title: Identification of signal transduction pathways involved in constitutive NF-kappaB activation in breast cancer cells.
abstract: Nuclear factor-kappaB (NF-kappaB) is usually maintained in an inactive form in the cytoplasm through its association with inhibitor of kappaB (IkappaB) proteins, and is activated upon stimulation of cells with a variety of signals. However, constitutive activation of NF-kappaB is observed in a number of cancers including breast cancer. The signaling pathways that are involved in constitutive NF-kappaB activation remain largely unknown. Using breast cancer cell lines derived from transgenic mice that overexpress specific oncogene/growth factors in the mammary gland, we show that heregulin but not her2/neu, c-Myc or v-Ha-ras plays a major role in constitutive NF-kappaB activation. Her2/neu potentiated tumor necrosis factor alpha (TNFalpha)-inducible NF-kappaB activation whereas c-Myc potentiated 12-o-tetracecanyolphorbol-13-acetate (TPA)-induced NF-kappaB activation. Heregulin-mediated NF-kappaB activation correlated with phosphorylation of epidermal growth factor receptor (EGFR) and ErbB3 but not her2/neu. Tryphostin AG1517, which inhibits heregulin-mediated phosphorylation of EGFR, her2/neu and ErbB3 reduced NF-kappaB activation. In contrast, emodin, which blocks phosphorylation of her2/neu by heregulin, failed to reduce NF-kappaB activation. These results suggest that heregulin induces NF-kappaB independent of her2/neu. PI3 kinase/AKT, protein kinase A (PKA) and IkappaB kinase appear to be downstream signaling molecules involved in NF-kappaB activation as specific inhibitors of these kinases but not inhibitors of ERK/MAP kinase or protein kinase C reduced heregulin-mediated NF-kappaB activation. Based on these results, we propose that heregulin increases the expression of pro-invasive, pro-metastatic and anti-apoptotic genes in cancer cells through autocrine activation of NF-kappaB, which leads to invasive and drug-resistant growth of breast cancer.
authors.affiliation: Walther Oncology Center, Indiana University School of Medicine, Indianapolis, Indiana, IN 46202, USA.
authors.forename: Poornima
authors.initials: P
authors.lastname: Bhat-Nakshatri
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Sweeney
authors.forename: Harikrishna
authors.initials: H
authors.lastname: Nakshatri
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D066246:ErbB Receptors / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D051550:I-kappa B Kinase; D051379:Mice; D008822:Mice, Transgenic; D009025:Morpholines / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D020890:Neuregulin-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015689:Oncogene Protein p21(ras) / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D002867:Chromones; D017868:Cyclic AMP-Dependent Protein Kinases; D066246:ErbB Receptors; D005419:Flavonoids; D051550:I-kappa B Kinase; D009025:Morpholines; D016328:NF-kappa B; D020890:Neuregulin-1; D015689:Oncogene Protein p21(ras); D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D016271:Proto-Oncogene Proteins c-myc; D018719:Erb-b2 Receptor Tyrosine Kinases; D014409:Tumor Necrosis Factor-alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C496564:Chuk protein, mouse; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one