Pathway enrichment analysis. For ontology analysis, gene lists were analyzed using DAVID software (KEGG pathways). The complete set of genes featured in the microarrays was used as the reference background. The three numbers on the right represent the number of deregulated mRNAs, the overall number of genes within the pathway and the p value, respectively. Data are presented for genes targeted by at least one of the 7 miRNAs and that were found repressed in SKM1 AZA resistant cells.
ARTICLE ABSTRACT
Purpose: 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).Experimental Design: 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 in vitro. We next evaluated anti-DNMT1 miRNA expression in pretreatment bone marrow samples derived from 75 patients treated with azacitidine for HRMDS or AML.Results: Seven miRNAs, including 5 that in silico 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 (P = 0.04) and higher relapse rates (P = 0.03), as well as shorter progression-free (PFS; P = 0.004) and overall survival (OS; P = 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.Conclusions: 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. Clin Cancer Res; 23(12); 3025–34. ©2016 AACR.
