Dual Inhibition Of BRD4 And PI3K By SF2523 Suppresses Human Prostate Cancer Cell Growth In Vitro And In Vivo

Purpose:Bromodomain-containing protein 4(BRD4)and phosphatidylinositol 3-kinase(PI3K)are both key oncogenic proteins in human prostate cancer.In the current study,we examined the anti-prostate cancer cell activity by SF2523,a BRD4 and PI3K dual inhibitor.The underlying signaling mechanisms were also analyzed.Research contents and methods:MTT assay,clonogenicity assay and[H3]Thymidine DNA incorporation assay were utilized to examine the potential effection of SF2523 in the survival and proliferation of primary human prostate cancer cells and primary human prostate epithelial cells.Apoptosis assay(TUNEL staining),caspase-3/-9 activity assay,Western blotting assay and Annexin V-PI FACS assay were applied to test the potential effection of SF2523 in the cell apoptosis of primary human prostate cancer cells and primary human prostate epithelial cells.We compared the anti-prostate cancer cell activity between SF2523 and other known BRD4 or PI3K-AKT-mTOR inhibitors.Western blotting assay was performed to test the expression BRD4 regulatory protein(cyclin D1,c-Myc and androgen receptor)and activation of PI3K-Akt-mTOR pathway before and after SF2523 treatment in the primary human prostatic cancer cells.A severely combined immunodeficient(SCID)mice prostate cancer cell xenograft model was established to test the anti-prostate cancer cell activity of SF2523 in vivo.The prostate cancer cell xenografts were separated,and tumor tissues were subjected to Western blotting assay and immunohistochemistry(IHC)assay,expression and activation of BRD4-regulated proteins and PI3K-Akt-mTOR pathway were detected.Results:SF2523 powerfully inhibited the survival and proliferation of primary human prostate cancer cells.SF2523 induced apoptosis activation in prostate cancer cells.SF2523 was yet non-cytotoxic to the prostate epithelial cells.SF2523 was more potent than other known BRD4 or PI3K inhibitors in inhibiting prostate cancer cells;SF2523 downregulated BRD4-regulated genes(cyclin D1,c-Myc and androgen receptor)and almost blocked AKT-S6K1 activation in the prostate cancer cells.In vivo,SF2523 intraperitoneal administration at the well-tolerated dose inhibited human prostate cancer heterograft growth in severely combined immunodeficient(SCID)mice.BRD4-regulated genes(cyclin D1,c-Myc and androgen receptor)and AKT-S6K1 activation were inhibited in SF2523-treated tumors.Conclusion:Dual inhibition of BRD4 and PI3K by SF2523 suppresses human prostate cancer cell growth in vitro and in vivo.