The Promoter Hypermethylation Status Of Tumor Suppressor Gene Fas In Esophageal Squamous Cell Cancers

Objective: To investigate the methylation of Fas gene in esophageal squamous cell carcinoma tissues, adjacent tissues, the normal tissue, preoperativeand postoperative plasma and its expression. Discuss the role of Fas in the occurrence and development of esophageal squamous cell carcinoma and its clinical significance.Methods: 72 cases of esophageal squamous cell carcinoma specimens from January 2014 to January 2015 in the First Affiliated Hospital of Soochow University, each case was taken from the cancer tissue, adjacent tissue(away from the tumor margin 0.5cm) and the normal tissue(normal esophageal mucosa above 5cm). Of the 72 patients, 54 are males and 18 are females. Their ages are from 43 to 82 years old and the median age is 62 years old. According to UICC’s esophagus cancer TNM staging standard(2009), of the 72 cases, 11 cases are in stage I, 31 cases in stage II, 26 cases in stage III, and 4 cases in stage IV, including 30 cases of high differentiation carcinoma, 26 cases of middle differentiation carcinoma and 16 cases of low differentiation carcinoma, which include 13 cases of upper esophageal cancer, 35 cases of middle esophageal cancer, 24 cases of lower esophageal carcinoma. Specimens were stored in liquid nitrogen in the last half hour after surgical resection and transferred to-80℃refrigerator, all patients had not received radiotherapy and chemotherapy before operation. 66 cases of esophageal cancer patients before and after surgery were left to take blood 2ml, the plasma was kept in therefrigerator of-80℃ refrigerator after centrifugation.Using methylation specific PCR(MSP) to detect Fas gene methylation in plasma and tissues of the above. The expression of Fas gene was detected by RT-PCR method and immunohistochemical S-P method, and the experimental results were statistically analyzed with the clinical and case data.Results:1、Expression of Fas gene in esophageal cancer tissues, adjacent tissues and normal mucosa tissuesthe expression rates of Fas gene in 72 cases of esophageal cancer tissues, adjacent tissues and normal mucosa tissues were respectively 23.6%(17/72), 70.8%(51/72) and 90.3%(65/72), the expression rate of Fas in cancer tissues was significantly lower than that in adjacent tissues andnormal mucosa tissues(χ2=71.537,P<0.05).2、Methylation status of Fas gene in esophageal cancer tissues, adjacent tissues and normal mucosa tissuesThe positive rates of Fas were respectively 66.7%(48/72), 12.5%(9/72) and 5.6%(4/72) in 72 cases of esophageal cancer tissues, adjacent tissues and normal mucosa tissues. The positive rate of methylation in cancer tissues(66.7%) was significantly higher than that in the adjacent tissues(12.5%) and the normal tissues(5.6%)(χ2=79.546,P<0.05); Methylation status of esophageal cancer was not related to gender, age, location, degree of differentiation and TNM stage(P>0.05).3、The relationship between Fas gene expression and methylation in esophageal cancerThe Fas gene expression rate was 23.6%(17/72) in 72 cases of esophageal cancer.The expression rate was significantly lower than that in adjacent tissues andnormal mucosa tissues.Among the 48 positive samples, only 4(8.33%) of Fas gene expression were detected. However, among 24 Fas gene methylation negative samples, 13(54.17%) cases were detected. The expression of Fas gene in these methylation positive samples was significantly lower than that in methylation negative samples and both into a significant negative correlation(χ2=18.635,P<0.05).4、Methylation status of Fas gene in plasma of patients with esophageal cancer before and after operationThe rates of Fas methylation in plasma of 66 patients with esophageal cancer before and after operation were respectively 45.5%(30/66), 16.7%(11/66); Preoperative plasma Fas methylation was positive in 30 of 19 patients who turned negative after radical resection of esophageal cancer, the rate of Fas methylation in plasma was significantly lower than that before operation(χ2=12.772,P<0.05); The methylation of Fas gene was not detected in the plasma of the patients with methylation negative in esophageal cancer before and after operation.Conclusions:1、The expression of tumor suppressor gene Fas in esophageal cancer is decreased, and the occurrence of Fas methylation is one of the important mechanisms.2、The methylation status of Fas gene in plasma is closely related to the methylation status of tumor tissue.3、Fas gene may be an important indicator of early diagnosis and clinical therapeutic effect, and also the important target of gene therapy of esophageal cancer.