The research was supported by the NIH grant R44CA239845.
Not applicable.
This invention relates generally to a method to isolate proteins and phosphoproteins from biofluids, such as urine, for biomarker discovery or for clinical detection. More particularly, this invention relates to non-invasive early disease diagnosis, disease monitoring and disease classification. In one aspect, this invention relates to unique proteins and phosphoproteins capable of differentiating bladder cancer urine from healthy urine and inflammation control urine. In another aspect, this invention relates to early-stage detection of bladder cancer by urine test.
Bladder cancer is the most common cancer of the urinary tract, affecting close to 400,000 people worldwide (72). Despite not being the highest-incidence, it is the most expensive cancer to treat per patient in the U.S. due to the necessary on-going treatment and monitoring with a re-occurrence rate of 50-80% (73). Most of the current bladder cancer marker tests depend on invasive cystoscopy or the presence of exfoliated cancer cells in urine. The typical sensitivity for current tests is 40-80% (74,75), as a result, low tumor burden (low-grade tumors), tumor heterogeneity, or tumor cells that do not exfoliate into urine leave room for improvement in early detection. While some urine-based tests have been approved by the FDA, none of them are routinely used or incorporated into clinical guidelines due to opportunities for improvement in sensitivity (76). Recent studies found that when given a choice between a bladder cancer molecular marker test with <90% sensitivity or cystoscopy (the invasive current standard test for bladder cancer detection), the patients and urologists chose the invasive cystoscopy (77). So, in order to fulfill the market need, a new non-invasive cancer test needs to perform with >90% sensitivity.
Currently the most widespread method for clinical cancer profiling and diagnosis involves a tumor biopsy, an invasive and painful procedure, and one that certainly is impractical for early-stage detection. As cancer becomes a more chronic disease that requires active monitoring over longer periods of time, tissue biopsies on a continuous basis are no longer a realistic scenario. As a result, “liquid biopsies”—analysis of biofluids such as plasma, serum, urine—have gained much attention as a potentially useful source of diagnostic biomarkers. Liquid biopsies offer numerous advantages for a clinical analysis, including non-invasive collection, a suitable sample source for longitudinal disease monitoring, better screenshot of tumor heterogeneity, higher stability and sample volumes, faster processing times, lower rejection rates and cost. However, the most common focus of liquid biopsy—CTCs and ctDNA—still have room for improvement. Improvements can be made with the heterogeneity and extreme rarity of the circulating tumor cells (CTCs) (1). Similarly, circulating DNA (ctDNA) is highly fragmented and exists in very small, often not detectable amounts. This makes opportunity for early disease detection tests development. For example, in bladder cancer, CTCs were found in only 23% of the preoperative patients and did not have any predictive value for survival (2). As a result, only a limited number of effective clinical CTC or ctDNA diagnostics tests are currently on the market. To date, only two such in vitro diagnostics (IVD) tests have been approved by the FDA—Janssen Diagnostics' CellSearch and Cobas EGFR Mutation Test. However, negative results from these tests still require a follow-up biopsy. The lack of other approvals over the past decade further highlights the need for non-invasive early cancer detection tests with high sensitivity.
A new field has generated a lot of interest over the past few years—profiling of cell-secreted extracellular vesicles (EVs). EVs offer all the same attractive advantages of a liquid biopsy offered by CTCs and ctDNA. These generally include smaller size exosomes derived from multivesicular endosome-based secretions, and microvesicles (MVs) derived from the plasma membrane (3-5). The EVs provide an effective and ubiquitous method for intercellular communication and removal of excess materials and are utilized by every cell type studied to date. As these are shed into every biological fluid and embody a good representation of their parent cell, analysis of the EV cargo has great potential for biomarker discovery and disease diagnosis (6). Notably, researchers have also found many differentiating characteristics of the cancer cell-derived cargo, including gene mutations, active miRNA and proteins, which possess metastatic properties (7-11).
