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 CDK19 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.

Journal of Cancer. 2019 Jun 09*** epublish ***

Lu Lu, Yanmin Li, Hui Wen, Chenchen Feng

Department of Pathology, Huashan Hospital, Fudan University, Shanghai 200040, PR China., Department of Urology and Institute of Urology, First Affiliated Hospital of Gannan Medical University, Ganzhou, Jiangxi, 341000, China., Department of Urology, Huashan Hospital, Fudan University, Shanghai 200040, PR China.