In advanced prostate cancer, CREB (cAMP-responsive element-binding protein) binding protein (CBP) and its homolog EP300 are highly expressed; targeting the bromodomain of CBP is a new strategy for the treatment of prostate cancer. In the current study we identified Y08197, a novel 1-(indolizin-3-yl) ethanone derivative, as a selective inhibitor of CBP/EP300 bromodomain and explored its antitumor activity against prostate cancer cell lines in vitro. In the AlphaScreen assay, we demonstrated that Y08197 dose-dependently inhibited the CBP bromodomain with an IC50 value at 100.67 ± 3.30 nM. Y08197 also exhibited high selectivity for CBP/EP300 over other bromodomain-containing proteins. In LNCaP, 22Rv1 and VCaP prostate cancer cells, treatment with Y08197 (1, 5 μM) strongly affected downstream signaling transduction, thus markedly inhibiting the expression of androgen receptor (AR)-regulated genes PSA, KLK2, TMPRSS2, and oncogenes C-MYC and ERG. Notably, Y08197 potently inhibited cell growth in several AR-positive prostate cancer cell lines including LNCaP, 22Rv1, VCaP, and C4-2B. In 22Rv1 prostate cancer cells, treatment with Y08197 (1, 4, 16 μM) dose-dependently induced G0/G1 phase arrest and apoptosis. Furthermore, treatment with Y08197 (5 μM) significantly decreased ERG-induced invasive capacity of 22Rv1 prostate cancer cells detected in wound-healing assay and cell migration assay. Taken together, CBP/EP300 inhibitor Y08197 represents a promising lead compound for development as new therapeutics for the treatment of castration-resistant prostate cancer.
Keywords: 1-(indolizin-3-yl) ethanone derivative; CBP; EP300; Y08197; bromodomain inhibitor; prostate cancer.