Particularly promising are the findings that these EV-based disease markers can be identified well before the onset of symptoms or physiological detection of a tumor. This makes them favorable candidates for early-stage cancer and other disease detection. In addition, EVs are membrane-covered nanoparticles, which protects the inside contents from external proteases and other enzymes (12-14). Applicants reason that these features make EVs a promising source to advance proteins and phosphoproteins as disease markers, considering that many phosphorylation events directly reflect molecular and physiological status of a tumor (15, 16). Despite some encouraging success in the analysis of exosomes for DNA, RNA and protein content, the methods and data for examination of EV phosphoproteomes are not as far along in development. The studies carried out to date include either data from urine, only 14 phosphoproteins identified from 400 mL urine (17), or 82 phosphoproteins identified through analysis of cell culture media, which may not be directly relevant to clinical biomarkers (18). Besides Applicants' recent publications (19, 20, 80), no other fruitful phosphoprotein analysis studies using plasma, urine or cerebrospinal fluid (CSF) are known.
Current EV/Exosome Analyses.
Given the immaturity of EV analysis, a standardized method for collecting and processing EVs has not yet been developed (21). Most studies rely on differential centrifugation, with ultracentrifugation (UC) as the final step. However, this approach has room for advancement for use in a clinical setting due to opportunities for improvement in reproducibility (11, 22). In addition, multiple publications have shown that the exosome recovery rate after ultracentrifugation is only about 5-25% (23-25). Several other groups have published and commercialized new methods for EV isolation, which include polymer-induced precipitation (26, 27), antibody-based capture (28, 29), affinity filtration (30), size-exclusion chromatography (25, 31), among others. Each one has its own opportunities for enhancement, including recovery rate (usually similar or less than ultracentrifugation) and contamination levels (22, 24, 25, 30, 32-37). While these can certainly be used as a faster alternative to UC, at 5-25% published yields, their efficiency of isolation still leaves much room for improvement. High levels of free protein, which may not be a major concern for RNA/DNA analysis (focus of the majority of exosome researchers), provides another avenue for development of the current methods for the proposed phosphoproteome analysis. While genetic testing is very valuable, it could greatly benefit from an additional layer of biological information.
The ability to detect the genome output—active proteins—can provide useful real-time information about the organism's physiological functions and disease progression, particularly in cancer. Oncologists understand the value of protein testing and immunoassays and can easily interpret the results. Compared to gene panel testing, immunoassays are also relatively inexpensive and are more likely to get reimbursed. Nonetheless, the genetic screens are currently dominating the new biomarkers market and the area of molecular diagnostics because the technology for genomic readout and reproducible quantitation is readily available and highly robust.
Protein phosphorylation is a key control mechanism for cellular regulatory pathways, and one often targeted by drug developers to create inhibitors that block signaling pathways involved in cancer and other diseases. However, due to active phosphatases in biofluids, there are few detectable phosphoproteins available for disease status analysis. No successful urine phosphoproteomics results have been reported, besides a recently accepted manuscript (20).
The invention now will be described more fully hereinafter with reference to the accompanying drawings, which are intended to be read in conjunction with both this summary, the detailed description and any preferred and/or particular embodiments specifically discussed or otherwise disclosed. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of illustration only and so that this disclosure will be thorough, complete and will fully convey the full scope of the invention to those skilled in the art.
Motivated by the urgent need to develop better biomarkers for early non-invasive diagnosis of bladder cancer, we implemented the approach to discover EV biomarkers directly from urine samples. We applied Extracellular Vesicles total recovery and purification (EVtrap) EV enrichment method to urine samples to isolate EVs for subsequent liquid chromatography—mass spectrometry analysis. EVtrap enables the capture of EVs onto functionalized magnetic beads modified with a combination of hydrophilic and lipophilic groups that have a unique affinity toward lipid-coated EVs (Wu et al. 2018). Over 95% recovery yield can be achieved by EVtrap with less contamination from soluble proteins, a significant improvement over current commercially available methods as well as ultracentrifugation.
Processing and enrichment of EVs through EVtrap enabled the removal of soluble proteins, retaining vesicle associated proteins which are more stable in circulation and have enhanced signals from cancer tissues. The protein profiles in EV concentrates are different from protein profiles naturally occurring in patient urine.
In one aspect, this disclosure is related to a robust method for the identification and detection of new biomarkers based on proteins and protein phosphorylation—a true measure of dynamic activity and cellular signaling, for the purposes of disease diagnosis, prognosis, detection, monitoring, patient stratification, drug response analysis, therapy selection, or the like.
The proposed method introduces a novel platform technology to isolate proteins and phosphoproteins from biofluids, such as urine, for biomarker discovery or for clinical detection.
