الفهرس 
Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
Carcinogenesis is a multistep process and carcinoma progresses as the result of accumulated genetic alterations that cause the cell to escape the normal controls on cell growth and differentiation.Stomach cancer is the second most common neoplasm, representing approximately 10% of newly diagnosed malignancies and accounting for more than 12% of cancer deaths. Helicobacter pylori (H.pylori) infection and the expression of apoptosisrelated proteins (bcl2 and p53) have recently been argued to be important factors of gastric carcinogenesisApoptosis is the prevalent form of programmed cell death that when altered, contributes to a number of human diseases, including cancer. Two apoptosis related antigens, Bcl2 and p53, have been suggested to play an important role in tumor progression by affecting the magnitude of tumor cell apoptosis, or by altering the proliferation of tumor cells.The series of genetic changes leading to malignancy in gastric cancer is well reported. This include mutation of p53 tumor suppressor gene which is a major step in carcinogenesis and the most common genetic defect known to occur in diverse human carcinomas including gastric cancer. The p53 gene is a tumor suppressor gene located on the short arm of chromosome 17. It encodes a 53 KDa nuclear phosphoprotein (p53 protein), which binds to and modulates the expression of genes important for DNA repair, cell division and cell death by apoptosis. This gene regulates the onset of DNA replication at G1S boundary and p53 is also a component of a spindle check point that ensures the maintenance of diploidy.It is now well established that most p53 missence mutations alter the conformation of the protein leading to a prolonged half life. There is an accumulation in the nucleus of the tumor cell, the levels of which can be determined by immunological methods. By contrast, the product of the wild type gene is undetectable because of its short half life. The accumulation of mutant p53 protein in tumor cells can be released into the extracellular environment, such as into the serum, and can thus be examined by ELISA.Most of the previous studies have used immunohistochemistry for the detection of the accumulation of the mutated proteins, although it is relatively subjective. So, it would be helpful to have a more sensitive method such as immunoblotting technique and the ELISA assay, which does not require a tissue specimen and is easy to perform.The bcl2 proto oncogene was cloned from the break point region of the chromosomal translocation. Bcl2 family proteins are key regulators of apoptosis and play an essential role in cancer. Bcl2 contributes to neoplastic cell expansion by preventing normal cell turnover caused by physiological cell death mechanisms.There is increasing evidence to suggest that gastric infection with the bacterium H.pylori infection damages gastric barrier function and stimulates gastric cell proliferation, which leads to mucosal repair, but which can also induce cellular DNA damage. The most frequent epiphenomenona of DNA alteration is activation of oncogenes and/ or mutation of tumor suppressor genes. The role of these genes has been studied in many types of carcinogenesis and, to a lesser extent, in gastric carcinogenesis, but their interrelation with H.pylori infection has yet to be defined.The aim of this study was to design the use of immunological techniques such as, immunoblotting and immunostaining for the demonstration of the mutant p53 and bcl2 proteins accumulation in tumor cells and to use ELISA assay as a simple assay for investigated serum p53 and bcl2 antigen concentrations. We also study the association of H.pylori infection as a risk factor for the development of gastric carcinoma with expression of mutant p53 and bcl2 genes.In this study, IgA antibodies against H.pylori in serum gave seropositive in 31 (68.9%) obtained from 45 gastric cancer patients assayed by ELISA technique. The seropositive H.pylori was more frequently in gastric tumors larger than 5 cm (82.1%) than tumors less than 5 cm (47.1%) in size. Positive H.pylori was also significantly evident in the antrum (80%) more than in the body (69.2%) or cardia (28.6%) (p=0.03). Also,seropositive H.pylori was detected in 42.9% of tumors showed negative apoptotic index, 72.2% in mild apoptosis index and in 75% of moderate to marked apoptosis index. Although, there was a tendency of increasing apoptosis index in seropositive H.pylori, it did not reach statistical significance (p=0.26). A positive association was found between H.pylori seropositive and tumor stage. where, H.pylori seropositive was more frequently in stage III and stage II than stage I (p=0.004, p=0.02, respectively).The p53 protein concentration in the patients sera with gastric cancer was detected by ELISA technique. The serum concentration of p53 protein ranged from 0.28 to 0.58 ng/ml, with average 0.41(R+(B0.07 ng/ml. These concentration were significantly higher than those in healthy blood donors as a negative control 0.19(R+ (B0.11 (p=0.001). Positive serum p53 protein samples were found in 17 out of 45 gastric cancer patients examined (37.8%). where, serum p53 protein concentration above the cut off value 0.42 ng/ml was defined as positive. Positive serum p53 protein was detected more frequently in large lesions >5 cm (42.9%), compared to small lesions <5 cm (29.4%) (p=0.36). A significant correlation was found between serum p53 antigen and tumor stage (p=0.003). where, the incidence of serum p53 protein was more frequently in stage III (65%) than stage II (9.1%) and stage I (21.4%). Also, the positive rate of serum p53 protein was (70.6%) in positive H.pylori infection and (29.4%) in negative H.pylori infection, was a significant difference (p=0.008).The occurrence of p53 expression was analyzed in 45 cases of gastric cancer cases by western blotting analysis, using an anti human p53 monoclonal antibody. The nuclear protein extract from human gastric tumor specimens was immunoblotted relative to protein standards of known molecular weight. Monoclonal antibody p53 detects a single band of 53 KDa in 31/45 (68.9%) of the gastric tumor specimens examined. whereas, no bands were detected in the normal gastric mucosa.