title: Role of STAT3 Phosphorylation in Ethanol-Mediated Proliferation of Breast Cancer Cells.
abstract: OBJECTIVE
  In this study, we investigated the molecular mechanism involved in ethanol (EtOH)-mediated proliferation of breast cancer cells.
  
  
  METHODS
  EtOH concentration was optimized by studying its effect on cell proliferation in MCF-7 and MDA MB-231 cells. We used flow cytometry and immunoblot analysis to evaluate the increased proliferation caused by the optimized concentrations of EtOH. The mechanism of EtOH-mediated proliferation was determined using reactive oxygen species (ROS) release assay, reverse transcription polymerase chain reaction, and immunoblot studies. Gene silencing followed by quantitative real-time polymerase chain reaction studies and inhibitor studies indicated the involvement of signal transducer and activator of transcription 3 (STAT3) in EtOH-mediated breast cancer proliferation.
  
  
  RESULTS
  Exposure to EtOH caused an increase in cell proliferation and an accumulation of cells in S-phase in MCF-7 (347 µM EtOH) and MDA MB-231 (173 µM EtOH) cells. Additionally, increased release of ROS and the expression of pro-inflammatory cytokines, such as interleukin 6 and tumor necrosis factor α, confirmed that the proliferation was induced by the ROS-linked inflammatory response in breast cancer. The proinflammatory response was followed by phosphorylation of STAT3. The importance of STAT3 activation in EtOH-mediated proliferation was confirmed through the silencing of STAT3, followed by an investigation on the expression of cyclins and matrix metalloproteinases. Finally, studies using specific inhibitors indicated that the EtOH-mediated effect on STAT3 activation could be regulated by phosphoinositide-3-kinase and Janus kinase 2.
  
  
  CONCLUSIONS
  The study demonstrates the involvement of STAT3 signaling in EtOH-mediated breast cancer proliferation.
authors.affiliation: Department of Biotechnology, Anna University, Chennai, India.
authors.forename: Poornima Devi
authors.initials: PD
authors.lastname: Narayanan
authors.affiliation: Department of Biochemistry, University of Madras, Chennai, India.
authors.forename: Sangeetha Kadapakkam
authors.initials: SK
authors.lastname: Nandabalan
authors.affiliation: Department of Biotechnology, Anna University, Chennai, India.; Centre for Food Technology, Department of Biotechnology, Anna University, Chennai, India.
authors.forename: Lakshmi Subhadra
authors.initials: LS
authors.lastname: Baddireddi
keywords: Breast neoplasms; Cell proliferation; Ethanol; Inflammation