The value of placental glutathione S-transferase and gamma-glutamyl transpeptidase as markers of altered foci during hamster pouch carcinogenesis.

This study investigated the value of an immunohistochemical demonstration of placental glutathione S-transferase (GST-P) and a histochemical demonstration of gamma-glutamyl transpeptidase (GGT) for the detection of putative preneoplastic lesions and squamous cell carcinomas in the Syrian golden hamster buccal pouches treated with 7,12-dimethylbenz[a]anthracene (DMBA). The results showed that GST-P foci appeared earlier than GGT foci, that the GST-P foci were much more numerous than GGT foci and that most of the GGT positive foci were GST-P positive. All tumors stained strongly positive for GST-P. Only 62.5% of tumors stained for GGT and the staining was usually weak and involved only the superficial layer of the epithelium or keratin, suggesting that the enzyme activity in the basal cells had decreased with formation of neoplasms. The length percentage of basal cells that were GST-P positive increased rapidly during the experiment and by week 12, 25% of the basal cells exhibited GST-P staining. Such rapid expansion of the putative initiated cells may explain the early development of chemically induced invasive squamous cell carcinoma (weeks 10-12) in 100% of hamsters.