AUTOCRINE MOTILITY FACTOR SIGNALS INTEGRIN-MEDIATED METASTATIC MELANOMA CELL-ADHESION AND INVASION

The binding of autocrine motility factor (AMF) to its cell surface rec eptor, gp78, stimulates tumor cell motility. In this report, we provid e evidence that stimulation of gp78 by either AMF or a monoclonal anti body to gp78 (3F3A) increases adhesion and spreading of metastatic mur ine melanoma (B16a) cells on fibronectin. This gp78-regulated increase is mediated by up-regulation of surface alpha IIb beta 3 and alpha 5 beta 1 integrin receptors. In addition, AMF treatment of B16a cells in creased translocation of alpha IIb beta 3 and alpha 5 beta 1 from the cytoplasm to the cell surface. However, alpha IIb beta 3 and alpha 5 b eta 1 demonstrate separate and unique staining patterns at the surface of B16a cells in response to stimulation of gp78. Furthermore, stimul ation of B16a cells with AMF increased their invasion through Matrigel . This stimulated invasion was inhibited by antibodies to alpha IIb be ta 3 but not by antibodies to alpha 5 beta 1. The increased integrin s urface expression and function in response to AMF was blocked by N-ben zyl-N-hydroxy-5-phenylpentanamide, an inhibitor of 12-lipoxygenase, an d calphostin C, an inhibitor of protein kinase C. The results demonstr ate that AMF stimulates integrin-mediated B16a cell adhesion, spreadin g, and invasion, and these events are regulated by a signaling pathway involving 12-lipoxygenase and protein kinase C.