CSPG4 and sarcoma: CSPG4 interacts with integrin α2β1 upon collagen type VI binding to activate the phosphatidylinositol 3-kinase (PI3K) pathway in sarcoma cells.129 In addition, CSPG4 forms complexes with MMP-2 and membrane type 3 MMP on the surface of melanoma cells to facilitate MMP-2 activation and eventual degradation of the ECM.130