AZD5153 Inhibits Prostate Cancer Cell Growth in Vitro and in Vivo.

Bromodomain-containing protein 4 (BRD4) overexpression participates in prostate cancer progression by enhancing the transcriptional activity and expression of several key oncogenes. AZD5153 is a novel BRD4 inhibitor. Prostate cancer cells were treated with AZD5153. Cell survival was tested by MTT assay and clonogenicity assay. Cell proliferation was tested by [H3] DNA incorporation assay. Cell apoptosis was tested by caspase-3/-9 activity assay, Histone DNA ELISA assay, Annexin V FACS assay and TUNEL staining assay. Cell cycle progression was tested by propidium iodide (PI) FACS assay. Signaling was tested by Western blotting assay. The nude mice PC-3 xenograft model was applied to test AZD5153's activity in vivo. AZD5153 inhibited proliferation and survival of established and primary prostate cancer cells. AZD5153 induced apoptosis activation and cell cycle arrest in prostate cancer cells. AZD5153 was non-cytotoxic to the prostate epithelial cells. AZD5153 downregulated BRD4 targets (cyclin D1, Myc, Bcl-2, FOSL1 and CDK4) in PC-3 and primary prostate cancer cells. Further studies show that AKT could be the primary resistance factor of AZD5153. Pharmacological inhibition or genetic depletion of AKT induced BRD4 downregulation, sensitizing AZD5153-induced cytotoxicity in PC-3 cells. In vivo, AZD5153 oral administration inhibited PC-3 xenograft tumor growth in nude mice. Its anti-tumor activity was further enhanced with co-treatment of the AKT specific inhibitor MK-2206. Together, our results indicate a promising therapeutic value of the novel BRD4 inhibitor AZD5153 against prostate cancer cells.