MicroRNA-31 inhibits RhoA-mediated tumor invasion and chemotherapy resistance in MKN-45 gastric adenocarcinoma cells

Abstract

microRNAs are small single-stranded non-coding RNA molecules which modify gene expression by silencing potential target genes. The aberrant expression of RhoA, a small GTPase protein of Rho family, is involved in gastric cancer tumorigenesis. Since miR-31 is a pleomorphic molecule, we evaluated the miR-31/RhoA axis in inducing the malignant phenotype of gastric cancer cells MKN-45. Also, the clinicopathological significance of RhoA was investigated in a well-defined collection of gastric carcinomas which were embedded in tissue microarray blocks. Induction of miR-31 in MKN-45 followed by suppression of RhoA expression resulted in increased sensitivity to 5-fluorouracil, inhibition of cell proliferation, and invasion compared to the control groups. Immunohistochemical analysis in gastric adenocarcinoma patients' samples showed significantly higher expression of RhoA in diffuse versus intestinal subtype tumors ( P = 0.009), poorly differentiated versus well and moderately differentiated tumors ( P = 0.03) and the presence of vascular invasion versus the absence of vascular invasion ( P = 0.04). Our findings suggest a critical role for miR-31, as a tumor suppressor gene, in gastric cancer tumorigenesis by targeting the RhoA. Impact statement Gastric cancer ranks as the third leading cause of cancer-associated deaths worldwide. The RhoA gene encodes a small GTPase protein of Rho family (RhoA) that its dysregulation is associated with cell motility and invasion. A strong line of evidence supports the regulation of RhoA by a number of miRs, including miR-31 in tumors. Our findings revealed that miR-31 is involved in gastric cancer tumorigenesis as a tumor suppressor gene. Through down-regulation of RhoA, miR-31 decreased cell proliferation, migration, and invasion in gastric cancer cells. In addition, induction of miR-31 increased sensitivity to 5-FU; thus, increasing its tissue concentrations could be a potential target for treatment of gastric cancer in the future.

Regulation of RhoA GTPase and various transcription factors in the RhoA pathway

“…In addition, miR‐146a suppresses RhoA expression in MDA‐MB231 cells (Liu et al, ). Another microRNA, miR‐31, also reduced RhoA expression in gastric cancer cells MKN‐45 (Korourian, Roudi, Shariftabrizi, & Madjd, ). Loss of miR‐122 was also shown to be associated with poor prognosis in hepatocellular carcinoma progression along with cell migration and invasion and interestingly, RhoA 3′ UTR may be a binding site for miR‐122 (Wang et al, ).…”

Induced miR‐31 by 5‐fluorouracil exposure contributes to the resistance in colorectal tumors

“…In this study, we suggested that miR‐31 was related to the 5‐FU resistance in colorectal cancer. There are some reports that miR‐31 is related to the 5‐FU resistance in colorectal cancer . Korourian et al and Li et al reported that miR‐31 targeted RhoA, and a long non‐cording RNA for 5‐FU resistance, respectively .…”

<p>Research Progress in microRNA-Based Therapy for Gastric Cancer</p>

“…For example, overexpression of miR-939, miR-623, miR-429, miR-204, miR-124 or miR-31 was shown to enhance 5-FUinduced chemosensitivity by compromising tumor cell growth or inducing apoptosis. 9,[13][14][15][16][17][18][19] Among the above-mentioned miRNAs, miR-939 and miR-204 were the only two miRNAs with confirmed ability of reversing drug resistance both in vitro and in vivo, providing more convening evidence than others. 9,15 A role of miR-31 in chemosensitivity was reported by two separate research groups and may have more obvious effects.…”

“…9,15 A role of miR-31 in chemosensitivity was reported by two separate research groups and may have more obvious effects. [17][18][19] Moreover, reduced miR-6785-5p, miR-193-3p, or miR-147 expression could also increase the chemosensitivity of GC to 5-FU. [20][21][22] Interestingly, miR-193-3p and miR-147 both target phosphatase and tensin homolog (PTEN) to exert their functions in GC.…”