Background: Down-regulation of miRNA-15a and miRNA-16-1 is associated with Bcl-2 and Mcl-1 expression and chemoresistance in tumor cells. In this study, the combined effect of miRNA-15a and miRNA-16-1 on apoptosis and sensitivity of the chronic lymphocytic leukemia (CLL) cells to fludarabine and ABT-199 was investigated.
Materials and Methods: The experiment groups were as follows: ABT-199, negative control (NC) miRNA, miRNA-15a, miRNA-16, miRNA-15a+miRNA-16, NC miRNA+ABT-199, miRNA-15a+miRNA-16+ABT-199, erlotinib blank control, miRNA blank control and combination blank control. The expression levels of Bcl-2 and Mcl-1 were measured using quantitative real-time PCR (qRT-PCR). The effect of treatments on cell growth and survival was measured by trypan blue staining and MTT (3-[4, 5 dimethylthiazol-2-yl]-2, 5 diphenyltetrazolium bromide) assay, respectively. Apoptosis was measured using caspase-3 activity and ELISA cell death assays.
Results: Transfection of miRNA-15a or miRNA-16-1 significantly suppressed the expression of Bcl-2 and Mcl-1 in a time-dependent manner (P<0.05 versus negative control miRNA or blank control). Other experiments showed that up-regulation of miRNA-15a or miRNA-16-1 decreased cell growth, induced apoptosis, and synergistically lowered the IC50 value of fludarabine and ABT-199 in CLL cells. Moreover, co-transfection of two miRNAs showed a more significant effect on cell survival, apoptosis, and drug sensitivity than single transfection.
Conclusion: Our study shows that miRNA-15a and miRNA-16-1 can effectively enhance the anticancer effects of fludarabine and ABT-199 in CLL cells and may offer a new promising therapeutic strategy for CLL-resistant patients.