HER2 protein expression and gene amplification in androgen-independent prostate cancer

The role of the HER2 receptor remains uncertain in the pathogenesis and pro gression of human prostate cancer. Previous studies have reported widely, d ivergent rates for HER2 expression in primary prostate tumors, probably owi ng to significant methodologic differences in the studies. Few data exist a bout the frequency of HER2 protein overexpression and gene amplification in androgen-independent prostate cancer (AIPC) although recent xenograft mode ls suggest HER2 expression may be up-regulated in the transition from andro gen-dependent to androgen-independent disease. We studied the role of HER2 protein in AIPC by, immunohistochemical and fluorescence in situ hybridizat ion (FISH) anal,ses on AIPC specimens using well-characterized and validate d reagents. Fourteen (36%) of 39 specimens expressed HER2; however, only, 2 (5%) had moderate (2+) expression, and 2 (5%) had high-level (3+) expressi on. Two (6%) of 36 specimens had gene amplification by FISH. These data sug gest that HER2 protein overexpression and gene amplification are relatively , uncommon in AIPC.