Functional studies of miR-130a on the inhibitory pathways of apoptosis in patients with chronic myeloid leukemia

Abstract

The p53 mutation in chronic myeloid leukemia (CML) led to decreased overall survival and therapy resistance which was also closely correlated with the downstream proto-oncogenes BCL-2, TCL-1 and MCL-1. We in this study aimed to investigate the function of miR130a in p53 tumor suppressor signaling pathway. We performed microRNA (miRNA) expression profile analysis in CML cancer stem cells of 38 cases and extracted total RNA from peripheral blood of 143 cases. Standard curves of U6 and miRNA were made from 10-fold serial dilutions of the cDNA, which were quantified using real-time quantitative PCR with SYBR Green by ABI 7300. The p53 mutations and BCR/ABL mutation status analysis in CML patients were detected by PCR and direct sequencing. Candidate targets of miR130a of putative relevance in CML pathogenesis were analyzed by bioinformatics approach. We then used dual-luciferase activity assay to verify the target genes of miR130a and used western blot analysis to elucidate the mechanism of miR130a on modulating drug resistance. The levels of miR-130a expression in CML were significantly lower in poor prognostic subgroups, defined by prognostic factors including mutated BCR/ABL status, p53 and ATM deletions and p53 mutations. Furthermore, underexpression of miR-130a was significantly associated with shorter overall survival and treatment-free survival in CML patients. We demonstrated that miR130a function as tumor suppressors by inhibiting multiple anti-apoptosis proteins, including BCL-2, MCL-1 and XIAP. This was a direct effect because miR130a negatively regulated expression of a BCL-2/MCL-1/XIAP 3'untranslated region-based reporter construct. Transfection of miR130a mimics into CML cells from 30 patients without p53 aberrations led to significant increases in apoptosis compared with transfection with the miRNA control. Besides, enforced expression of miR130a had no significant drug-sensitization effect in CML cells from p53-attenuated patients. MiR-130a may have an important role in the pathogenesis of CML and may be useful for assessing prognosis in patients with CML. Moreover, miR130a may provide a possible therapeutic avenue and a sensitive indicator of the activity of the p53 in CML.