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.