representative experiment out of three is shown.
MDA-MB-231 cells were treated with three different siRNAs for the CHST11 gene. RNA was harvested after 48 hours and gene expression was assayed at the mRNA level (A). GAPDH was used as the house keeping gene to normalize mRNA-based expression data using the delta delta CT method. CHST11 mRNA levels are shown relative to mRNA level in cells treated with transfection agent only (vehicle). Data were log transformed and subjected to one way ANOVA with post-hocTukey's analysis. B) Binding of anti-CS-A (2H6 mAb) (top) and P-selectin (bottom) was tested at Day 6 post siRNA transfection. Binding of secondary antibodies only serves as control. Binding of anti-CS-A 2H6 mAb and recombinant human P-selectin to vehicle-treated and siRNA-treated MDA-MB-231 cells with the three siRNAs is shown. Mean fluorescent intensities of three independent experiments were log transformed and analyzed by ANOVA and post-hoc comparison. Treatment with CHST11 siRNA #31 significantly reduced mean fluorescent intensities for anti-CS-A 2H6 mAb (P≦0.015) and P-selectin (P≦0.001) binding, as compared with vehicle-treated cells.
A) CSPG4 mRNA was measured by qRT-PCR and normalized to 18S values and log transformed. Means and standard deviations are shown. Comparisons were made by ANOVA and post-hoc analysis. B) Cell surface expression of CSPG4 was examined in the indicated breast cancer cell lines by flow cytometry using anti-CSPG4 225.28 mAb (10 μg/ml). Open histogram shows binding of the secondary antibody only, while filled histogram shows anti-CSPG4 225.28 mAb binding. One representative experiment out of three is shown. C) Expression of CSPG4 was inhibited by transient transfection of MDA-MB-231 cells with CSPG4 siRNA that led to a decrease in the binding of P-selectin (D) and anti-CS-A (E) to transfected cells In C, D and E the filled histograms show the binding of secondary antibodies only (control), the open histograms with solid lines show binding to vehicle-treated cells while the open histograms with dotted lines show binding to the siRNA-transfected cells.
A) Secondary Ab binding (control) to CSPG-4-transfected M14 (M14-CSPG4). Anti-CSPG4 (mAb 225.28) binding to M14-mock-transfected is minimal (B), while the binding is high to CSPG4-transfected cells (C). D) Overlay histogram of 2H6 mAb (anti-CS-A) binding to the M14-mock-transfected (filled histogram) and M14-CSPG4 cell line (open histogram). E) P-selectin binds to M14-CSPG4 (open histogram, solid line) and not to M14-mock-transfected (filled histogram). Binding of P-selectin to M14-CSPG4 is reduced after treatment with chondroitinase ABC (dotted line shifted to the left). The experiment was repeated three times and one representative is shown.
mRNA expression was quantified by absolute quantification and the ratio of mRNA to 18S mRNA was calculated. The fold change in tumor sample compared to normal tissue sample in each subject was calculated and plotted. Circles denote individual observations, while squares with error bars represent group means with their 95% confidence intervals (CIs). CSPG4 and CHST11 were elevated 3.2 (P<0.02) and 1.8 (P=0.034) fold, respectively in tumor-containing samples over normal samples.
4T1 cells were treated with chondroitinase ABC or buffer and injected into the tail vein of BALB/c mice (10 per group). Mice were sacrificed 25 days later and the number of metastases to the lung was measured by clonogenic assay and expressed as “Lung Metastases”. Boxes show medians and quartiles while whiskers show ranges; plus signs indicate means. P=0.0002 by Wilcoxon rank-sum test.
A) Exon 1 from NCBI NM—018413.5 is shown (0 to +616) as is the CpG island (between −660 and +2100). The horizontal arrows indicate bisulfite genomic sequencing primers for semi-nested PCR. Primer A is the outside forward primer (Table 4), primer B is the nested forward primer (position +1490 & Table 4), and primer C is the reverse primer (position +1750 & Table 4). The genomic sequence (pre-bisulfite) between the B and C primers is shown below the map and B and C primer locations are underlined. CpG islands are in bold and underlined. The scale is in base pairs. B) Sections of bisulfite genomic sequencing results showing part of the CHST11 CpG island. Top: DNA of MCF-7 cells. In this top sequence CpG sites show prominent cytosine (C) peaks in the electropherogram and show C in the sequence because methylated cytosines are not changed to thymines (Ts) in the bisulfite reaction. Bottom: DNA of MDA-MB-231 cells. In this section CpG sites appear as TpG sites and are in the same sequence positions as the top CpGs. In the electropherogram for the MDA-MB-231 DNA most CpG sites have prominent T peaks because unmethylated Cs are changed to uracils in the bisulfite reaction. The Cs in MCF7 that are changed to T in MDA-MB-231 are underlined and bolded. C) Quantification of methylation levels of the CpG island in MCF7 and MDA-MB-231 cells. Methylation levels were averaged over 10 CpGs and 18 preparations for MCF7 and 16 preparations for MDA-MB-231 cells. Means and SEM are shown. Data were arcsin transformed and subjected to Mann-Whitney test to compare means.
Gene expression was assayed by real time RT-PCR (A) and flow cytometry (B). MCF7 cells were grown in the presence of various concentrations of 5AzadC for 5 days and then cells were harvested for RNA purification or staining with anti-CS-A mAb 2H6. A) CHST11 mRNA levels are shown relative to mRNA levels of cells grown in medium only. GAPDH was used as the house keeping gene to normalize mRNA-based expression data using the delta delta CT method. Data were log transformed and subjected to one way ANOVA with post-hoc Tukey's analysis. B) Cells were harvested and then stained with anti-CS-A mAb 2H6. Binding was analyzed by flow cytometry. Mean fluorescent intensities of two independent experiments were log transformed and analyzed by ANOVA and post-hoc comparison. ns, not significant as compared to control (0 μM 5AzadC). *, **, and ***, significantly different compared to control at P≦0.05, P≦0.01, and P≦0.001, respectively.
A) The expression of CHST11 was measured in MCF7, T-47D, ZR-75-1 and MDA-MB-231 cells by qRT-PCR and normalized using 18S. Data were analyzed by one-way ANOVA and post hoc analysis using data from 3 independent experiments. Means, standard deviations, statistically significant differences and P values are shown. B) through E) Single nucleotide resolution of DNA methylation in the CHST11 CpG island. DNA methylation was assessed by RRBS (Meissner, Mikkelsen et al. 2008). The peaks denote Cs covered with at least 10 reads. Methylation level percentage was calculated from the number of Cs after bisulfite treatment divided by the sum of Cs (methylated sites) and Ts (unmethylated sites). There is a total of 186 CpG dinucleotides in the CpG island, of which at least 75% were accessible to RRBS with a minimum coverage of 10 (average coverage at least 40). The x axis shows CHST11 in the coordinates relative to the transcription start site. The first exon is from position 1 to about position 600. Panels B, C, D, and E are respectively MCF-7, T-47D, ZR-75-1, and MDA-MB-231 cell lines.
CHST11 gene expression and methylation of ER-positive (BT-474) and two ER-negative cell lines with epithelial appearance (MDA-MB-468 and BT-20), as described in the legend to
A) CHST11 gene expression was evaluated in a panel of breast cancer cell lines (13 Luminal, 16 Her-2-amplified and 21 basal-like cell lines). The log-transformed normalized expression values was downloaded from Oncomine database and analyzed by one way ANOVA and Tukey's post hoc comparisons. P values comparing Her-2-amplified and basal-like subtypes with Luminal subtype are shown. B) CHST11 expression data in 158 invasive breast carcinomas were downloaded from Oncomine database and analyzed. The data of 7 specimens with no value were removed. 70 of the remainings were diagnosed as ER-negative and 81 as ER-positive. The Mann-Whitney test was performed to compare CHST11 expression in ER-negative versus ER-positive specimens and P-value is shown.
Expression levels in 61 normal breast and 76 invasive breast adenocarcinoma samples were analyzed. The dataset consists of Level 2 (processed) data from the TCGA data portal.
The dataset was 14 cutaneous melanoma samples and 4 normal skin.
The data set was 23 normal brain samples and 50 oligodendroglioma samples.
CHST11 gene expression was evaluated in a panel of breast cancer cell lines (13 Luminal, 16 Her-2-amplified and 21 basal-like cell lines). The log-transformed normalized expression values was downloaded from Oncomine database and analyzed by one way ANOVA and Tukey's post hoc comparisons. P values comparing Her-2-amplified and basal-like subtypes with Luminal subtype are shown.
CHST11 expression data in 158 invasive breast carcinomas were downloaded from Oncomine database and analyzed. The data of 7 specimens with no value were removed. 70 of the remainings were diagnosed as ER-negative and 81 as ER-positive. The Mann-Whitney test was performed to compare CHST11 expression in ER-negative versus ER-positive specimens and P-value is shown.
