Background: Circular RNAs (circRNAs), a novel type of noncoding RNA (ncRNA), are covalently linked circular configurations that form via a loop structure. Accumulating evidence indicates that circRNAs are potential biomarkers and key regulators of tumor development and progression. However, the precise roles of circRNAs in renal cell carcinoma (RCC) remain unknown. Methods: Through circRNA high-throughput sequencing of RCC cell lines, we identified the circRNA TLK1 (circTLK1) as a novel candidate circRNA derived from the TLK1 gene. qRT-PCR detected the mRNA, circRNA and miRNA expression levels in RCC tissues and cells. Loss-of function experiments were executed to detect the biological roles of circTLK1 in the RCC cell phenotypes in vitro and in vivo. RNA-FISH, RNA pull-down, dual-luciferase reporter, western blot and immunohistochemistry assays were used to investigate the molecular mechanisms underlying the functions of circTLK1. Results: circTLK1 is overexpressed in RCC, and expression is positively correlated with distant metastasis and unfavorable prognosis. Silencing circTLK1 significantly inhibited RCC cell proliferation, migration and invasion in vitro and in vivo. circTLK1 was mainly distributed in the cytoplasm and positively regulated CBX4 expression by sponging miR-136-5p. Forced CBX4 expression reversed the circTLK1 suppression-induced phenotypic inhibition of RCC cells. Moreover, CBX4 expression was positively correlated with VEGFA expression in RCC tissues. CBX4 knockdown significantly inhibited VEGFA expression in RCC cells. Conclusion: Collectively, our findings demonstrate that circTLK1 plays a critical role in RCC progression by sponging miR-136-5p to increase CBX4 expression. circTLK1 may act as a diagnostic biomarker and therapeutic target for RCC.

Background: Bladder cancer (Bca) is the most common malignant tumor of the urinary system. Circular RNAs (circRNAs) have been recognized as key regulators in tumorigenesis. However, the molecular mechanisms underlying circRNAs involved in the progression of BCa remain largely unknown.Methods: We detected the expression level of circular RNA TAF4B (circTAF4B) by qRT-PCR assay. Cell proliferation was evaluated by CCK-8 and colony formation assays. Wound healing and Transwell assays were performed to measure cell migration and invasion capability. Moreover, we performed qRT-PCR and western blotting assays to determine the expression levels of epithelial-mesenchymal transition (EMT) markers. A nuclear/cytoplasmic fractionation assay was used to measure the subcellular location of circTAF4B. RNA pull-down and dual-luciferase reporter assays were used to detect the target microRNA of circTAF4B. A mouse xenograft model was produced to analyze the effect of circTAF4B on the tumorigenesis of BCa.Results: In this study, we identified a novel circular RNA, circTAF4B, that is significantly upregulated in BCa and correlated with poor prognosis. Downregulated circTAF4B abolished the growth, metastasis and EMT process in BCa cells. Mechanistically, we found that circTAF4B facilitated the expression of transforming growth factor A (TGFA) by sponging miR-1298-5p. Finally, circTAF4B enhanced the proliferation and EMT process of BCa cells in vivo.Conclusion: In summary, our study demonstrated that circTAF4B played a carcinogenic role in the growth, metastasis, and EMT process of BCa by regulating the miR-1298-5p/TGFA axis. Thus, circTAF4B may become a diagnostic and therapeutic target for BCa.

Background: Increased activity of the transcription factor FOXC1 leads to elevated transcription of target genes, ultimately facilitating the progression of various cancer types. However, there are currently no literature reports on the role of FOXC1 in renal cell carcinoma. Methods: By using RT-qPCR, immunohistochemistry and Western blotting, FOXC1 mRNA and protein expression was evaluated. Gain of function experiments were utilized to assess the proliferation and metastasis ability of cells. A nude mouse model was created for transplanting tumors and establishing a lung metastasis model to observe cell proliferation and spread in a living organism. Various techniques including biological analysis, CHIP assay, luciferase assay, RT-qRCR and Western blotting experiments were utilized to investigate how FOXC1 contributes to the transcription of ABHD5 on a molecular level. FOXC1 was assessed by Western blot for its impact on AMPK/mTOR signaling pathway. Results: FOXC1 is down-regulated in RCC, causing unfavorable prognosis of patients with RCC. Further experiments showed that forced FOXC1 expression significantly restrains RCC cell growth and cell metastasis. Mechanically, FOXC1 promotes the transcription of ABHD5 to activate AMPK signal pathway to inhibit mTOR signal pathway. Finally, knockdown of ABHD5 recovered the inhibitory role of FOXC1 overexpression induced cell growth and metastasis suppression. Conclusion: In general, our study demonstrates that FOXC1 exerts its tumor suppressor role by promoting ABHD5 transcription to regulating AMPK/mTOR signal pathway. FOXC1 could serve as both a diagnostic indicator and potential treatment focus for RCC.