ESTAT3 Inhibitor AG-490 Inhibits the Growth of Prostate Cancer by miR-503-5p Both In Vivo and In Vitro

OBJECTIVE: To explore the effect and the related mechanism of STAT3 inhibitor AG-490 on inhibiting the proliferation of prostate cancer cells. METHODS: PC3 cells and DU145 cells were cultured stably and treated with AG-490 to detect the changes in the activity of PC3 cells and DU145 cells. Thirty 6-8 weeks male BALB/c nude mouse were randomly divided into a control group, a DMSO group, and an AG-490 group to detect differences in various indexes . RESULTS: The overexpression of miR-503-5p depends on the activation of STAT3. After treatment with AG-490, The proliferation and invasion of PC3 cells and DU145 cells and the expression of miR-503-5p were all reduced. Luciferase reporter assay demonstrated that the target proteins of miR-503-5p include PDCD4, TIMP-3, and PTEN. After treatment with AG-490, the expression of PDCD4, TIMP-3, and PTEN in cells was significantly up-regulated. IL-6-induced overexpression of miR-503-5p and restored the expression of STAT3, demonstrating the correlation between STAT3 and miR-503-5p. AG-490 can inhibit tumor growth and induce tumor cell apoptosis in the PC3 BALB/c nude mouse xenograft model. Western blotting and immunohistochemical staining showed that the expression levels of STAT3, Ki67, Bcl-2 and MMP-2 in the AG-490 group were significantly reduced, and the expression of PDCD4, TIMP-3 and PTEN increased. CONCLUSION: AG-490 can inhibit the growth of prostate cancer cells in a miR-503-5p-dependent manner by targeting STAT3. AG-490 is expected to become a new candidate drug for the treatment of prostate cancer.