A novel unidirectional cross-talk from the insulin-like growth factor-I receptor to leptin receptor in human breast cancer cells.
Obesity is a major risk factor for the development and progression of breast cancer. Increased circulating levels of the obesity-associated hormones leptin and insulin-like growth factor-I (IGF-I) and overexpression of the leptin receptor (Ob-R) and IGF-I receptor (IGF-IR) have been detected in a majority of breast cancer cases and during obesity. Due to correlations between increased leptin, Ob-R, IGF-I, and IGF-IR in breast cancer, we hypothesized that molecular interactions may exist between these two signaling pathways. Coimmunoprecipitation and immunoblotting showed that IGF-IR and Ob-R interact in the breast cancer cell lines MDA-MB-231, MCF7, BT474, and SKBR3. Stimulation of cells with IGF-I promoted Ob-R phosphorylation, which was blocked by IGF-IR kinase inhibition. In addition, IGF-I activated downstream signaling molecules in the leptin receptor and IGF-IR pathways. In contrast to IGF-I, leptin did not induce phosphorylation of IGF-IR, indicating that receptor cross-signaling is unidirectional, occurring from IGF-IR to Ob-R. Our results show, for the first time, a novel interaction and cross-talk between the IGF-I and leptin receptors in human breast cancer cells.
Ozbay
Tuba
T
Department of Pharmacology, Emory University, Suite 5001, 1510 Clifton Road, Atlanta, GA 30322, USA.
Nahta
Rita
R
D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D020738:Leptin / Q000494:pharmacology; D020239:Receptor Cross-Talk; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D054411:Receptors, Leptin / Q000378:metabolism*
D020738:Leptin; D054411:Receptors, Leptin; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1