In another aspect, this disclosure is related to a method that successfully demonstrates the feasibility of developing biofluid-derived EV phosphoproteins for cancer profiling. It has tremendous transformative potential for early cancer diagnosis, monitoring and classification based on actual activated pathways using urine as the source.
Further, once fully established, the method of the present disclosure can be implemented by scientists worldwide to analyze the direct signaling networks for a cancer of interest in a non-invasive manner.
Furthermore, once fully established, these new biomarkers can be employed either isolated or as part of a panel of biomarkers as a liquid biopsy in clinical scenarios: (1) as a surveillance test in high-risk patients, such as those with high-risk cystic diseases, hereditary risk of cancer, among others or (2) as a liquid biopsy for the longitudinal monitoring of treatment response in patients with already established cancer diagnosis.
In yet another aspect, this disclosure relates to a biomarker panel for detection and monitoring of bladder cancer. The approach will enable a truly non-invasive test and the first example of using phosphoproteins for early cancer diagnostics, especially in liquid biopsy setting.
Still further, it is envisioned to further apply this innovative procedure to validate and fully develop pre-determined biomarkers panels.
The above-mentioned and other features of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein:
The following detailed description includes references to the accompanying drawings, which forms a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the invention. The embodiments may be combined, other embodiments may be utilized, or structural, and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.
Before the present invention of this disclosure is described in such detail, however, it is to be understood that this invention is not limited to particular variations set forth and may, of course, vary. Various changes may be made to the invention described and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s), to the objective(s), spirit or scope of the present invention. All such modifications are intended to be within the scope of the disclosure made herein.
Unless otherwise indicated, the words and phrases presented in this document have their ordinary meanings to one of skill in the art. Such ordinary meanings can be obtained by reference to their use in the art and by reference to general and scientific dictionaries.
References in the specification to “one embodiment” indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
The following explanations of certain terms are meant to be illustrative rather than exhaustive. These terms have their ordinary meanings given by usage in the art and in addition include the following explanations.
Unless otherwise stated, a reference to a compound or component includes the compound or component by itself, as well as in combination with other compounds or components, such as mixtures of compounds.
As used herein, the term “and/or” refers to any one of the items, any combination of the items, or all of the items with which this term is associated.
As used herein, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise.
As used herein, the terms “include,” “for example,” “such as,” and the like are used illustratively and are not intended to limit the present invention.
As used herein, the terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances.
Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the teachings of the disclosure.
All publications, patents and patent applications cited herein, whether supra or infra, are hereby incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference.
While the invention has been described above in terms of specific embodiments, it is to be understood that the invention is not limited to these disclosed embodiments. Upon reading the teachings of this disclosure many modifications and other embodiments of the invention will come to mind of those skilled in the art to which this invention pertains, and which are intended to be and are covered by both this disclosure and the appended claims. It is indeed intended that the scope of the invention should be determined by proper interpretation and construction of the appended claims and their legal equivalents, as understood by those of skill in the art relying upon the disclosure in this specification and the attached drawings.
Extracellular Vesicles Total Recovery and Purification (EVtrap) Technology
Total EV and/or exosome capture and purification has been the focus of many recent studies, with particular consideration toward simple and easy protocol. The vast majority of the exosome analysis projects are based on the differential centrifugation. Although viable, this approach leaves room for improvements for the detection of EV biomarkers in a high-throughput automatable environment. Here, this disclosure introduces a novel non-antibody affinity beads-based capture method for effective EV isolation, termed EVtrap (Extracellular Vesicles total recovery and purification), directly from urine. It enables purification of the complete EV profile based on the lipid bilayer structure of these vesicles and the unique combination of the hydrophilic and aromatic lipophilic groups on the synthesized beads. The introductory manuscript of this technology was published in September 2018 (20).
Comparison of EV capture efficiency by Western Blot.
For the initial method validation, this disclosure compared the EVtrap approach with the “gold standard” ultracentrifugation method using 500 μL of urine for each test.
After the ultracentrifugation step (100K UC), the pellet was boiled and loaded on the gel directly or washed with PBS once or twice and centrifuged again. The supernatant from 100K UC step was concentrated and loaded on the gel in the same proportion.
The EVtrap method was carried out also using 500 μL urine: after 1-hour incubation, the supernatant (unbound fraction) was collected, concentrated and loaded on the gel. The captured EVs were eluted by incubation for 10 minutes with triethylamine. For recovery yield quantitation: the complete EV (exosome) population from 500 μL urine was concentrated and used as the exosome control.
