MiR-638 acts as a tumor suppressor gene in gastric cancer

Gastric cancer is one of the major causes of cancer mortality. Several microRNAs play a role in the tumor growth and invasion. However, the underlying molecular mechanism remains poorly understood. We detected the miR-638 expression levels in tumor samples and adjacent noncancerous tissues from 68 patients with gastric cancer as well as in the gastric cancer cell line SGC-7901 and SC-M1. The cell cycle was analyzed by flow cytometry, cell proliferation was observed by CCK-8 assay and cell invasion was detected using Transwell assay. MiR-638 was down-regulated in human GC tissues and its expression level was negatively correlated to TNM stage and lymph metastasis. In the cell lines, aberrant expression of miR-638 was related to the cell proliferation, cell cycle and invasion. We also found that SOX2 had a negative correlation with miR-638 in GC tissues, and miR-638 overexpression could decrease SOX2 expression level by directly binding the 3'-UTR of SOX2. in vitro, down-regulating SOX2 by siRNA could counteract the effect of miR-638 inhibitor on GC cells proliferation and invasion. Our results demonstrate that miR-638 may play a pivotal role in the growth and invasion of GC.