Altered placental glutathione S-transferase foci as a tumor marker during rat lingual carcinogenesis.

OBJECTIVE: To evaluate the value of placental glutathione S-transferase (GST-P) as a tumor marker during lingual carcinogenesis in two strains of rats. METHODS: Dark-Agouti (DA) and Wistar/Furth (WF) rats were given with 4-nitroquinoline 1-oxide (4NQO) in drinking water with a defined treatment schedule. Immunocytochemical expression of GST-P was studied using experimental materials obtained at 2, 4, 8, 12, 16, and 26 weeks of 4NQO treatment. GST-P+ foci in the tongue epithelium were counted for each experimental rat and quantitative data were compared between groups. RESULTS: The animal experiment demonstrated marked differences in tumorigenicity between the two strains of rats, with DA exhibiting earlier responses to 4NQO and having a higher tumor incidence than WF rats. GST-P+ foci occurred earlier in the tongue mucosa of DA rats than in that of WF. With continued 4NQO application, there was a progressive increase in the number and size of GST-P+ foci in both strains of animals, but those of DA groups revealed a greater increase in comparison to those of WF groups. CONCLUSIONS: These results indicate that GST-P is a sensitive marker that may reflect the metabolic patterns of preneoplastic cells during early stages of rat lingual carcinogenesis, and that rapid expansion of such putative initiated cells may have the propensity for malignant transformation.