18S, 18S ribosomal RNA; ANOVA, Analysis of Variance; CS, Chondroitin Sulfate; CS-GAGs, Chondroitin Sulfate Glycosaminoglycans; CS/DS, Chondroitin Sulfate/Dermatan Sulfate; CS/DS GAGs, Chondroitin Sulfate/Dermatan Sulfate Glycosaminoglycans; CHST3, Carbohydrate (chondroitin 6) sulfotransferase 3; CHST7, Carbohydrate (N-acetylglucosamine 6-O) sulfotransferase 7; CHST11, Carbohydrate (Chondroitin 4) Sulfotransferase 11; CHST12, Carbohydrate (Chondroitin 4) Sulfotransferase 12; CHST13; Carbohydrate (Chondroitin 4) Sulfotransferase 13; CHST14, Carbohydrate (N-acetylgalactosamine 4-O) Sulfotransferase 14; CHST15, Carbohydrate (N-acetylgalactosamine 4-sulfate 6-O) Sulfotransferase 15; CSPG4, Chondroitin Sulfate Proteoglycan 4; CS-A, Chondroitin Sulfate A unit; CS-E, Chondroitin Sulfate E unit; CSPG4, Chondroitin Sulfate Proteoglycan 4; DS, Dermatan Sulfate; DS4S-1, Dermatan 4-sulfotransferase 1; ER1, Estrogen Receptor 1; GAGs, Glycosaminoglycans; GalNAc, N-acetyl-D-galactosamine; GalNAc4S-6ST, N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase; GAPDH, Glyceraldehyde-3-phosphate dehydrogenase; GlcNAc, N-acetyl-D-glucosamine; GlcA, Glucuronic acid; IdoA, Iduronic acid; mAb, monoclonal Antibody; NPR-1, Neuropilin-1; PG, Proteoglycan; qRT-PCR, Quantitative Real-Time Polymerase Chain Reaction; SDC-1, Syndecan-1; SDC-4, Syndecan-4; siRNA, short interfering RNA; UAMS, University of Arkansas for Medical Sciences.
It is shown here in Example 1 that the CHST11 gene is highly expressed in aggressive breast cancer cells but significantly less so in less aggressive breast cancer cell lines. Furthermore, a positive correlation was observed between the expression levels of CHST11 and P-selectin binding to cells, which is a mechanism important for metastasis. Blocking the expression of CHST11 with siRNA inhibited CS-A expression and P-selectin binding to MDA-MB-231 cells. The carrier proteoglycan CSPG4 was also highly expressed on the aggressive breast cancer cell lines and contributed to the P-selectin binding and CS-A expression. In addition, CSPG4 and CHST11 were over-expressed in tumor-containing clinical tissue specimens compared with normal tissues. It was also shown that enzymatic removal of tumor-cell surface CS-GAGs significantly inhibited lung colonization of the 4T1 murine mammary cell line, which shows the importance of the CS-GAGs for metastasis and probably explains why CHST11 overexpression correlates with more aggressive cancer cell lines.
In Example 2, the inventors show that CHST11 overexpression in cancer tissues correlates with hypomethylation of the CHST11 gene. Likewise, the inventors have found that overexpression of the CSPG4 gene in cancer tissues correlates with hypomethylation of the CSP4 gene. This means that overexpression of the CHST11 and CSPG4 genes can be inferred in a tumor when the tumor tissue has these genes hypomethylated.
Direct measurement of gene expression requires living tumor cells or well-prepared frozen samples, but paraffin-embedded or catalogued stained tissues, can be used for DNA samples that will show whether these genes are hypomethylated or hypermethylated. Thus, it is easier to determine methylation state of these genes than to directly measure overexpression, and archived tumor tissue samples can be used to determine methylation status that cannot be used for measurement of gene overexpression.
The inventors have found that the expression of CHST11 and the methylation of its DNA sequence can be used for diagnostic/prognostic and predictive purposes. A combination of the expression of two sulfotransferases like CHST3 and CHST11 can be used. A combination of a CHST11 and structural proteoglycan genes such as CSPG4, syndecan-1, syndecan-4, or neuropilin-1 can be used.
But most preferably, expression level and/or methylation state of CHST11 in cancer tissue is used to provide a prognosis. This can be combined, most preferably with determination of overexpression and/or methylation state of CSPG4 in the cancer tissue.
Detection of high expression of CHST11 if combined with hypomethylation of a particular region of the CHST11 gene identify highly aggressive tumors (triple negative and basal-like). Detection of low expression due to hypermethylation will indicate less aggressive tumor cells (Estrogen receptor positive, Luminal-like). Low expression and a hypomethylated sequence indicate normal cells.
This can be used in primary tumor for prognostic purposes.
We have obtained data analyzed herein showing that CHST11 is overexpressed in many types of cancers.
The method can be used in circulating tumor cells (CTC) enriched and isolated from blood for predictive purposes.
The expression levels can also be used for detection and measuring of CTCs in blood.
The methylated DNA can be detected in plasma or serum samples for diagnostic and prognostic purposes.
The high expression of CHST11 can be combined with low expression of CHST3 for more accurate detection of cancer cells.
The high expression of CHST11 can be combined with high expression of CSPG4 for more accurate prognostic and predictive detection.
In particular embodiments of the methods of determining a prognosis of a cancer in a human, the cancer tissue sample tested for gene expression level or gene methylation status may be a blood sample, an enriched circulating tumor cell sample, a living or frozen tumor biopsy sample, or an archived paraffin-embedded tumor biopsy sample, for instance a fixed and stained paraffin-embedded slide preparation.
The cancer may be any cancer. In specific embodiments, it is breast cancer, an epithelial cancer generally, osteosarcoma, brain cancer, or a blood cancer (e.g., lymphoma, leukemia, or myeloma). In other specific embodiments, it may be melanoma, cervical cancer, esophagus cancer, head and neck cancer, or pancreatic cancer.
In the samples we have tested, particularly in the region of base pairs 1490-1850 (SEQ ID NO:37) (numbered from the transcription start site) of the CHST11 gene (NCBI accession number NG—029810.1), methylation in tumor samples at most CpG sites is either above 90% or below 10%. Thus, it is clear whether a sample is hypomethylated or hypermethylated.
Expression levels of cancer tissue samples can be assayed by real time PCR. The levels can be compared a low expression sample such as MCF-7 cells or a high expression sample, such as MDA-MB-231 cells.
For analysis of circulating epithelial tumor cells, the cells can be enriched by use of the ROSETTESEP® Human Circulating Epithelial Tumor Cell Enrichment Cocktail (Stem Cell Technologies, Vancouver, Canada). The ROSETTESEP™ Human Circulating Epithelial Tumor Cell Cocktail is designed to enrich circulating epithelial tumor cells from fresh whole blood by negative selection. Unwanted cells are targeted for removal with Tetrameric Antibody Complexes recognizing CD2, CD16, CD19, CD36, CD38, CD45, CD66b and glycophorin A on red blood cells (RBCs). When centrifuged over a buoyant density medium such as Ficoll, the unwanted cells pellet along with the RBCs. The purified tumor cells are present as a highly enriched population at the interface between the plasma and the buoyant density medium.
Thus, again, one embodiment A method of determining a prognosis of a cancer in a human comprising: (1) determining expression level of CHST11 in a cancer tissue sample or determining methylation status of CHST11 gene in a cancer tissue sample; and/or (2) determining expression level of CSPG4 in a cancer tissue sample or determining methylation status of CSPG4 gene in a cancer tissue sample. For both CHST11 and CSPG4, high expression is indicative of more aggressive tumors and tumors more likely to metastasize. And for CHST11 and CSPG4, hypomethylation of the genes in tumor samples correlates with high expression of the genes.
Expression levels are preferably determined by real-time PCR amplifying mRNA from living tumor biopsy tissues or from circulating tumor cells. Where antibodies are available to the proteins, expression levels can also be determined by measuring levels of the CHST11 product or CSPG4 protein.
Having a prognosis that indicates a less aggressive tumor type or a more aggressive tumor type has benefits for both the treating physician and the patient. It can help inform decisions about how aggressively to treat the cancer. It also allows patients to have a better idea of how much time they may have left to live or how likely they are to survive the cancer, and thus to plan their lives, and also helps them to decide which treatments they want to undergo.
The more aggressive tumor types indicated by overexpression of CHST11 have the traits of appearing more mesenchymal and less epithelial. They are more prone to invade the basement membrane, and thus more invasive. And they are more prone to metastasize.
