The proliferation and differentiation of normal prostate epithelial cells depends upon the action of androgens produced by the testis. Prostate cancers retain the ability to respond to androgens in the initial stages of cancer development, but progressively become independent of exogenous androgens in advanced stages of the disease while maintaining the expression of functional androgen receptor (AR). In the present study, we have determined the potential of prostate cancer cells to synthesize androgens from cholesterol which may be involved in intracrine regulation of AR in advanced stages of the disease‥ Established androgen-independent prostate cancer cell lines, PC3 and DU145 cells, expressed mRNA and proteins for scavenger receptor type B1 (SRB1), steroidogenic acute regulatory (StAR) protein, cytochrome P450 cholesterol side chain cleavage (P450scc), 3β-hydroxysteroid dehydrogenase (3β-HSD) and other enzymes involved in androgen biosynthesis. Expression of all these proteins and enzymes was significantly higher in the androgen-independent derivative of LNCaP prostate cancer cells (C81) than in the androgen-dependent cell line (C33). In serum-free cultures, the androgen-independent C81 cells secreted ~5 fold higher testosterone than C33 cells as determined in the conditioned media by immunoassays. These cells could also directly convert radioactive cholesterol into testosterone which was identified by thin layer chromatography. These results for the first time show that prostate cancer cells in advanced stages of the disease could synthesize androgens from cholesterol and hence are not dependent upon testicular and/or adrenal androgens.

Diverse cellular processes relevant to cancer progression are regulated by the acetylation status of proteins. Among such processes is chromatin remodeling via histone proteins, controlled by opposing histone deacetylase (HDAC) and histone acetyltransferase (HAT) enzymes. Histone deacetylase inhibitors (HDACi) show great promise in preclinical cancer models, but clinical trials treating solid tumors have failed to improve patient survival. This is due in part to an inability of HDACi to effectively accumulate in cancerous cells. To address this problem we designed HDACi with secondary pharmacophores to facilitate selective accumulation in malignant cells. We present the first example of HDACi compounds targeted to prostate tumors by equipping them with the additional ability to bind the androgen receptor (AR) with non-steroidal antiandrogen moieties. Leads among these new dual-acting molecules bind to the AR and halt AR transcriptional activity at lower concentrations than clinical antiandrogens. They inhibit key isoforms of HDAC with low nanomolar potency. Fluorescent microscopy reveals varying degrees of AR nuclear localization in response to these compounds that correlates with their HDAC activity. These biological properties translate into potent anticancer activity against hormone dependent (AR+) LNCaP and to a lesser extent against hormone independent (AR−) DU145 prostate cancer, while having greatly reduced toxicity in non-cancerous cells. This illustrates that engaging multiple biological targets with a single chemical probe can achieve both potent and cell-type selective responses.

Diverse cellular processes relevant to cancer progression are regulated by the acetylation status of proteins, such as chromatin remodeling via histone proteins, controlled by opposing histone deacetylase (HDAC) and histone acetyltransferase (HAT) enzymes. Histone deacetylase inhibitors (HDACi) show great promise in preclinical cancer models, but clinical trials for solid tumors have failed to improve patient survival. This is due in part to an inability of HDACi to effectively accumulate in cancerous cells. To address this problem we designed HDACi with secondary pharmacophores to facilitate selective enrichment in malignant cells. We present the first example of HDACi compounds targeted to prostate tumors by equipping them (via “click” chemistry) with the secondary ability to bind the androgen receptor (AR) with non-steroidal antiandrogen moieties. Leads among these new duel-acting molecules bind to the AR and halt AR transcriptional activity at lower concentrations than clinical antiandrogens. They inhibit key isoforms of HDAC with improved potency over clinically approved HDACi, SAHA. Fluorescent microscopy reveals varying degrees of AR nuclear localization in response to these compounds. These biological properties translate into anticancer activity against hormone independent (AR-) DU145 prostate cancer, and even more so against hormone dependent (AR+) LNCaP, while having greatly reduced toxicity in non-cancerous cells. These compounds illustrate a “smart bomb” approach towards achieving selective, safe, and potent cancer therapies. Citation Format: Berkley E. Gryder, Michelle J. Akbashev, Michael K. Rood, Paulette Dillard, Shafiq Khan, Adegboyega K. Oyelere. Selectively targeting prostate cancer with antiandrogen-equipped histone deacetylase inhibitors. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Jun 19-22, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2013;73(13 Suppl):Abstract nr B50.