Alpha‐Melanocyte‐Stimulating Hormone Immunoreactivity in Human Melanoma Metastases Extracts

Abstract

Seven human melanoma metastases were extracted in order to check the possible presence of any .alpha.-melanocyte stimulating hormone (MSH) immunoreactivity. The aim of that study was to provide some explanation for, mainly, two observations that we have already made and reported: 1) increased plasma .alpha.-MSH levels in melanoma of tumour-bearing patients as compared with tumour-free patients; 2) the presence of specific .alpha.-MSH receptors on human melanoma cells in culture. We could measure large amounts of immunoreactive .alpha.-MSH in all tumours ranging from 0.31 to 4.27 pmoles per g of wet tissue. Further identification of the extracted material by high-performance liquid chromatography revealed compounds of higher molecular weight and more hydrophobic than synthetic .alpha.-MSH. In addition, purified extracts could also displace 125I-labelled .alpha.-MSH from its cellular binding sites in an .alpha.-MSH specific radio-receptor binding assay. Our findings would suggest a possible presence of some hormone precursor(s) inside the melanoma tumours.