title: Src family kinases mediate epidermal growth factor receptor signaling from lipid rafts in breast cancer cells.
abstract: Activation of the epidermal growth factor receptor (EGFR) regulates cellular proliferation, survival, and migration of breast cancer cells. In particular, EGFR recruits signaling proteins to the cell membrane leading to their phosphorylation and activation. However, EGFR also localizes to other cellular structures, including endosomes, mitochondrion, and nuclei. Recently, we demonstrated that lipid raft localization of EGFR in triple-negative breast cancer cell lines promotes EGFR protein-dependent, EGFR kinase-independent activation of Akt. Here, we further define the mechanism by which lipid rafts regulate EGFR signaling to Akt. Specifically, we show that the non-receptor tyrosine kinase c-Src co-localizes and co-associates with EGFR and lipid rafts. Breast cancer cells resistant to treatment with EGFR inhibitors, were also resistant to treatment with Src family kinase (SFK) inhibitors; however, the combination of EGFR and SFK inhibitors synergistically decreases cell viability. We found that this decrease in cell viability observed with EGFR and SFK inhibitor co-treatment correlates with loss of Akt phosphorylation. In addition, we found that in breast cancer cell lines with EGFR and c-Src co-localized to lipid rafts, phospho-inositide 3 kinase (PI3K) was also associated with lipid rafts. Together, the data herein suggest that lipid rafts provide a platform for the interaction of EGFR, c-Src, and PI3K, leading to activation of cellular survival signaling in breast cancer cells.
authors.affiliation: Department of Pharmacology, Karmanos Cancer Institute, Wayne State University, Detroit, MI, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Irwin
authors.forename: Natacha
authors.initials: N
authors.lastname: Bohin
authors.forename: Julie L
authors.initials: JL
authors.lastname: Boerner
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D004357:Drug Synergism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005260:Female; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D047428:Protein Kinase Inhibitors; D066246:ErbB Receptors; D019061:src-Family Kinases; D051058:Oncogene Protein v-akt