MicroRNA-149 Increases the Sensitivity of Colorectal Cancer Cells to 5-Fluorouracil by Targeting Forkhead Box Transcription Factor FOXM1

Background/Aims: MicroRNAs (miRNAs) have been consistently demonstrated to be involved in colorectal cancer as either tumour oncogenes or tumour suppressors. However, the detailed role of miR-520a-3p in colorectal cancer remains poorly understood. Methods: Quantitative RT-PCR and western blotting assays were used to measure miR-520a-3p and EGFR expression levels in colorectal cancer tissues, respectively. Luciferase reporter assay was employed to validate the direct targeting of EGFR by miR-520a-3p. Cell migration, apoptosis and cell cycle assays were performed to analyse the biological functions of miR-520a-3p and EGFR in colorectal cancer cells. In vivo experiment was performed to analyse the effects of miR-520a-3p and EGFR on the growth of colorectal cancer xenografts in mice. Results: In this study, we found that miR-520a-3p was most likely to target the EGFR 3’-UTR, which was experimentally validated. In addition, we investigated the biological effects of EGFR inhibition by miR-520a-3p both in vitro and In vivo and found that miR-520a-3p could suppress cell migration, promote apoptosis, lead to colorectal cancer cell cycle arrest at the G0/G1 phase, and decelerate tumour growth in xenograft mice, potentially by targeting EGFR. Conclusions: This study highlights a tumour suppressor role for miR-520a-3p in colorectal cancer via the regulation of EGFR expression. Thus, miR-520a-3p may be a novel molecular therapeutic target for colorectal cancer.

Section: Discussionmentioning

confidence: 99%

A Novel Role for MiR-520a-3p in Regulating EGFR Expression in Colorectal Cancer

Zhang

Liu

et al. 2017

“…Many studies have demonstrated that miRNAs play key roles in the regulation of cellular growth, differentiation, proliferation, and apoptosis [4]. Furthermore, it has been shown that miRNAs can function as tumor suppressors or oncogenes and are involved in various biological processes such as tumor initiation, tumor progression and drug resistance in various types of cancer, including CRC [5-10]. miR-21, a putative oncogene, is most frequently over-expressed in various malignancies, and it has been implicated in multiple malignancy-related processes including uncontrolled cell proliferation, inhibition of apoptosis and promotion of invasion and metastasis [11-13].…”

Section: Introductionmentioning

confidence: 99%

MicroRNA-21 (Mir-21) Promotes Cell Growth and Invasion by Repressing Tumor Suppressor PTEN in Colorectal Cancer

Wu¹,

Song²,

Xiong³

et al. 2017

165

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.

“…However, drug resistance usually occurs during the course of platinum-based chemotherapy [32], which remains a major obstacle for effective treatment of CRC. It has been reported that some miRNAs are able to change the drug sensitivity of cancer cells [18][19][20]. In the present study, we focused on miR-20a which may be associated with cisplatin sensitivity in CRC.…”

Section: Discussionmentioning

confidence: 97%

Knockdown of MiR-20a Enhances Sensitivity of Colorectal Cancer Cells to Cisplatin by Increasing ASK1 Expression

Zhang

et al. 2018

Background/Aims: Platinum-based chemotherapy is one of the most important strategies for treatment of colorectal cancer. To improve the therapeutic efficiency, adjuvant drugs were sought to sensitize colorectal cancer cells to platinum-based agents such as cisplatin. As previous research has shown that miRNAs are associated with chemosensitivity, we aimed to alter miRNA regulation in colorectal cancer cells to increase their chemosensitivity. Methods: MTT assays were performed to determine the viability of HT29, SW480, and LoVo cells. Quantitative real time polymerase chain reaction (qRT-PCR) was performed to examine the expression of miR-20a in these cell lines. Regulation of the miR-20a/ASK1 axis was confirmed by western blotting and luciferase reporter assays. After treatment with miR-20a inhibitor (anti-miR-20a) and cisplatin, production of reactive oxygen species (ROS), mitochondrial membrane potential, and apoptosis were measured by flow cytometry. Activation of ASK1, Bcl-xl, JNK, and caspase-9, -7, and -3 was detected by western blotting. Results: miR-20a was overexpressed in colorectal cancer cell lines. Furthermore, knockdown of miR-20a increased the sensitivity of colorectal cancer cells to cisplatin treatment in vitro and in vivo. We demonstrated that the ASK1 gene was the target of miR-20a, and knockdown of miR-20a increased the expression of ASK1 in colorectal cancer cells. As cisplatin treatment induced production of ROS, knockdown of miR-20a enhanced ROS signaling through promoting the phosphorylation of ASK1. Phosphorylation of JNK and the subsequent mitochondrial apoptosis were triggered by the combination of cisplatin and anti-miR-20a. Conclusions: Knockdown of miR-20a enhanced sensitivity of colorectal cancer cells to cisplatin through the ROS/ASK1/JNK pathway.