In some cases, sensitivity or resistance to certain drugs can also be indicated by expression levels of CHST11 and CSPG4. CHST11 high expressing cells are more sensitive to daunorubicin (Gyorffy B, et al. Oncogene. 2005 Nov. 17; 24(51):7542-51.), to Selumetinib (an inhibitor of MEK and MAPK/ERK kinases; Garnett, M J. et al Nature 2012 Mar. 28; 483(7391):570-5), and CHIR-265 (an inhibitor of RAF and VEGFR; Barretina, J. et al Nature. 2012 Mar. 28; 483(7391):603-7.), and less sensitive to cisplatin (Gyorffy, B. et al. Int J. Cancer. 2006 Apr. 1; 118(7):1699-712) and trastuzumab (Neve, R M. Et al, Cancer Cell. 2006 December; 10(6):515-27).
The CHST11 gene sequence is genbank nucleotide accession number NG—029810.1.
The transcription start stie in this gene is at nucleotide 5001. This is position 1 in
The cDNA for the human CSPG4 gene is genbank accession number NM—001897.4. The gene is located on chromosome 15, accession number NC—000015.9. The transcription start is at nucleotide 76005190. Exon 1 begins at nucleotide 76005097. This gene sequence can be used to test for methylation.
Summary:
We have previously demonstrated that chondroitin sulfate glycosaminoglycans (CS-GAGs) on breast cancer cells function as P-selectin ligands. This study was performed to identify the carrier proteoglycan (PG) and the sulfotransferase gene involved in synthesis of the surface P-selectin-reactive CS-GAGs in human breast cancer cells with high metastatic capacity, as well as to determine a direct role for CS-GAGs in metastatic spread.
Quantitative real-time PCR (qRT-PCR) and flow cytometry assays were used to detect the expression of genes involved in the sulfation and presentation of chondroitin in several human breast cancer cell lines. Transient transfection of the human breast cancer cell line MDA-MB-231 with the siRNAs for carbohydrate (chondroitin 4) sulfotransferase-11 (CHST11) and chondroitin sulfate proteoglycan 4 (CSPG4) was used to investigate the involvement of these genes in expression of surface P-selectin ligands. The expression of CSPG4 and CHST11 in 15 primary invasive breast cancer clinical specimens was assessed by qRT-PCR. The role of CS-GAGs in metastasis was tested using the 4T1 murine mammary cell line (10 mice per group).
The CHST11 gene was highly expressed in aggressive breast cancer cells but significantly less so in less aggressive breast cancer cell lines. A positive correlation was observed between the expression levels of CHST11 and P-selectin binding to cells (P<0.0001). Blocking the expression of CHST11 with siRNA inhibited CS-A expression and P-selectin binding to MDA-MB-231 cells. The carrier proteoglycan CSPG4 was highly expressed on the aggressive breast cancer cell lines and contributed to the P-selectin binding and CS-A expression. In addition, CSPG4 and CHST11 were over-expressed in tumor-containing clinical tissue specimens compared with normal tissues. Enzymatic removal of tumor-cell surface CS-GAGs significantly inhibited lung colonization of the 4T1 murine mammary cell line (P=0.0002).
Cell surface P-selectin binding depends on CHST11 gene expression. CSPG4 serves as a P-selectin ligand through its CS chain and participates in P-selectin binding to the highly metastatic breast cancer cells. Removal of CS-GAGs greatly reduces metastatic lung colonization by 4T1 cells. The data strongly indicate that CS-GAGs and their biosynthetic pathways are promising targets for the development of anti-metastatic therapies.
Tumor-associated glycans play a significant role in promoting aggressive and metastatic behavior of malignant cells [1-5], participating in cell-cell and cell-extracellular matrix interactions that promote tumor cell adhesion and migration. Among glycans that play a critical role in stromal tumor cell interactions are glycosaminoglycans (GAGs) attached to proteoglycans (PGs). Altered production levels of PGs and structural changes in their GAGs are reported in many neoplastic tissues [6-10]. GAGs are polysaccharide chains covalently attached to protein cores that together comprise PGs [6, 11] and based on the prevalence of GAG chains, chondroitin sulfate (CS)/dermatan sulfate (DS) PGs (CS/DS-PGs), heparan sulfate PGs and keratan sulfate PGs have been described [12]. Increased production of CS/DS-GAGs is found in transformed fibroblasts and mammary carcinoma cells [8, 13, 14] and it has been shown that these polysaccharides contribute to fibrosarcoma cell proliferation, adhesion and migration [15].
Several studies have disclosed the critical involvement of P-selectin in the facilitation of blood borne metastases [16-18]. P-selectin/ligand interaction often requires sialylated and fucosylated carbohydrate such as sialyl Lewis X and sialyl Lewis A [19]; however, P-selectin also binds to heparan sulfate, certain sulfated glycolipids and CS/DS-GAGs [20-23]. In previous studies we found that CS/DS-GAGs are expressed on the cell surface of murine and human breast cancer cell lines with high metastatic capacity and that they play a major role in P-selectin binding and P-selectin-mediated adhesion of cancer cells to platelets and endothelial cells [24]. However, variation in the abundance and function of CS/DS relative to tumor cell phenotypic properties and P-selectin binding are not well defined. It is likely that P-selectin binding to tumor cells and the functional consequences of such binding are dependent on which sulfotransferases define the relevant CS/DS and which core proteins carry the CS polysaccharide.
CS/DS expression is controlled by many enzymes in a complex biosynthetic pathway and this leads to considerable variation in structure and function. The chondroitin backbone of CS/DS-GAGs consists of repetitive disaccharide units containing D-glucuronic acid (GlcA) and N-acetyl-D-galactosamine (GalNAc) residues, or varying proportions of L-iduronic acid (IdoA) in place of GlcA [25, 26]. Major structural variability of the CS/DS chains is due to the sulfation positions in repeating disaccharide units by the site-specific activities of sulfotransferases that produce the variants CS-A, CS-B (dermatan sulfate, DS), CS-C, CS-D and CS-E [26, 27]. CHST3, CHST7, CHST11, CHST12, CHST13, CHST14 and CHST15 are the enzymes that sulfate the GalNAc residues of chondroitin polymers. The expression levels of these enzymes are hypothesized to affect the production of P-selectin ligands. CHST11 and CHST13 share specificity, as they mediate 4-0 sulfation of chondroitin [28-30]. CHST12 and CHST14 mediate mostly 4-0 sulfation of DS units [30, 31]. CHST3 and CHST7 share specificity for 6-0 sulfation of chondroitin [32, 33]. CHST15 transfers sulfate to the carbon-6 of an already 4-0 sulfated GalNAc residue producing oversulfated CS-E [34]. The relationship between the relative expression of these sulfotransferases with the expression of P-selectin-reactive CS/DS-GAGs has not been reported and is addressed in this paper.
The variation, abundance and function of CS/DS-GAGs are also affected by the expression of the PG core protein presenting them. Syndecan-1 (SDC-1), syndecan-4 (SDC-4), neuropilin-1 (NRP-1) and CSPG4 are considered major pro-malignancy membrane proteins capable of carrying CS chains [35-39]. Among these PGs, CSPG4 exclusively carries CS chains [40, 41]. CSPG4 is a human homolog of Rat NG2, which is also known as High Molecular Weight Melanoma Associated Antigen and Melanoma Chondroitin Sulfate Proteoglycan [40, 42, 43]. This tumor-associated cell surface PG potentiates cell motility [44-46]. CSPG4 is also linked to cancer stem cells via signaling mechanisms [39, 45]. Therefore, studying whether this PG interacts directly with P-selectin is of particular interest.
Depending on CSPG4's relative expression levels, this PG might be a major core protein presenting CS-GAGs on an aggressive subset of tumor cells, interacting with P-selectin. In the current study we investigated whether CSPG4, via its CS/DS chain can serve as a P-selectin ligand and whether expression of specific chondroitin sulfotransferases contributes to P-selectin interaction with cells. We further examined the involvement of CS-GAG chains in lung colonization by the 4T1 mammary cell line with and without enzymatic removal of CS-GAGs in a murine experimental metastasis model. Our data show for the first time that P-selectin can bind to tumor cells via CSPG4 and that CHST11 expression is linked to P-selectin-reactive cell surface CS/DS-GAGs. The results directly link CS/DS-GAGs to the metastatic spread of breast cancer. These findings have significant implications for understanding mechanisms of breast cancer metastasis, paving the way towards developing alternative strategies to treat and prevent metastasis.
Anti-CS-A mAb 2H6 was from Associates of Cape Cod/Seikagaku America (Falmouth, Mass., USA), anti-CSPG4 mAb 225.28 was made as described [47, 48], and recombinant human P-selectin/Fc (human IgG) was from R&D Systems (Minneapolis, Minn., USA). Fluorescence-conjugated anti-human IgG, anti-mouse IgM and chondroitinase ABC were from Sigma (St. Louis, Mo., USA). R-Phycoerythrin-conjugated polyclonal goat anti-mouse F(ab′)2 fragment was from Dako North America, Inc. (Carpinteria, Calif., USA). DNA primers were from Integrated DNA Technologies (IDT, Coralville, Iowa, USA). Real-time PCR reagents were from Applied Biosystems (Foster City, Calif., USA). Pre-designed siRNA sequences were from Ambion (Austin, Tex., USA) and Santa Cruz Biotechnology Inc. (Santa Cruz, Calif., USA). siPORT™ NeoFX™ Transfection Agent was from Ambion. TRIzol reagent was from Invitrogen (Carlsbad, Calif., USA).
