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: Since the combined actions of lncRNAs and miRNAs have been considered to be involved in the occurrence and development of various neoplasms, the main purpose of this study was to discover whether and how lncRNA H19 and miR-194 influenced the epithelial-mesenchymal transition (EMT) process of colorectal adenocarcinoma (CRA). Methods: Totally 214 pairs of CRA and adjacent normal tissues were collected, and 5 human CRA cell lines (i.e. HCT116, HT-29, RKO SW280 and Lovo) were purchased. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was adopted to quantify the H19 and miR-194-5p expressions in cells and tissues. The expressions of FoxM1, E-cadherin, vimentin, N-cadherin were determined using western blot. On the side, si-H19, si-NC, miR-194-5p mimic, miR-194-5p inhibitor and negative control (NC) were transfected into CRA cell lines. Meanwhile, the invasive, migratory and proliferative conditions of the cells were assessed through transwell, wound healing and colony-forming experiments, with final verification of the relationship between H19 and miR-194-5p employing dual-luciferase reporter gene assay. Results: Highly-expressed H19, lowly-expressed miR-194-5p, low-grade differentiation and lymph node metastasis appeared as the independent predictors of unfavorable prognosis in CRA patients’ (all P< 0.05). It indicated that FoxM1 expression displayed positive correlations with H19 expression, yet negative associations with miR-194-5p expression within CRA tissues (P< 0.05). In addition, transfection of H19-siRNA and miR-145-5p mimic triggered a conspicuous increase in E-cadherin expression, as well as an evidently down-regulation in vimentin and N-cadherin expressions within HT29 and RKO cells (P< 0.05). On the other hand, the invasive and migratory capacities of CRA cells were significantly hindered (P< 0.05). Moreover, the luciferase reporter gene assay confirmed that H19 modified miR-194-5p expression through directly targeting at it (P< 0.05). Ultimately, FoxM1 could reverse the role of miR-194-5p in inhibiting invasion, migration and EMT of CRA cells (P< 0.05). Conclusion: LncRNA H19/miR-194/FoxM1 axis could serve as a profound target for the diagnosis and treatment of CRA.