Circ_0000658 knockdown inhibits epithelial-mesenchymal transition in bladder cancer via miR-498-induced HMGA2 downregulation.

BACKGROUND: Epithelial-mesenchymal transition (EMT) has been associated with the angiogenesis and oncogenic phenotypes of multiple malignant tumors including bladder cancer (BCa). Circular RNAs (circRNAs) are recognized as crucial regulators in the EMT. This study aims to illustrate the possible role of circular RNA_0000658 (circ_0000658) in BCa and the underlying molecular mechanism. METHODS: The expression of circ_0000658, microRNA (miR)-498, and high mobility group AT-hook 2 (HMGA2) was assessed in cancer and adjacent normal tissue collected from BCa patients and human BCa cell lines (MGH-U3, T24, 5637 and SW780). BCa cells were transduced with a series of overexpression or shRNA plasmids to clarify the function of circ_0000658 and miR-498 on the oncogenic phenotypes and EMT of BCa cells. Further, we established nude mice xenografted with BCa cells to validate the roles of circ_0000658 on tumor growth in vivo. RESULTS: Circ_0000658 was highly expressed in BCa tissue samples and cell lines, which indicated a poor prognosis of BCa patients. Circ_0000658 competitively bound to miR-498 and thus restricted miR-498 expression. Meanwhile, circ_0000658 weakened the binding of miR-498 to the target gene HMGA2 and upregulated the HMGA2 expression. Circ_0000658 elevation or miR-498 knockdown augmented oncogenic phenotypes and EMT of BCa cells, corresponding to a reduction in the expression of ß-catenin and E-cadherin as well as an increase in the expression of N-cadherin, Slug, Snail, ZEB1 and Twist. Inhibition of HMGA2 reversed the effects of circ_0000658 overexpression on tumor growth in vivo. CONCLUSION: Altogether, our study uncovered the tumor-promoting role of circ_0000658 in BCa via the miR-498/HMGA2 axis.

Long Noncoding RNA KIF9-AS1 Regulates Transforming Growth Factor-ß and Autophagy Signaling to Enhance Renal Cell Carcinoma Chemoresistance via microRNA-497-5p.

Renal cell carcinoma (RCC) has been regarded as one of the most malignant tumor types. Chemotherapy (such as sorafenib) is used as common strategy for treating RCC. To date, whether long noncoding RNA KIF9-AS1 is involved in RCC progression and drug resistance remains unknown. In this investigation, we detected gene expression levels by western blot and RT-qPCR. MTT and TUNEL experiments were used to show cell viability and apoptosis, respectively. KIF9-AS1 overexpression led to enhanced cell viability, increased IC50 value of sorafenib, and decreased apoptosis. miR-497-5p acted as key interaction factor for KIF9-AS1 in RCC. More importantly, we found that transforming growth factor-ß and autophagy signaling pathways were both critical effectors for mediating KIF9-AS1/miR-497-5p axis-induced drug resistance phenotypes (cell viability, IC50, apoptosis) of RCC. In conclusion, our study revealed that KIF9-AS1 played a positive role in drug resistance of RCC cells to sorafenib, potentially driving the development of targeted diagnostic and therapeutical approaches.