THE IMMUNOHISTOCHEMICAL LOCALIZATION OF DRUG-METABOLIZING-ENZYMES IN PROSTATE-CANCER

The major groups of enzymes involved in activating and detoxifying the rapeutic drugs, not least several anti-cancer drugs, include the cytoc hromes P350 (P450s), epoxide hydrolase, and glutathione S-transferases (GSTs). The expression of these enzymes in malignant tumours is one p ossible mechanism of anti-cancer drug resistance. This study has inves tigated the presence, cellular localization, and distribution of drug- metabolizing enzymes in prostate cancer. The P450 subfamilies CYP1A, C YP2C, and CYP3A were present in 63, 25, and 61 per cent of tumours, re spectively. Epoxide hydrolase was identified in 96 per cent of tumours . GST-a and GST-mu were expressed in 29 and 41 per cent of tumours, re spectively, while there was no immunoreactivity for the pi form of GST . The absence of GST-pi in prostate cancer contrasts with the frequent expression of GST-pi observed in other types of malignant tumour. In non-neoplastic prostatic epithelium, there was expression of CYP1A, CY P2C, epoxide hydrolase, and the different forms of GST, while there wa s no apparent immunoreactivity for CYP3A.