Mechanisms of Resistance to Decitabine in the Myelodysplastic Syndrome

Abstract

PurposeThe DNA methylation inhibitor 5-aza-2′-deoxycytidine (DAC) is approved for the treatment of myelodysplastic syndromes (MDS), but resistance to DAC develops during treatment and mechanisms of resistance remain unknown. Therefore, we investigated mechanisms of primary and secondary resistance to DAC in MDS.Patients and MethodsWe performed Quantitative Real-Time PCR to examine expression of genes related to DAC metabolism prior to therapy in 32 responders and non-responders with MDS as well as 14 patients who achieved a complete remission and subsequently relapsed while on therapy (secondary resistance). We then performed quantitative methylation analyses by bisulfite pyrosequencing of 10 genes as well as Methylated CpG Island Amplification Microarray (MCAM) analysis of global methylation in secondary resistance.ResultsMost genes showed no differences by response, but the CDA/DCK ratio was 3 fold higher in non-responders than responders (P<.05), suggesting that this could be a mechanism of primary resistance. There were no significant differences at relapse in DAC metabolism genes, and no DCK mutations were detected. Global methylation measured by the LINE1 assay was lower at relapse than at diagnosis (P<.05). On average, the methylation of 10 genes was lower at relapse (16.1%) compared to diagnosis (18.1%) (P<.05).MCAM analysis showed decreased methylation of an average of 4.5% (range 0.6%–9.7%) of the genes at relapse. By contrast, new cytogenetic changes were found in 20% of patients.ConclusionPharmacological mechanisms are involved in primary resistance to DAC, whereas hypomethylation does not prevent a relapse for patients with DAC treatment.

Lack of cross‐resistance to FF‐10501, an inhibitor of inosine‐5′‐monophosphate dehydrogenase, in azacitidine‐resistant cell lines selected from SKM‐1 and MOLM‐13 leukemia cell lines

“…Loss of DCK function is reported to be one of the mechanisms of decitabine resistance (Qin et al. 2009, 2011). Unexpectedly, the expression levels of DCK in the azacitidine‐resistant cells in the present study were not changed, although those azacitidine‐resistant cells showed strong cross‐resistance to decitabine.…”

“…2014) and deoxycytidine kinase (DCK) (Qin et al. 2009, 2011) are responsible for the resistance of azacitidine and decitabine, respectively, as the UCKs and the DCK are required for the HMAs to form their phosphorylated active metabolites. These metabolic changes observed in HMA resistance may have an impact on the efficacies of other antimetabolic agents, such as cytarabine, for the treatment of AML, that is, a possible risk of cross‐resistance in the treatment of MDS and/or AML.…”

Artesunate-enhanced apoptosis of human high-risk myelodysplastic cells induced by the DNA methyltransferase inhibitor decitabine

“…Other FDA approved treatments, namely DAC and AZA, have been used in low-intensity MDS therapeutic regimens. However, due to untargeted DNA damage and mutagenesis, and the occurrence of primary and secondary resistance, DAC and AZA have demonstrated limited clinical responses (12,15). The future of MDS-targeted therapies may therefore require combinations of novel drugs.…”

“…The survival rate at relapse following an initial response to treatment is poor. One study identified that primary resistance to treatment resulted from the abnormal active metabolism of DAC, and that secondary resistance was due to the unbalanced activation of downstream pathways, such as the nuclear factor-κB (NF-κB) and phosphatidylinositol 3-phosphate/AKT pathways, which limited the clinical effect of DAC (15).…”

Epigenetics in Cancer: The Myelodysplastic Syndrome as a Model to Study Epigenetic Alterations as Diagnostic and Prognostic Biomarkers

“…Clinical response to hypomethylating drugs in vivo is complex and may involve differentiation and immune activating components. Cytogenetic analysis showed that MDS patients after relapse using decitabine showed evolution in 20% patients with abnormalities such -7, del(16q) and +8 (Qin et al, 2011).…”