[Immunohistochemical analysis of ras gene expression in human melanomas and melanocytic nevi]

Ras oncogene expression of malignant melanoma and melanocytic nevus has been immunohistochemically analyzed using monoclonal antibodies which were generated against ras oncogene products (p21ras) derived from Harvey sarcoma virus. Freshly frozen tissues from 11 melanomas and 8 melanocytic nevi were examined by immunofluorescence method, and also, formalin-fixed and paraffin-embedded tissues from 26 melanomas and 24 melanocytic nevi by ABC method. There existed differences of p21ras expressions by the type of melanoma that nodular melanoma, epithelioid cell type melanoma, and deeply invaded melanoma revealed higher reactivity with anti-p21ras monoclonal antibody than the other types. The reactivity of melanomas were, thus, well correlated to the degree of malignancy of melanomas. In melanocytic nevi, dermally located nevus cells had relatively strong reactivity with anti-p21ras monoclonal antibody in contrast to junctional type nevi and the nevus cells located in the epidermis in compound type nevi which did not show the positive reaction. p21ras expressions in both melanomas and melanocytic nevi may represent a marker of the immature state of cells corresponding to early stages of the melanocyte evolution as well as the morphologic and enzymologic characteristics.