Insulin and IGF are peptides pivotal to numerous functions such as cellular growth, proliferation, metabolism, glucose homeostasis, cell differentiation, and apoptosisInsulin and IGF are peptides having 40–80 % homology making it challenging, although not impossible, to explain insulin and IGF-1 ligand receptor interaction. Insulin/IGF signaling system mainly comprises of three ligands—IGF-1, IGF-2, and insulin, which in turn interact with at least six receptors:  the type I IGF receptor (IGF-1R), the IRA (IR-A), the IRB (IR-B), hybrid receptors of IGF and IR-A, hybrid receptors of IGF and IR-B, and hybrid receptors of IR-A and IR-B. In vivo and in vitro experimental models have highlighted increased insulin, IGF-1 and IGF-2 signaling to be responsible for enhancing tumorigenesis. Signaling of IGF as growth hormone plays a fundamental role in regulating embryonic growth as well as specific differentiation in most adult tissues. The activated IR tyrosine kinase activates several substrates including IR substrate proteins (IRS1-4), Gab-1, Cbl, and Shc, Phosphatidyl Inositol 3-Kinase (PIK3), Akt, mTOR, MAPK, and signal regulatory protein family.


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