Abstract LB-331: Bidirectional crosstalk between leptin and IGF-1 signaling transactivates epidermal growth factor receptor and promotes invasion and migration of triple-negative breast cancer cells

Abstract

Abstract Introduction: Obesity is an independent risk factor for breast cancer and obese breast cancer patients exhibit a higher risk for larger tumor burden, increased metastasis, and poor response to endocrine therapy. Obesity affects breast carcinogenesis by autocrine and paracrine effects of adipocytokine leptin and IGF-1. We have previously shown that leptin induces growth stimulation of breast cancer cells by recruiting histone acetyltransferases and mediator complex to cyclin D1 promoter via activation of Stat3. In the present study, we found a novel bidirectional crosstalk between IGF-1 and leptin signaling that promotes invasion and migration of triple-negative (ER, PR, HER2 negative) breast cancer cells MDA-MB-231, MDA-MB-468, MDA-MB-435, and HCC-1806. Methods and Results: IGF-1 induced significant tyrosine phosphorylation of leptin receptor (Ob-Rb) and leptin induced tyrosine phosphorylation of IGF-1 receptor (IGF-1R). Combined treatment of leptin and IGF-1 induced synergistic activation of both Ob-Rb and IGF-1R along with activation of Akt and ERK. Furthermore, IGF-1 and leptin synergistically transactivated epidermal growth factor receptor (EGFR) and induced proliferation of triple negative breast cancer cells. We also found that tyrosine phosphorylation of EGFR induced by combined treatment of leptin and IGF-1 was significantly inhibited not only by EGFR tyrosine kinase inhibitor AG1478 but also with a broad-spectrum matrix metalloproteinase inhibitor, GM6001, indicating that leptin and IGF-1 induced EGFR transactivation is dependent on proteolytic release of EGFR ligands. Intriguingly, we also found that combined treatment of leptin and IGF-1 potently induced invasion of triple negative breast cancer cells in Matrigel invasion and quantitative Electric Cell-Substrate Impedance Sensing invasion assays. Inhibition of leptin and IGF-1 mediated EGFR activation using a highly potent, reversible inhibitor of HER1/EGFR tyrosine kinase (erlotinib) or dual EGFR/HER2 kinase inhibitor (lapatinib) effectively inhibited leptin and IGF-1 induced invasion. Also, inhibition of EGFR activation using erlotinib and lapatinib reduced leptin- and IGF-1 induced migration of triple negative breast cancer cells. Conclusions: Taken together, these data indicate a novel bidirectional crosstalk between leptin and IGF-1 signaling that transactivates EGFR and promotes metastatic properties, invasion, and migration of triple negative breast carcinoma cells. Our novel findings indicate the possibility of using EGFR inhibitors erlotinib and lapatinib to counter the pro-cancerous effects of leptin and IGF-1 signaling in triple negative breast cancers.