m6A-modification regulated circ-CCT3 acts as the sponge of miR-378a-3p to promote hepatocellular carcinoma progression

Background: Circular RNA (circRNA) plays a critical role in tumour progression. Circ-CCT3, a particularly abundant circRNA, was proposed to be involved in tumorigenesis. However, the role of circ-CCT3 in hepatocellular carcinoma remains elusive.Methods: Here, circ-CCT3 (a circRNA derived from exons 3, 4 and 5 of the CCT3 gene, hsa_circ_0004680) was identified by circRNA microarray and validated by qRT-PCR. RNA immunoprecipitation (RIP) was performed to confirm the binding between ALKBH5 along with METTL3 and circ-CCT3. Methylated RNA Immunoprecipitation (MeRIP) was used to detect the N6-methyladenosine (m ²A) levels of circ-CCT3. CircRNAs in vivo precipitation, luciferase reporter assay, biotin-coupled microRNA capture, and fluorescence in situ hybridization were conducted to assess the interaction between circ-CCT3 and miR-378a-3p. The functions of circ-CCT3 in HCC were evaluated both in vitro and in vivo.Results: We demonstrated that circ-CCT3 was highly expressed in HCC which indicated the poor prognosis. Circ-CCT3 expression served as an independent risk factor for overall survival in patients with HCC. Knocking-down of circ-CCT3 inhibited the proliferation, invasion and migration of HCC cells, and angiogenesis of HUVEC. Mechanistically, ALKBH5 and METTL3 could bind and regulate m A-modification of circ-CCT3. Further, circ-CCT3 upregulated the expression of FLT-1 by sponging miR-378a-3p.Conclusions: Circ-CCT3 was significantly up-regulated in HCC and promoted liver cancer development via miR-378a-3p-FLT1 axis. It was also found that circ-CCT3 was under m A-modification mediated by ALKBH5 and METTL3. Our study highlights circ-CCT3 as a potential therapeutic target of HCC treatment, which provides a novel understanding on mechanisms of circRNAs in HCC progression.

CircCRIM1 Promotes Hepatocellular Carcinoma Proliferation and Angiogenesis by Sponging miR-378a-3p and Regulating SKP2 Expression

Mounting evidence has demonstrated that circular RNAs have an important function in tumorigenesis and cancer evolvement. CircCRIM1 has been shown to be a poor prognostic element in multiple human malignancies. However, the clinical significance and mechanism of circCRIM1 in hepatocellular carcinoma (HCC) is still unclear. The present study confirmed the expression level of circCRIM1 using quantitative real-time PCR. In addition, circCRIM1 siRNA and overexpression vectors were used for transfection into LM3 or Huh7 cells to down- or up-regulate the expression of circCRIM1. In vitro and in vivo experiments were performed to explore the function of circCRIM1 in HCC. RNA pull-down, RNA immunoprecipitation, fluorescent in situ hybridization, and luciferase reporter assays were conducted to confirm the relationship between miR-378a-3p and circCRIM1 or S-phase kinase-associated protein 2 (SKP2) in HCC. Then, circCRIM1 was up-regulated in HCC and its expression level was significantly associated with poor prognosis and clinicopathologic characteristics. CircCRIM1 enhanced the proliferation and angiogenesis of HCC cells in vitro and promoted xenograft growth in vivo. Moreover, circCRIM1 upregulated the expression of SKP2 by functioning as a sponge for miR-378a-3p. These findings suggest that circCRIM1 boosts the HCC progression via the miR-378-3p/SKP2 axis and may act as a crucial epigenetic therapeutic molecule target in HCC.

MiR-378a-3p enhances adipogenesis by targeting mitogen-activated protein kinase 1

Previous studies showed that miR-378a plays important roles in adipogenesis and obesity; however, the precise mechanisms of action remain unknown. Here, we found that miR-378a-3p expression is up-regulated in adipose tissues of high fat diet-induced obese mice, as well as during the differentiation of 3T3-L1 preadipocytes. Mir-378a-3p induced adipogenesis by targeting mitogen-activated protein kinase 1 (MAPK1). Overexpression of miR-378a-3p or silencing MAPK1 reduced MAPK1 expression and enhanced adipogenesis, whereas blockage of endogenous miR-378a-3p had the opposite effect, suggesting that miR-378a-3p promotes the adipogenesis of 3T3-L1 cells by targeting MAPK1.

Clinical and biological significance of miR-378a-3p and miR-378a-5p in colorectal cancer

To investigate miR-378a-3p and miR-378a-5p expression and their relationships with the clinicopathological features of colorectal cancer (CRC). Our results showed that miR-378a-3p and miR-378a-5p expression were dramatically lower in CRC cell lines and tissues than that in adjacent normal colorectal mucosal tissues, respectively. MiR-378a-3p and miR-378a-5p expression were significantly associated with histological differentiation and TNM stage, respectively. CRC patients with low miR-378a-3p and miR-378a-5p expression had a significantly shorter survival time than those patients with high miR-378a-3p and miR-378a-5p expression (p<0.001, p<0.001), respectively. Univariate and multivariable Cox regression analysis showed that tumour size, TNM stage, miR-378a-3p expression and miR-378a-5p expression were independent prognostic factors for CRC patients. Ectopic miR-378a-3p or miR-378a-5p expression inhibited cellular proliferation and colony formation, induced apoptosis and G1-phase cell cycle arrest in CRC cells, but had no effect on migration and invasion of CRC cells. Furthermore, miR-378a-3p over-expression or down-regulation could inhibit or enhance insulin-like growth factor 1 receptor (IGF1R) expression in CRC cells. There was a significantly negative correlation between IGF1R protein expression and miR-378a-3p expression in CRC tissues. MiR-378a-3p over-expression or down-regulation suppressed or enhanced phosphorylated-ERK1/2 protein level, but had no effect on phosphorylated-Akt protein level. In conclusion, miR-378a-3p and miR-378a-5p expression might play an important role as tumour suppressor gene in the initial stage of carcinogenesis of CRC.