Gene expression profiling of myelodysplastic CD34+ hematopoietic stem cells treated in vitro with decitabine

Silylation of Deoxynucleotide Analog Yields an Orally Available Drug with Antileukemia Effects

DNA methyltransferase inhibitors have improved the prognosis of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). However, because these agents are easily degraded by cytidine deaminase (CDA), they must be administered intravenously or subcutaneously. Recently, two orally bioavailable DNA methyltransferase inhibitors, CC-486 and ASTX727, were approved. In previous work, we developed 5-O-trialkylsilylated decitabines that resist degradation by CDA. However, the effects of silylation of a deoxynucleotide analog and enzymatic cleavage of silylation have not been fully elucidated. Enteric administration of OR21 in a cynomolgus monkey model led to high plasma concentrations and hypomethylation, and in a mouse model, oral administration of enteric-coated OR21 led to high plasma concentrations. The drug became biologically active after release of decitabine (DAC) from OR21 following removal of the 5'-O-trisilylate substituent. Toxicities were tolerable and lower than those of DAC. Transcriptome and methylome analysis of MDS and AML cell lines revealed that OR21 increased expression of genes associated with tumor suppression, cell differentiation, and immune system processes by altering regional promoter methylation, indicating that these pathways play pivotal roles in the action of hypomethylating agents. OR21 induced cell differentiation via upregulation of the late cell differentiation drivers CEBPE and GATA-1 Thus, silylation of a deoxynucleotide analog can confer oral bioavailability without new toxicities. Both in vivo and in vitro, OR21 exerted antileukemia effects, and had a better safety profile than DAC. Together, our findings indicate that OR21 is a promising candidate drug for phase I study as an alternative to azacitidine or decitabine.

In vitro effect of eltrombopag alone and in combination with azacitidine on megakaryopoiesis in patients with myelodysplastic syndrome

Thrombocytopenia is a severe complication for patients with myelodysplastic syndrome (MDS). Eltrombopag increases platelet count in MDS patients but its combination with azacitidine elicited controversial results. We aimed to quantify the colony forming units of megakaryocytes (CFU-Mk) obtained from CD34+ bone marrow cells isolated from patients with MDS and from healthy donors that were cultured in vitro in the presence or absence of azacitidine and with or without the sequential addition of eltrombopag to the culture medium. CD34+ bone marrow cells from 6 MDS patients and 3 controls were expanded in vitro and cultured for 3 days with or without azacitidine. Subsequently, a CFU-Mk assay was performed in presence or absence of eltrombopag. The addition of eltrombopag in the CFU-Mk assay after mock treatment of CD34+ cells increased the number of CFU-Mk in both controls and patients. On the contrary, using azacitidine pretreated CD34+ cells, eltrombopag minimally increased CFU-Mk in controls and produced heterogeneous response in MDS patients with no change in two patients and CFU-Mk increase in four patients. In vitro CFU-Mk assay suggest that some MDS patients are likely to benefit from the sequential addition of eltrombopag after azacitidine treatment, in the context of a personalized medicine.

Combination therapy with epigenetic-targeted and chemotherapeutic drugs delivered by nanoparticles to enhance the chemotherapy response and overcome resistance by breast cancer stem cells

Aberrant DNA hypermethylation is critical in the regulation of renewal and maintenance of cancer stem cells (CSCs), which represent targets for carcinogenic initiation by chemical and environmental agents. The administration of decitabine (DAC), which is a DNA hypermethylation inhibitor, is an attractive approach to enhancing the chemotherapeutic response and overcoming drug resistance by CSCs. In this study, we investigated whether low-dose DAC encapsulated in nanoparticles could be used to sensitize bulk breast cancer cells and CSCs to chemotherapy. In vitro studies revealed that treatment with nanoparticles loaded with low-dose DAC (NPDAC) combined with nanoparticles loaded with doxorubicin (NPDOX) better reduced the proportion of CSCs with high aldehyde dehydrogenase activity (ALDH(hi)) in the mammospheres of MDA-MB-231 cells, and better overcame the drug resistance by ALDH(hi) cells. Subsequently, systemic delivery of NPDAC significantly down-regulated the expression of DNMT1 and DNMT3b in a MB-MDA-231 xenograft murine model and induced increased caspase-9 expression, which contributed to the increased sensitivity of the bulk cancer cells and CSCs to NPDOX treatment. Importantly, the combined treatment of NPDAC and NPDOX resulted in the lowest proportion of ALDH(hi) CSCs and the highest proportion of apoptotic tumor cells, and the best tumor suppressive effects in inhibiting breast cancer growth.

Reduced rRNA expression and increased rDNA promoter methylation in CD34+ cells of patients with myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are clonal disorders of hematopoietic stem cells characterized by ineffective hematopoiesis. The DNA-hypomethylating agents 5-azacytidine and 5-aza-2'-deoxycytidine are effective treatments for patients with MDS, increasing the time to progression to acute myelogenous leukemia and improving overall response rates. Although genome-wide increases in DNA methylation have been documented in BM cells from MDS patients, the methylation signatures of specific gene promoters have not been correlated with the clinical response to these therapies. Recently, attention has been drawn to the potential etiologic role of decreased expression of specific ribosomal proteins in MDS and in other BM failure states. Therefore, we investigated whether rRNA expression is dysregulated in MDS. We found significantly decreased rRNA expression and increased rDNA promoter methylation in CD34(+) hematopoietic progenitor cells from the majority of MDS patients compared with normal controls. Treatment of myeloid cell lines with 5-aza-2'-deoxycytidine resulted in a significant decrease in the methylation of the rDNA promoter and an increase in rRNA levels. These observations suggest that an increase in rDNA promoter methylation can result in decreased rRNA synthesis that may contribute to defective hematopoiesis and BM failure in some patients with MDS.

Methylation of the p73 gene in patients with myelodysplastic syndromes: correlations with apoptosis and prognosis

The identification of epigenetically inactivated tumor suppressor genes may shed additional light on the pathogenesis of myelodysplastic syndromes (MDS) and lead to the identification of potential therapeutic targets for demethylating agents. In this study, the methylation status of the p73 gene promoter was analyzed by methylation-specific PCR (MS-PCR) in bone marrow (BM) samples from 126 adult patients with de novo MDS. The results of the MS-PCR were confirmed by bisulfite sequencing. In addition, we analyzed p73 expression using real-time PCR. The apoptosis of BM cells was examined by flow cytometry. The methylation of the p73 gene was observed in 36.5 % of cases. There were strong correlations between p73 methylation and the marrow blast levels (p  =  0.037) and the WHO classification (p  =  0.016). The frequency of p73 methylation was significantly correlated with the International Prognostic Scoring System subgroup ( r  =  0.904, p  <  0.001). Moreover, a decrease in the transcription of p73 was accompanied by methylation (p  =  0.032). Although the level of apoptosis in the BM samples of the methylated group was not significantly lower than that in the unmethylated group (p  =  0.094), decitabine treatment restored p73 expression and increased the level of cytarabine (ara-C)-induced apoptosis in vitro. The median survival time of patients with p73 methylation was shorter than that for patients without p73 methylation (15 vs. > 33 months, respectively, p  =  0.002). A multivariate analysis also indicated that the p73 methylation status was the independent factor that impacted overall survival. In conclusion, p73 methylation is common in patients with MDS and is associated with poor prognosis. Our results provide further evidence for the involvement of epigenetic dysregulation in the pathogenesis of MDS.