Association Of SNP Of MnSOD Promoter Gene With Susceptibilities And Radiosensitivity Of Esophageal Squamous Cell Carcinoma

Objective: To investigate the Association of single nucleotide polymorphisms(SNP) of Mananese superoxide dismutase (MnSOD) promoter gene with susceptibilities and radiosensitivity of esophageal squamous cell carcinoma(SCC).Method: 103 patients with esophageal SCC were recruited from the radiotherapy department of the Fourth Hospital of Hebei Medical University from September 2006 to december 2007. All patients were confirmed by histology. 195 healthy volunteers who had no clinical evidence of esophageal SCC were randomly selected from Chinese blood donors as control subjects. All cases and controls were from Chinese Han population. Five milliliter of venous blood from each subject was drawn in Vacutainer tubes containing EDTA and stored at 4℃.The genomic DNA was extracted within one week after bleeding by using proteinase K digestion followed by a salting out procedure. We analyzed the allele and genotype frequencies of MnSOD (-9T/C) using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Clinically, esophageal SCC was staged according to the UICC of 1997 classification. All patients were given to the 3DCRT group or the conventional radiotherapy group.The GTV was defined as any visible tumor on the image. The CTV was defined as the GTV plus a 3cm margin superior and inferior to the primary tumor and a 0.8cm~1.0cm radial margin. The PTV was defined as the CTV plus a 0.5cm longitudinal margin and a 0.5cm radial margin; In the conventional radiotherapy group,the portal was outlined on the conventional simulator. The target center was defined according to the presentation on barium and 1.5cm lateral margin from the border of GTV were included in the CTV. The involved regional lymphatics were also included in the CTV when the lymph's diameter was biger than 1cm. The prescribed dose was 60 Gy to 66 Gy in 6 weeks to 6.5weeks. The therapeutic effect was evaluated according to the image of barium swallow before and after radiotherapy,Genotype frequencies and allele frequencies were compared in the patients and the controls using Chi-squared (χ2) analysis and logistic regression.Results: 1 MnSOD promoter SNP with susceptibility to esophageal SCC: A significant difference was observed in the MnSOD allelotype distribution among esophageal SCC and healthy controls (χ2=4.645 P<0.05). Individuals with the C allele (C/T+C/C genotype) had significantly higher risk to develop esophageal SCC compared with the T/T, the adjusted odds ratio was 1.89 (95%CI=1.05~3.39); 2 Correlation of MnSOD (-9T>C) genotype to diseased region of esophageal SCC: The frequencies of T/T and C/T+C/C allelotype among three stagings were 83.3%,16.7%;76.5%, 23.5%;66.0%, 34.0% respectively. There was no statistical difference in allelotype distribution between four kinds of diseased regions of esophageal SCC(χ2=3.079 P>0.05). 3 Correlation of MnSOD (-9T>C)genotype to the length of esophageal SCC: A significant difference was observed in the MnSOD allelotype distribution among the different length of esophageal SCC (χ2=5.147, P<0.05).4 Correlation of MnSOD genotype to clinical stage of esophageal SCC: There were 93 cases completed radiotherapy which included 12 cases of stageⅠ, 34 cases of stageⅡand 47 cases of stageⅢ. The frequencies of T/T and C/T+C/C allelotype among three stages were 83.3%, 16.7%;76.5%, 23.5%;66.0%, 34.0% respectively. There was no statistical difference in allelotype distribution between three kinds of clinical stage. 5 Correlation of MnSOD genotype to curative effect of esophageal SCC: The frequencies of T/T and C/T+C/C allelotype among three grades of curative effect were 59.1%, 40.9%; 77.8%, 22.2%; 62.5%, 37.5% respectively. There was no statistical difference in allelotype distribution between three grades. In a further research we found that when the length was five centimeters or less than five centimeters there was no statistical difference in allelotype distribution between three grades of curative effect. But when the length was more than five centimeters a significant difference was observed in the MnSOD allelotype distribution among of differents of length. (χ2=2.658, P<0.05) .That was to say the curative effect of patients with C/T+C/C allelotype is better than patients with allelotype T/T when the length was more than five centimeters.Conclusion: 1 Individuals with the C allele (C/T+C/C genotype) had significantly higher risk to develop esophageal SCC compared with the T/T, the adjusted odds ratio was 1.89; 2 The association of the MnSOD(-9T>C) were not found to be associated with and staging of esophageal squamous cell carcinoma. 3 The curative effect of patients with C/T+C/C allelotype is better than patients with allelotype T/T among the patients with more than five centimeters tumor size.