Abstract LB-007: Interaction between integrin α4β1 and IGF1 and its role in IGF signaling in hematologic malignancies

Integrins are transmembrane αβ heterodimers that function as cell adhesion receptors. Integrins are aberrantly overexpressed in cancer cells and also in tumor-associated cells. They are involved in cancer cell proliferation, invasion and survival. It has been proposed that the interaction between integrin α4β1, a major integrin in hematologic cancer, and VCAM-1 and fibronectin is responsible for drug resistance in these malignances, since antagonists to this integrin reduce drug resistance. However these results are based on the assumption that VCAM-1 and fibronectin are the only ligands for α4β1. Insulin-like growth factor 1 (IGF1) signaling plays a critical role in drug resistance and radio resistance hematologic cancer. IGF1 is a polypeptide hormone that binds to tyrosine kinase receptor IGF1R and activates the PI3K/Akt signaling pathway. This pathway is involved in cell proliferation, survival, and inhibition of apoptosis. In various types of cancer IGF1 is over expressed and the PI3K/Akt pathway is activated at a much higher rate than in normal cells. This results in the growth of cancer cells and resistance to chemotherapy. IGF1 signaling is implicated in drug resistance, and is a good therapeutic target in hematologic cancers. It is unclear if α4β1 and IGF signaling work independently in drug resistance. Recently we established that IGF1 binds to integrins αvβ3 and α6β4, and subsequent integrin-IGF1-IGF1R ternary complex formation is a critical step in IGF signaling in non-hematologic cancer. We developed the R36E/R37E IGF1 mutant that is defective in integrin binding and a dominant-negative antagonist of IGF signaling. Here we show that IGF1 is a ligand for integrin α4β1 and induces a ternary complex with IGF1R and α4β1. Antagonists to integrin α4β1 and the R36E/R37E IGF1 mutant reduced intracellular signaling in Chinese hamster ovary cells expressing human integrin α4 (α4-CHO cells) and also in different hematologic cancer cells such as Reh, Molt-4, U937 and JY cells. These results suggest that integrin α4β1 is involved in IGF signaling through direct binding to IGF1 in hematologic cancer. The α4β1-IGF1 interaction is a novel therapeutic target for drug resistance in hematologic cancer. Citation Format: Dora M. Cedano Prieto, Jessica Yu, Yoko Takada, Yoshikazu Takada. Interaction between integrin α4β1 and IGF1 and its role in IGF signaling in hematologic malignancies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-007.