MicroRNA-133a functions as a tumor suppressor in gastric cancer.

MicroRNAs (miRNAs) are small and highly conserved non-coding RNAs that regulate gene expression of target mRNAs through posttranscriptional inhibition involved in the tumorigenesis and progression of multiple malignancies. Although miR-133a has been shown to function as a tumor suppressor in some cancers, the clinical significance and function of miR-133a in gastric cancer remain unclear. Hence, we were focused on the expression and mechanisms of miR-133a in the development of gastric cancer in this study. It was found that the expression of miR-133a was downregulated (P<0.001), while transgelin-2 (TAGLN2) was upregulated (P<0.05) in primary gastric cancer tissues, compared to the adjacent non-cancerous tissues (ANCT). Furthermore, decreased expression of miR-133a and increased expression of TAGLN2 were both associated with lymph node metastases in patients with gastric cancer (P<0.001; P=0.011). Functional analysis studies revealed that ectopic expression of miR-133a reduced cell proliferation and invasion, and induced cell apoptosis and cycle arrest via suppressing the level of TAGLN2 from transcriptional and translational levels and downregulated the expression of proliferating cell nuclear antigen (PCNA) and matrix metalloproteinase-2 (MMP-2) in gastric cancer cells. In conclusion, these results demonstrate that decreased expression of miR-133a is associated with the lymph node metastases of patients with gastric cancer. Overexpression of miR-133a inhibits cell growth and invasion and induces cell apoptosis and cycle arrest through repressing TAGLN2 gene, suggesting that miR-133a might be used as a biomarker or therapeutic target for the treatment of gastric cancer.