title: ErbB4 promotes cyclooxygenase-2 expression and cell survival in colon epithelial cells.
abstract: The ErbB4 receptor tyrosine kinase is expressed at high levels in human and mouse colitis, and inhibits colon epithelial cell apoptosis in the presence of proinflammatory cytokines. In this study, we investigated the molecular mechanisms responsible for ErbB4-induced cell survival. In cultured mouse colon epithelial cells, ErbB4 overexpression resulted in increased levels of cyclooxygenase-2 (COX-2) mRNA and protein; in contrast, ErbB4 knockdown with siRNA blocked COX-2 accumulation in response to tumor necrosis factor. Although ErbB4 is expressed as up to four isoforms in epithelial tissues, its ability to promote COX-2 expression was isoform independent. ErbB4-stimulated COX-2 induction was associated with an increase in mRNA half-life and was blocked by inhibition of Src, phosphatidylinositol (PI) 3-kinase, or epidermal growth factor receptor (EGFR). Furthermore, ErbB4 expression promoted EGFR phosphorylation in the presence of heregulin, implicating ErbB4-EGFR heterodimerization in these responses. As to the cellular responses to ErbB4 activation, increased survival of ErbB4-expressing cells in the presence of proinflammatory cytokines was sensitive to the COX-2 inhibitor celecoxib. Furthermore, ErbB4-overexpressing cells acquired the ability to form colonies in soft agar, indicative of cellular transformation, also in a celecoxib-sensitive manner. Together our data indicate that ErbB4 is a key regulator of COX-2 expression and cellular survival in colon epithelial cells, acting in concert with EGFR through a Src- and PI 3-kinase-dependent mechanism. These results suggest that chronic overexpression of ErbB4 in the context of inflammation could contribute to colitis-associated tumorigenesis by inhibiting colonocyte apoptosis.
authors.affiliation: Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232-0696, USA. mark.frey@vanderbilt.edu
authors.forename: Mark R
authors.initials: MR
authors.lastname: Frey
authors.forename: Valda C
authors.initials: VC
authors.lastname: Hilliard
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Mullane
authors.forename: D Brent
authors.initials: DB
authors.lastname: Polk
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D003106:Colon / Q000473:pathology; D003110:Colonic Neoplasms / Q000209:etiology / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D004790:Enzyme Induction; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology / Q000473:pathology; D051379:Mice; D020890:Neuregulin-1 / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering; D066247:Receptor, ErbB-4; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
chemical_list: D020890:Neuregulin-1; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D051546:Cyclooxygenase 2; D058539:Phosphatidylinositol 3-Kinase; C587689:ERBB4 protein, human; D066246:ErbB Receptors; C587690:Erbb4 protein, mouse; D066247:Receptor, ErbB-4; D051057:Proto-Oncogene Proteins c-akt