| Objective: Gastric cancer is one of malignant tumors that are higher in morbidity and mortality, with the forth place in morbidity and second place in mortality of the malignant tumors across the world[1,2]. Nowadays, morbidity and death toll of gastric cancer is in the first place of all the malignant tumors separately, there are 160,000 persons died suffering from gastric cancer each year, and posed serious threat to the health and lives[3]. As the advance of the medical treatment, the research of the diagnosis and treatment of gastric cancer is improving, but the mortality is still on the rise year by year, with grim prevention and control situation[4]. Therefore, exploration on the pathogenesis of gastric cancer, early detection and diagnosis and cure is still the key point of present study[5,6]. In recent years, there is growing recognition in epigenetics research of malignant tumors. Studies have shown that DNA methylation is an important epigenetic mechanism, and plays an important role in the pathogenesis of gastric cancer. In the body’s defense system to peroxidase, glutathione peroxidase(GPX) is one of the important parts, which played a specific function to the removal of human body’s reactive oxygen species composition such as hydrogen peroxide and lipid peroxides, of which the GPX3 is an important extracellular subtype of the GPX[7]. Research has shown that methylation of the Cp G island in high GPX3 gene promoter can make GPX3 down-regulated expression, and increased of peroxide content in human body, and participate in the process of malignant tumor. This group of methylation PCR(MSP) method was used to detect the GPX3 gene promoter region methylation status in blood of the gastric cancer and normal control group samples, the immunohistochemical method was used to detect protein expression of control group GPX3 in gastric cancer tissue samples and the normal tissue specimens, then to discuss the GPX3 gene promoter Cp G island methylation in gastric cancer mechanism and the relation between clinical pathological features.Methods: This paper adopt the study of case-control method, and collected 70 cases from the inpatients during 2012 to2014 in the hospital, All entrants went through detailed survey and understanding of the personal and family history, so that rule out other tumors. All the entrants in cases were agreed to provide clinical specimens for the scientific research and signed the informed consent.Group of chronic gastritis has 35 cases, gastric cancer group has 35 examples, gastritis group has 18 cases of male, 17 cases of female, with ages from 35 to 75 years old, average age 60.35 ± 4.54 years old. Gastric cancer group has 21 cases of male and 14 cases of female, with ages 45-80, mean age 65.65± 4.34 years old, two groups of patients have no statistical differences in age and gender. 2 ml whole blood was extracted from each cases, stored and transport in liquid nitrogen tank immediately, then put the specimens deposited in the- 80 ℃refrigerator for further testing. Genomic DNA was extracted from each blood specimens respectively, and bisulfite treatment after methylation specific PCR(MSP) method is used to detect island methylation level in their blood specimens GPX3 gene promoter. Gastritis group kept the gastric mucosal tissue specimens through gastroscopy. Patients with gastric cancer group were through gastric resection surgery in the department of general surgery, central necrosis area and foci were taken as cancer specimens with the matching distance of 5 cm adjacent to the cancerous tissues area as tissue specimens. All cases of surgery in the treatment has not been received radiotherapy and chemotherapy earlier, the pathological results were confirmed by pathological histology experts detection. Target tissue samples to wax embedding, GPX3 protein expression were detect by using immunohistochemical method in tissue from stomach gastritis group, gastritis cancer and adjacent to carcinoma specimens. According to the results between the groups whether there are differences with corresponding analysis, SPSS 16.0 software was used to statistical analysis, measurement data were expressed by normal distribution and homogeneity of variance to mean standard deviation, comparisons between groups were carried out statistical analysis by inspection. count data were expressed as percentage, comparisons between groups were carried out statistical analysis by c2 inspection, the results with P < 0.05 was statistically significant.Results:1 Through the analysis of GPX3 promoter methylation status of Cp G island in blood specimens from gastritis group 28.57%(10/35) and gastric carcinoma group(23/35,65.71%), results showed that methylation expression in gastric cancer group was obviously higher than that of gastritis group, the difference was statistically significant(P< 0.05).2 GPX3 methylation status Gastric cancer group is related to the lymph node metastasis of the tumor, the difference was statistically significant(P < 0.05), and is unrelated to age, sex, tumor differentiation degree, infiltration, TNM staging of different patients, these differences don’t have statistically significance(P > 0.05).3 By examining GPX3 protein expression in each tissue samples, GPX3 protein expression level from chronic gastritis group(26/35,74.29%) and adjacent to gastric carcinoma 65.71%(23/35) is high, and significantly higher than that of gastric carcinoma group(13/35,37.15%), the difference was statistically significant(P< 0.05).4 GPX3 protein expression level from chronic gastritis group(26/35,74.29%) and adjacent to gastric carcinoma 65.71%(23/35) compares fairly, these differences don’t have statistically significance(P> 0.05).5 GPX3 protein expression from Gastric cancer group is related to the lymph node metastasis of the tumor, the difference was statistically significant(P<0.05), and is unrelated to age, sex, tumor differentiation degree, infiltration, TNM staging of different patients, these differences don’t have statistically significance(P> 0.05).Conclusions:1 GPX3 promoter Cp G island methylation degree is high in gastric cancer blood specimen, and GPX3 protein expression in cancer tissue samples significantly lowered, maybe related to methylation, the results suggest that the occurrence of gastric cancer associated with GPX3 promoter region methylation.2 The expression of GPX3 promoter Cp G island methylation in Gastric cancer lymph node metastasis group is significantly higher than that of non-gastric cancer lymph node metastasis group, and suggests that GPX3 promoter Cp G island methylation is related to the process of gastric cancer. GPX3 has the potential to be warning molecular target that estimate the prognosis of gastric cancer progression.3 GPX3 promoter Cp G island methylation degree and GPX3 protein expression in cancerous tissue specimens in the gastric cancer group’s blood spicemen is unrelated to age, sex, tumor differentiation degree, infiltration, TNM staging of different patients, and account for more GPX3 participation mechanism associated gastric cancer progression.4 GPX3 promoter Cp G island methylation in chronic gastritis group level is low, and the GPX3 protein expression level in tissue samples is high, which can explain GPX3 can be used as a suppressor gene in control cell progression of a tumor.5 GPX3 protein expression in tissue samples adjacent to carcinoma and chronic gastritis is consistent with each other, and significantly higher than that of the cancer tissue, which suggests that GPX3 play certain role in controlling cell malignant transformation. |
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