The putative tumor suppressor microRNA-497 modulates gastric cancer cell proliferation and invasion by repressing eIF4E

https://doi.org/10.1016/j.bbrc.2014.05.011Get rights and content

Highlights

  • MiR-497 expression was down-regulated in GC patients and GC cell lines.

  • MiR-497 inhibited cell proliferation and invasion of GC cells in vitro.

  • MiR-497 modulated eIF4E expression in GC cells.

  • Restoration of miR-497 decreased tumor growth and metastasis in vivo.

Abstract

Accumulating evidence has shown that microRNAs are involved in multiple processes in gastric cancer (GC) development and progression. Aberrant expression of miR-497 has been frequently reported in cancer studies; however, the role and mechanism of its function in GC remains unknown. Here, we reported that miR-497 was frequently downregulated in GC tissues and associated with aggressive clinicopathological features of GC patients. Further in vitro observations showed that the enforced expression of miR-497 inhibited cell proliferation by blocking the G1/S transition and decreased the invasion of GC cells, implying that miR-497 functions as a tumor suppressor in the progression of GC. In vivo study indicated that restoration of miR-497 inhibited tumor growth and metastasis. Luciferase assays revealed that miR-497 inhibited eIF4E expression by targeting the binding sites in the 3′-untranslated region of eIF4E mRNA. qRT-PCR and Western blot assays verified that miR-497 reduced eIF4E expression at both the mRNA and protein levels. A reverse correlation between miR-497 and eIF4E expression was noted in GC tissues. Taken together, our results identify a crucial tumor suppressive role of miR-497 in the progression of GC and suggest that miR-497 might be an anticancer therapeutic target for GC patients.

Introduction

MicroRNAs (miRNAs) are a class of endogenous non-coding RNAs of 19–25 nucleotides in length that suppress protein expression through base pairing with the 3′-untranslated region (3′-UTR) [1]. Mounting studies have documented a functional contribution of specific miRNAs in diverse biological processes [2], [3]. In addition, miRNAs have been discovered to have a role in progression and metastasis of human cancers recently [4], [5].

Gastric cancer (GC), one of the most common malignancies, ranks the second highest in the mortality rate worldwide [6]. The development of GC is a multistep process with accumulation of genetic and epigenetic changes. A growing body of evidence indicates that aberrant expression of miRNAs is involved in the progression of GC [7], [8]. MiRNAs that deregulated in GC have been identified as modulators of cell growth, apoptosis, migration, and invasion [9], [10]. A previous study indicated that miR-497 was down-regulated in GC [11]. However, the underlying mechanism of miR-497 in GC was unexplored.

Eukaryotic translation initiation factor 4E (eIF4E), a key player in translational control, has been found to contribute to tumor occurrence and development [12], [13], [14]. Over-expression of eIF4E results in the enhanced expression of various oncogenes, such as cyclin D1, VEGF, and MMP-9 [15]. Although eIF4E control of the translation of many oncogenes has been well documented, the upstream regulation of eIF4E itself is seldom reported.

In the present study, we found that low expression of miR-497 was associated with poor prognostic phenotype of GC. Furthermore, we identify that miR-497 can regulate the proliferation and invasion of GC cells by targeting directly the eIF4E gene.

Section snippets

Cell lines and patient samples

Human GC cell lines and immortalized normal gastric mucosal epithelial cell line (GES-1) were purchased from the Institute of Biochemistry and Cell Biology of the Chinese Academy of Sciences (Shanghai, China). All cell lines were maintained in a humid wet atmosphere containing 5%CO2 at 37 °C in RPMI-1640 medium supplemented with 10% newborn bovine serum, 100 U/mL penicillin, and 100 mg/mL streptomycin. GC tissues were obtained from cancer center of Guangzhou Medical University. All GC specimens

Lower levels of miR-497 are frequently detected in GC tissues and associates with poorer overall survival of GC patients

Real-time PCR was performed to examine the expression levels of miR-497 in 36 pairs of GC and adjacent non-neoplastic tissues. As shown in Fig. 1 A, the expression levels of miR-497 were significantly decreased in GC tissues compared to adjacent non-neoplastic tissues (P < 0.05). The in situ hybridization assay also showed that miR-497 was down-regulated in GC tissues when compared with the non-neoplastic tissues (Fig. 1B).We further found that the expression level of miR-497 was lower in GC cell

Discussion

Despite the advancements in treatment options, improvements in GC patient survival have been limited owing to lack of early detection. Biomarkers to improve GC diagnosis, prognosis and prediction of treatment response therefore represent opportunities to improve patient outcome. In recent years, investigation of epigenetic biomarkers such as miRNA expression, have implicated that these alterations may be enticing translational biomarker candidates in GC. In the present study, we sought to

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