Human breast cancer MCF7, MDA-MB-231, MDA-MB-468 cell lines and the murine 4T1 cell line were from ATCC (Manassas, Va., USA). Human MDA-MET cells were selected in vivo for their bone colonizing phenotype [49]. 4T1 cells were used within 10 passages and less than six months after receipt. We confirmed cell line identities by the Human Cell Line Authentication test (Genetica DNA Laboratories, Inc. Cincinnati, Ohio, USA). The melanoma cell lines M14 and M14-CSPG4, stably transfected to express CSPG4, were used as homologous CSPG4-non-expressing and expressing cell lines [50] and were characterized by real-time PCR for CSPG4 expression. Cells were cultured in a base medium supplemented with 10% heat-inactivated fetal bovine serum (Life Technologies, Carlsbad, Calif., USA), 50 units/mL penicillin, and 50 μg/mL streptomycin. Base medium for MDA-MB-231, MDA-MET, MDA-MB-468, and 4T1 was DMEM (Fisher Scientific, Pittsburgh, Pa., USA). For MCF7 base medium was MEM (Fisher Scientific) supplemented with 0.1 mM non-essential amino acids, 1 mM sodium pyruvate, and 0.01 mg/ml insulin (Invitrogen). For M14 and M14/CSPG4 RPMI 1640 medium (Fisher Scientific) was used with the addition of 500 μg/ml G418 (Invitrogen). Cells are checked every six months to be free from Mycoplasma contamination using the MycoAlert® Mycoplasma Detection Kit (Lonza Rockland Inc., Rockland, Me., USA).
De-identified frozen specimens from 15 female breast cancer patients diagnosed with invasive ductal carcinoma were provided by the University of Arkansas for Medical Sciences (UAMS) Tissue Procurement Facility. Specimens were matched for each donor to have both tumor-free and tumor-containing breast tissues. According to the policy of the Tissue Procurement Facility, patients signed consent forms to donate excess specimen tissue and to allow use of related pathological data for research purposes, which were approved by the UAMS Institutional Review Board. For this study, an active human tissue use protocol approved by the UAMS Institutional Review Board was used. In this protocol, informed consent was waived due to the use of de-identified specimens with no link to patient identifiers.
Total RNA Isolation and qRT-PCR
Total RNA was isolated from cultured cells and tumor tissues using TRIzol reagent, following the manufacturer's instructions. The quantity and quality of the isolated RNA was determined by Agilent 2100 Bioanalyzer (Palo Alto, Calif., USA). One μg of total RNA was reverse-transcribed using random-hexamer primers with TaqMan Reverse Transcription Reagents (Applied Biosystems). Reverse-transcribed RNA was amplified with SYBR Green PCR Master Mix (Applied Biosystems) plus 0.3 μM of gene-specific upstream and downstream primers during 40 cycles on an Applied Biosystems 7500 Fast Realtime cycler. Data were analyzed by absolute and relative quantification. In absolute quantification, data were expressed in relation to 18S RNA, where the standard curves were generated using pooled RNA from the samples assayed. In relative quantification, the 2 (−Delta Delta C(T)) method was used to assess the target transcript in a treatment group relative to that of an untreated control group using expression of an internal control (reference gene) to normalize data [51]. Expression of GAPDH and β-actin was used as internal control. Each cycle consisted of denaturation at 95° C. for 15 s, and annealing and extension at 60° C. for 60 s. The primer sequences are shown in Table 1.
Binding of the recombinant human P-selectin/Fc molecule, anti-CS-A (2H6) and anti-CSPG4 (225.28) mAb to cells was determined using flow cytometry as previously described [24]. Briefly, cells were incubated with mAb or P-selectin/Fc, washed and stained with FITC-conjugated anti-mouse IgM or anti-human IgG prior to binding detection by flow cytometry. R-phycoerythrin-conjugated polyclonal goat anti-mouse F(ab′)2 was used as secondary for detection of anti-CSPG4 binding.
Switching Off Gene Expression with siRNA
Three pre-designed siRNA sequences for CHST11 (Ambion) were used (Table 1). NG2 siRNA (sc-40771) from Santa Cruz Biotechnology, Inc. was used for inhibition of CSPG4. These sequences were transfected into cells growing in tissue culture using the siPORT™ NeoFX™ Transfection Agent, and mRNA levels were determined 48 hours later by real-time PCR. Expression of GAPDH was used as reference control. Reactivity of anti-CS-A mAb 2116 and human recombinant P-selectin was assessed 144 hours after siRNA transfection. Transfection with GAPDH siRNA (Ambion) was used as control.
BALB/c female mice (six to eight weeks old) were from Harlan Laboratories (Indianapolis, Ind., USA). We used 4T1 cells in an experimental metastasis model [24]. Cells were treated with chondroitinase ABC in HBSS buffer with protease inhibitors [24], or with the buffer and protease inhibitor alone (no chondroitinase ABC treatment) before inoculation through the tail vein. Each mouse (10 mice per group) received 2×104 4T1 cells. Mice were sacrificed 25 days after tumor cell injection and lungs were harvested to determine clonogenic cells by growing cells in medium containing 6-thioguanine [52]. Animal studies have been reviewed and approved by the Institutional Care and Use Committee of UAMS.
For comparison of gene expression between cell lines, the raw amount for each mRNA was normalized to the control mRNA (18S) amount and then log transformed, and analyzed via one-way ANOVA with Tukey's post-hoc procedure. For the tissue comparisons of gene expression in patient samples, the tumor/normal expression ratios for each patient were log-transformed and subjected to one-sample t-tests. For siRNA effects on relative mRNA levels mean fluorescence intensities of antibody binding were log transformed and analyzed via ANOVA and Tukey's post-hoc procedure. Associations between mean fluorescence intensities of P-selectin binding and quantities of sulfotransferase transcripts were characterized using Pearson correlation tests on log-transformed data. In order to check the validity of assumptions for running Pearson's test, Spearman correlation analysis was also performed and when correlation coefficients were similar, assumptions were considered valid. For clonogenic assay comparisons, the number of clonogenic lung metastases was analyzed between groups by the Wilcoxon rank-sum test.
CHST11 is Overexpressed in Aggressive Human Breast Cancer Cell Lines and its Expression Correlates with P-Selectin Binding
We have shown that CS/DS-GAGs expressed on the cell surface of MDA-MB-231 and MDA-MET human breast cancer cells function as P-selectin ligand and that exogenous CS-E efficiently inhibits P-selectin binding to cells [24]. Among the major sulfotransferases able to sulfate the GlaNAC residue of the chondroitin disaccharide, CHST11, CHST12, and CHST13 are chondroitin 4-sulfotransferases, able to catalyze sulfation of chondroitin on the carbon-4 position of GalNAc sugars in disaccharide GAG units, producing primarily CS-A units (GlcAβ1-3GalNAc (4-SO4)) [28-30]. CHST14, dermatan 4-sulfotransferase 1 (D4ST-1), is specific for 4-O sulfation of the GalNAc in CS-B (DS) units after dermatan sulfate epimerase activity and its specificity can be shared by CHST12 [30, 31]. CHST3 and CHST7 are chondroitin 6-sulfotransferases that transfer sulfate to carbon-6 position of GalNAc, competing with 4-sulfotransferases for the same substrate, producing primarily CS—C units (GlcAβ1-3GalNAc (6-SO4)) [32, 33]. CHST15, GalNAc 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST), transfers sulfate to the carbon-6 of a 4-sulfated GalNAc, producing CS-E (GlcAβ1-3GalNAc (4-, 6-SO4)) [34].
Quantitative real-time PCR was used to monitor the expression levels of these genes in several human breast cancer cell lines differing in their cancer phenotype. The human breast cancer cell lines MCF7, MDA-MB-468, MDA-MB-231, and MDA-MET represent increasing aggressiveness and metastatic capacity (MCF7<MDA-MB-468<MDA-MB-231=MDA-MET). While expression of all genes was detected in these breast cancer cells, CHST13 expression was observed to be very low with no significant differences in expression between cell lines (
Flow cytometry analysis of the binding of the anti-CS-A mAb 2H6, consistent with qRT-PCR data, indicates that the expression of CS-A was lower in the least aggressive MCF7 cell line and high in the most aggressive MDA-MB-231 and MDA-MET cell lines (
Our data indicate that CHST11 is required for P-selectin binding. To confirm a role of 4-O sulfated structures in P-selectin binding, the expression of CHST11 in MDA-MB-231 cells was inhibited by siRNA. We observed that CHST11 mRNA levels, anti-CS-A binding and P-selectin binding were all significantly reduced upon treatment with the three siRNAs tested (
We repeated the CHST11 siRNA assay and did not observe any effect on the CSPG4 transcript or its surface expression as assayed by anti-CSPG4 mAb (Additional file 1). GAPDH siRNA was used as control in siRNA assays and reduced GAPDH mRNA by 75% in multiple assays (data not shown). Treatment of MDA-MB-231 cells with GAPDH siRNA did not inhibit CHST11 expression (data not shown). CHST11 siRNA sequences did not affect expression of GAPDH (data not shown). Therefore the expression of CS-A and binding of P-selectin to this cell line depends on the expression of the CHST11 gene.
