IMMUNOHISTOCHEMICAL DEMONSTRATION OF EPITHELIAL GLUTATHIONE-S-TRANSFERASE ISOENZYMES IN NORMAL, BENIGN, PREMALIGNANT AND MALIGNANT HUMAN ORAL-MUCOSA

The expression and localization of glutathione S-transferase (GST) iso enzymes in the epithelium of normal oral mucosa (n=9), overlying react ive fibrous hyperplasia (n=9), and of potentially malignant [leukoplak ia (n=25), submucous fibrosis (n=12), verrucous hyperplasia (n=16)] an d malignant [squamous cell carcinoma (n=36), verrucous carcinoma (n=13 )] oral lesions were examined immunohistochemically using polyclonal a ntibodies raised against GST isoenzymes (alpha, mu and pi) with the st andard avidin-biotin-peroxidase complex (ABC) method. GST alpha, mu an d pi were almost completely absent in the epithelium of normal oral mu cosa and overlying benign fibrous tissues. GST alpha staining was cyto plasmic and focally positive, while GST mu staining was similar to but weaker than that seen for GST alpha. GST pi showed both cytoplasmic a nd nuclear staining and was expressed in 60% of leukoplakias with mild dysplasia (n=15), 80% of leukoplakias with moderate to severe dysplas ia (n=10). 75% of submucous fibrosis samples (n=12), 75% of verrucous hyperplasias (n=16), 77% of verrucous carcinomas (n=13), 81% of well-d ifferentiated squamous cell carcinomas (n=26) and 70% of moderate- to poorly-differentiated squamous cell carcinomas (n=10). In addition, GS T pi expression was independent of the state of differentiation of ora l cancers. Since GST pi was significantly over-expressed in the oral p remalignant and malignant lesions, the kinetics of GST pi-positive cel ls and the value of GST pi as a tumor marker in oral carcinogenesis ne ed further investigation.