EXPRESSION OF THE C-MET HGF RECEPTOR IN HUMAN MELANOCYTIC NEOPLASMS -DEMONSTRATION OF THE RELATIONSHIP TO MALIGNANT-MELANOMA TUMOR PROGRESSION

The c-MET proto-oncogene encodes the receptor for the Hepatocyte Growt h Factor/Scatter Factor, which is known to mediate mitogenic, motogeni c and invasive responses of several cell types. We have analysed by im munohistochemistry and biochemically the expression of c-MET in benign and malignant melanocytic lesions. The Met/HGF receptor which in the melanocytic lineage displays the structural features of the authentic receptor was undetectable in tissue melanocytes and in nevocytic nevi. Only four out of 23 primary melanomas scored positive. Expression was increased to a significant level in 17 out of the 44 metastatic lesio ns examined. The c-MET expression was homogeneous in multiple metastas es from the same patients. Comparative analyses showed both lack of co rrelation with the expression of the tumour progression associated ICA M-1 adhesion molecule and, in 23% of cases, co-expression with the c-K IT encoded receptor. These findings show that the c-MET gene is expres sed at late stages of melanoma progression and suggest that the presen ce of Met/HGF receptor may contribute to the acquisition of an invasiv e phenotype.