Melanoma cell migration is upregulated by tumour necrosis factor-alpha and suppressed by alpha-melanocyte-stimulating hormone

We reported recently that the inflammatory cytokine tumour necrosis factor alpha (TNF-alpha) can upregulate integrin expression, cell attachment and invasion of cells through fibronectin in a human melanoma cell line (HBL). Furthermore, the actions of TNF-alpha were suppressed by the addition of an anti-inflammatory peptide alpha-melanocyte-stimulating hormone (alpha-MSH). In the current study, we extend this work investigating to what extent TNF-alpha might stimulate melanoma invasion by promoting cell migration and whether alpha-MSH is also inhibitory. Two human melanoma cell lines were examined in vitro (HBL and C8161) using a scratch migration assay. Analysis using either time-lapse video microscopy or imaging software analysis of migrating 'fronts' of cells revealed that C8161 cells migrated more rapidly than HBL cells. However, when cells were stimulated with TNF-alpha both cell types responded with a significant increase in migration distance over a 16-26 h incubation time. alpha-Melanocyte-stimulating hormone had an inhibitory effect on TNF-alpha-stimulated migration for HBL cells, completely blocking migration at 10(-9) M. In contrast, C8161 cells did not respond to alpha-MSH (as these cells have a loss-of-function melanocortin-1 receptor). However, stable transfection of C8161 cells with the wild-type melanocortin-1 receptor produced cells whose migration was significantly inhibited by alpha-MSH. In addition, the use of a neutralising antibody to the beta(1)-integrin subunit significantly reduced migration in both cell types. This data therefore supports an inflammatory environment promoting melanoma cell migration, and in addition shows that alpha-MSH can inhibit inflammatory stimulated migration. The data also support a fundamental role of the beta(1)-integrin receptor in melanoma cell migration.