Bcl-2 proto-oncogene expression in low- and high-grade prostatic intraepithelial neoplasia

OBJECTIVE: To determine the incidence of bcl-2 protein expression in low- and high-grade prostatic intra-epithelial neoplasia (PIN) lesions, and to explore the role of bcl-2 in prostatic tumorigenesis. Materials and methods Immunoreactivity for bcl-2 was examined in 10 samples of benign prostatic hyperplasia (BPH), 13 of primary prostatic adenocarcinoma, 15 of high-grade PIN and 18 of low-grade PIN. All immunostaining results were scored for the approximate percentage of positive tumour cells and relative immunostaining intensity (score range 0-12). RESULTS: In all BPH samples, bcl-2 staining was detected consistently in the basal cell layer of the ducts and acini, but no staining was ever apparent in luminal cells. The immunoreactivity for bcl-2 was heterogeneous in the prostatic carcinomas and bcl-2 protein expression was present in six samples. In these six bcl-2-positive tumours, the mean (range) staining score was 1.15 (1-6). There was detectable expression of bcl-2 in low- and high-grade PIN in all cell layers; immunoreactivity was present in 10 of 15 high-grade PIN lesions, with a mean (range) score of 1.14 (1-4), and in 12 of 18 samples of low-grade PIN, with a mean (range) score of 1.77 (1-6). CONCLUSIONS: The high incidence of bcl-2 protein expression in low- and high-grade PIN lesions suggests that bcl-2 protein expression is associated with early prostate tumorigenesis.