Synthetic oligonucleotides as inducers of erythroid differentiation

Abstract

The invention refers to a synthetic double-stranded oligonucleotide having a length comprised between 10 and 50 bases and a nucleic acid sequence selected from the group consisting of: (a) sequences corresponding to a selected portion of the promoter of human γ-globin gene; and (b) sequences corresponding to a selected portion of the human genomic region comprised between the γ-globin gene and the δβ-cluster, for use as an inducer of erythroid differentiation.

Description

[0001] The present invention relates to the use of synthetic oligonucleotides which are capable of inducing erythroid differentiation for the manufacture of a medicament for the therapeutic treatment of β-thalassemia and neoplastic diseases, and to a pharmaceutical composition including at least one of the said oligonucleotides and a pharmaceutically acceptable carrier.

[0002] The existence of compounds which are able to induce the synthesis of fetal haemoglobin (HbF) in adults is known since long (1-7).

[0003] These compounds, herein referred to as “biological response modifiers”, are able to activate the transcription of embryonic and fetal globin genes and to induce erythroid differentiation.

[0004] In human adults, the activation of the transcription of γ-globin genes leads to the production of HbF, which mimicks a HPFH (High Persistance of Fetal Hemoglobin) phenotype; this could reduce the severity of β-thalassemia in affected patients (8). Accordingly, recent studies have been focused on the search of compounds able to stimulate γ-globin gene expression at high levels, in an attempt to reduce transfusions in β-thalassemia patients (12, 13).

[0005] In addition, as it has been recently described (9, 10), a combined treatment with different biological response modifiers could lead to a further increase of the expression of γ-globin genes.

[0006] It is further known (11) that the treatment of neoplastic cells with compounds which are able to induce differentiation could be of interest in the therapy of some neoplastic diseases.

[0007] The object of the present invention is to find new biological response modifiers to be proposed for the treatment of β-thalassemia and/or neoplastic diseases, which exhibit low toxicity in vivo and a high level of induction of γ-globin gene expression.

[0008] Molecules which are able to induce differentiation, exhibiting only minor cytotoxic effects in vivo, could in fact reduce side effects when administered to patients in clinical trials.

[0009] The present inventors have unexpectedly found that double-stranded oligonucleotides having a nucleic acid sequence corresponding to portions of the β-like gene cluster, in particular to some sequences of the promoter of the human γ-globin gene and to some sequences comprised between the γ-globin gene and the δβ-gene region, show the said activity.

[0010] The present invention therefore provides a synthetic double-stranded oligonucleotide having a nucleic acid sequence selected from the group consisting of:

[0011] a) sequences corresponding to a selected portion of the promoter of human γ-globin gene; and

[0012] b) sequences corresponding to a selected portion of the human genomic region comprised between the γ-globin gene and the δβ-cluster,

[0013] for use as an inducer of erythroid differentiation.

[0014] The nucleic acid sequence of the promoter of human γ-globin is SEQ. ID NO:1 and the nucleic acid sequence of the human genomic region comprised between the γ-globin gene and the δβ-cluster is SEQ. ID NO:2.

[0015] Advantageously, the double-stranded oligonucleotide of the invention has a length comprised between 10 and 50 bases, preferably between 10 and 30 bases, and a nucleic acid sequence corresponding to a selected portion of SEQ. ID NO:1 or SEQ. ID NO:2.

[0016] Preferably, the double-stranded oligonucleotide of the invention has a nucleic acid sequence selected within the portion of SEQ. ID NO:1 comprised between positions 220 and 290.

[0017] In the present description, the term “oligonucleotide” is meant to include also an oligonucleotide wherein the backbone has been modified according to the approaches commonly used for improving oligonucleotides' properties such as cellular uptake, target binding and/or stability. Such modifications include for example the modification of the linkage between the base and/or the sugar moieties. Among the current derivatives and/or techniques available for improving the oligonucleotides performances are the conjugation with lipophilic moieties, chimeric technology, peptide nucleic acids, aptamers.

[0018] As it will be further illustrated in the example, it has also been found that double-stranded oligonucleotides having a nucleic acid sequence as set forth in SEQ. ID NO:3, SEQ. ID NO:4 (corresponding to selected regions of the promoter of the human γ-globin gene), SEQ. ID NO:5 and SEQ. ID NO:6 (corresponding to selected regions comprised between the human γδβ-globin gene cluster are particularly suitable for inducing a high expression of γ-globin genes.

[0019] Therefore, the nucleic acid sequence of the double-stranded oligonucleotide of the invention is more preferably selected from the group consisting of SEQ. ID No:3, SEQ. ID NO: 4, SEQ. ID No:5 and SEQ. ID NO: 6.

[0020] The synthetic oligonucleotides of the invention are able to act by mimicking human γ-globin gene regulatory sequences and by potentially interacting with nuclear proteins, including transcription factors.

[0021] The person skilled in the art knows how to obtain a double stranded oligonucleotide; for example it may be obtained by synthesising a single-stranded oligonucleotide and then specifically annealing the single-stranded oligonucleotide with its complementary strand by forming Watson-Crick hydrogen bonds.

[0022] The annealing between the two complementary strands may be obtained for example by incubating the DNA in a solution of 150 mM NaCl at room temperature for about two hours. Methods for the synthesis of single-stranded oligonucleotides are found for example in (20).

[0023] In one embodiment of the invention, the synthetic double stranded oligonucleotide is used as an inducer of erythroid differentiation in combination with a second biological response modifier, preferably selected from the group consisting of cytosine arabinoside, retinoic acid, plicamycin, chromomycin, hydroxyurea, guanosine triphosphate (GTP), guanosine diphosphate (GDP), and guanosine monophosphate (GMP). Cytosine arabinoside and retinoic acid are more preferred.

