Expression And Clinical Significance Of TS, DNA-PKcs And GST-π In Gastric Carcinoma: A Tissue Microarray Analysis

IntroductionGastric cancer is the most common gastrointestinal carcinoma in China,which mortality and mortality ranks second in all kinds of the malignant tumors.Operation is the primary treatment for early stage of gastric cancer, and chemotherapy is the most important adjuvant therapy, while chemotherapy is the primary method for advanced stage of gastric cancer. Because of the primary and acquired tumor insensitivity to chemotherapeutics, multidrug resistance often influences the effect of chemotherapy, which is one of the most common and difficult clinical problems in antineoplastic therapy.The phenomenon of tumor cell's cross-resistance to anticancer drugs which chemical constitutions are completely different and mechanisms of action are various is so-called multidrug resistance(MDR).Its mechanism is extremely complicated, and the followings are fundamentally identified at present:①drug-transport proteins,poss-essing the function of drug pumping;②drug metabolism enzymes,participating in detoxicating function, such as glutathione-S-transferase-Pi (GST-π), et al;③drug target enzymes, such as thymidylate synthase (TS),which quantitate or qualitative alteration can directly contribute to therapeutic effects;④DNA damage repair,such as DNA-dependent protein kinase catalytic subunit (DNA-PKcs),et al;⑤cell cycle arrest and apoptosis-related genes;⑥signal transducting system-related genes.Chemotherapy is the one major therapeutic method for gastric carcinoma, of which fluorouracil and platinum are the fundamental antineoplastic drugs. While multi-drug resistance(MDR) often interfere with the effect, three enzymes (TS,DNAPKcs and GST-π) play important roles in the multidrug resistance to chemotherapy. There is no current report on combined detection of TS,DNA-PKcs and GST-πin gastric carcinoma,so this study was designed to investigate the expression of TS,DNA-PKcs and GST-πand their clinical significance in gastric carcinomas.Methods1. Patients:124 gastric cancer cases underwent completely resected operation, which were enrolled from the first affiliated hospital of China Medical University (CMU) and Liaoning Cancer Hospital, and none of them underwent chemotherapyeut-ics before operation. There were 92 male and 32 female patients with median age of 60 years. The histologic type of all cases is adencarcinoma with 11 cases of well differentiation(8.9%),29 moderated diferentiation (23.4%) and 84 poor diferentiation (67.7%).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%). 16 normal tissue cases were selected as controls, which were 5 centimeters far from gastric cancer tissues.2. Materials:The monoclonal antibodies against DNA-PKcs was purchased from Newmarkers Biotechnology,Inc, the monoclonal antibodies against TS and GST-π,S-P immunohistochemical kits and DAB substrate solution were purchased from Fuzhou Maixin Biotechnology, Inc.3. Methods:Immunohistochemical staining S-P method was performed on tissue microarray sections made of 124 cases of gastric carcinoma and 16 cases of paracancerous tissue. All slides were treated with citric acid buffer (PH=6.0) to recover the antigen activity in autoclave.4. Assessment:Outcome definition of DNA-PKcs was stained yellow particles in nucleus, and outcome definition of TS and GST-πwere stained yellow particles in cytosol or nucleus.Judging reference is followed by positive cells≤10% as negative, and＞10% as positive.5. Statistical analysis:Statistical methods Chi-square test, Spearman rank correlation test and Fisher exact test were performed by SPSS software version 11.5. The statistical difference was considered significant when P＜0.05.Results1. The positive expression rates of TS and GST-πin gastric carcinoma were 81.5% and 76.6%, respectively. They were all significantly higher than those in normal tissues (P＜0.05), while the positive expression rate of DNA-PKcs in gastric carcinoma was 69.4%, which was similar to that in normal tissues (P＞0.05).2. The positive expression rates of TS and DNA-PKcs in poor differentiated adenocarcinoma were significantly higher than those in well and moderated differentiated adenocarcinoma(P＜0.05). The expression of GST-πin well and moderated differentiated adenocarcinoma were significantly higher than that in poor differentiated adenocarcinoma (P＜0.05). The positive expression rate of TS was correlated with TNM staging, which means TS expression increased with clinical TNM staging (P＜0.05); the positive expression level of DNA-PKcs was associated with the lymph node status (P＜0.05).3. There was a positive relationship between the expression of TS and DNA-PKcs (r_s=0.178,P＜0.05),while there was no correlation between the expression of GST-πand TS as well as GST-πand DNA-PKcs (P＞0.05).Conclusion 1. The advantages of constructing tissue microarray and detection by irnmunohistochemical staining are displayed in many respects, in which it possesses higher output, lower cost, less error and greater validity.2. TS and GST-πmay be important factors to cause primary drug-resistance in gastric carcinoma, and the positive expressions of TS and DNA-PKcs are associated with poor differentiation, late clinical stage and lymph node metastasis, which indirectly represents that TS and DNA-PKcs may become prognostic indicators for gastric carcinoma.3. There was a positive relationship between the expression of TS and DNA-PKcs, which possibly reflects that the coordination between DNA duplication and DNA damage repair of the tumor cells.4. TS,DNA-PKcs and GST-πplay different roles through different mechanisms in multi-drug resistance to gastric cancer, which reflects that the multi-drug resistance mechanisms in gastric cancer are the results of interaction of multiple genes.