Metastasis gene NEDD9 acts through integrin β3 and Src to promote mesenchymal motility and inhibit amoeboid motility.

Abstract

NEDD9, a member of the Cas family of signal transduction molecules, is amplified at the genetic level in melanoma and elevated expression levels have been shown to correlate with melanoma progression and metastasis. While NEDD9 interacts with the guanine nucleotide exchange factor DOCK3 to promote Rac activation and the elongated, mesenchymal-type of tumor cell invasion, the molecular mechanisms through which NEDD9 promotes melanoma metastasis are not fully understood. We show that signalling through increased NEDD9 levels requires integrin β3 signalling, leads to elevated phosphorylation of integrin β3 resulting in increased Src and FAK but decreased ROCK signalling to drive elongated, mesenchymal-type invasion in environments that contain vitronectin. NEDD9 over-expression does not affect ROCK signalling through activation of RhoA but decreases ROCKII signalling through Src dependent phosphorylation of a negative regulatory site Tyr 722. In NEDD9 over-expressing melanoma cells, inhibition of Src with dasatinib results in a switch from Rac driven elongated, mesenchymal-type invasion to ROCK dependent rounded, amoeboid invasion. These findings brings into question whether dasatinib would work as a therapeutic agent to block melanoma invasion and metastasis; a combination treatment of dasatinib and a ROCK inhibitor may be a better alternative based on the in vitro data presented here in order to inhibit both elongated, mesenchymal-type and rounded, amoeboid motility.