Analysis Of The Level Of The Methylated CpG Site In RNF180 DNA Promoter From Gastric Cancer Patients

ObjectiveWe detected the methylated status of 43 CpG sites of the core function promoter region(-192/+126) of Ring finger protein 180 DNA and analyzed the clinical significance of the methylated status of the 43 Cp G sites to the prognosis of gastric cancer patients, and investigated the relationship between the methylated status of 43 Cp G sites and clinical pathologic feature, and deduced which methylated Cp G sites can cause worse prognosis to gastric cancer patients.MethodsWe collected 400 fresh-frozen tissues from gastric cancer patients who underwent the curative gastrectomy during April 2003 and December 2007 at the Department of Gastroenterology, Tianjin Medical University Cancer Hospital. All tumor tissues were histologically verified as adenocarcinoma. All of the 480 patients didn’t receive radiotherapy, chemotherapy and biologic treatment before surgery. Genomic DNA was extracted from the 400 gastric cancer tissues, and the methylated statuses of 43 Cp G sites of the core function promoter region of the RNF180 DNA of the 480 gastric cancer patients were analyzed by Bisulfite genomic sequencing.Results1. The methylated Cp G site counts in the core function promoter region of RNF180 DNA ranged from 0 to 43 by BGS, and 59 gastric cancer patients had no methylated Cp G site and 341 gastric cancer patients had methylated Cp G site in the RNF180 DNA promoter.2. According to the Cut-off point of methylated Cp G site counts by Kaplan-Meier, we found that 51.25%(205/400)patients possessed eight or more methylated Cp G sites and 48.75%(195/400)patients possessed seven or less methylated Cp G sites. With the univariate survival analysis, ten clinicopathological characteristics had statistical significance for overall survival: T stage(P=0.012), N stage(p<0.001), extent of lymph node metastasis(p<0.001), Lauren classification(P=0.014), methylated Cp G site count(P=0.002), methylated-116 Cp G site(P=0.041), methylated-80 Cp G site(P=0.045), methylated +97 Cp G site(P=0.021), methylated +102 Cp G site (P=0.037), methylated(-116、-80、+97、+102) Cp G sites(P<0.001). Above ten factors were included in a multivariate Cox proportional hazards model to adjust for the effects of covariates. Through the multivariate analysis of the ten factors, N stage(p<0.001), methylated(-116、-80、+97、+102) Cp G sites(P=0.010) were further demonstrated as the independent predictors of the overall survival for gastric cancer patients after surgery.3. The location of lymph node metastasis was remarkable associated with methylated Cp G site count. It is that patients with eight or more methylated Cp G sites had higher extragastric lymph node mtastatic rate than those with seven or less methylated Cp G sites(49.76% v 34.87%, P=0.010);Patients with eight or more methylated Cp G sites had higher methylated rate of combined(-116、-80、+97、+102) Cp G sites than those with seven or less methylated Cp G sites(91.70% v 13.33%,P<0.001).Meanwhile, patients with the methylated-80 Cp G site had higher N3 stage lymph node metastatic rate(46.09% v 35.66%,P=0.024);Conclusions1.The methylated status of Cp G sites in the core function promoter region of RNF180 DNA may be a prognostic predictor of gastric cancer.2.The methylated status of-116 Cp G、-80 Cp G、+97 Cp G、+102Cp G sites in the core function promoter region of RNF180 DNA maybe play a vital role in the process of the formation and development of gastric cancer.