IGF1R and neoplasm: We observed notable differences among domain specific anti-IGF1R antibodies with regards to their ability to 1) inhibit ligand binding and ligand-induced activation of IGF1R and INSR, 2) downregulate IGF1R and INSR expression, 3) inhibit cell proliferation and tumor growth, and 4) activate IGF1R and INSR in the absence of ligand.