Fig. 4From: IGF-IR signaling in epithelial to mesenchymal transition and targeting IGF-IR therapy: overview and new insightsModel of IGF system inhibition strategies and resistance mechanisms. Strategies to target the IGF-I/IGF-IR axis included increasing circulating levels of IGF-I and blocking kinase activation of the IGF-IR. The mechanisms of drug resistance are mainly in abnormal autocrine or paracrine expression of ligand IGF-I, not shut down receptor signaling completely (hybrid receptor or IR signaling) or activation of alternative signaling pathway (EGFR or HER2 signaling pathways). IR, insulin receptor; TKI, tyrosine kinase inhibitor; EGFR, epidermal growth factor receptor; HER2, epidermal growth factor 2 receptorBack to article page