Overexpression of miR-15b Promotes Resistance to Sunitinib in Renal Cell Carcinoma

Aim: Sunitinib remains the frontline treatment for metastatic clear-cell renal cell carcinoma (ccRCC). Drug resistance is inevitable and related mechanism warrant insightful elaboration. Methods: In silico data mining of GEO and TCGA datasets was performed to identify potential target micro-RNA. In vitro and in vivo studies were performed to validate findings. Results: Reproduction of GEO datasets revealed miR-15b significantly upregulated in sunitinib-resistant ccRCC. Five out of seven ccRCC cell lines demonstrated significantly overexpressed miR-15b after sunitinib treatment. Vector-mediated overexpression of miR-15b significantly induced resistance to sunitinib in ccRCC cells. Overexpression of miR-15b significantly induced less population in G1 phase of cell cycle and less apoptosis in cells treated sunitinib. Expression of genes negatively correlated with miR-15b in TCGA ccRCC (KIRC) dataset were cross-referenced with predicted targets of miR-15b and CCNC was selected as potential target for resistance mediation. Overexpression of miR-15b suppressed CCNC expression and protein (Cyclin C) levels. Cyclin C-associated proteins CDKI9 and CDK8 were also suppressed following miR-15b overexpression. Silencing of CCNC mimicked overexpression of miR-25 inducing cell cycle progression passing G1 phase and less apoptosis in ccRCC cells treated by sunitinib. Overexpression of miR-15b also counteracted suppression of migration and colony formation by sunitinib in ccRCC cell lines. In vivo mouse xenograft models showed recovered tumor growth with miR-15b expression in mice treated with sunitinib. Conclusion: We here show miR-15b as a possible culprit for sunitinib resistance in ccRCC. Targeting miR-15b could potentially overcome drug resistance and related mechanism warrants further investigation.