DNA and histone methylation in gastric carcinogenesis

Epigenetic alterations contribute significantly to the development and progression of gastric cancer,one of the leading causes of cancer death worldwide.Epigenetics refers to the number of modifications of the chromatin structure that affect gene expression without altering the primary sequence of DNA,and these changes lead to transcriptional activation or silencing of the gene.Over the years,the study of epigenetic processes has increased,and novel therapeutic approaches that target DNA methylation and histone modifications have emerged.A greater understanding of epigenetics and the therapeutic potential of manipulating these processes is necessary for gastric cancer treatment.Here,we review recent research on the effects of aberrant DNA and histone methylation on the onset and progression of gastric tumors and the development of compounds that target enzymes that regulate the epigenome.

Presence of c.3956del C mutation in familial adenomatous polyposis patients from Brazil

AIM: To characterize APC gene mutations and correlate them with patient phenotypes in individuals diagnosed with familial adenomatous polyposis(FAP) in northern Brazil. METHODS: A total of 15 individuals diagnosed with FAP from 5 different families from the north of Brazil were analyzed in this study. In addition to patients with histopathological diagnosis of FAP,family members who had not developed the disease were also tested in order to identify mutations and for possible genetic counseling. All analyzed patients or their guardians signed a consent form approved by the Research Ethics Committee of the Jo?o de Barros Barreto University Hospital(Belem,Brazil). DNA extracted from the peripheral blood of a member of each of the affected families was subjected to direct sequencing. The proband of each family was sequenced to identify germline mutations using the Ion Torrent platform. To validate the detected mutations,Sanger sequencing was also performed. The samples from all patients were also tested for the identification of mutations by real-time quantitative polymerase chain reaction using the amplification refractory mutation system. RESULTS: Through interviews with relatives and a search of medical records,it was possible to construct genograms for three of the five families included in the study. All 15 patients from the five families with FAP exhibited mutations in the APC gene,and all mutations were detected in exon 15 of the APC gene. In addition to the patients with a histological diagnosis of FAP,family members without disease symptoms showed the mutation in the APC gene. In the present study,we detected two of the three most frequent germline mutations in the literature: the mutation at codon 1309 and the mutation at codon 1061. The presence of c.3956 del C mutation was found in all families from this study,and suggests that this mutation was introduced in the population of the State of Pará through ancestor immigration(i.e.,a de novo mutation that arose in one member belonging to this state from Brazil). CONCLUSION: Regardless of its origin,the c.3956 del C mutation is a strong candidate biomarker of this hereditary cancer syndrome in families of northern Brazil.

Identification of IL11RA and MELK amplification in gastric cancer by comprehensive genomic profiling of gastric cancer cell lines

AIM To identify common copy number alterations on gastric cancer cell lines.METHODS Four gastric cancer cell lines(ACP02, ACP03, AGP01 and PG100) underwent chromosomal comparative genome hybridization and array comparative genome hybridization. We also confirmed the results by fluorescence in situ hybridization analysis using the bacterial artificial chromosome clone and quantitative real time PCR analysis.RESULTS The amplification of 9p13.3 was detected in all cell lines by both methodologies. An increase in the copy number of 9p13.3 was also confirmed by fluorescence in situ hybridization analysis. Moreover, the interleukin 11 receptor alpha(IL11RA) and maternal embryonic leucine zipper kinase(MELK) genes, which are present in the 9p13.3 amplicon, revealed gains of the MELK gene in all the cell lines studied. Additionally, a gain in the copy number of IL11 RA and MELK was observed in 19.1%(13/68) and 55.9%(38/68) of primary gastric adenocarcinoma samples, respectively. CONCLUSION The characterization of a small gain region at 9p13.3 in gastric cancer cell lines and primary gastric adenocarcinoma samples has revealed MELK as a candidate target gene that is possibly related to the development of gastric cancer.