Leptin receptor expression and cell signaling in breast cancer

Int J Oncol. 2006 Apr;28(4):985-93.

Abstract

Obesity is considered a risk factor for many cancers, including breast cancer. Our laboratory has previously shown that leptin is mitogenic in many cancer cell lines, including breast. Information regarding the effects of high leptin levels on leptin receptor expression and signaling is lacking. The purpose of this study was to characterize leptin receptor expression in response to leptin in breast cancer cells. In addition, SOCS-3 expression (a leptin inducible inhibitor of leptin signaling), plus MAPK and PI3K signaling, were examined to determine their role in leptin-induced cell proliferation. Breast cancer cell lines, ZR75-1 and HTB-26, were treated with 0, 4, 40 or 80 ng/ml of leptin. Multiplex RT-PCR was performed to determine relative mRNA expression levels of the human short (huOB-Ra) or long (huOB-Rb) leptin receptor isoforms, or SOCS-3. MAPK and PI3K signaling was analyzed by phosphorylation of ERK and Akt, respectively, via Western blotting. Cell proliferation and inhibitor studies were analyzed by MTT assay. HTB-26 and ZR75-1 both expressed huOB-Ra, huOB-Rb and SOCS-3 mRNA; however, mRNA expression levels generally remained unchanged over time with leptin treatment. MAPK and PI3K pathways were activated in the presence of leptin over time. MAPK and PI3K inhibitors significantly blocked leptin-induced proliferation. Higher levels of circulating leptin contribute to breast cancer proliferation by activation of the MAPK and PI3K signaling pathways involved in cell growth and survival. The mitogenic effects of leptin are not a consequence of altered leptin receptor or SOCS-3 mRNA expression.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Blotting, Western
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Butadienes / pharmacology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Chromones / pharmacology
  • Dose-Response Relationship, Drug
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Leptin / pharmacology
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / metabolism
  • Morpholines / pharmacology
  • Nitriles / pharmacology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation / drug effects
  • Receptors, Cell Surface / genetics*
  • Receptors, Leptin
  • Signal Transduction*
  • Suppressor of Cytokine Signaling 3 Protein
  • Suppressor of Cytokine Signaling Proteins / genetics
  • Time Factors

Substances

  • Butadienes
  • Chromones
  • Enzyme Inhibitors
  • Leptin
  • Morpholines
  • Nitriles
  • Phosphoinositide-3 Kinase Inhibitors
  • Receptors, Cell Surface
  • Receptors, Leptin
  • SOCS3 protein, human
  • Suppressor of Cytokine Signaling 3 Protein
  • Suppressor of Cytokine Signaling Proteins
  • U 0126
  • leptin receptor, human
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Mitogen-Activated Protein Kinases