p130Cas mediates the transforming properties of the anaplastic lymphoma kinase

Translocations of the Anaplastic Lymphoma Kinase (ALK) gene have been described in Anaplastic Large Cells Lymphomas (ALCL) and in stromal tumors. The most frequent translocation t(2;5) generates the fusion protein NPM-ALK with intrinsic tyrosine kinase activity. Along with transformation, NPM-ALK induces morphologic changes in fibroblasts and lymphoid cells, suggesting a direct role of ALK in cell shaping. In this study, we used a mass spectrometry based proteomic approach to search for proteins involved in cytoskeleton remodelling and identified p130Cas as a novel interactor of NPM-ALK. In 293 cells, in fibroblasts as well as in human ALK positive lymphoma cell lines, NPM-ALK was able to bind p130Cas and to induce its phosphorylation. Both the effects were dependent on ALK kinase activity and on the adaptor protein Grb2 since no binding or phosphorylation were found with the kinase-dead mutant NPM-ALKK210R or in the presence of a Grb2 dominant negative protein. Phosphorylation of p130Cas by NPM-ALK was partially independent from Src kinase activity, as it was still detectable in SYF-/- cells. Finally, p130Cas-/- fibroblasts expressing NPM-ALK showed impaired actin filament depolimerization and were no longer transformed compared to wild type cells, indicating an essential role of p130Cas activation in ALK mediated transformation.