Also unique to the myeloma cells compared to carcinoma or endothelial cells is that IGF-1R in the pre-assembled Sdc1-coupled ternary receptor complex is constitutively active (40); it is not dependent on cell adhesion or IGF-1, although exogenous IGF1 stimulates increased levels of IGF-1R activation. Here, IGF1R is linked to plasma cell myeloma.