MicroRNA-21 promotes TGF-β1-induced epithelial-mesenchymal transition in gastric cancer through up-regulating PTEN expression.

Chang Li,Xiao-Xue Bai,Lei Song,Lian-Jun Ma,Zhuo Zhang,Ming-Fu Cui

doi:10.18632/oncotarget.11888

Abstract

This study aimed to explore the effects of miR-21 and PTEN/Akt signaling pathway on TGF-β1-induced epithelial-mesenchymal transition (EMT) in gastric cancer (GC). GC tissues and adjacent tissues were collected from 83 patients. The qRT-PCR assay was performed to detect miR-21 expression. The expressions of PTEN, Akt and p-Akt were detected by immunohistochemistry. After 48 h of treatment with TGF-β1 (10 ng/mL), the SGC-7901 and KATO-III cells were divided into the blank, negative control (NC), miR-21 inhibitors, PTEN-siRNA and miR-21 inhibitors + PTEN-siRNA groups. EMT related factors and PTEN expressions were detected by qRT-PCR assay and Western blotting. The scratch test was conducted to observe cell migration. Xenograft tumor model in nude mice was used to evaluate the effects of miR-21 on EMT of GC cells in vivo. In GC tissues, the expressions of miR-21, Akt and p-Akt were up-regulated, while PTEN expression was down-regulated. Gene and protein expressions of E-cadherin and PTEN in the miR-21 inhibitors group were higher than the blank, NC, PTEN-siRNA and miR-21 inhibitors + PTEN-siRNA groups, while the expressions of N-cadherin, β-catenin, Vimentin and Slug in the miR-21 inhibitors group were lower than other groups. MiR-21 inhibitors significantly inhibit cell migration and invasion in GC cell lines. In vivo xenograft experiment revealed that miR-21 inhibitor inhibits the growth of transplanted tumor through up-regulating E-cadherin and PTEN expressions and down-regulating the expressions of N-cadherin, β-catenin, Vimentin and Slug. These results suggest that miR-21 could promote TGF-β1-induced EMT in GC cells through up-regulating PTEN expression.

Highlights

Gastric cancer (GC) is one of the most common malignant tumors of digestive system
The correlation analysis demonstrated that there was a negative correlation between miR-21 and PTEN in gastric cancer (GC) (r = −0.865, P < 0.01), while positive correlations were found between miR-21 and Akt/ p-Akt in GC (Akt: r = 0.747, P < 0.001; pAkt: r = 0.804, P < 0.01)
Our results demonstrated that the expressions of miR-21, Akt and p-Akt were significantly higher in the 83 GC tissues than those in adjacent normal tissues, but the expression of PTEN was significantly lower than that in adjacent normal tissue, which indicated that the expressions of miR-21, Akt, p-Akt and PTEN were related to GC

Summary

Introduction

Gastric cancer (GC) is one of the most common malignant tumors of digestive system. With study on the molecular biological mechanism of GC appearing, developing and transiting, targeted drug therapy for GC attracted more concern in clinical trials [3]. The pathogenic factors of GC include environmental factors, diet, infections and host genes, among which the abnormalities in gene expression, especially the abnormal expression of the encoded protein of oncogenes or tumor-suppressor genes, play an important role in the pathogenesis of GC [4, 5]. Epithelial-mesenchymal transition (EMT) in GC is the key factor for GC cell metastasis and is the primary cause of GC death. Study on gene regulation mechanism of EMT in GC has great significance [6]

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