Recent in situ studies suggest the alpha V
beta 3 integrin is a tumour progression marker in
melanoma. We analyzed 5 human
melanoma cell lines for their expression of the
vitronectin binding alpha V beta 3 and alpha V beta 5
integrins using flow cytometry. The role of these receptors in cell attachment, spreading and migration was investigated using attachment assays, video time lapse spreading and migration assays and with function blocking
monoclonal antibodies. Cell lines derived from later stages of
tumor progression exhibited high levels of alpha V beta 3 expression, whereas no similar correlation with alpha V beta 5 expression was identified. Cell attachment, spreading and migration response on
vitronectin correlated well with the expression level of the alpha V beta 3 but not the alpha V beta 5
vitronectin receptor. Blocking of the alpha V
beta 3 integrin resulted in a significant decrease in cell attachment, spreading and motility whereas the function blocking antibody against the alpha V
beta 5 integrin only inhibited cell attachment in cell lines with the highest level of expression of this
integrin. Taken together, our study indicates that the level of expression of the alpha V beta 3 and alpha V beta 5
integrins is heterogeneous in
melanoma cell lines and that the alpha V
beta 5 integrin, if present, may function only during the initial cell attachment whereas the alpha V beta 3 plays an important role in cell spreading and cell migration as well.