The Methylation Status Of Global DNA And Bcl-2/p53in Gallbladder Carinoma

Objcetive:Gallbladder carcinoma (GBC) is a relatively uncommon neoplasmthat demonstrates considerable geographic and gender variation inincidence. GBC is a highly malignant neoplasm with a poor prognosis,with most cases diagnosed at advanced stages. Most studies have focusedon mutations of dominant oncogenes (K-ras) or tumor suppressor genes(TSGs)[TP53, P16,INK4A, and FHIT)]. Genome wide and specificchromosome arm allelotyping analyses indicated that allelic losses atmultiple sites of the genome are frequent in this neoplasm, suggesting theinvolvement of multiple TSGs in its pathogenesis. Recently, using aRNA-b ased global gene expression microarray analysis of!22,000transcripts in a series of biliary tract tumors including10GBC specimens,detected a number of abnormally expressed genes, most of which had notbeen described previously in these tumor types. DNA methylation of thepromoter regions is emerging as the major mechanism of inactivationof TSGs, and the abnormal methylation profile of human tumors hasbeen studied in the recent years. Individual tumor types frequently havecharacteristic patterns of acquired aberrant methylation. In many cases,aberrant methylation of the CpG island genes has been correlated with aloss of gene expression, and it is proposed that DNA methylationprovides analternative pathway to gene deletion or mutation for the lossof TSG function. The understanding of the methylation profile of tumorsmay impact on several clinical issues, including early detection, chemoprevention, prognosis, and cancer treatment.There is a clear worldwideassociation between GBC and cholelithiasis and chronic inflammation of the gallbladder [chronic cholecystitis (CC)], which are present in almostall GBC specimens.There is limited information about the molecularchanges involved in the pathogenesis of GBC. In GBC, there is verylimited information regarding abnormal methylation of cancer relatedgenes. The aim of this atudy is to investigate the differences ofmethylation status(Global DNA methylation/Bcl-2/p53) betweenGallbladder carcinoma and Chronic cholecystitis patients.Methods:We retrospective analysized45cases of gallbladder cancer tissuesamples collected in the Inner Mongolia Autonomous Region Hospitaland40cases of cholecystitis histopathology specimens in the InnerMongolia Autonomous Region Hospital. Baseline datas of patientwere collected, inluding the patients’ gender, age, tumor size, TNM stage,tumor markers, tumor pathological type and surgical methods. Afterextraction of DNA and RNA in the organization, We investigated theglobal DNA methylation using an innovative enzyme-linkedimmunosorbent assay. The methylation specific polymerase chainreaction was used to detect methylation status of Bcl-2and p53. Thesefindings were compared between45GBCs and40CCs. Byfluorescence quantitative PCR P53and Bcl-2gene expression weredected in specimens.Results:The global DNA methylation levels in gallbladder carcinoma (4.87±1.1%) is less than the cholecystitis genome methylation levels (6.278±0.91%), p <0.05; Of the Bcl-2gene,45cases of GBC specimens,methylation cases had occurred in6patients(17.7%);40cases of CC, themethylation status is17%. There is no significant difference about Bcl-2methylation (p>0.05) between the two groups. Of the p53gene, and29cases of45cases of GBC organization was methylation (64%),7casesof40cases of CC tissue was methylated (17.5%), the difference wasstatistically significant (p <0.05) between the two groups. Bcl-2mRNA expression level of GBC was0.66±0.16, CC of Bcl-2mRNA expressionlevel was0.33±0.14, the difference was not statistically significant (p<0.05). P53mRNA level of the GBC was0.55±0.17, p53mRNA levelof the CC was0.90±0.10, and the difference was statistically significant(p <0.05).In GBC, Global DNA methylation was lower than in CC(4.87±1.1%VS6.278±0.91%, p<0.05). The gene of p53was significantly higherfrequencies of methylation in GBC compared with CC(64%VS17.5%,p>0.05). But, no difference in Bcl-2（17.7%VS17%，p>0.05）.Conclusions:We found that by the study, compared with CC,the GBC globalDNA methylation levels ws reduced, There is no significant changes inBcl-2gene methylation status, while the P53gene is hypermethylated.Gloal DNA hypomethylation and p53hypermethylation may be one ofthe molecular mechanisms of gallbladder cancer. In short, the occurrenceof the GBC by the double impact of genetic and environmental, someregional differences, epigenetic regulation is very important in the way inwhich they arise, due to the conditions of this study, and limited technical,GBC other oncogenes and tumor suppressor genes The methylation statusshould be further explored.Global hypomethylation and p53hypermethylation may be an important molecular mechanism in GBCpathogenesis.