RAS P21 OVEREXPRESSION IS A LATE EVENT IN PROSTATE-CANCER

Several lines of evidence implicate the ras oncogene in tumorigenesis. However, changes in ras oncogene is uncommon in prostate cancer. We e valuated tumors from 55 patients with metastatic prostate cancer (50 l ymph nodes, 5 bone metastases), 10 patients with localized cancers and 35 diethylstilbestrol treated primary tumors. Also, 15 patients with benign prostatic hyperplasia and 23 with prostatic intraepithelial neo plasia (PIN) were investigated for ras p21 expression. Avidin biotin i mmunoperoxidase was used on formalin-fixed, paraffin-embedded tissues with the Pan-ras (Ab-1) monoclonal antibody. Antibody titration demons trated expression of ras p21 in none of the benign, PIN or DES-treated primary tumor specimens. However, 30% of untreated primary tumors and 94.5% of metastatic tumors (94% of lymph node metastases, 100% of bon e metastases) showed expression (p=0.00002). Semi-quantitative evaluat ion of ras protein expression revealed a significant correlation with Gleason score in lymph node metastases (p=0.001). This study suggests a possible role of ras oncogene in prostate cancer progression, metast asis and androgen independency.