title: hTERT methylation and expression in gastric cancer.
abstract: Gastric cancer is the second most prevalent cause of cancer death worldwide. DNA methylation is a common event in gastric carcinogenesis. hTERT seems to be the rate-limiting determinant of telomerase activation, which is responsible for stability and life span. hTERT hypermethylation has been associated with telomerase expression. In the present study, we investigated the promoter methylation status and hTERT protein expression in gastric cancer and normal mucosa samples. One hundred and nine gastric cancer and 53 normal mucosa samples were investigated through methylation-specific PCR. Immunohistochemistry was analysed using peroxidase in 55 gastric cancer and 18 normal gastric mucosa samples. This is the first study evaluating hTERT methylation status in gastric carcinogenesis. We did not observe hTERT protein expression in normal gastric mucosa. Moreover, hTERT expression was observed in 80% of tumours and was associated with gastric cancer (p < 0.0001). Partial methylation was the most frequent pattern in gastric samples, even in normal mucosa. The frequency of specimens presenting hypermethylation was significantly higher in tumours than in normal mucosa samples (p = 0.0002), although the presence of hypermethylated promoter was not associated with a higher frequency of hTERT expression. A low correlation between hTERT protein expression and methylation was verified in gastric cancer samples. There was a clear difference in the frequency of hTERT expression and methylation within tumoral and non-tumoral tissues. Methylation status and telomerase expression may be useful for the diagnosis of gastric cancer and may have an impact on the anti-telomerase strategy for cancer therapy.
authors.affiliation: Disciplina de Genética, Departamento de Morfologia e Genética, Universidade Federal de São Paulo, São Paulo, SP, Brasil.
authors.forename: Carolina Oliveira
authors.initials: CO
authors.lastname: Gigek
authors.forename: Mariana Ferreira
authors.initials: MF
authors.lastname: Leal
authors.forename: Patricia Natalia Oliveira
authors.initials: PN
authors.lastname: Silva
authors.forename: Luara Carolina Frias
authors.initials: LC
authors.lastname: Lisboa
authors.forename: Eleonidas Moura
authors.initials: EM
authors.lastname: Lima
authors.forename: Danielle Queiroz
authors.initials: DQ
authors.lastname: Calcagno
authors.forename: Paulo Pimentel
authors.initials: PP
authors.lastname: Assumpção
authors.forename: Rommel Rodriguez
authors.initials: RR
authors.lastname: Burbano
authors.forename: Marilia de Arruda Cardoso
authors.initials: Mde A
authors.lastname: Smith
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000378:metabolism; D019175:DNA Methylation; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000235:genetics*; D019098:Telomerase / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; D019098:Telomerase