Background: Circular RNAs (circRNAs) are a class of non-coding RNAs broadly expressed in cells of various species. However, the molecular mechanisms that link circRNAs with colorectal cancer (CRC) are not well understood. In the present study, we attempted to provide novel basis for targeted therapy for CRC from the aspect of circRNA–microRNA (miRNA)–mRNA interaction. Methods: We investigated the expression of circRNAs in five paired CRC tissues and adjacent non-tumor tissues by microarray analysis. Differentially expressed circRNAs were identified between CRC tissues and non-cancerous matched tissues. We focused on hsa_circ_0005100, which is located on chromosome 1 and derived from FMN2, and thus we named it as circFMN2. The expression of circFMN2 was detected in 88 CRC tissues and cell lines by quantitative real-time PCR. Functional assays were performed to evaluate the effects of circFMN2 on proliferation in vitro, and on tumorigenesis in vivo. The relationship between circFMN2 and miR-1182 was confirmed by luciferase reporter assay. Results: circFMN2 was found to be significantly up-regulated in CRC tissues and cell lines. Moreover, knockdown of circFMN2 significantly inhibited cell proliferation and migration in vitro. Bioinformatics analysis predicted that there is a circFMN2/miR-1182/hTERT axis in CRC progression. Dual-luciferase reporter system validated the direct interaction of circFMN2, miR-1182, hTERT. Western blot verified that inhibition of circFMN2 decreased hTERT expression. Importantly, we demonstrated that circFMN2 was up-regulated in serum exosomes from CRC patients. Conclusion: In conclusion, circFMN2 is a central component linking circRNAs to progression of CRC via an miR-1182/hTERT axis.

miRNAs are a class of endogenous non-coding RNA, which can regulate downstream target genes through binding to the 3'UTR of those genes. Numerous studies have indicated that abnormal expression of miRNAs is implicated in tumor development. Aberrant expression of miR-31 has been found in various cancers, including colorectal cancer. Here, we show that miR-31 is upregulated in human colon cancer tissues and cell lines, and that repression of miR-31 inhibited colon cancer cell proliferation and colony formation in soft agarose. To further elucidate the mechanism underlying the role of miR-31 in promoting colon cancer, we used online miRNA target prediction databases and found that the tumor suppressor RhoTBT1 may be a target of miR-31. Imunohistochemistry assay revealed that RhoBTB1 was significantly decreased in HT29 cells. In addition, ectopic expression of miR-31 reduced RhoBTB1 in the colon cancer cell line HT29. The results suggested that suppression of RhoBTB1 may be responsible for colon tumorigenesis, which was inhibited directly by miR-31. The results of MTT and soft agarose colony-formation assays showed that knockdown of RhoBTB1 by RNAi induced cell proliferation, and colony formation in soft agarose, which mimicked the function of miR-31. This further suggested that suppression of RhoBTB1 was responsible for colon tumorigenesis. In conclusion, we found that miR-31 acts as an oncogene in colon cancer and identified RhoBTB1 as a new target of miR-31 further study demonstrated that miR-31 contributed to the development of colon cancer at least partly by targeting RhoBTB1.

Background/Aims: Endothelial-to-mesenchymal transition (EndMT) of glomerular endothelial cells (GEnCs) can induce albuminuria in diabetic nephropathy. Melatonin attenuates diabetic nephropathy, but its role and mechanism in EndMT of GEnCs in diabetic nephropathy remain unknown. Methods: The effect of melatonin on EndMT induced by transforming growth factor (TGF)-β2 in human renal GEnCs was determined by assaying the expression of endothelial marker cells (VE-cadherin and CD31) and mesenchymal cells (α-SMA and Snail), as well as monolayer permeability. The molecular mechanism of melatonin in these processes was focused on miR-497/ROCK signaling. Furthermore, the effect and mechanism of melatonin in EndMT were confirmed in glomeruli of rats with streptozotocin-induced diabetes. Results: Melatonin increased expression of VE-cadherin and CD31 and inhibited α-SMA and Snail levels that were altered by TGF-β2 in GEnCs. Melatonin treatment reduced expression and activity of ROCK1 and ROCK2, which suppressed TGF-β2-induced hyperpermeability of GEnCs and EndMT of GEnCs. Melatonin reduced ROCK1 and ROCK2 expression and activity in TGF-β2-stimulated GEnCs by enhancing expression of miR-497, which targets ROCK1 and ROCK2. Furthermore, we found that melatonin inhibited EndMT in glomeruli and albuminuria in rats with streptozotocin-induced diabetes. MiR-497 expression increased, whereas ROCK1 and ROCK2 expression and activity decreased in melatonin-treated diabetic rats. Conclusion: Melatonin attenuated EndMT of GEnCs via regulating miR-497/ROCK signaling in diabetic nephropathy. This study improves understanding of EndMT and the role of melatonin in diabetic nephropathy.