alpha-Melanocyte stimulating hormone can reduce T-cell interaction with melanoma cells in vitro

This study was undertaken to investigate whether alpha-melanocyte stimulati ng hormone (alpha MSH) influences the interaction of melanoma cells with T- lymphocytes in the light of previous work from our laboratories showing tha t aMSH can reduce tumour necrosis factor-alpha (TNF alpha) stimulated ICAM- 1 upregulation in both normal and transformed melanocytes. Two cutaneous me lanoma cell lines - A375-SM and HBL - were examined initially. A375-SM cell s gave only a two-fold increase in T-cell proliferation, which was not much improved by the pretreatment of the melanoma cells with cytokines. HBL cel ls induced a three-fold increase in T-cell proliferation, which was slightl y enhanced by the addition of cytokines. Neither cell line expressed B7(1). HBL cells expressed a low level of B7(2), whereas A375-SM cells had little , if any, B7(2) expression. Addition of alpha MSH reduced the interaction b etween these cutaneous melanoma cells and T-lymphocytes in some, but not al l, conditions. An ocular melanoma cell line transfected with B7 showed a mo dest interaction with T-cells (in two out of three donors) and this respons e was reduced by the addition of alpha MSH. Pretreatment of the transfected line with cytokines markedly enhanced stimulation of T-cell proliferation by these tumour cells, and alpha MSH reduced the interaction between melano ma cells and T-cells for two out of three donors. In summary, under experim ental conditions where melanoma cell stimulation of T-cells occurred (gener ally pretreatment of the cells with interferon-gamma gave the most convinci ng response), alpha MSH reduced this response in the majority of experiment s, providing preliminary evidence to confirm the hypothesis that MSH may as sist melanoma cells to evade interaction with immune cells. (C) 2000 Lippin cott Williams & Wilkins.