Polycomb-mediated silencing of miR-8 is required for maintenance of intestinal stemness in Drosophila melanogaster.

Balancing maintenance of self-renewal and differentiation is a key property of adult stem cells. The epigenetic mechanisms controlling this balance remain largely unknown. Herein, we report that the Polycomb Repressive Complex 2 (PRC2) is required for maintenance of the intestinal stem cell (ISC) pool in the adult female Drosophila melanogaster. We show that loss of PRC2 activity in ISCs by RNAi-mediated knockdown or genetic ablation of the enzymatic subunit Enhancer of zeste, E(z), results in loss of stemness and precocious differentiation of enteroblasts to enterocytes. Mechanistically, we have identified the microRNA miR-8 as a critical target of E(z)/PRC2-mediated tri-methylation of histone H3 at Lys27 (H3K27me3) and uncovered a dynamic relationship between E(z), miR-8 and Notch signaling in controlling stemness versus differentiation of ISCs. Collectively, these findings uncover a hitherto unrecognized epigenetic layer in the regulation of stem cell specification that safeguards intestinal homeostasis.

CYP17A1 and Androgen-Receptor Expression in Prostate Carcinoma Tissues and Cancer Cell Lines.

BACKGROUND: CYP17A1 is involved in the steroidogenesis of dehydroepiandrosterone and androstenedione. CYP17A is a target for the hormonal treatment of prostate cancer (PCa). OBJECTIVES: To investigate the role of CYP17A1 as a driver of PCa growth. MATERIALS AND METHODS: We examined the expression of CYP17A1 and of androgen receptors (AR) in PCa specimens and in PCa cell lines. RESULTS: CYP17A1 was strongly expressed in the cytoplasm of PCa cells (median 50% of cancer cells, range 0-100%). The nuclear AR expression in cancer cells was directly related with CYP17A1 (p < 0.0001, r = 0.51). The hormone dependent 22Rv1 cell line expressed the CYP17A1 and AR protein and mRNA, in contrast to the PC3 and DU145 cell lines (p < 0.0001). Testosterone and dexamethasone induced nuclear expression of AR and this effect was abolished by abiraterone. CYP17A1 levels were not affected by the incubation with testosterone, while abiraterone significantly reduced its expression. Abiraterone reduced the growth rate and migration of testosterone stimulated 22Rv1 cells. CONCLUSIONS: CYP17A1 is strongly expressed in half about of human prostate carcinomas, implying an intracellular androgen synthesis by cancer cells. Abiraterone effectively blocked nuclear accumulation of AR and suppressed CYP17A1 expression. CYP17A1 may function as a biomarker to select the best hormonal anticancer therapy.

Comparison of the effect of the antiandrogen apalutamide (ARN-509) versus bicalutamide on the androgen receptor pathway in prostate cancer cell lines.

Apalutamide (ARN-509) is an antiandrogen that binds selectively to androgen receptors (AR) and does not show antagonist-to-agonist switch like bicalutamide. We compared the activity of ARN versus bicalutamide on prostate cancer cell lines. The 22Rv1, PC3, and DU145 cell lines were used to study the effect of ARN and bicalutamide on the expression cytoplasmic/nuclear kinetics of AR, AR-V7 variant, phosphorylated AR, as well as the levels of the AR downstream proteins prostate-specific antigen and TMPRSS2, under exposure to testosterone and/or hypoxia. The effects on autophagic flux (LC3A, p62, TFEB, LAMP2a, cathepsin D) and cell metabolism-related enzymes (hypoxia-inducible factor 1α/2α, BNIP3, carbonic anhydrase 9, LDHA, PDH, PDH-kinase) were also studied. The 22Rv1 cell line responded to testosterone by increasing the nuclear entry of AR, AR-V7, and phosphorylated AR and by increasing the levels of prostate-specific antigen and TMPRSS2. This effect was strongly abrogated by ARN and to a clearly lower extent by bicalutamide at 10 µmol/l, both in normoxia and in hypoxia. ARN had a stronger antiproliferative effect than bicalutamide, which was prominent in the 22Rv1 hormone-responsive cell line, and completely repressed cell proliferation at a concentration of 100 µmol/l. No effect of testosterone or of antiandrogens on autophagy flux, hypoxia-related proteins, or metabolism enzyme levels was noted. The PC3 and DU145 cell lines showed poor expression of the proteins and were not responsive to testosterone. On the basis of in-vitro studies, evidence has been reported that ARN is more potent than bicalutamide in blocking the AR pathway in normoxia and in hypoxia. This reflects a more robust, dose-dependent, repressive effect on cell proliferation.