Background/Aims: MicroRNA-21 (miR-21) has been demonstrated to play an important role in carcinogenesis; however, its mechanism of action in colorectal cancer (CRC) has not been fully elucidated. The aim of the present study was to explore the oncogenic function of miR-21 and its molecular mechanism in CRC. Methods: A total of 105 paired tumor and tumor-adjacent normal tissue specimens from CRC patients and two CRC cell lines (HCT-116 and SW480) were studied. The protein and mRNA expression levels of PTEN and miR-21 were examined using western blot analysis and real-time reverse transcription-PCR (qRT-PCR). Furthermore, we transfected CRC cells with different combinations of ectopic-expression vector or shRNA expression vector of miR-21 and phosphatase and tensin homolog (PTEN) to modulate the expression levels of miR-21 and PTEN respectively, and then analyzed the phenotypic alterations of CRC cells. Tumorigenesis was also evaluated by xenografting HCT-116 cells into nude mice. Results: In this study, we showed that miR-21 expression was significantly up-regulated in CRC compared to that in normal tissues. Patients with advanced Tumor-Node-Metastasis (TNM) stage, lymph node metastasis, local invasion and higher serum carcinoembryonic antigen (CEA) levels displayed significantly high expression of miR-21. The PTEN protein level in CRC tissues and cells was inversely correlated with miR-21 expression. Furthermore, the transfection of CRC cells with pre-miR-21 could inhibit apoptosis and promote cellular proliferation, invasion, cell cycle progression and growth of xenografts in nude mice, whereas the transfection of miR-21-specific shRNA resulted in the opposite phenomena. In addition, silencing or elevating PTEN protein could partially reverse the effect of miR-21-specific shRNA or pre-miR-21 on apoptosis, cell cycle distribution, and invasion of CRC cells. Moreover, over-expression or knockdown of miR-21 altered the protein expression of PTEN and phosphorylated Akt (p-AKT). Conclusion: miR-21 can modulate the malignant phenotypes such as proliferation, anti-apoptosis, cell cycle progression and invasion of CRC cells by down-regulating PTEN protein expression. The results of study might improve our understanding of the regulatory mechanism of miR-21 and provide useful targets and approaches for the clinical diagnosis and therapy of CRC.

The global morbidity and mortality of colorectal cancer (CRC) are ranked the third among gastrointestinal tumors in the world. MiR-451a is associated with several types of cancer, including CRC. However, the roles and mechanisms of miR-451a in CRC have not been elucidated. BAP31 is a predicted target gene of miR-451a in our suppression subtractive hybridization library. Its relationship with miR-451a and function in CRC are unclear. We hypothesized that miR-451a could induce apoptosis through suppressing BAP31 in CRC. Immunohistochemistry and real-time PCR were used to measure BAP31 expressions in CRC tissues and pericarcinous tissues from 57 CRC patients and CRC cell lines. Dual-luciferase reporter assay was used to detect the binding of miR-451a to BAP31. The expression of BAP31 protein in CRC tissues was significantly higher than that in pericarcinous tissues, which was correlated with distant metastasis and advanced clinical stages of CRC patients. The expression of BAP31 was higher in HCT116, HT29, SW620, and DLD cells than that in the normal colonic epithelial cell line NCM460. The expression of BAP31 was absolutely down-regulated when over-expressing miR-451a in HCT116 and SW620 cells compared with control cells. Mir-451a inhibited the expression of BAP31 by binding to its 5’-UTR. Over-expressing miR-451a or silencing BAP31 suppressed the proliferation and apoptosis of CRC cells by increasing the expressions of endoplasmic reticulum stress (ERS)-associated proteins, including GRP78/BIP, BAX, and PERK/elF2α/ATF4/CHOP, which resulted in increased ERS, cytoplasmic calcium ion flowing, and apoptosis of CRC cells. These changes resulting from over-expressing miR-451a were reversed by over-expressing BAP31 with mutated miR-451a-binding sites. Over-expressing miR-451a or silencing BAP31 inhibited tumor growth by inducing ERS. The present study demonstrated that miR-451a can inhibit proliferation and increase apoptosis through inducing ERS by binding to the 5’-UTR of BAP31 in CRC.

ORIGINAL RESEARCH ARTICLEpopulations, 7 with the most common genotype 4,4 and the most common allele 4. Allele 7 of the VNTR, Association analysis of the although the second most common in Caucasians, [7][8][9][10] has not been previously observed in Chinese popudopamine D4 gene exon III lations and is very rare in Japanese. 7 This allele was also not found in our control group as expected, but VNTR and heroin abuse in two heroin abuse patients showed 7-repeat alleles (genotype 4,7 and 5,7 respectively) and there was also Chinese subjects a higher frequency of the 5-repeat in this group. Overall, no significant difference was observed between T Li 1,2 , K Xu 2 , H Deng 2 , G Cai 2 , J Liu 2 , X Liu 2 , patients and controls for genotype ( 2 = 8.20; P = 0.16) R Wang 3 , X Xiang 4 , J Zhao 1 , RM Murray 1 , or allele frequency ( 2 = 7.04; P = 0.07), although the PC Sham 1 and DA Collier 1 allele-wise result approached significance.

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