[0024] Also within the scope of the invention is the use of a synthetic double stranded oligonucleotide as previously defined, eventually in combination with a second biological response modifier as previously defined, for the manufacture of a medicament for the treatment of β-thalassemia and/or neoplastic diseases.

[0025] The present invention also provides a pharmaceutical composition comprising at least a synthetic double stranded oligonucleotide as previously defined, eventually in combination with a second biological response modifier as previously defined, and a pharmaceutically acceptable carrier.

[0026] The activity of the double stranded synthetic oligonucleotides of the invention as inducers of erythroid differentiation has been assessed by determining the level of erythroid differentiation induced in a human cultured cell line, as reported in Table 1.

[0027] The following example is provided by way of illustration only and is not intended to limit in any way the scope of the invention.

EXAMPLE

[0028] The biological activity of the double stranded oligonucleotides represented by SEQ. ID NO: 3, SEQ. ID NO: 4, SEQ. ID NO: 5 and SEQ. ID NO: 6 has been evaluated by determining the ability of these oligonucleotides to induce erythroid differentiation of the human erythroleukemia K562 cell line, which is able to undergo erythroid differentiation and to increase γ-globin gene expression following treatment with a suitable biological response modifier (14-17). The level of erythroid differentiation has been evaluated by the benzidine-staining (16). The production of haemoglobin has been evaluated by cellulose acetate gel electrophoresis of cytoplasmic extracts and benzidine staining of the gels (16). The expression of γ-globin genes has been evaluated by RT-PCR (reverse transcriptase PCR) (18).

[0029] These assays have been performed after 6 days of induction with the above indicated double stranded oligonucleotides.

TABLE 1
	Optimal	aErythroid
Oligonucleotide	Concentration	differentiation
(SEQ. ID NOs)	(μg/ml)	(%)
3	10	55
4	10	40
5	10	57
6	10	38
aErythroid differentiation = proportion of benzidine-positive K562 cells.

[0030] In order to analyse hemoglobin production by erythroid induced K562 cells, 2 μl of total fresh post-mitochondrial cell lysates were electrophoresed on cellulose acetate strips in Tris-ethylenediamine-tetraacetic acid (EDTA)-borate buffer. After an electrophoresis of 30 min at 5 mA, the gels were stained with benzidine/hydrogen peroxide (1% benzidine in 4.3 M acetic acid, 3% H2O2) and photographed. The data obtained show that the Hb produced following erythroid induction is mainly Hb Portland. Quantitative real-time PCR assay (21) of γ-globin mRNA transcripts was carried out with the use of gene-specific double fluorescently labeled probes in a 7700 Sequence Detector (PE Biosystems, Warrington Cheshire, UK). The following primer and probe sequences were used for real-time PCR: γ-globin forward primer, 5′-TGG CAA GAA GGT GCT GAC TTC-3′ (SEQ. ID NO:7); γ-globin reverse primer, 5′-TCA CTC AGC TGG GCA AAG G-3′ (SEQ. ID. NO:8); γ-globin probe, 5′-FAM-TGG GAG ATG CCA TAA AGC ACC TGG-TAMRA-3′ (SEQ. ID NO:9), where the fluorescent reporter FAM and the quencher TAMRA are 6-carboxy fluorescein (FAM) and 6-carboxy-N,N,N′,N′-tetramethylrhodamine (TAMRA) respectively. The results obtained give evidence for an increase of γ-globin mRNA production. For instance, the oligonucleotide corresponding to SEQ. ID NO:3 induced a nine-fold increase of γ-globin mRNA production with respect to uninduced K562 cells.

[0031] The high level of biological activity and the expected low level of in vivo cytotoxicity of the oligonucleotides of the invention allow to propose these molecules as promising candidates for use in the development of pharmacological approaches for the treatment of β-thalassemia and/or neoplastic diseases.

REFERENCES

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Claims

1. A synthetic double-stranded oligonucleotide having a length comprised between 10 and 50 bases and a nucleic acid sequence selected from the group consisting of: a) sequences corresponding to a selected portion of the sequence comprised between positions 220 and 290 of SEQ. ID NO: 1; and b) sequences corresponding to a selected portion of the human genomic region comprised between the γ-globin gene and the δβ-cluster, for use as an inducer of erythroid differentiation.

2. The synthetic oligonucleotide according to claim 1, characterised in that the nucleic acid sequence of the said human genomic region comprised between the, γ-globin gene and the δβ-cluster is SEQ. ID NO:2.

3. The synthetic oligonucleotide according to claim 1 or 2, characterised in that it has a nucleic acid sequence selected from the group consisting of SEQ. ID NO: 3, SEQ ID NO: 4, SEQ. ID NO: 5 and SEQ. ID NO: 6.

4. The synthetic oligonucleotide according to any of claims 1 to 3, in combination with a second biological response modifier selected from the group consisting of cytosine arabinoside, retinoic acid, plicamycin, chromomycin, hydroxyurea, guanosine triphosphate (GTP), guanosine diphosphate (GDP), guanosine monophosphate (GMP).

5. Use of a synthetic double-stranded oligonucleotide according to any of claims 1 to 4, for the manufacture of a medicament for the treatment of β-thalassemia.

6. Use of a synthetic double-stranded oligonucleotide according to any of claims 1 to 4, for the manufacture of a medicament for the treatment of neoplastic diseases.

7. A pharmaceutical composition comprising at least a synthetic double-stranded oligonucleotide according to any of claims 1 to 4 and a pharmaceutically acceptable carrier.

8. A method for preparing a synthetic double-stranded oligonucleotide according to any of claims 1 to 3, comprising the steps of; (a) synthesising a corresponding single-stranded oligonucleotide; and (b) annealing the single-stranded oligonucleotide with its complementary strand.