Androgen receptor gene amplification and protein expression in recurrent prostate cancer

The androgen receptor (AR) is highly expressed in androgen dependent and recurrent prostate cancer, suggesting that it has a role in tumor growth and progression after androgen deprivation. AR amplification may contribute to androgen receptor activation in relative androgen absence.

Formalin fixed and frozen specimens of recurrent prostate cancer were obtained by transurethral resection from men with increasing serum level of prostate specific antigen in whom urinary retention developed. AR amplification and X-chromosome number were determined by 2-color fluorescence in situ hybridization, and AR protein expression was determined by automated image analysis. We compared clinical characteristics and survival of patients with recurrent prostate cancer whose tumors did or did not exhibit AR amplification and X-chromosome polysomy.

Thirty-three percent of the 24 recurrent prostate cancer specimens 8 (33%) showed AR amplification. AR was more intensely immunostained in tumors with amplified (AMP) AR (mean optical density 0.36 +/- 0.07) than in tumors lacking amplification (NO AMP) (mean optical density 0.24 +/- 0.09). No differences were found between the 2 groups when comparing serum levels of prostate specific antigen (AMP 11.9, 14.8; NO AMP 26.0, 60.3), Gleason sum (AMP 9.0, 0.5; NO AMP 9.0, 1.0), clinical TNM stage (AMP 4 cases M0, M1 4; NO AMP 8 M0, 8 M1), race (AMP 6 white and 2 black men, NO AMP white and 7 black men) or survival in months (AMP 47.5, 28.5; NO AMP 33.5, 72.0). Three of the recurrent prostate cancer specimens (13%) demonstrated X-chromosome copy number 2 or greater and no differences were found when comparing clinical characteristics between these groups.

AR amplification in recurrent prostate cancer results in higher levels of AR protein expression but does not affect survival.