Expression of Bcl-2, Bax, and p53 in high-grade prostatic intraepithelial neoplasia and localized prostate cancer: relationship with apoptosis and proliferation.

BACKGROUND

Apoptosis-regulating genes have been shown to be important in the biology of prostate cancer. The aim of this study was to examine and correlate the expression of the apoptosis-regulating genes bcl-2, bax, and p53 with the frequency of apoptosis and rate of proliferation in benign prostatic epithelium (BP), prostate cancer, and high-grade prostatic intraepithelial neoplasia (HGPIN), which is currently considered the most likely precursor of prostate cancer.

METHODS

Forty-four patients with histologically proven prostate cancer were investigated. All the men underwent radical prostatectomy. Immunohistochemistry was performed to assess expression of bcl-2, bax, and p53, and proliferation rate, as measured by the Ki-67 index. The frequency of apoptotic bodies was assessed by morphological criteria.

RESULTS

The apoptotic index (AI) was highest in prostate cancer, and was significantly greater in HGPIN compared to benign prostate. The Ki-67 index was greatest in cancer, intermediate in HGPIN, and lowest in BP. The AI was increased in areas of BP in patients treated with neoadjuvant androgen ablation. No change in AI was seen in treated cases of HGPIN or cancer. Accumulation of p53 protein was infrequent in prostate cancer (2/43: 4.6%), and was absent in HGPIN. Bcl-2 overexpression was present in 2.3% of cancers (1/43) and in 34.9% of cases of HGPIN (15/43). Bax expression was seen in all cases of cancer and HGPIN. There was no correlation between bcl-2 expression and the apoptotic and Ki-67 indices in HGPIN.

CONCLUSIONS

p53 and bcl-2 expression is infrequent in clinically organ confined prostate cancer. Bcl-2 expression is significantly higher in HGPIN than in both the associated prostate cancer and BP. The AI and Ki-67 index appeared intermediate in the putative precursor lesion HGPIN compared to prostate cancer and BP.