Ki-67 antigen and P53 protein expression in benign and malignant prostatic lesions. Immunohistochemical quantitative study.

Ki-67 and P53 expression were studied using immunohistochemistry on tissue samples obtained during transurethral electroresection or needle biopsy in 62 patients with prostatic lesions: group 1 (n = 15)--benign prostatic hyperplasia (BPH), group 2 (n = 10)--high-grade prostatic intraepithelial neoplasia (PIN 3), group 3 (n = 10)--low-grade prostatic carcinoma (PC, Gleason score 2-4), group 4 (n = 12) intermediate-grade prostatic carcinoma (PC, Gleason score 5-7) and group 5 (n = 15) high-grade prostatic carcinoma (PC, Gleason score 8-10). Moreover, in the groups examined the associations between expression of Ki-67 and P53 were analysed. Paraffin-embedded tissue samples were immunostained with monoclonal antibody anti-P53 and polyclonal antibody anti-Ki-67 using avidinbiotin-peroxidase method. Our study revealed lack of Ki-67 and P53 immunoreactivity in BPH. Only 3 out of 10 high-grade PIN exhibited Ki-67 positivity, but there was no immunopositivity of P53 protein in this group. Although immunopositivity of Ki-67 increased with the histological grade of prostatic cancer, the differences in Ki-67 expression between intermediate and high-grade cancer did not reach statistical significance. A similar level of Ki-67 reactivity in intermediately-differentiated and poorly-differentiated prostate cancer suggests a similar biology of these cancers. P53 protein positivity was noted in 62.2% cases of prostate cancer. Moreover, the highest level of P53 accumulation in intermediate-grade carcinomas may predict the aggressive progression and risk of metastases in these cases. No significant differences in P53 immunopositivity between low-grade and high-grade PC were noted. Interestingly, only in low-grade PC there was a significant positive correlation between expression of Ki-67 and P53 protein.