All samples described above were loaded on the same gel and detected by Western Blot using a primary antibody for CD9 (common exosome marker). This experiment was carried out 5 separate times. A representative Western Blot is shown in
For additional recovery and purity assessment, besides ultracentrifugation, this disclosure also sought to compare other frequently used approaches. This disclosure used three common commercially available methods: including Qiagen's membrane affinity spin method, Hitachi's size-based filtration tube and Invitrogen's polymer-based exosome precipitation. Direct urine was used in each case and 500 μL equivalent was run after capture on two different gels and detected by anti-CD9 antibody (
In order to enable reliable analysis of clinical samples, the method must be highly reproducible by different users and over time. This disclosure tested the coefficient of variation (CV) of EVtrap capture by running 5 separate experiments using 0.5 mL urine on 5 different days carried out by two independent researchers. The eluted samples were then loaded on the same gel and the exosomal CD9 signal was quantified.
While Western Blot-based detection (as used in preliminary evaluation studies) does allow simple analysis of EV markers, there is opportunity for improvement since it tends to work for a few targets at a time, with good antibodies available. Mass spectrometry (MS) analysis enables the detection and quantitation of hundreds or thousands of proteins in a single experiment, while uncovering previously unknown targets. Hence, MS is the method of choice for current cancer biomarker discovery efforts, often coupled with liquid chromatography (LC).
Comparison of EV capture efficiency by LC-MS.
For the LC-MS analysis, this disclosure used 200 μL of urine as the starting material. As a control, ultracentrifugation (100K UC) pellet was used directly for protein extraction. The EVtrap method was then carried out on the supernatant from the 100K UC sample to analyze the exosomes left after the ultracentrifugation step. For the sample comparison, the EVtrap method was also carried out on the 10K supernatant and on 200 μL direct urine.
Using a single 90-min LC-MS gradient, the EVtrap method as disclosed herein was able to identify over 16,000 unique peptides from approximately 2,000 unique proteins. By comparison, ultracentrifugation method produced approximately 7,200 unique peptides from approximately 1,100 unique proteins.
EVtrap Capture Efficiency.
This disclosure further utilized label-free quantitation to compare all of the proteins identified by each method. In this experiment, this disclosure identified and quantified 94 out of 100 common exosome markers published in ExoCarta (39-41). All of them showed a significant increase after EVtrap capture compared to ultracentrifugation. This is noteworthy because many other studies have shown that different methods enrich different exosome populations with various success rates (34, 42). With EVtrap, it appears that the complete EV profile is recovered. As an example of the data, this disclosure listed a few common exosome markers in a bar chart in
EVtrap and Phosphoproteome Analysis.
With the ability of EVtrap to enable improved LC-MS analysis of urinary EVs, this disclosure further sought to apply this approach for phosphoproteome analysis. Despite the increasing interest in biofluid EVs, methods for EV phosphoproteome analysis provide opportunity for improvement in reporting, except a couple of recent publications (19, 20). Indeed, this disclosure's preliminary data have demonstrated that the suggested published EV workflows (43-47) provide opportunities for improvement for subsequent phosphoproteome analysis. It is therefore understood that other methods for EV isolation may be utilized when optimized, such as the commonly used commercial EV isolation methods: Qiagen ExoEASY (membrane filtration), Cell Guidance System Exo-spin (size-exclusion chromatography (SEC)), Thermo Fisher Total Exosome Isolation Reagent (TEIR) (precipitation), JSR Life Sciences ExoCAP (antibody immunoprecipitation (IP)) and 101Bio PureExo kit (precipitation).
For preliminary phosphoproteomic analyses, this disclosure used 10 mL of urine for each treatment, including EVtrap and ultracentrifugation (100K UC).
EVtrap capture was utilized for urine EV proteome and phosphoproteome analysis. This disclosure utilized the EVtrap method for the discovery of novel urinary biomarkers from bladder cancer patients, for the purposes of bladder cancer diagnosis, prognosis, detection, monitoring, patient stratification, drug response analysis, therapy selection, or the like. Here, both urine EV proteomics and phosphoproteomics were carried out to examine both sets of potential biomarkers.
