Figure 1.

IGF-1R activation and regulation. IGF ligand, IGF-1, or IGF-2 activates IGF-1R and its downstream signaling as modified from the picture in reference [1]. It also causes ligand binding-induced receptor internalization, which degrades IGF-1R through lysosome (normal cells) or proteosome (lung cancer cells) pathways. Sp1 is the major transcriptional factor of the IGF-1R gene and is negatively regulated by p53, BRCA1, and WT1. IGF-1R mAb or IGF-1R TKI blocks IGF-1R activation and inhibits tumor growth.