title: Leptin augments proliferation of breast cancer cells via transactivation of HER2.
abstract: Excessive fat mass is a risk factor for postmenopausal breast cancer. Leptin, a fat cell-derived peptide hormone, elicits a growth-stimulating effect in breast cancer cells with leptin receptor expression, although the leptin-induced signal in malignant cells is not fully understood. Here, we found that exogenous leptin induced tyrosine phosphorylation of HER2 in SKBR3 cells, which showed marked overexpression of HER2. Phosphorylation of HER2 was detected at 2 min and continued up to 120 min after the start of stimulation. Leptin-induced HER2 phosphorylation was partially reduced by an epidermal growth factor receptor inhibitor, AG1478, or a Janus-activated kinase inhibitor, AG490. Leptin also induced phosphorylation of extracellular signal-regulated kinase 1/2, which was mostly abrogated by a HER2 tyrosine kinase inhibitor, AG825. In a proliferation assay, addition of 500 ng/mL leptin increased the proliferation of SKBR3, which was totally inhibited by AG825. Collectively, our data suggest that leptin can transactivate HER2 through both epidermal growth factor receptor and Janus-activated kinase 2 activation, which can cause the growth of breast cancer cells with HER2 overexpression.
authors.affiliation: Department of Surgery, Division of Surgical Oncology, University of Tokyo, Tokyo, Japan. dsouma-tky@umin.ac.jp
authors.forename: Daisuke
authors.initials: D
authors.lastname: Soma
authors.forename: Joji
authors.initials: J
authors.lastname: Kitayama
authors.forename: Hiroharu
authors.initials: H
authors.lastname: Yamashita
authors.forename: Hideyo
authors.initials: H
authors.lastname: Miyato
authors.forename: Makoto
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Nagawa
mesh_terms: D001943:Breast Neoplasms; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D018734:Genes, erbB-2 / Q000235:genetics* / Q000502:physiology; D006728:Hormones / Q000494:pharmacology*; D006801:Humans; D020738:Leptin / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D054411:Receptors, Leptin / Q000502:physiology; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
chemical_list: D006728:Hormones; D020738:Leptin; D054411:Receptors, Leptin