Because CS/DS-GAG expression and function depends on the composition of PGs expressed, studying the nature of the PG(s) involved in presentation of P-selectin-reactive CS/DS is important. Such studies should help us understand the functional consequences of CS/DS-GAG, PG and P-selectin interactions and provide data that may, in future studies, be used to manipulate the expression of the polysaccharide by targeting the core protein(s). Several membrane PGs, including SDC-1, SDC-4, NRP-1, and CSPG4 can potentially present GAG chains on the surface of tumor cells [53-55]. CSPG4 is the only cell surface PG that is exclusively decorated with CS-GAGs [41] and therefore, it may play a major role in forming cell surface CS-GAGs. We compared the expression of CSPG4 in the above described human breast cancer cell lines. The results of qRT-PCR indicate that the less aggressive epithelial-like cell lines MCF7 and MDA-MB-468 did not express CSPG4, while the gene was highly expressed in the highly aggressive mesenchymal-like cell lines MDA-MB-231 and MDA-MET (
Because CSPG4 is abundant on aggressive cells, we hypothesized that it may function as a major core protein presenting CS-A and CS-related P-selectin ligands. We used CSPG4 siRNA to inhibit CSPG4 expression (Additional file 2). Inhibiting CSPG4 transcript in turn inhibited cell surface expression of the PG (
In order to confirm that P-selectin binds to CSPG4 we used CSPG4-transfected M14 melanoma cell line available in the lab. In prescreening of the M14 cell line, it appeared that this cell line expresses CHST11 with low binding of anti-CS-A 2H6 mAb and P-selectin, indicating that this cell line and its transfected version are excellent candidates for studying participation of CSPG4 and its CS GAGs in P-selectin binding. We observed that anti-CSPG4 225.28 mAb reacted with the transfected cells (M14-CSPG4) but not with mock-transfected M14 cells (
2.43 (±0.56)
2.15 (±0.8)
1.55 (±0.20)
1.96 (±0.07)
2.09 (±0.18)
0.22 (±0.03)
0.13 (±0.04)
0.86 (±0.07)
1.50 (±0.30)
1.90 (±0.11)
4.84 (±0.59)
In order to establish a translational relevance, we examined the expression of CSPG4 and CHST11 in specimens from breast cancer patients to compare the level of expression of these genes between normal and malignant tissues. Frozen sample-pair specimens from 15 breast cancer patients diagnosed with invasive ductal carcinoma were obtained from the UAMS tissue bank. In each sample pair, a tumor-containing sample was matched with tumor-free tissue from the same donor. We observed that these genes were overexpressed in tumor-containing tissues versus normal tissues (
We have previously suggested a role for CS/DS-GAGs in metastasis of the murine mammary cell line 4T1 [24]. To directly link CS/DS-GAGs to tumor metastasis, we examined whether removal of the cell surface CS/DS-GAGs affects metastasis of 4T1 cells in vivo. Here we demonstrate that removing CS/DS-GAGs by treating cells with chondroitinase ABC attenuated lung metastases in the 4T1 murine tumor model (
Tumor cell dissemination by platelets leads to colonization of cancer cells to secondary organs resulting in poor prognosis and high mortality of cancer patients. P-selectin is present on activated platelets and endothelial cells while CS/DS-GAGs on the surface of breast cancer cells with high metastatic potential serve as P-selectin ligands [24]. The role of P-selectin in heterotypic adhesion is a critical component determining the efficiency of tumor cell dissemination [16, 17]. The study of P-selectin-reactive molecules on tumor cells is crucial for the assessment of metastatic risk and the development of possible ways of dealing with metastatic disease. Such studies are needed to ultimately reveal the functional consequences of P-selectin/ligand interaction in tumor progression, making specific links between platelets and tumor metastasis.
Our results suggest the CHST11 gene as a major player in production of such P-selectin ligands. The results using CHST11 siRNA further suggest that among the chondroitin sulfotransferases tested, CHST11 expression has a rate limiting role in constructing both CS-A chains and P-selectin ligands on MDA-MB-231 cells. This data directly links expression of the CHST11 gene to P-selectin-reactive GAGs on this cell line and has significant implications for further functional studies. CS-A is an immediate product of CHST11 expression and is considered a precursor in forming CS-E units [57]. P-selectin has been shown to bind to CS-E [23]. We have also shown that exogenous CS-E inhibits P-selectin binding to cancer cells [24]. While we do not rule out participation of CS-E in P-selectin binding, our data do not support CS-E as the P-selectin reactive GAG unit on these cells. The combined high expression of these two genes may associate with P-selectin-reactive glycans and aggressiveness. This possibility should be investigated in future studies. However, the data indicate that the expression of the CHST11 gene in tumor cells is associated with synthesis of P-selectin ligands and a metastatic phenotype. Others have suggested a role for CS-A in tumor progression and metastasis in a melanoma model [46]. However, our data suggest that surface presentation of CS-A may be required but is not sufficient for a metastatic phenotype to occur. Besides its role in constructing CS-A, CHST11 also plays a role in chain elongation and production of more CS [57]. Chain elongation activity of CHST11 with a fine balance in the expression of other enzymes might be needed for constructing conformational epitopes. Thus, CHST11 activity may lead to larger CS polymers with multiple sequences embedded with distinct sulfation patterns resulted from activity of multiple sulfotransferases, leading to the production of conformational epitopes or highly concentrated sequences with specific reactivities. Thereby, the expression of CHST11 may correlate better with the tumor cells' aggressive phenotype than does the prevalence of any particular CS isomers.
Interestingly, our current results implicate CSPG4 in the presentation of CS moieties as P-selectin ligands. CSPG4 exclusively presents CS-GAGs, and the data described here suggest that these structures interact with P-selectin and, therefore, may contribute to distant metastasis of tumor cells. Our data indicate that P-selectin binds to CSPG4 through CS-GAGs and that CSPG4 is involved in P-selectin binding to CSPG4-expressing breast cancer cells. However, other PGs may also participate in P-selectin binding as expression of SDC-4 and NRP-1 is also higher in MDA-MB-231 and MDA-MET. Lack of expression of CSPG4 in MDA-MB-468 further suggests that anti-CS-A and P-selectin binding to these cells is probably due to expression of other PGs and not CSPG4. However, because of the role of CSPG4 in signaling and tumor phenotype, we speculate that its interaction with P-selectin may lead to an exclusive tumor cell activation and consequently survival in circulation. Therefore, concerted upregulation of CSPG4 and CHST11 may induce expression of a unique molecular entity that may increase the metastatic capabilities of tumor cells. More studies are needed to understand the consequences of P-selectin binding to CS-GAGs of multiple PGs and to reveal how and at what stage of the metastatic cascade the CS-GAGs and their carrier proteins contribute to metastasis.
We have shown glycan interactions with P-selectin and the significance of P-selectin binding in metastasis of a murine mammary cell line [24, 52]. Our previous findings support the concept that CS chains promote survival in the circulation and tumor cell extravasation via P-selectin-mediated binding to platelets and endothelial cells. In the current study, the significance of the cell surface expression of CS-GAGs in a breast cancer model is established. The data demonstrate that enzymatic removal of the CS chains significantly attenuated formation of lung metastases in a highly metastatic mammary cell line. Others have shown that P-selectin ligands are critical components of heterotypic adhesion, determining the efficiency of tumor cell dissemination [16, 17]. Sugahara's group demonstrated that highly sulfated CS-GAGs, in particular CS-E, are involved in metastasis of murine lung carcinoma and osteosarcoma cells [58, 59]. However, our data suggest a role for 4-0 sulfation of chondroitin in the metastatic phenotype. CHST11 expression results in the synthesis of a particular Chonroitin sulfate important for cell-cell adhesion and metastasis. Moreover, the data suggest that the presence of CS/DS-GAGs may not be sufficient for a phenotype with high metastatic capacity to occur. The data emphasize a combination of the polysaccharide and a core protein as a pro-metastatic entity or prometastatic code. Future studies are needed to understand the contribution of each PG in P-selectin mediated tumor cell behavior.
