IGF1R and breast cancer: In normal cells, IGF1R signaling regulates differentiation, proliferation, motility, and anti-apoptosis; however, IGF1R signaling has also been strongly linked to the progression of cancer [19,20], with mutations affecting the IGF1R or the related insulin receptor (INSR) signaling pathway noted in 43% of stomach cancer tumors [21] and activated IGF1R detected in 50% of breast cancers across multiple subtypes [21,22].