Ultraviolet radiation induces release of MIA: a new mechanism for UVR-induced progression of melanoma.

MIA is a potent melanoma detachment factor that interferes with cellular adherence by binding to fibronectin and laminin, blocking their interaction with alpha4beta1 and alpha5beta1 integrins. The direct correlation between serum MIA levels of patients with progressing melanomas and tumor load supports a role for MIA as a melanoma progression factor. The goal of this study was to determine the effect of ultraviolet radiation (UVR), activating ras mutation, or loss of p53 function on MIA expression and release from melanoma cells. We previously showed that transfection of a mutant constitutively active ras into the melanoma cell line, WM35, induces a phenotypic change from radial to vertical growth, exhibiting increased proliferation and migration. Here, we report that MIA release was elevated in a ras-transfected cell line. In addition, loss of functional p53, using a dominant negative construct, substantially lowered the level of MIA release compared to control. UVR stimulated release of MIA into the extracellular compartment in both the control and ras-transfected cell lines. In addition, MIA mRNA was increased following UVR in all cell lines tested. By inducing either apoptosis or necrosis, we were able to confirm that MIA protein is not released from cells due to cell death alone. We have identified a transcriptional effect of UVR on MIA expression and have shown that release of MIA protein is dependent upon functional p53. We propose that UVR-induced production and release of MIA may promote the detachment of radial and vertical growth phase melanomas from basement membrane or matrix proteins, serving as a unique progression mechanism for melanoma.