Crosstalk between IGF-1R and other Tumor Promoting Pathways

Insulin-like growth factor 1 receptor (IGF-1R) is important in cancer pathogenesis and progression. While its signaling pathway is an interesting therapeutic target, recent clinical trials have exhibited limited effects; however, significant crosstalks between IGF- 1R and other signaling pathways have garnered increasing attention. These complex networks include interactions between IGF-1R and receptor tyrosine kinases (RTKs), including insulin receptor (IR), epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor (VEGFR), mesenchymal-epithelial transition factor (MET), platelet-derived growth factor receptor (PDGFR), and fibroblast growth factor receptor (FGFR). Furthermore, IGF-1R also is related to steroid hormones, including estrogen receptors alpha and beta (ER! and ER"), androgen receptor (AR), and progesterone receptor (PR). Cumulatively, actions of crosstalk between IGF-1R, and RTKs/steroid hormones promote tumorigenesis, as demonstrated by the effectiveness of recently proposed therapeutic strategies. These therapeutic strategies, primarily pertaining to crosstalk-cotargeting, exhibited notable advantages in overcoming resistance to conventional chemotherapy and conventional endocrine therapy. Furthermore, these techniques offer benefits beyond the limited effects of single- agent targeting previously reported. Thus, the role of crosstalk between IGF-1R and RTKs/steroid hormones, including strategies to block these pathways in combination with recent development in this field, were reviewed and the potential future cancer therapeutics suggested by this rationale were considered. Keywords: Insulin-like growth factor 1 receptor, receptor tyrosine kinases, steroids, tumorigenesis, cancer, crosstalk, cell signaling, cotargeting.