IMMUNOREACTIVITY OF ALPHA-MELANOCYTE-STIMULATING HORMONE, ADRENOCORTICOTROPIC HORMONE AND BETA-ENDORPHIN IN CUTANEOUS MALIGNANT-MELANOMA AND BENIGN MELANOCYTIC NEVI

Melanocyte-stimulating hormone (MSH) has been reported to enhance the experimental metastatic behaviour of melanoma cells in the mouse model . alpha-MSH production and MSH receptor (melanocortin 1 receptor gene) expression have been detected in cultured normal human melanocytes an d metastasized melanomas, The exact role of MSH in the metastatic beha viour of human melanoma cells is, however, not yet known. To clarify a possible role of proopiomelanocortin (POMC)-derived peptides, includi ng alpha-MSH, in melanoma development and progression, we analysed imm unohistochemically the localization of alpha-MSH, adrenocorticotrophic hormone (ACTH) and beta-endorphin in various kinds of benign pigmente d naevocytic lesions and malignant melanomas, Three of 21 samples of c ommon and dysplastic naevi showed detectable alpha-MSH staining in nae vus cells, and five and six of 15 samples were weakly positive for ACT H and beta-endorphin staining, respectively. In melanoma samples, 24 o f 45, 23 of 39 and 30 of 42 samples showed positive staining with alph a-MSH, ACTH and beta-endorphin antibodies, respectively, Furthermore, staining for all three antibodies was noted to be more intense and dif fuse in samples of nodular melanoma, vertically growing acral lentigin ous melanoma and superficial spreading melanoma as well as metastatic lesions compared with those of naevi, Although it is yet to be determi ned whether or not this strong staining for POMC-derived peptides in a dvanced melanoma cells indicates a role of autocrine or paracrine regu lation, our results suggest a possible involvement of POMC gene produc ts in melanoma progression.