We further showed that the expression of CHST11 and CSPG4 is elevated in tumor tissues from breast cancer patients. Consistent with our data, CHST11 expression has been shown to be greater in human breast carcinoma compared to normal breast tissue [60] and in malignant plasma cells from myeloma patients compared to normal bone-marrow plasma cells [61].
The current research should lead to future studies of functional relationships between CS and tumor progression. Existing knowledge and further mechanistic studies might suggest CS-GAGs and their presenting PGs as targets for antimetastatic therapies. In support of work done in melanoma [62] and recent studies in breast cancer [39], the studies outlined here strongly suggest that CSPG4 can be an available target for immunotherapy of breast cancer. However, in order to efficiently block tumor cell dissemination by interrupting P-selectin/CS interaction, targeting any single PG does not seem enough as other PGs can probably compensate and support metastatic processes. In this regard, global targeting of specific CS isomers may be a particularly effective approach.
Breast cancer cell surface is decorated with CS-GAGs and due to tumor-specific expression patterns of chondroitin sulfotransferases and PGs, the composition and binding specificity of these polysaccharides differ from those of normal tissues. Therefore, these molecules and their interaction with P-selectin should be considered as viable targets for the development of novel therapeutic strategies.
This study demonstrates the significance of CS-GAGs in the lung colonization of an aggressive murine mammary cell line. The study reveals that CSPG4 can serve as a P-selectin ligand through its CS chain and that the expression of the CHST11 gene controls P-selectin reactive CS-GAGs formation. The data suggest that CS-GAGs, their biosynthetic pathway, or the core protein carrying them can be potential-targets for the development of therapeutic strategies for treatment of aggressive breast tumors. The knowledge and perspective gained from this line of research together with further mechanistic studies may pave the road to target CS-GAGs, their carrier PGs and their interaction with P-selectin as novel antimetastatic therapies.
We have shown that the expression levels of carbohydrate (chondroitin 4) sulfotransferase-11 (CHST11) correlate with the expression of P-selectin-reactive surface chondroitin sulfate (CS) and aggressiveness of human breast cancer cells. This study was performed to further evaluate the expression of the CHST11 gene in breast cancer and determine whether the expression of this gene is controlled by DNA methylation. Expression analysis of Oncomine datasets revealed that the expression of CHST11 is significantly higher in cancer tissues with the expression levels correlating with tumor progression and aggressiveness. Our data demonstrate that the expression of CHST11 and its immediate product chondroitin sulfate A (CS-A) was high in the estrogen receptor (ER)-negative MDA-MB-231 cell line and very low in ER-positive MCF7 cells. We observed very low levels of DNA methylation in a CpG island of CHST11 in ER-negative cells but very high levels in the same region in ER-positive cells. Treatment of MCF7 cells with 5AzadC increased the expression of CHST11 and CS-A in a dose-dependent manner. The data suggest that breast cancer cells may use DNA methylation as a mechanism to control the expression of CHST11. The results demonstrate the utility of CHST11 expression and its DNA methylation status as potential biomarkers in breast cancer.
CHST11 is a key enzyme in the biosynthesis of chondroitin sulfates (CS) and its action on chondroitin chains can lead to the production of chondroitin sulfate A, B and E (CS-A, CS-B, CS-E) (Mikami et al. 2003; Uyama et al. 2006). Several studies, including ours, suggest roles for CS-A, CS-B, and CS-E in tumor progression and metastasis (Iida et al. 2007; Monzavi-Karbassi et al. 2007; Li et al. 2008). Recently, we reported that the expression levels of the CHST11 gene correlate with CS-A expression, P-selectin binding and aggressiveness of human breast cancer cell lines (Cooney et al. 2011). We have shown that removing CS chains and blocking P-selectin interaction with breast cancer cells significantly attenuates metastasis (Monzavi-Karbassi, Stanley et al. 2007; Cooney, Jousheghany et al. 2011). Based upon our results we hypothesize that CHST11 expression, by affecting the cell surface CS profile and construction of P-selectin-reactive epitopes, plays a significant role in the metastatic behavior of breast cancer. Therefore, for a potential future use in the development of therapeutic or diagnostic strategies targeting CHST11 gene, understanding the mechanisms controlling CHST11 expression is important.
Aberrant DNA methylation is a mechanism controlling gene expression and is involved in tumor initiation and progression (Feinberg et al. 1988; Narayan et al. 1998; Baylin et al. 2001; Ehrlich 2002; Szyf et al. 2004; Cooney 2008). The expression of several glycosaminoglycan (GAGs) sulfotransferases is associated with DNA methylation (Miyamoto et al. 2003; Bui et al. 2010; Tokuyama et al. 2010). A clear association between DNA methylation, expression levels of CHST11 and its final products such as CS-A and metastatic potential has not been established.
We show here and in Example 1 that the expression levels of CHST11 can predict progression of the breast disease and more aggressive phenotypes. Our investigation of the methylation status of CHST11 in breast cancer cells clearly demonstrates an association between lack of expression of this gene and hypermethylation of a CpG island of its DNA. The 5AzadC treatment of less aggressive epithelial-like luminal human MCF7 cells lacking CHST11 expression, led to a dose response increase in the expression of the gene and its product CS-A. Given the role of CS in cell-cell interaction resulting in tumor growth and metastasis, these findings have significant implications for the development of novel prognostic and therapeutic approaches targeting CS.
Reagents.
Anti-CS-A mAb 2H6 was from Associates of Cape Cod/Seikagaku America (Falmouth, Mass.). Fluorescence-conjugated, anti-mouse IgM and 5-aza-2′-deoxycytidine (5AzadC) were from Sigma (St. Louis, Mo.). Primers were from Integrated DNA Technologies (IDT, Coralville, Iowa). Real-time PCR reagents were from Applied Biosystems (Foster City, Calif.). TRIzol reagent was from Invitrogen (Carlsbad, Calif.), FailSafe PCR PreMix Selection kits and Enzyme Mix were from Epicentre Biotechnologies (Madison, Wis.). Alkaline phosphatase (rAPid) was from Roche (Nutley, N.J.).
Analysis of Oncomine Cancer Gene Microarray Database.
For comparison of CHST11 mRNA expression between cancer and normal tissues, between ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC), and between tumors of different nuclear grades, we selected datasets from the Oncomine cancer microarray database (Compendia Biosciences; Ann Arbor, Mich., USA). This database was also used to compare expression levels of CHST11 between ER-negative and ER-positive patients' specimens and among a panel of cell lines that represent luminal, Her-2-amplified and basal-like molecular subtypes of breast cancer. Log-transformed, median-centered and normalized expression values (Rhodes et al. 2004) were extracted, analyzed and graphed accordingly.
Cell Lines.
Cell lines MCF7, MDA-MB-231, MDA-MB-468, T47-D, and ZR-75-1 were from ATCC (Manassas, Va.). MDA-MB-231, MDA-MB-468, T47-D, and ZR-75-1 cells were cultured in DMEM supplemented with 10% heat-inactivated fetal bovine serum (Life Technologies), 50 units/mL penicillin, and 50 μg/mL streptomycin. MCF7 were grown as described before (Cooney, Jousheghany et al. 2011). Cells are checked every six months to be free from Mycoplasma contamination using the MycoAlert® Mycoplasma Detection Kit (Lonza Rockland Inc., Rockland, Me.).
Total RNA Isolation and Quantitative Real Time RT-PCR (qRT-PCR).
Total RNA was isolated from cultured cells using TRIzol reagent, following the manufacturer's instructions. The quantity and quality of the isolated RNA was determined, using an Agilent 2100 Bioanalyzer (Palo Alto, Calif.). One μg of total RNA was reverse-transcribed using random-hexamer primers with TaqMan Reverse Transcription Reagents (Applied Biosystems). Reverse-transcribed RNA was amplified with SYBR Green PCR Master Mix (Applied Biosystems) plus 0.3 μM of gene-specific upstream and downstream primers during 40 cycles on an Applied Biosystems 7900 HT Fast Real Time System. Data were analyzed by absolute and relative quantification. In absolute quantification, data were expressed in relation to 18S RNA, where the standard curves were generated using pooled RNA from the samples assayed. In relative quantification, the 2(−Delta Delta C(T)) method was used to assess the target transcript in a treatment group to that of untreated control using expression of an internal control (reference gene) to normalize data (Livak and Schmittgen 2001). Expression of GAPDH was used as internal control. The primer sequences are shown in Table 4.
Digital Gene Expression.
Second generation mRNA-sequencing data generated with the 75 by directional protocol for the Illumina Idea Challenge (illumine.com/landing/idea) project was used to evaluate digital gene expression of CHST11. We followed the method of Mortazavi et al. (Mortazavi et al. 2008) to estimate the number of expressed transcripts of the CHST11 gene CCHST11 by taking into account the number of reads mapping to the gene NCHST11, mapped gene length LCHST11, total number of reads mapped on the known exons of the sequenced transcriptome NT, and the total length of the mapped transcriptome LT as:
We used this equation to estimate the number of expressed copies of the regions analyzed by the RT-PCR.
