title: STAT6 mediates interleukin-4 growth inhibition in human breast cancer cells.
abstract: In addition to acting as a hematopoietic growth factor, interleukin-4 (IL-4) inhibits growth of some transformed cells in vitro and in vivo. In this study, we show that insulin receptor substrate (IRS)-1, IRS-2, and signal transducer and activator of transcription 6 (STAT6) are phosphorylated following IL-4 treatment in MCF-7 breast cancer cells. STAT6 DNA binding is enhanced by IL-4 treatment. STAT6 activation occurs even after IRS-1 depletion, suggesting the two pathways are independent. To examine the role of STAT6 in IL-4-mediated growth inhibition and apoptosis, a full-length STAT6 cDNA was transfected into MCF-7 cells. Transient overexpression of STAT6 resulted in both cytoplasmic and nuclear expression of the protein, increased DNA binding in response to IL-4, and increased transactivation of an IL-4 responsive promoter. In STAT6-transfected cells, basal proliferation was reduced whereas apoptosis was increased. Finally, stable expression of STAT6 resulted in reduced foci formation compared to vector-transfected cells alone. These results suggest STAT6 is required for IL-4-mediated growth inhibition and induction of apoptosis in human breast cancer cells.
authors.affiliation: Department of Medicine, Division of Oncology, University of Texas Health Science Center, San Antonio, TX 78284, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Gooch
authors.forename: Barbara
authors.initials: B
authors.lastname: Christy
authors.forename: Douglas
authors.initials: D
authors.lastname: Yee
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D015847:Interleukin-4 / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000502:physiology; D050800:STAT6 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000473:pathology
chemical_list: D018076:DNA, Complementary; D006131:Growth Inhibitors; C526292:IRS1 protein, human; C526297:IRS2 protein, human; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D015534:Trans-Activators; D015847:Interleukin-4