Targeting circDGKD Intercepts TKI’s Effects on Up-Regulation of Estrogen Receptor β and Vasculogenic Mimicry in Renal Cell Carcinoma

SIMPLE SUMMARY: Our aim was to elucidate the molecular mechanisms of how tyrosine kinase inhibitors, including sunitinib, contribute to vasculogenic mimicry (VM) formation and progression in renal cell carcinoma. We demonstrated that sunitinib and axitinib could induce ERβ expression in RCC cell lines and ERβ transcriptionally up-regulated the circular RNA of DGKD (circDGKD, hsa_circ_0058763) expression. The circDGKD could sponge tumor suppressor miR-125-5p family members and consequently led to increased VE-cadherin, the key adhesion molecule in the VM formation process, which is targeted by miR-125-5p at the 3′ UTR, providing novel targets for combination therapy in clinical metastatic RCC patients. ABSTRACT: Vasculogenic mimicry (VM) has been reported as an alternative channel to increase tumor nutrient supplies and accelerate tumor progression, and is associated with poor survival prognosis in multiple cancers, including renal cell carcinoma (RCC). The currently used anti-angiogenic treatment for metastatic RCC, sunitinib, a tyrosine kinase inhibitor (TKI), has been reported to induce VM formation. Previously we identified that the estrogen receptor β (ERβ) functions as an oncogenic factor to promote RCC progression, supported by the analytic results from The Cancer Genome Atlas (TCGA) database. We have also found evidence that sunitinib induces RCC VM formation by up-regulating ERβ expression. In this study, we further demonstrated that treatment with sunitinib, as well as axitinib, another TKI, could induce ERβ expression in RCC cell lines. Clinical clear cell RCC (ccRCC) patients with higher ERβ expression are more likely to be found VE-cadherin positive and VM positive. Mechanism dissection showed that TKI- induced ERβ transcriptionally up-regulates the circular RNA of DGKD (circDGKD, hsa_circ_0058763), which enhances VE-cadherin expression by sponging the microRNA miR-125-5p family. Targeting circDGKD intercepts sunitinib-pretreatment-induced RCC VM formation, reduces metastases and improves survival in an experimental orthotopic animal model. Targeting ERβ/circDGKD signals may improve the TKI efficacy and provide novel combination therapies for metastatic RCC.