5AzadC Treatment.
5AzadC was dissolved in ice-cold phosphate-buffered saline, filter sterilized at 4° C. and the resulting solution used to treat the MCF7 cell line. For dose-response experiments, cells were harvested 5 days after the initial treatment. Cell growth medium was refreshed every other day.
Extraction and Bisulfite Modification of DNA.
DNA from cells was extracted as described before (Leakey et al. 2008). DNA was bisulfite modified with an Epitect Kit (Qiagen, Valencia, Calif.) using 300 ng of DNA per reaction. PCR was performed using a FailSafe PCR PreMix Selection kit and FailSafe Enzyme Mix. Each 25 μl PCR reaction included 1.0 μM of each primer, 2.5 units of the FailSafe Enzyme Mix and 12.5 μl of the FailSafe PCR Premixes A or C. Bisulfite-modified genomic DNA was amplified by seminested PCR using two sets of primers for part of intron1 that is within a CpG island spanning exon 1 of the CHST11 gene (Genbank NM—000012 and exon 1 located with NM—018413). The same amplification profile was used for both reactions of the seminested PCR: 1 cycle at 80° C. for 1 min, 1 cycle at 94° C. for 1 min; 1 cycle at (95° C. for 1 min, 54° C. for 1 min, 72° C. for 1 min); 1 cycle at (95° C. for 1 min, 53° C. for 1 min, 72° C. for 1 min); 1 cycle at (95° C. for 1 min, 52° C. for 1 min, 72° C. for 1 min); 1 cycle at (95° C. for 1 min, 51° C. for 1 min, 72° C. for 1 min); 36 cycles at (95° C. for 1 min, 50° C. for 1 min, 72° C. for 1 min); 72° C. for 5 min and cooling to 4° C.
A forward, outside primer and reverse primer were used for CHST11 for the first reaction (Table 4). A second, semi-nested, PCR was then performed on 1 μl of the amplificate (in a 25 μl PCR reaction) using a forward nested primer and the reverse primer from the first reaction (346 bp PCR product, Table 4). The primers were designed using MethPrimer web software (Li and Dahiya 2002, available from Urogene). The CpG island was defined using CpG Island Searcher set on the default criteria for defining CpG islands (Takai and Jones 2003) (cpgislands.us.edu/cpg.aspx).
Bisulfite genomic sequencing (BGS) and methylation level quantification.
BGS was performed as described before (Leakey, Zielinski et al. 2008) with the following minor modifications. We used rAPid alkaline phosphatase and PCR products were sequenced using the nested forward (upstream) CHST11 primer. We also analyzed DNA methylation in the region spanning more than 1.5 kb of the CHST11 CpG island with reduced representation bisulfite sequencing (RRBS, (Meissner et al. 2008; Smith et al. 2009)) data generated on breast cancer cell lines for the Illumina Idea Challenge (illumina.com/landing/idea). RRBS selects DNA fragments up to 220 by in the vicinity of MspI recognition sites (C.CGG) (Meissner, Mikkelsen et al. 2008). We only considered CpG dinucleotides with coverage larger than 10×. The percentage of methylation was inferred from the number of methylated reads divided by the sum of methylated and unmethylated reads. All reads were mapped to the hg18 release of the human genome Second generation sequencing DNA methylation results were plotted in Matlab (available from Mathworks).
Statistical Analysis.
The Chi-square test for trend was performed for gene expression across tumor grade. The Mann-Whitney test was performed to compare gene expression between DCIS and IDC and between ER-negative and ER-positive cancer specimens. For 5AzadC induced fold change in gene expression, the mRNA levels of the non-zero doses for each transcript and experimental replication were normalized to that of the zero-dose control, transformed to their base-10 logarithms, and analyzed for trend with dose via one-way ANOVA. For comparison of gene expression between cell lines, the raw amount for each mRNA was log transformed and normalized to the control mRNA (18S) amount, and analyzed via one-way ANOVA with Tukey's post-hoc procedure. The same was used to compare gene expression between subtypes of cell lines. Percent methylation was Arcsin transformed and then analyzed via Mann-Whitney test. Statistical analyses were performed using Excel (Microsoft, Seattle, Wash.) or GraphPad Prism version 5.00 for Windows, (GraphPad Software, San Diego, Calif. All P values were 2-sided.
We reported previously that CHST11 is overexpressed in tumor tissues versus normal breast tissues (Cooney, Jousheghany et al. 2011). Here, we confirmed the overexpression of CHST11 in malignant tissues, analyzing multiple datasets using the Oncomine database (Table 5). To investigate the association of CHST11 overexpression with tumor progression, we interrogated two separate datasets in the Oncomine database. In a dataset comparing DCIS with IDC (Schuetz et al. 2006), we found a significant increase in the expression of CHST11 in IDC samples (
++TCGA, The Cancer Genome Atlas - Invasive Breast Carcinoma Gene Expression Data.
CS-A, the immediate product of CHST11 expression, has been found to play a role in metastasis and progression of cancer cells (Iida, Wilhelmson et al. 2007; Cooney, Jousheghany et al. 2011). We demonstrated previously that the level of expression of CHST11 and CS-A was high in highly metastatic MDA-MB-231 cells, while it was significantly lower in MCF7 cells as assayed by qRT-PCR and flow cytometry (Cooney, Jousheghany et al. 2011). To examine whether DNA methylation controls variation and regulation of CHST11 in breast cancer cell lines, we examined DNA methylation of the CHST11 sequence in a section of its CpG island covering part of its promoter, its first exon, and a portion of its first intron (
Treatment of MCF7 cells with 5AzadC increases the expression of CHST11 and CS-A.
To further demonstrate that low expression of CHST11 in the MCF7 cell line is due to hypermethylation status of the CHST11 CpG island, the MCF7 cells were treated with 5AzadC and gene expression was evaluated. Upon 5AzadC treatment, we observed a significant increase in the expression of CHST11 mRNA (
Our previous data suggest that CHST11 expression can be low in ER-positive and high in ER-negative breast cancer cell lines (Cooney, Jousheghany et al. 2011). To further explore this possibility we examined the expression of CHST11 in two other ER-positive cell lines, T47-D and ZR-75-1 by qRT-PCR (
To confirm a role for methylation status of the CHST11 CpG island in the expression control of this gene, we further analyzed second generation DNA methylation sequencing data on breast cancer cell lines (Illumina Idea Challenge). This method provided information on DNA methylation at a single nucleotide resolution across 162 out of 186 CpGs in the ˜2.5 kb long CHST11 CpG island. Methylation analysis of Illumina Idea Challenge data of these cell lines indicate a hypermethylated CpG island of CHST11 gene in the T47-D and ZR-75-1 cell lines, similar to MCF7 cells (FIG. 11B,C,D). A very hypomethylated state was observed for the same sequence extracted from MDA-MB-231 cells (
Next, we examined the methylation status of another ER-positive cell line BT-474 and two triple-negative cell lines MDA-MB-468 and BT-20, both with epithelial appearance (
Our data suggest that CHST11 expression is low in luminal cell lines and high in basal-like cell lines (Table 6). To further explore this possibility, we analyzed an Oncomine dataset that screened 50 breast cancer cell lines representative of molecular subtypes (Luminal, Her2-amplified, or Basal-like) (Hoeflich et al. 2009). We observed that the expression of CHST11 in basal-like cell lines is significantly higher than luminal cell types (
Our cell line-based data suggest that the expression of CHST11 is associated with ER status. We further analyzed the Gluck breast dataset (Gluck, Ross et al. 2011) and compared CHST11 expression levels between ER-negative and ER-positive specimens from breast cancer patients (
We have previously shown that removal or blocking of CS on the surface of breast cancer cells inhibits metastasis (Monzavi-Karbassi, Stanley et al. 2007; Cooney, Jousheghany et al. 2011). We have demonstrated that the expression levels of CHST11 correlate with the expression of P-selectin-reactive surface CS and aggressiveness of human breast cancer cells (Cooney, Jousheghany et al. 2011). Here, we report that the CHST11 gene is overexpressed in cancer tissues and its overexpression correlates with progression and aggressive phenotypes of the disease. Therefore, studying the regulation CHST11 gene expression and its relationship to metastasis is relevant. Our data suggest that the expression can be controlled by DNA methylation. Aberrant DNA methylation is involved in tumor initiation and progression (Feinberg, Gehrke et al. 1988; Narayan, Ji et al. 1998; Baylin, Esteller et al. 2001; Ehrlich 2002; Szyf, Pakneshan et al. 2004; Cooney 2008). Hypermethylation of tumor suppressor genes is a common mechanism of gene silencing observed in cancer, and similarly, DNA hypomethylation can contribute to overexpression of tumor-promoting genes. DNA hypomethylation is associated with advanced stages, metastatic phenotypes, and drug-resistant variants of breast cancer (Soares et al. 1999; David et al. 2004; Pakneshan et al. 2004; Szyf, Pakneshan et al. 2004; Chekhun et al. 2006).
