INTEGRIN EXPRESSION IN HUMAN-MELANOMA CELL-LINES - HETEROGENEITY OF VITRONECTIN RECEPTOR COMPOSITION AND FUNCTION

Ten human melanoma cell lines were examined for integrin-receptor expression using a panel of antibodies directed against different integrin subunits. Considerable heterogeneity was detected for levels of expression of 7 integrins, including the alpha-v-beta-3 vitronectin receptor where a correlation between tumorigenic capacity in athymic nude mice and alpha-v-beta-3 levels was found. Detailed analysis of the vitronectin receptor on these lines revealed heterogeneity of composition. In one cell line, VUP, an alpha-v-beta-1 association was detected and, by antibody-inhibition studies, this receptor was shown to bind vitronectin as its ligand. In another line, DX3, evidence was obtained which indicated that apart from the alpha-v-beta-3 receptor the alpha-v was able to associate with another beta subunit which was not beta-3. The existence of these alternative forms of the vitronectin receptor in this small sample of tumours of common origin might explain why the capacity to bind to fibrinogen and vitronectin substrates by these cells did not necessarily correlate with alpha-v-beta-3 levels.