Evaluating Anti‐Androgen Resistance by In‐Vitro Selection

Anti‐androgens, such as flutamide and bicalutamide (Casodex®), used alone or in conjunction with chemical castration, have been used in the treatment of prostate cancer (PCa) for decades. However, as many as 30%–40% of patients treated with anti‐androgens acquire a therapy‐resistant phenotype after one to three years of treatment. Furthermore, some patients experience clinical improvement upon cessation of anti‐androgens, a condition known as anti‐androgen withdrawal syndrome. Anti‐androgen withdrawal syndrome has been associated with mutations to the AR that cause an agonist response to anti‐androgens and is one of the most difficult forms of PCa to treat. The goal of this project is to redesign anti‐androgens to evade molecular mechanisms that lead to anti‐androgen withdrawal syndrome. To accomplish this, novel analogs, PLM1 and PLM6, were developed that remain antagonists towards three AR mutants associated with anti‐androgen withdrawal syndrome. In this study, long‐term growth analyses of the human LNCaP cell line in the presence of PLM1, PLM6, or bicalutamide have been performed to identify potential AR mutants that would represent an anti‐androgen withdrawal phenotype. After approximately 4–6 weeks, resistant colonies developed and were selected. DNA sequence data of the resistant colonies showed various AR mutations. PLM6 proved to be superior to PLM1 as fewer resistant colonies were observed compared to bicalutamide and PLM1. This suggests that PLM6 may be effective against this form of resistant PCa. This work is supported by the Howard Hughes Medical Institute Undergraduate Science Education program and the National Institutes of Health, NIDDK; 3‐R01‐DK054257‐09.