Oestrogenic steroids and melanoma cell interaction with adjacent skin cells influence invasion of melanoma cells in vitro.

The invasion of melanoma is complex and multi-staged and involves changes in both cell/extracellular matrix (ECM) and cell/cell interactions. Female steroids and alpha-MSH have also been reported to influence metastatic melanoma progression, but their mechanisms of action are unknown. Accordingly, our aim was to establish in vitro models to examine (a) the influence of sex steroids and alpha-melanocyte-stimulating hormone (alpha-MSH) on tumour invasion and the influence of (b) ECM proteins and (c) adjacent cells on melanoma invasion. In the first model, melanoma cell invasion through fibronectin over 20 hr under serum-free conditions was used to investigate the effects of 17beta-oestradiol and oestrone on the invasion of human melanoma cell lines, A375-SM and HBL. A375-SM, but not HBL cells, proved very susceptible to inhibition by female steroids. However, invasion of the HBL line was inhibited by alpha-MSH. Using the second model of reconstructed human skin based on de-epidermised acellular dermis, we found that the HBL cells on their own failed to invade into the dermis (irrespective of the presence or absence of the basement membrane). However, there was a significant synergistic interaction between keratinocytes, fibroblasts and HBL cells, such that a modest invasion of HBLs into the dermis was seen within 2 weeks when other skin cells were present. In contrast, A375-SM cells showed a significant ability to invade the dermis in the absence of other cells, with less invasion when other skin cells were present. In summary, these models have provided new information on the extent to which melanoma cell invasion is sensitive to oestrogenic steroids and to alpha-MSH and to interaction, not only with adjacent skin cells but also to the presence of basement membrane antigens.