IMMUNOHISTOCHEMICAL STUDY OF ALPHA-CLASS, MU-CLASS AND PI-CLASS GLUTATHIONE-S-TRANSFERASE EXPRESSION IN MALIGNANT-MELANOMA

Human pi, mu and alpha class glutathione S transferases (GST) have bee n localized immunohistologically in normal skin, naevi and melanoma. P i GSTs were found principally in the stratum basalis and, to a lesser extent, in the superficial layers. Normal melanocytes showed strong nu clear and cytoplasmatic staining. Distribution of GST mu in the epider mis showed that only the stratum basale, where melanocytes are located , stained well but with weak nuclear staining. Normal melanocytes were also well stained. The alpha GSTs were relatively abundant in the upp er strata and to a lesser extent, in the basal layers. The absence of nuclear staining gives these cells a target appearance. Normal melanoc ytes showed strong cytoplasmatic staining. The pi GSTs seem to be most persistently. and strongly expressed in malignant melanoma (MM), but mu GSTs are also found, whereas the alpha GSTs were only occasionally present, The finding of the GST mu in the melanocytes of the basal lay er raises new questions regarding the role of GST mu in these cells be cause of the inherent risk of MM in individuals with a congenital defi ciency of this isoenzyme. The role of GSTs in the resistance of cells to chemotherapy is also discussed.