miR-133a, directly targeted USP39, suppresses cell proliferation and predicts prognosis of gastric cancer

Gastric cancer has high incidence and mortality, and the mortality ranks second only to lung cancer. Downregulation of miR-133a has been observed in certain types of tumors, and it is involved in gastric cancer. The aim of the present study was to explore the molecular mechanisms of miR-133a and ubiquitin-specific protease 39 (USP39) in gastric cancer. Western blot analysis and RT-PCR were employed to measure miR-133a and USP39 expression. To confirm whether miR-133a targeted USP39, we conducted a luciferase reporter assay. We utilized 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay to detect the effects of miR-133a on gastric cell proliferation. miR-133a was significantly downregulated in cancer tissues and cell lines (HGC-27 and MGC-803), while the expression level of USP39 was higher in tumor tissues than in paracancerous tissues. Upregulated expression of miR-133a and/or USP39 downregulation could inhibit cell proliferation in gastric cancer cells. Furthermore, USP39 was identified as a direct target of miR-133a and the inverse relationship between them was also observed. USP39 was a firsthand target of miR-133a and there was a negative correlation between them. In addition, a low expression of miR-133a or overexpression of USP39 predicted poor prognosis. In conclusion, miR-133a may be a novel therapeutic target of microRNA-mediated suppression of cell proliferation in CC, but the role of the miR-133a/USP39 axis in CC progression needs further study.