Placental glutathione S-transferase isoenzyme expression in polycyclic aromatic hydrocarbon-induced hamster buccal pouch mucosa.

Placental glutathione S-transferase (GST-P) immunohistochemical activity in polycyclic aromatic hydrocarbon (PAH)-induced hamster buccal pouch mucosa (HBPM) was investigated. Equimolar concentrations of 3,4-benzo[a]pyrene (BP), benz[a]anthracene (BA) and 20-methylcholanthrene (MC) in mineral oil solution were applied three times per week for up to 20 weeks to bilateral pouches of the hamsters. Control pouches were treated with 7,12-dimethylbenz[a]anthracene (DMBA), turpentine and mineral oil, respectively. A significant increase in the number of GST-P foci in the dysplastic pouches was found when compared with the hyperkeratotic and hyperplastic pouches after 5 weeks' DMBA treatment. The average numbers of GST-P positive stainings were significantly higher in DMBA-treated groups than in BP-, BA- and MC-treated groups killed at 5, 20, 30 and 40 weeks. No GST-P positivity was found in any pouches treated with turpentine and mineral oil observed at various periods. These results highlight the carcinogen-specificity of GST-P chemically induced in HBPM and indicate that induction of GST-P in pouch mucosa is linked with the carcinogenic potency of PAHs. The present study underpins the hypothesis that GST-P chemically induced in HBPM is an early marker of ongoing squamous cell carcinogenesis.