RESUMO
BACKGROUND: Chronic inflammation due to Helicobacter pylori (H. pylori) infection promotes gastric carcinogenesis. Tumour necrosis factor-α (TNF-α), a key mediator of inflammation, induces cell survival or apoptosis by binding to two receptors (TNFR1 and TNFR2). TNFR1 can induce both survival and apoptosis, while TNFR2 results only in cell survival. The dysregulation of these processes may contribute to carcinogenesis. AIM: To evaluate the effects of TNFR1 and TNFR2 downregulation in AGS cells treated with H. pylori extract on the TNF-α pathway. METHODS: AGS cell lines containing TNFR1 and TNFR2 receptors downregulated by specific shRNAs and nonsilenced AGS cells were treated with H. pylori extract for 6 h. Subsequently, quantitative polymerase chain reaction with TaqMan® assays was used for the relative quantification of the mRNAs (TNFA, TNFR1, TNFR2, TRADD, TRAF2, CFLIP, NFKB1, NFKB2, CASP8, CASP3) and miRNAs (miR-19a, miR-34a, miR-103a, miR-130a, miR-181c) related to the TNF-α signalling pathway. Flow cytometry was employed for cell cycle analysis and apoptosis assays. RESULTS: In nonsilenced AGS cells, H. pylori extract treatment increased the expression of genes involved in cell survival and inhibited both apoptosis (NFKB1, NFKB2 and CFLIP) and the TNFR1 receptor. TNFR1 downregulation significantly decreased the expression of the TRADD and CFLIP genes, although no change was observed in the cellular process or miRNA expression. In contrast, TNFR2 downregulation decreased the expression of the TRADD and TRAF2 genes, which are both important downstream mediators of the TNFR1-mediated pathway, as well as that of the NFKB1 and CFLIP genes, while upregulating the expression of miR-19a and miR-34a. Consequently, a reduction in the number of cells in the G0/G1 phase and an increase in the number of cells in the S phase were observed, as well as the promotion of early apoptosis. CONCLUSION: Our findings mainly highlight the important role of TNFR2 in the TNF-α pathway in gastric cancer, indicating that silencing it can reduce the expression of survival and anti-apoptotic genes.
Assuntos
MicroRNAs , Neoplasias Gástricas , Fator 2 Associado a Receptor de TNF/metabolismo , Apoptose , Carcinogênese , Ciclo Celular , Regulação para Baixo , Expressão Gênica , Humanos , Inflamação , MicroRNAs/genética , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Receptores Tipo II do Fator de Necrose Tumoral/genética , Neoplasias Gástricas/genética , Proteína de Domínio de Morte Associada a Receptor de TNF/metabolismo , Fator 2 Associado a Receptor de TNF/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
AIM: The aim of this study was to investigate genetic changes of the TP53 (tumor protein p53) and FHIT (fragile histidine triad) genes in precursor lesion such as chronic esophagitis (CE) and in esophageal squamous cell carcinoma (ESCC). MATERIALS AND METHODS: PCR-Single Strand Conformation Polymorphism (SSCP) analysis and DNA sequencing in 30 CE and 10 ESCC specimens were performed. RESULTS: DNA sequencing indicated two novel mutations in the TP53 exons 5 (codon 147) and 6 (codon 197) in 2/9 SSCP positive cases of ESCC, but no mutation was found in the CE. The SIFT (Sorting Intolerant From Tolerant) web-based program showed that missense variant at codon 197 of TP53 could affect the protein function. Additionally, polymorphisms of the TP53 exon 4 (codon 36 and 72) and of the FHIT exon 7 (codon 88) were observed in 4/11 (36%) cases of CE and 6/9 (67%) SSCP positive cases of ESCC after DNA sequencing. CONCLUSION: TP53 gene mutations are not common events in CE, but are frequent in ESCC, and as polymorphisms of TP53 and FHIT may confer a greater risk for the development of esophageal carcinoma, further studies are required.
Assuntos
Hidrolases Anidrido Ácido/genética , Carcinoma de Células Escamosas/genética , Neoplasias Esofágicas/genética , Esofagite/genética , Mutação/genética , Proteínas de Neoplasias/genética , Polimorfismo Genético/genética , Proteína Supressora de Tumor p53/genética , Adulto , Idoso , Estudos de Casos e Controles , Metilação de DNA , Esôfago/metabolismo , Esôfago/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita SimplesRESUMO
BACKGROUND: Chagas disease patients with longstanding megaesophagus have a significantly increased risk for esophageal carcinoma. MATERIALS AND METHODS: PCR-SSCP analysis and DNA sequencing of esophageal mucosa from Chagas disease patients (with or without megaesophagus) in the exons of the TP53, CDKN2A and FHIT genes were performed. RESULTS: SSCP analysis showed a mobility shift in 2/20 patients with grade IV megaesophagus (CDKN2A exon 1 and FHIT exon 7) and in 1/10 patients without megaesophagus (TP53 exons 5 and 8). However, DNA sequencing indicated a silent mutation in exon 7 of the FHIT gene (GCT --> GCC) in codon 88 in only one case of megaesophagus. CONCLUSION: Gene mutations are rare events in the exons investigated in esophageal mucosa of Chagas disease patients and further investigations are important to clarify the possible involvement of this silent mutation in exon 7 (FHIT gene) in the advanced grades of megaesophagus and esophageal carcinogenesis.
