Study On The Correlation Of Tumor-Suppressor Genes RUNX3, DAPK Promoter Methylation And Protein Expression With Pathological Features Of Gastric Carcinoma

Objective Tumor-suppressor genes methylation and gastric cancer closely, the relationship between the study found in all phases of cancer of the stomach could detect have genetically methylation existence, even pre-cancerous stage can also be found. This experiment by detecting tumor-suppressor genes RUNX3, DAPK promoter methylation, evaluation two kinds of gastric cancer suppressor methylation status, and screened might benefit stomach cancer gene diagnosis of early specificity. The expression of RUNX3 and DAPK protein were detected to analyse the relationship between the promoter hypermethylation and the loss of protein expression.Methods Samples were divided into three groups:54 cases of GC tissues, corresponding 5cm adjacent nonmalignant gastric mucosa tissues. Genomic DNA was extracted from tissues by using Phenol/CHCl2, and then treated with bisulfite. The quantitative methylation-specific PCR (QMSP) was adopted to detect the promoter CpG islands hypermethylation of RUNX3 and DAPK gene in the above-mentioned three kinds of specimens. The Western-Blot method was used to dected the expession of p16 and DAPK protein.Results In 54 cases of GC tissues, the positive rates of hypermethylation on promoter region of RUNX3 and DAPK were 77.8%(42/54) and 90.7%(49/54) respectively. In the corresponding adjacent nonmalignant gastric mucosa tissues, the positive rates of hypermethylation on promoter region of RUNX3 and DAPK were detected in38.9%(21/54),40.7%(22/54) respectively, the frequency of RUNX3 and DAPK promoter methylation in tumor tissues were significantly higher than adjacent nonmalignant tissues (P<0.001). The frequency of RUNX3 promoter methylation in tumor tissues of GC patients was significantly associated with TNM, the extent of differentiation, tumor diameter and lymph node metastasis (P<0.05), the frequency of DAPK promoter methylation was significantly associated with TNM, extent of differentiation, depth of infiltration (P<0.05). RUNX3, DAPK protein expression cut/fault rate respectively 81.5%(44/54),94.4%(51/54) was significantly higher than the corresponding carcinoma normal tissue 12.3%(7/54),9.3%(5/54) (P< 0.001). GC tissue of RUNX3, DAPK gene high methylation positie with its protein expression down-regulated or missing, while carcinoma with normal tissue adjacent to the contrary.Conclusions Aberrant methylation of RUNX3 and DAPK gene promoter is a frequent event in GC, promoter methylation is one of the important mechanism leading to the weak and loss of protein expression, it may play an important role in the occurrence and development of gastric cancer. The aberrant hypermethylation of RUNX3 and DAPK gene promoter may provide useful information for assessment of the malignant degree and lymph node metastasis of gastric cancer.