Objective  To verify the expression of miR-125a-5p, signal transducer and activator of transcription 3 (STAT3) in gastric cancer and their biological functions.

  Methods  Gastric cancer tissues were isolated from 30 patients with gastric cancer, and real-time fluorescent quantitative PCR (qRT-PCR) and Western blot (WB) were used to detect expression of miR-125a-5p and STAT3 in gastric cancer tissue and non-cancerous gastric tissue. After cell transfection, Cell Counting Kit-8 (CCK-8) was used to detect cell viability, and flow cytometry was used to detect cell cycle and apoptosis. Transwell migration test was used to detect migrating cells. The target relationship between miR-125a-5p and STAT3 was verified by dual luciferase reporter gene detection. The tumor inhibitory effect of miR-125a-5p was verified by tumor formation experiment in nude mice in vivo.

  Results  The expression of miR-125a-5p in gastric cancer tissue was significantly lower than that in non-cancerous gastric tissue (P < 0.05). In gastric cancer cell lines, the expression of miR-125a-5p was also significantly lower than that in the normal epithelial cells (P < 0.05). In addition, authors transfected gastric cancer cells with miR-125a-5p mimics, and the results showed that the over-expression of miR-125a-5p was able to inhibit the proliferation, migration and invasion of gastric cancer cells by targeting STAT3. Tumor formation experiment in nude mice verified that over-expression of miR-125a-5p was able to inhibit tumor proliferation and promote tumor cell apoptosis.

  Conclusion  MiR-125a-5p can inhibit tumors by inhibiting the expression of STAT3, and these findings will provide reliable theoretical bases for clinical targeted therapy and early selection of biomarkers.