Methylation silencing of sulfotransferases, other than CHST11, is reported in breast cancer cell lines and clinical samples (Miyamoto, Asada et al. 2003). We find that CHST11 overexpression is accompanied by CHST11 gene hypomethylation and by increased levels of CHST11's immediate product, CS-A, in aggressive mesenchymal-like ER-negative breast cancer cell lines. Based upon our results, it seems that a combination of hypomethylation and high expression occurs in mesenchymal-like ER-negative cancer cells. In several ER-positive cell lines we found that CHST11 DNA is hypermethylated. Hypermethylation of CHST11 (and very low to no expression) clearly differentiates the least aggressive, ER-positive cells from the more aggressive ER-negative cells we tested. It needs to be pointed out that in less aggressive ER-negative cells that are epithelial-like (e.g. MDA-MB-468), hypomethylation is accompanied by intermediate expression of CHST11, suggesting involvement of other mechanisms in controlling the expression levels of this gene. It has been demonstrated that TGFβ1 can stimulate the expression of the CHST11 gene, implicating the TGF-β signaling pathway in expression control of this gene (Kluppel et al. 2002; Willis et al. 2009). However, using expression levels of CHST1 transcript, it might be possible to distinguish aggressive mesenchymal-like ER-negative cell lines, ie. MDA-MB-231, from less aggressive epithelial-like ER-negative cell lines, ie MDA-MB-468. Comparing the expression of epithelial and mesenchymal discriminators like vimentin, E-cadherin, and N-caderin, Blick and colleagues (Blick et al. 2008) found very similar pattern regarding vimentin expression levels in these two cell lines. Vimentin was overexpressed in MDA-MB-231 and its expression in MDA-MB-468 cells was moderate. The expression of E-cadherin or N-cadherin did not discriminate between these two cell lines. We examined several datasets in the Oncomine database for the expression of CHST11 and its relation to ER status or more aggressive molecular subtypes. We observed that overexpression is higher and more prevalent among ER-negative specimens and basal-like molecular subtype compared to ER-positive specimens and luminal cell lines, respectively. Others have shown that vimentin, the most widely used marker for mesenchymal phenotype, is absent in the majority of luminal cell lines but overexpressed in basal-like cell lines (Hugo et al. 2007; Blick, Widodo et al. 2008). Future studies on well-characterized clinical specimens are needed to determine the correlation between the expression of epithelial/mesenchymal markers and CHST11.
Our study illustrates an example of a gene, where methylation is lower and expression is higher as the cancer phenotype becomes more aggressive. In contrast, the main trend is widespread gene hypermethylation as cancers go from less aggressive to more aggressive phenotypes (Andrews et al. 2010; Wolff et al. 2010). Our data are consistent with some other models of metastatic and/or more aggressive cancers exemplifying tumor promoting genes like urokinase plasminogen activator (uPA), PAX3 and Ezrin that are less methylated and/or more highly expressed in the more aggressive cancer forms (Pakneshan, Szyf et al. 2004; Kurmasheva et al. 2005). This less frequent pattern of gene methylation between cancers with low and high aggressiveness suggests that the expression of these genes is necessary for the more aggressive phenotypes (because their change is counter to the trend).
The recognition that silencing of tumor suppressor genes through promoter hypermethylation plays a significant role in tumorigenesis (MacLeod et al. 1995; Ramchandani et al. 1997) has led to the clinical use of hypomethylating agents including 5-AzadC (Fenaux 2005). However, the expression of several pro-tumor genes is induced by DNA hypomethylation (Pakneshan, Szyf et al. 2004; Ehrlich 2006; Yu et al. 2010). The expression of such genes, including CHST11, may be activated by the clinical use of hypomethylating agents and this may promote more aggressive forms of breast cancer. In this regard, our data, in agreement with others (Szyf et al. 2004; Ateeq et al. 2008), suggest that therapeutic use of such demethylating agents may be effective in early developmental stages of breast cancer, but may promote tumor metastasis and recurrence later in the course of the disease. Histone deacetylase inhibitors can also hypomethylate genes and change their expression levels in breast cancer cell lines (Meeran et al. 2010) and their combination with metabolic therapies may modify their action (Cooney 2010). Therefore, additional studies are needed to determine if some agents or mechanisms of hypomethylation are more or less likely to promote tumor metastasis.
Epithelial-mesenchymal transition has been linked to cancer stem cells and ER-negative phenotypes (Mani et al. 2008; Blick et al. 2010; Jeong et al. 2012). An association between basal-like phenotype and cancer stem cells has been demonstrated (Honeth et al. 2008). Therefore, higher expression levels of CHST11 in mesenchymal versus epithelial cells, in basal-like versus luminal cells, or in ER-negative versus ER-positive cells and specimens may implicate CHST11 expression in the epithelial-mesenchymal transition and may also relate the expression of this gene to cancer stem cells (Thiery 2002; Al-Hajj et al. 2003; Mani, Guo et al. 2008). An increase in the expression of CHST11 may accompany cellular epithelial-mesenchymal transition programming and may serve as a prognostic/predictive biomarker or a therapeutic target for cancer stem cells. Interestingly the elevated expression is accompanied by the hypomethylated status of a CpG island, indicating that both methylation status and expression level, or a combination of two can be potentially employed to evaluate the patient outcome. We expect to validate these observations in clinical samples for correlation with hormone status, cancer stage and patient survival and response to therapy in future studies.
We have shown that the expression of CHST11, which is a major determinant of CS-A, is modulated by DNA methylation. Therefore DNA methylation plays an important role in the remodeling of CS in breast tumors. Our data strongly suggest that the expression of CHST11 and its role in defining metastatic potential of tumor cells should be seriously considered when demethylating agents are used for medical treatment in breast cancer patients. Moreover, the methylation and expression of the CHST11 gene have potential as predictive and prognostic biomarkers. Given the importance of detection of circulating tumor cells in patients diagnosed with high stage breast cancer and predicting response in patients undergoing chemotherapy (Muller et al. 2006; Armstrong et al. 2011) a combination of methylation status and the expression of this gene could be valuable for the detection of circulating tumor cells and simultaneous characterization of patient response. Together, our data suggest that CHST11 can be targeted for development of novel prognostic/predictive biomarkers.
We have analyzed CHST11 gene expression levels from matched tumor and nontumor tissue samples from several datasets to show that CHST11 expression level is significantly higher in several types of cancer than in the corresponding normal tissue.
We have also shown that CHST11 is overexpressed in cutaneous melanoma compared to melanocytic skin nevus (4.52 fold higher, P=3.49E-7). The data set was 45 cutaneous melanoma and 18 benign melanocytic skin nevus.
The same CHST11 overexpression was observed in cercival squamous cell carcinoma compared to normal cervix. (Fold change 2.41, P=7.22E-5.) Forty cervical squamous cell carcinoma samples from 35 patients and 5 normal cervix samples were analyzed.
CHST11 overexpression was seen for esophagus cancer (Fold change 1.521, P=7.51E-12). Fifty-three esophageal squamous cell carcinoma samples and 53 adjacent paired normal esophagus samples were analyzed.
CHST11 was overexpressed in head and neck cancer (Fold change 4.073, P=5.03E-8). Forty-one head and neck squamous cell carcinoma and 13 buccal mucosa samples were analyzed on Affymetrix U133A microarrays.
The same CHST11 overexpression was observed for pancreatic cancer. (Fold change 3.061, P=6.02E-11.) Paired pancreatic ductal adenocarcinoma (n=39) and normal pancreas (n=39) samples from 36 patients were analyzed.
We have also found that CHST11 overexpression correlates with occurrence of metastasis in breast cancer patients during 5-years post diagnosis. The CHST11 expression levels were compared between breast cancer patients that subsequently had no Metastatic Event at 5 Years (69 patients) and those with a Metastatic Event at 5 Years (6 patients). The data set was from Oncomime. Those that subsequently had a metastatic event had significantly higher CHST11 expression (Fold change 1.456, P=6.80E-4).
Kieber-Emmons, T. (2007). Chondroitin sulfate glycosaminoglycans as major P-selectin ligands on metastatic breast cancer cell lines. Int J Cancer 120, 1179-1191.
All patents, patent publications, and other references cited are hereby incorporated by reference.
This application claims priority under 35 U.S.C. 119 from U.S. Provisional application No. 61/626,646, filed Oct. 1, 2011, the contents of which are incorporated herein by reference in their entirety.
This invention was made with government support under a Clinical and Translational Science Award 1UL1RR029884 from the National Institutes of Health National Center for Advancing Translational Sciences. The government has certain rights in this invention.
| Number | Date | Country | |
|---|---|---|---|
| 61626646 | Oct 2011 | US |
