| IntroductionTissue microarray/tissue chip, is a newly developed array - bases high throughput technique with a conspicuous characteristic of small volume rich in information that facilitates gene expression investigation of very large numbers of tumors simultaneously. It is suitable to immunohistochemistry, DNA or RNA in situ hybridization with high efficiency and flexibility, and its results are highly uniform with remarkable credibility and comparability. Many reports have demonstrated that tissue microarray/tissue chip is a new powerful technique in pathology of tumors investigation. There have been some reports on investigating the expressions of tumor - related markers in gastrc carcinoma and its precancer-ous lesions with the tissue microarray during past five years.Gastric carcinoma is one of the commonest malignancies in China,. but the molecular mechanism of carcinogenesis, progression and metastasis of gastric carcinoma remained elusive. p73 gene is a new member of the tumor - suppressor gene p53 family, and has been regarded as a candidate of tumor - suppressor gene, because p73 gene encodes a protein that shares structural and functional homology with the p53 gene product. But recently, many studies have shown that the abnormal p73 gene is associated with neuroblastoma, malignant melanoma , prostatic carcinoma, and lung cancer. Som studies also indicated that there was a some extent correlation between the abnormal expression of P73 gene coding protein and the carcinogenesis and progression of gastric carcinoma. However, the molecular mechanism of carcinogenesis and progression of gastric cancer related to p73 gene is still unknown.ObjectiveTo detect the expressions of p73 and mp53 gene coding proteins in gastric carcinoma and their matched adjacent mucosa with methods of tissue - microar-ray and immunohistochamistry;to investigate the clinico - pathological significance of the relationship between p73 protein expression and the clinico - pathological behavior of gastric carcinoma, and to explore the mechanism of p73 involvement in carcinogenesis and progression of gastric cancer.Materials and MethodsClinical materials and tissue microarray construction;Surgically removed specimens of primary gastric carcinoma and their metastatic tumors as well as matched adjacent normal mucosa, intestinal metaplasia and dysplasia of the stomach were all retrieved from the pathological files of Cancer Institute, China Medical University and Tumor Hospital of Liaoning Province. Two paraffin blocks of tissue microarray were constructed using a Tissue Array Machine (Steve Leighton Beecher Instruments, USA) , Block A containing 101 (32 gastric cancer and 32 matched non - cancer mucosa, 5 dysplasia, 32 intestinal metaplasia) and Block B containing 124 ( 72 gastric cancer and 47 matched non -cancer mucosa, 1 dysplasia, 4 intestinal metaplasia) small cylindrical samples from archives of paraffin - embedded tissue blocks, 1. 0mm each in diameter. Four jxm thick series sections were then cut and stored for use.Immunohistochemistry: The SABC immunohistochemical stainning method was used in this study. The rabbit against human p73 polyclonal antibodiy (working dilution was 1:100) was bought from Bosder Com. , Wuhan. The monoclonal antibody against p53 ( ready to use) and SABC staining kit were from Zhonghshan Biotech Com. , Beijing. Known positive slides were used for positive control;and for negative control, tissue sections were incubated with 0. 01M PBS instead of the primary antibodies.Criteria for judging results: Brown grains existing in cytoplasm or nucleuswere considered as positive for p73 protein and nucleus for mp53 protein expression. Slides were scored semi - quantitatively based on staining intensity and distribution. Positive rate was assessed by the percent of positive cells in all counted cells (in 2 random chosen fields, x 400) and grades are;negative ( - ) , positive rate <5%;weakly positive ( + ) : 5 -25%;moderately positive ( ++ ) : 25 -50%;strongly positive ( +++ ) : >50%.Statistic analysis: All data were analyzed by SPSS 12.0 statistical software to evaluate the differences between different groups via chi - square test and correlation coefficient. A value of P <0. 05 was considered significant, and P < 0.01 remarkably significant.ResultsCases qualified for data analysis: After immunostaining, the cases qualified for grading and analysis were 139 (28 cases of normal gastric mucosa, 25 intestinal metaplasia, 5 dysplasia and 81 gastric cancer ). The positive immunoreac-tion for p73 protein located at the nuclear and/or cytoplasm, and mp53 at the unclear of cells.P73 protein expression in gastric cancer and precancerous lesions and the normal gastric mucosa: The positive rate of p73 expression in gastric cancer(90. 1% )was significantly higher than that in normal gastric mucosa (17. 9% ) ,P < 0. 01;The positive rate of p73 in intestinal metaplasia(44. 0% ) and dysplasia (80.0%) were significantly higher than that in the normal gastric mucosa(17. 9% ) ,respectively, P <0.05;While there was no significant difference between the p73 expressions in dysplasia and intestinal mateplasia, P >0. 05. The p73 positive rate in the tumor with Bor. III/IV type (92. 9%/100%) was significantly higer than that in the cancer with Bor. II type (57.1%), P<0.05. The positive rates of p73 protein expression in gastric cancers with metastasis (lymph node metastasis 94. 4% , liver metastasis 100% , ovarian metastasis 100% ) were significantly higher than that in the cancers without any metastasis (76. 2%), P<0.05.Relationship between the expressions of p73 and mp53 protein in gastriccancers;There was a close correlation between the expressions of p73 and mp53 gene coding protein in gastric carcinomas, P <0.01, r =0. 286.Conclusions1. There was a close correlation between the expression of p73 protein and carcinogenesis and progression of gastric cancer. P73 protein has similar construction to p53 protein, but its expression showed a positive correlation with mutant p53 protein expression( P <0. 01) . This finding indicates that p73 may play an role in the carcinogenesis of the stomach not as a tumor - suppressor gene, but as a simulant mutant p53 gene inhibiting the function of wild p53 gene. Further study is needed to illuminate the mechanism of gastric carcinogenesis related to p73.2. In pathology of tumor investigation, tissue microarray is a new powerful technique with a conspicuous characteristic of small volume rich in information that facilitates gene expression investigation of very large numbers of tumors simultaneously , and must be widely employed in tumor pathologic diagnosis and research in near future. |
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