IRS1 and cancer: Physiologically, insulin and insulin-like growth factor-1 (IGF1) largely regulate carbohydrate and lipid metabolism and storage and protein synthesis via transmembrane receptor binding and activation of receptor tyrosine kinase and subsequent activation of intracellular insulin receptor substrate-1 (IRS1); however, insulin and IGF1-mediated signaling pathways are also implicated in pathogenesis and progression of several cancers via the activation of the Ras/Raf/MEK/ERK, PI3K/Akt/mTORC1, and GSK3β/β-catenin pathways [5,44].