Study On Aberrant Promoter CpG Islands Methylation Of P16, RUNX3 And CHFR Genes In Gastric Cancer Tissues

ObjectiveThe aberrant CpG islands methylation of DNA promoter is one of the important mechanisms which induce the inactivation of tumor suppressor genes in the occurrence and development of gastric cancer. In this study, the methylation level of CpG islands of p16, RUNX3 and CHFR genes promoter in gastric carcinoma tissues and corresponding neighboring tissues and normal gastric mucosa were detected by combination of methylation-specific polymerase chain reaction (MSP) and bisulfite sequence polymerase chain reaction (BSP) methods, and to explore the relationship between the aberrant methylation of these three genes and the clinical parameters of the gastric cancer.MethodsA total of 61 patients diagnosed as primary gastric cancer without receiving any radiotherapy or chemotherapy before operation were collected. During their surgical resection, both the carcinoma specimens and the matched neighboring tissues were taken from the patients, and thirty normal gastric mucosa were collected as control group. Methylation-specific polymerase chain reaction (MSP) and bisulfite sequence polymerase chain reaction (BSP) methods were used to detect the aberrant CpG islands methylation of p16 and RUNX3 and CHFR genes promoter from these specimens.Results1. The aberrant CpG islands methylation of p16 gene promoter The positive rate of methylation of p16 gene was found to be 68.8% (42/61) in gastric cancer tissues, 6.5% (4/61) in the matched neighboring tissues and 3.3% (1/30) in the normal gastric mucosa. The positive rate of methylation of p16 gene in the former group was significantly higher than that in the latter two groups (p<0.05).In carcinoma specimens, the positive rate of methylation of p16 gene of poorly differentiated and undifferentiated group was significantly higher than that of well-differentiated and moderately differentiated group (p<0.05). And the positive rate of methylation of p16 gene in which presenced lymphonode metabasis group was significantly higher than that of absenced lymphonode metabasis group (p<0.05). The positive rate of methylation of p16 gene in T3 and T4 stages was significantly higher than that in T1 and T2 stages (p<0.05). While no significant difference was found in other clinical parameters including the age, gender, stage of pathology, the size of tumor and the number of lymphonode metabasis (p>0.05).2. The aberrant methylation of CpG islands of RUNX3 gene promoterThe positive rate of methylation of RUNX3 gene was found to be 54.0% (33/61) in gastric cancer tissues, 8.1% (5/61) in the matched neighboring tissues and 0% (0/30) in normal gastric mucosa. The positive rate of methylation of RUNX3 gene in the former group was significantly higher than that in the latter two groups (p<0.05).The positive rate of methylation of RUNX3 gene from carcinoma tissues larger than 5cm was significantly higher than that from the tissues samller than 5cm (p<0.05). While no significant difference was found in other clinical parameters including the age, gender, invasion depth, degree of histological differentiation, stage of pathology and the involvement of lymph node (p>0.05). 3. The aberrant methylation of CpG islands of CHFR gene promoterThe positive rate of methylation of CHFR gene was found to be 40.9% (25/61) in gastric cancer tissues, 9.8% (6/61) in the matched neighboring tissues and 0% (0/30) in normal gastric mucosa. The positive rate of methylation of CHFR gene in the former group was significantly higher than that in the latter two groups (p<0.05).The positive rate of methylation of CHFR gene from carcinoma tissues larger than 5cm was significantly higher than that from the tissues samller than 5cm (p<0.05). While no significant difference was found in other clinical parameters including the age, gender, invasion depth, degree of histological differentiation, stage of pathology and the involvement of lymph node from the carcinoma specimens group (p>0.05).4. The aberrant methylation between P16 and RUNX3 gene, P16 and CHFR gene, RUNX3 and CHFR gene in gastric cancer tissues had no significant correlation or consistency. (p>0.05).Conclusions1. The aberrant CpG islands methylation of p16, RUNX3 and CHFR gene promoter were existed both in carcinoma specimens and matched neighboring tissues, and the positive rate in carcinoma tissues was significantly higher. It indicated that the aberrant CpG islands methylation of tumor suppressor genes promoter is a early and frequent event with specificity during the occurrence and development of gastric cancer. The aberrant promoter CpG islands methylation existed simultaneously in many tumor suppressor genes is one of the important mechanisms which induced the occurrence of gastric cancer.2. Methylation of the promoter CpG islands of p16, RUNX3 and CHFR genes were increasing gradually from normal gastric mucosa, neighboring tissues to carcinoma specimens, indicating that aberrant methylation of these three genes can used as a sensitive parameter in the early diagnosis of gastric cancer.3. Aberrant promoter CpG islands methylation of p16 gene is significant associated with the degree of histological differentiation, invasion depth and lymphonode metastasis status of gastric cancer tissues. It can be a good parameter to evaluate the degree of histological differentiation invasion, lymphonode metastasis status and invasion depth of gastric cancer.4. Aberrant promoter CpG islands methylation of RUNX3 and CHFR gene of gastric cancer specimens was significantly correlated with the tumor size. It can be used to evaluate the growth of gastric cancer cell in gastric cancer.