miRNA-21 sensitizes gastrointestinal stromal tumors (GISTs) cells to Imatinib via targeting B-cell lymphoma 2 (Bcl-2).

Abstract miRNA-21 (miRNA-21) has recently been recognized to tumor suppressive in various types of cancers. However, the role of miRNA-21 in gastrointestinal stromal tumors (GISTs) is still ambiguous. In this study, we investigated the regulation by miRNA-21 on the sensitivity of gastrointestinal stromal tumors (GISTs) cells to Imatinib. We examined the expression of miRNA-21 and B-cell lymphoma 2 (Bcl-2) in GIST specimens by the real-time quantitative PCR assay (RT-qPCR). Then we explored the regulation by miRNA-21 on the Bcl-2 expression by the RT-qPCR assay, Western blotting assay and the luciferase assay in GIST-T1 cells. In addition, we examined the influence of miRNA-21 on the sensitivity to Imatinib of GIST-T1 cells with colony forming assay and apoptotic assay. Results indicated that miRNA-21 expression was suppressed in GIST tissues. And we identified putative miRNA-21 binding sites within the 3'-untranslated region (3'-UTR) of the human Bcl-2 gene. Transient transfection of miRNA-21 mimics into human GIST GIST-T1 cell line significantly downregulated the Bcl-2 expression in both mRNA and protein levels. Moreover, the miRNA-21 mimics transfection markedly aggravated the Imatinib-mediated growth inhibition and apoptosis induction in GIST-T1 cells. Our results demonstrated that miRNA-21 suppressed Bcl-2 expression in GIST cells and could function as a potent tumor suppressor in GIST. And the miRNA-21 promotion could sensitize GIST cells to Imatinib. It implies a potential role in the GIST treatment.