For the first experiment this disclosure pooled together 27 healthy, 10 inflammation, 4 low-grade and 21 high-grade bladder cancer urine samples into 4 separate samples analyzed in triplicate. In this large pooled experiment, 259 proteins and 222 phosphoproteins were quantified as significantly increased (>4-fold) in bladder cancer. The statistically significant protein and phosphorite changes were identified by P-value as significant based on a two-sample t-test with a permutation-based 0.05 FDR cutoff. The overall quantitation numbers, EV markers, EV protein and phosphoprotein intensity differences and select phosphoproteins log-scale intensity heatmap are shown in
This disclosure then carried out the follow-up EVtrap+LCMS experiments using individual urine samples. For the phosphoproteome analysis, this disclosure processed 23 healthy urine samples, 4 inflammation/infection samples and 18 bladder cancer samples. For the proteome evaluation, the distribution was 23 healthy, 4 inflammation, and 11 bladder cancer samples. In total, each individual sample was analyzed in triplicate by quantitative mass spectrometry, producing a total of 2,769 quantified unique proteins and over 11,000 quantified unique phosphorites. This disclosure carried out linear regression statistical analysis at P-value <0.05 to narrow down the panel of potential biomarkers to those with highest statistical significance and largest intensity changes (majority were >10-fold increased).
From these data, this disclosure generated an initial list containing 83 proteins and phosphoproteins that were consistently present in bladder cancer urine but at very low amounts or not detectable in any control samples. We carried out additional LC-MS analyses of 29 new healthy urine EV samples and 39 new bladder cancer urine EV samples. These efforts identified over 7,000 proteins and over 5,000 phosphoproteins. Finally, the panel of potential biomarkers from all of the above experiments contained 594 proteins and phosphoproteins that have the potential to differentiate bladder cancer from non-cancer urine samples.
We identified 289 upregulated proteins and 78 upregulated phosphoproteins that increased in abundance at least 4-fold in bladder cancer at P-value <0.05. These results are visualized in
From this dataset, in
Analysis of Gene Ontology pathways of these data showed a significant enrichment of cancer networks in upregulated proteins and phosphoproteins (
Finally, we carried out a validation experiment for bladder cancer biomarkers using a new cohort of 74 control urine samples and 102 urine samples from bladder cancer individuals. As before, the EVs from urine were enriched using EVtrap, and the resulting EV proteins were identified and quantified using LC-MS. This validation experiment confirmed many of the bladder cancer EV protein biomarkers previously identified.
The most recent results for the significantly upregulated and downregulated EV proteins in bladder cancer are visualized in
The samples from Example 1 were subsequently split into a training set (70% of the samples) and test set (30%). The algorithm was trained using the training set, and then checked on the test set to see its accuracy. As shown in
We also did ROC curve analysis of the top markers validated in this experiment, and found that the best combination of markers can result in AUC of 98% (
In this disclosure, the applicants have demonstrated the feasibility and clinical ability of the newly discovered urine biomarkers to discriminate between cancer and non-cancer samples. This disclosure discovered hundreds of proteins and phosphoproteins that appear to change significantly in bladder cancer urine EVs compared to healthy or inflamed urine samples. This disclosure narrowed this list down to about 590 potential markers that demonstrate the most statistically significant differentiation between the cases. Most of them show at least 4-fold change on a highly consistent and reproducible level at p-value <0.0001.
This highlights the primary advantage of using phosphoproteomic analysis for biomarker discovery. It is not necessarily the case that these proteins are always differentially phosphorylated in urine EVs. But rather that they are very low-abundant signaling proteins which are loaded into EVs and are commonly phosphorylated. Typically, they are not detectable by standard proteomic analysis. Phosphoproteome enrichment thus removes the common higher abundant proteins and peptides, while isolating and bringing to the forefront these phosphorylated low-abundant targets. The ability to increase the volume of urine utilized for phosphoproteomics from 0.2 mL to about 10 mL also contributes to the detection and quantitation of these targets. Therefore, even though multiple biomarkers were discovered through phosphoproteomic experiments, it is most likely the whole protein amount changes in the EVs. And, thus, these targets can be detectable by regular antibody assays without having to develop specific phospho-antibodies.
While this disclosure has been described as having an exemplary design, the present disclosure may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains.
This U.S. patent application claims priority to U.S. Provisional Application No. 63/038,151 filed Jun. 12, 2020, to the above-named inventors, the disclosure of which is considered part of the disclosure of this application and is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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63038151 | Jun 2020 | US |