Expression And Clinical Significance Of MGMT,DNA-PKcs In Gastric Carcinoma

IntroductionGastric cancer is a familiar malignant gastrointestinal tumor which seriously threatens people's health.The treatment of Gastric cancer is a combination composed of surgery,chemotherapy,radiotherapy and molecular targeted therapy.For the past few years,people pay more and more attention to carcinoma therapy.The presence of O~6-alkylguanine in DNA can have a number of deleterious cellular effects as this adduct is one of the principal cytotoxic,mutagenic and carcinogenic lesions induced by exposure to alkylating agents.By repairing O~6-alkylguanine in DNA,O~6-alkylguanine-DNA-alkyltransferase(MGMT) provides protection against these effects.The alkyl group from the O~6 position is transferred to a cysteine in the protein in a process that regenerates the guanine base but inactivates the repair protein.The DNA-PKcs is comprised of the catalytic subunit of DNA-PK and the KuT0 and Ku80 subunits.DNA-PK is another nuclear protein involved in the detection and repair of DNA damage.This serine-threonine kinase is activated by the presence of double-strand breaks in DNA and phosphorylates several DNA-binding proteins, including the p53 tumor suppressor gene product and numerous transcription factors(e.g.C-fos,Spl)Researches on combination determination of MGMT and DNA-PKcs were rare, and there was no report on the relationship between their expression and clinicopathological parameters both in domestic and foreign countries.Now clinical treatment mostly depended on experience.The combination markers determination of MGMT and DNA-PKcs and prognosis of much value was still scarce,which is an urgent problem to be solved.In this study,we detected the expression of MGMT and DNA-PKcs by using tissue chip technology and immunohistochemical SP methods to investigate the expression,as well as to study the correlation with clinicopathological parameters in human gastric cancer and significance.Methods1,Patients124 gastric cancer cases underwent completely resected operation,which were enrolled from the first affiliated hospital of China Medical University(CMU) and Liaoning Cancer Hospital from October 2005 to August 2006,and none of them underwent chemotherapeutics before operation.All the cases included 92 male and 32 female patients with median age of 60 years,ranged from 24 to 85 years.The histologic type of all cases is adencarcinoma with 40 cases of well differentiation(32.3%),25 moderated diferentiation(20.1%) and 59 poor diferentiation(47.6%).There were 76 cases with muscular layer invasion(61.3%) and 48 placenta percreta invasion(38.7%). There were 100 cases with lymph node metastasis(80.6%).There were 17 cases in stageⅠ(13.7%),46 in stageⅡ(37.1%),37 in stageⅢ(29.8%)and 24 in stageⅣ(19.4%).2,MaterialsThe monoclonal antibodies against MGMT,DNA-PKcs S-P immunohisto -chemical kits and DAB substrate solution were purchased from Fuzhou Maixin Biotechnology,Inc.3,MethodsImmunohistochemical staining S-P method was performed on tissue microarray sections made of 124 cases of gastric carcinoma.All slides were treated with citric acid buffer(PH=6.0) to recover the antigen activity in autoclave.4,AssessmentOutcome definition of MGMT and DNA-PKcs and were stained yellow particles in nucleus or cytosol.Judging reference is followed by dyeing cells numbers and intensity,which product 0～1 as negative,2～4 as positive,＞4 as strongly positive. 5,Statistical analysisStatistical methods Chi-square test and Spearman rank correlation test were performed by SPSS soft-ware version 13.0.The statistical difference was considered significant when P＜0.05.ResultsThe positive expression rates of MGMT and DNA-PKcs in gastric carcinoma were 58.9%(73/124),31.5%(39/124).The positive expression rates of MGMT was correlated with differentiation and sex(P＜0.05).There was a positive relationship between the expression of MGMT and DNA-PKcs(r=0.342,P=0.000).Conclusion1,The positive expression rates of MGMT in gastric carcinoma was high, respectively,the positive expression rate of DNA-PKcs in gastric carcinoma was low.2,The positive expression rates of MGMT was correlated with differentiation and sex.None of them was associate with age,lymph node metastasis.3,There was a positive relationship between the expression of MGMT and DNA-PKcs.