Human androgen receptor expression in prostate cancer following androgen ablation.

Abstract

Metastatic prostate cancer kills patients because their tumor cells fail to respond to combined androgen blockade (CAB) or respond and then relapse. To understand the molecular basis of androgen-insensitive growth of prostate tumor cells, we evaluated changes in human androgen receptor gene (hAR) mRNA levels in patients with prostate cancer treated with CAB. The study was carried out using quantitative reverse-transcriptase polymerase chain reaction analysis. The level of hAR mRNA were compared to serum prostate-specific antigen and the mutant status of p53 in the tumor. hAR was expressed in 44 of 46 tumors from untreated patients, as opposed to 30 of 45 from those who had received CAB (p = 0.001). These 30 were from 8 of 9 stage D patients and from 22 of 36 patients on downsizing CAB therapy prior to radical prostatectomy. Expression was most often seen in high stages (56% of stage B vs. 89% of stage D) and high grades (52% of Gleason 3-7 vs. 92% of Gleason 8-10, p = 0.015). No tumor with a missense p53 mutation had hAR expression following CAB. Twenty-two patients following CAB were found to have undetectable serum prostate-specific antigen levels, while their tumor expressed hAR. hAR expression after CAB is seen preferentially in high-grade, high-stage tumors, the type of prostate carcinomas that fail to have a durable remission. Undetectable serum prostate-specific antigen from tumors that remain hAR positive may predict relapse after hormonal ablative therapy.