Involvement Of MicroRNAs In The Drug Resistance Of Leukemia And Lymphoma Cell Lines

Objective: To investigat the possible role of miR-181a in AML Ara-C resistance andthe role of miR-21in DLBCL CHOP chemotherapy regimen resistance.Method: MicroRNAs expression were measured by realtime PCR. Cell viability wasdetected by MTT assay. Protein expressions were measured by western blotting.Caspase activity was examined by florescence assay. miR-181a was overexpressed byretroviral transduction. miR-21was knockdown with antisense oligonucleotides.luciferase activity assay was used to validate the target genes.Bcl-2expresstion wassilenced by siRNA transfection. PTEN expresstion was upregulated by lentiviraltransduction. Inhibition of NF-kB activity was achieved by siRNAtransfection.Results:（1） We found that miR-181a expression was downregulated in theAra-C-resistant cell line HL-60/Ara-C compared with its parental cell line HL-60.Overexpression of miR-181a in HL-60/Ara-C cells sensitized the cells to Ara-Ctreatment. Furthermore, Bcl-2was confirmed as a direct miR-181a target byimmunoblot analysis and reporter gene assays. Knockdown of Bcl-2mimicked theeffect of enforced miR-181a expression by reducing cell viability. In addition, theapoptosis pathway was activated by cytochrome C release and caspase9/caspase3activation after miR-181a overexpression.（2）Knockdown of miR-21with antisenseoligonucleotides significantly increased the cytotoxic effects of the CHOP regimen inCRL2631cells. A luciferase reporter assay showed that PTEN is a target gene ofmiR-21in CRL2631cells, and subsequent experiments demonstrated that miR-21impacts the PI3K/AKT signaling pathway through the regulation of PTEN, therebyaffecting cellular sensitivity to the CHOP chemotherapeutic regimen. Furthermore,knockdown of NF-KB decreased miR-21expression and sensitized CRL2631cells to CHOP treatment.Conclusion:（1）This study for the first time demonstrated that downregulation ofmiR-181a and upregulation of Bcl-2in leukaemia cells confer resistance toAra-C-based therapy.（2）MicroRNA-21regulates the sensitivity of diffuse largeB-cell lymphoma cells to the CHOP chemotherapy regimen by regulating PTENexpression.