Introduction: Tyrosine kinase inhibitors (TKIs), pazopanib and sunitinib, are widely used in renal cell carcinoma (RCC) therapy by inhibiting tumor angiogenesis. However, most patients become insensitive or develop resistance toward TKI therapy eventually, and the underlying mechanisms have not yet been fully elucidated. Our goal is to reveal the molecular mechanisms of TKI resistant RCC to find a potential combination therapy for TKI-resistant RCC. Methods: The human RCC cell lines: 786-O, A498, Caki-1, and SW-839 were used. Lentiviral plasmids were used to generate gene engineering tools. The qPCR and Western blot were used to evaluate the gene expressions at RNA and protein levels, respectively. Vasculogenic mimicry (VM) assays were performed to examine vascular-like structure formation ability of cancer cells. Protein-DNA binding complexes were detected by Chromatin immunoprecipitation (ChIP) assays. The human DGKD promoter region was cloned into pGL3 vector for Luciferase Assays. Preclinical mouse RCC model was used to evaluate the anti-cancer effect of pazopanib and circRNA-DGKD blockage in TKI resistant RCC. Results: TKI resistant RCC cells showed increased ability of forming VM to counteract the TKI-suppression function both in vivo and in vitro. Mechanism dissection revealed that pazopanib (or sunitinib)-resistant RCC cells had an increased ERß, consequently enhancing the circRNA-DGKD expression. In turn, circRNA-DGKD could increase VE-cadherin expression via sponging the miR-125-5p. Supportively, targeting circRNA-DGKD intercepted the RCC VM formation, reduced metastases and improved survival in an orthotopic RCC mouse model. Collectively, the findings may aid in the development of novel therapies for metastatic or TKI-resistant RCC. Conclusions: Our study reveals that the resistance to TKIs (pazopanib or sunitinib) occurs by increasing vasculogenic mimicry (VM) ability to counteract the TKI angiogenesis suppression function. Furthermore, we find a potential therapy to more effectively treat TKI resistant RCC by blocking ERß/circRNA-DGKD/miR-125-5p/VE-cadherin pathway together with pazopanib administration. SOURCE OF Funding: This work was partially supported by URMC Urology Department Research fund and George H. Whipple Professorship Endowment.
