RESUMEN
BACKGROUND & AIMS: Gastrokines are stomach mucus cell-secreted proteins; 2 gastrokines are known, GKN1 and GKN2. Gastrokine expression is lost in gastric cancer, indicating a possible function in tumor suppression. We have identified a third gastrokine gene in mammals. METHODS: Gkn3 was characterized by studies of molecular structure, evolutionary conservation, and tissue expression as well as transcriptional/translational outcome in mouse genetic models of gastric pathology. The functional consequences of Gkn3 overexpression were evaluated in transfected cell lines. RESULTS: Gkn3 encodes a secreted (approximately 19 kilodalton) protein that is co-expressed with trefoil factor (Tff)2 in the distal stomach and discriminates a Griffinia simplicifolia lectin (GS)-II-positive mucus neck cell (MNC) subpopulation in the proximal stomach. In humans, widespread homozygosity for a premature stop codon polymorphism, W59X, has likely rendered GKN3 non-functional. Population genetic analysis revealed an ancestral GKN3 read-through allele that predominates in Africans and indicates the rapid expansion of W59X among non-Africans during recent evolution. Mouse Gkn3 expression is strongly up-regulated in (Tff2-deficient) gastric atrophy, a pre-cancerous state that is typically associated with Helicobacter pylori and marks a non-proliferative, GS-II positive lineage with features of spasmolytic polypeptide-expressing metaplasia (SPEM). Gkn3 overexpression inhibits proliferation in gastric epithelial cell lines, independently of incubation with recombinant human TFF2 or apoptosis. CONCLUSIONS: Gkn3 encodes a novel, functionally distinct gastrokine that is overexpressed and might restrain epithelial cell proliferation in gastric atrophy. Spread of the human GKN3 stop allele W59X might have been selected for among non-Africans because of its effects on pre-neoplastic outcomes in the stomach.
Asunto(s)
Proteínas Portadoras/genética , Mucosa Gástrica/metabolismo , Proteínas de la Membrana/genética , Lesiones Precancerosas/genética , Neoplasias Gástricas/genética , Adaptación Fisiológica/genética , Secuencia de Aminoácidos , Animales , Apoptosis , Pueblo Asiatico/genética , Atrofia , Población Negra/genética , Proteínas Portadoras/metabolismo , Línea Celular , Proliferación Celular , Codón sin Sentido , Secuencia Conservada , Modelos Animales de Enfermedad , Evolución Molecular , Mucosa Gástrica/patología , Frecuencia de los Genes , Genotipo , Homocigoto , Humanos , Proteínas de la Membrana/metabolismo , Metaplasia , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Datos de Secuencia Molecular , Mucinas/deficiencia , Mucinas/genética , Mucinas/metabolismo , Proteínas Musculares/deficiencia , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Pan troglodytes , Péptidos/deficiencia , Péptidos/genética , Péptidos/metabolismo , Fenotipo , Polimorfismo de Nucleótido Simple , Lesiones Precancerosas/metabolismo , Lesiones Precancerosas/patología , Proteínas Recombinantes/metabolismo , Estómago/patología , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/patología , Factores de Tiempo , Transfección , Factor Trefoil-2 , Población Blanca/genéticaRESUMEN
BACKGROUND & AIMS: Trefoil factors (TFFs) regulate mucosal repair and suppress tumor formation in the stomach. Tff1 deficiency results in gastric cancer, whereas Tff2 deficiency increases gastric inflammation. TFF2 expression is frequently lost in gastric neoplasms, but the nature of the silencing mechanism and associated impact on tumorigenesis have not been determined. METHODS: We investigated the epigenetic silencing of TFF2 in gastric biopsy specimens from individuals with Helicobacter pylori-positive gastritis, intestinal metaplasia, gastric cancer, and disease-free controls. TFF2 function and methylation were manipulated in gastric cancer cell lines. The effects of Tff2 deficiency on tumor growth were investigated in the gp130(F/F) mouse model of gastric cancer. RESULTS: In human tissue samples, DNA methylation at the TFF2 promoter began at the time of H pylori infection and increased throughout gastric tumor progression. TFF2 methylation levels were inversely correlated with TFF2 messenger RNA levels and could be used to discriminate between disease-free controls, H pylori-infected, and tumor tissues. Genome demethylation restored TFF2 expression in gastric cancer cell lines, so TFF2 silencing requires methylation. In Tff2-deficient gp130(F/F)/Tff2(-/-) mice, proliferation of mucosal cells and release of T helper cell type-1 (Th-1) 1 cytokines increased, whereas expression of gastric tumor suppressor genes and Th-2 cytokines were reduced, compared with gp130(F/F)controls. The fundus of gp130(F/F)/Tff2(-/-) mice displayed glandular atrophy and metaplasia, indicating accelerated preneoplasia. Experimental H pylori infection in wild-type mice reduced antral expression of Tff2 by increased promoter methylation. CONCLUSIONS: TFF2 negatively regulates preneoplastic progression and subsequent tumor development in the stomach, a role that is subverted by promoter methylation during H pylori infection.
Asunto(s)
Gastritis , Infecciones por Helicobacter/genética , Helicobacter pylori , Mucinas/genética , Proteínas Musculares/genética , Péptidos/genética , Neoplasias Gástricas , Animales , Atrofia , Línea Celular Tumoral , Receptor gp130 de Citocinas/genética , Metilación de ADN/fisiología , Epigenómica , Gastritis/genética , Gastritis/microbiología , Gastritis/patología , Regulación Neoplásica de la Expresión Génica/fisiología , Silenciador del Gen/fisiología , Infecciones por Helicobacter/patología , Humanos , Metaplasia , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Transducción de Señal/fisiología , Neoplasias Gástricas/genética , Neoplasias Gástricas/microbiología , Neoplasias Gástricas/patología , Células TH1/fisiología , Factor Trefoil-2RESUMEN
RegI (Regenerating islet derived-1) was originally characterized as a growth factor involved in pancreatic islet cell regeneration. It is also considered a gastrointestinal mitogen as its expression is increased during pathologies involving aberrant cell proliferation that can lead to neoplasia. However, the absolute requirement for RegI to directly stimulate gastric mucosal cell proliferation in vivo requires further investigation. We used RegI-deficient mice to determine the requirement for RegI in normal gastric mucosal development, wound healing, hyperplasia and tumourigenesis. We found that epithelial repair of acetic acid ulcers in compound mutant RegI/gastrin-deficient mice was significantly reduced compared to wild type, RegI-deficient or gastrin-deficient mice. In contrast, RegI was dispensable for normal gastric mucosal development, hyperplasia in HKbeta-deficient mice and tumourigenesis in gp130(F/F) mice. Although RegI was not required for proliferation in these pathological models, expression of multiple Reg family members were increased during gp130(F/F) tumourigenesis. Interestingly, loss of RegI in gp130(F/F) mice resulted in decreased expression of other Reg family members. Our results indicate that RegI and gastrin may synergistically regulate gastric mucosal proliferation during certain pathological settings like wound healing while gastric epithelial proliferation in other pathologies may require coordinated expression of multiple Reg genes.