An miRNA–DNMT1 Axis Is Involved in Azacitidine Resistance and Predicts Survival in Higher-Risk Myelodysplastic Syndrome and Low Blast Count Acute Myeloid Leukemia

Abstract

<b>Purpose:</b> Azacitidine inhibits DNA methyltransferases, including DNMT1, and is currently the standard of care for patients with higher-risk myelodysplastic syndrome (HRMDS) or low blast count acute myeloid leukemia (AML).<b>Experimental Design:</b> The expression of 754 miRNAs was compared in azacitidine-resistant and azacitidine-sensitive myelodysplastic syndrome cells. We investigated the role of differentially expressed miRNAs on DNMT1 expression and azacitidine resistance <i>in vitro</i> We next evaluated anti-DNMT1 miRNA expression in pretreatment bone marrow samples derived from 75 patients treated with azacitidine for HRMDS or AML.<b>Results:</b> Seven miRNAs, including 5 that <i>in silico</i> targeted the DNMT1 3' UTR, were repressed in azacitidine-resistant cells in which DNMT1 protein levels were significantly higher. Ectopic anti-DNMT1 miRNA expression decreased DNMT1 expression and increased azacitidine sensitivity, whereas specific inhibition of endogenous anti-DNMT1 miRNAs increased DNMT1 expression and triggered azacitidine resistance. In patients treated with azacitidine, decreased expression of anti-DNMT1 miRNAs was associated with poor outcome. miR-126* had the strongest prognostic impact. Patients with miR-126*^low myelodysplastic syndrome had significantly lower response rates (<i>P</i> = 0.04) and higher relapse rates (<i>P</i> = 0.03), as well as shorter progression-free (PFS; <i>P</i> = 0.004) and overall survival (OS; <i>P</i> = 0.004). Multivariate analysis showed that age, miR-126* expression, and revised International Prognostic Scoring System risk independently predicted PFS and OS. In 15 patient samples collected over time, decreased miRNA expression levels were associated with secondary resistance.<b>Conclusions:</b> A decreased expression of anti-DNMT1 miRNAs might account for azacitidine resistance in HRMDS and AML, and measuring miRNA expression before and during treatment might help predict primary or secondary azacitidine resistance. <i>Clin Cancer Res; 23(12); 3025-34. ©2016 AACR</i>.