Gamma-glutamyl transpeptidase activity during carcinogenesis of hamster buccal pouch epithelium

Gamma-glutamyl transpeptidase (GGT) activity has been demonstrated histochemically in a number of experimentally induced neoplasms and has been suggested as a label for potential precursors for the development of squamous cell carcinomas. This study explores the kinetics of GGT-stained cell populations, their correlation with the hypothesized initiated cells and evidence of malignant transformation of epithelium in hamster buccal pouch by a 15-week regime of tri-weekly topical application of 7, 12-dimethylbenz[a]anthracene (DMBA) in mineral oil. GGT-positive foci were detected histochemically in tissue sections as early as 1 week after application of the carcinogen, when there was no morphological evidence of dysplasia. The average number of the GGT-positive foci in each experimental period was found to increase with time. Even though the majority of the foci were small, consisting of only a single cell or a small group of cells, a few larger GGT-positive lesions were noted, particularly in the later period of the experiment. A total of 66 grossly visible neoplasms were found. Thirty-seven of these were submitted for GGT staining. Thirty-two (86.5%) of these showed patchy GGT activity, primarily in the superficial epithelial cells and/or the keratin. In the non-neoplastic epithelium, the GGT staining could involve any or all layers of cells. GGT activity was not detected in untreated or mineral oil-treated mucosa. The results of this study support the hypothesis that GGT activity may label potential precursors for the development of squamous cell carcinomas.