Expression And Significance Of Survivin And Fas In Carcinogenesis Of Gastric Mucosa And Its Relation With H.Pylori Infection

BackgroundGastric carcinoma is among the most frequent causes of cancer death in the world. The development of gastric cancer, like many other malignancies, is a multi-step process featuring the accumulation of several genetic alterations; not only including the activation of OF oncogenes and the inactivation of tumor suppress genes, but also involving the inhibition of apoptosis genes. Imbalance of cell proliferation and apoptosis leads to the development of cancers, and may directly influence the biological behavior of carcinomas. Several apoptosis genes including pro-apoptotic genes such as Fas, Bax, Bak, Bcl-xs, Bad and anti-apoptotic genes such as Bcl-2, Bcl-xl, Mcl, IAP family (including Survivin) are involved in carcinogenesis and tumor progression. The imbalance between pro-apoptotic genes and anti-apoptotic genes plays a critical role in development and progression of gastric cancer. Survivin is a novel member of the inhibitor of apoptosis family and determines the susceptibility of tumor cells to pro-apoptotic stimuli. Just like other IAP members, survivin can suppress apoptosis through combination with Caspase-3, Caspase-7. Moreover, Survivin is also crucial for mitosis and cell cycle progression. It has reported that survivin is undetectable in terminally differentiated adult tissues and becomes prominently expressed in transformed cell lines and in most common human cancers of esophagus, colon, pancreas, prostate and breast. Some data indicate that high expression of survivin is correlated with poor prognosis and chemotherapy resistance. But the pathogenic role of Survivin in gastric cancer progression is largely unknown. The Fas-Fas ligand system is one of the factors involved in cell deathsignaling. Aberrations in the signaling pathways leading to Fas-mediated apoptosis in tumor cells have been reported in a variety of human malignant tumors. However, the Fas-mediated apoptotic pathway has not been sufficiently elucidated in human carcinogenesis of gastric mucosa. Epidemiological studies have consistently demonstrated the association between H. pylori infection and the risk of gastric cancer. Helicobacter pylori infection is strongly associated gastric cancer. Their functions and correlation between Survivin and Fas in carcinogenesis of gastric mucosa and its relation with H.pylori infection are updately unknown.OBJECTIVES: To investigate the expression and the clinical significance of both apoptosis genes, Survivin and Fas, in human tissues of chronic superficial gastritis, chronic atrophic gastritis with intestinal metaplasia, with atypical hyperplasia and gastric carcinoma and to study the correlation between two genes in gastric cancer. Further more we also want to explore the role of these apoptosis genes and their relation with HP infection in the carcinogenesis and progression of gastric cancer and molecular mechanisms of relevant immune escape.METHODS: The expression of Survivin-mRNA , Fas-mRNA and The expression of Survivin protein, Fas protein were detected respectively by in situ hybridization and streptavidin-peroxidase (S-P) immunohistochemistry method in Formalin-fixed paraffin and embedded human tissues and fresh frozen tissue samples, including 12 cases of nomal gastric mucosa, 22 cases of superficial gastritis, 25 cases of chronic atrophic gastritis with intestinal metaplasiaCIM), 37 cases of chronic atrophic gastritis with atypical hyperplasia and 52 cases of gastric carcinoma. Rapid Urease Test and HP special histological staining were used to evaluate H.pylori infection status in all the above patients' tissues. We also observed the correlation of Survivin and Fas expression with HP infection status, the relationship between Survivin-mRNA and Fas -mRNA expression in gastric cancer patients. The correlation of Survivin and Fas expression with the cancer histological classification, invasive depth, metastasis and TNM staging were also determined.RESULTS:Chapter 1: 1 Expression of survivin in clinical materialsThe positive rates of surviving-mRNA in patients with chronic atrophic gastritis with intestinal metaplasia, atypical hyperplasia and gastric cancer were 28% and43.2% and 69.2% respectively. In contrast, no surviving-mRNA and survivin protein expression was detectable in the normal gastric mucosa and in superficial gastritis samples. Survivin-mRNA expression in gastric cancer tissues were significantly higher than that in patients with chronic atrophic gastritis with intestinal metaplasia, atypical hyperplasia (p<0.01 and p<0.05). The expression rates of survivin protein in patients with chronic atrophic gastritis with intestinal metaplasia, atypical hyperplasia and gastric cancer were 16%,37.8% and 63.5%,respectively. Expression of survivin protein in all the above specimens was consistent with that of survivin-mRNA, also showed an ascending tendency. The frequency of survivin protein expression in gastric cancer tissues were significantly higher than that in patients with chronic atrophic gastritis with intestinal metaplasia, atypical hyperplasia (p<0.01 and p<0.05).2 Relationship between expression levels of survivin and clinicopathological parameters of gastric carcinomaStaining for survivin-mRNA and survivin protein were observed primarily in the cytoplasm and membrane of the gastric cancer cells. The percentage of survivin-mRNA and survivin protein expression in patients with high differentiation , moderate differentiation and Un-differentiation or poor-differentiation of gastric cancer were 59.2%> 62.5% and 88.2%, up-regulated gradually. The positive rates of survivin-mRNA and survivin protein in patients with poor-differentiated and undifferentiated cancer were significantly higher compared with that in highly differentiated cancer (p<0.05). The expressive level of survivin-mRNA and survivin protein in patients with positive lymph node metastasis were significantly greater than that in patients without lymph node metastasis (p<0.05). No significant relationship was identified between survivin-mRNA, survivin protein and invasive depth (p>0.05). Patients with metastasis showed a significantly increased survivin-mRNA and survivin protein expression as compared with those without metastasis (p<0.05).3 Association of expression levels of survivin with HP infectionThere was a positive relation between the expression of survivin-mRNA , survivin protein and HP infection rates in patients with chronic atrophic gastritis with atypical hyperplasia(p>0.05).No association were found between the expression of survivin-mRNA, survivin protein and HP infection rates in in patients with chronic atrophic gastritis with intestinal metaplasia and gastric cancer.4 Correlation between survivin-mRNA and Fas-mRNA expressionSignificantly negative relationship was found between the expression of survivin-mRNA and Fas-mRNA in patients with gastric carcinoma. The expressive level of Fas—mRNA in patients with Survivin—mRNA positive was greatly lower than that was observed in survivin-negative patients(P<0.05). Chapter 2:1 Expression of Fas in clinical materialsThe positivity of Fas-mRNA in the normal control, patients with superficial gastritis, chronic atrophic gastritis with intestinal metaplasia, with atypical hyperplasia and gastric cancer were 88.3%> 11.3%, 68%,64.9% and 36.5% respectively, which was down-regulated progressively during the course. Expression of Fas protein in all the above specimens was similarly consistent with that of Fas-mRNA, also showed a descending tendency. No significant difference existed between normal gastric mucosa and other non-cancerous lesions. Fas-mRNA and Fas protein expression in gastric cancer tissues were significantly lower than in the normal controls and patients with chronic atrophic gastritis with atypical hyperplasia (p<0.01, for all).2 Relationship between expression levels of Fas and clinicopathological parameters of gastric carcinomaStaining for Fas-mRNA and Fas protein were observed primarily in the cytoplasm of the gastric cancer cells. The positive percentage of Fas-mRNA and Fas protein expression in patients with high differentiation , moderate differentiation and Un-differentiation or poor-differentiation of gastric cancer were 48.2%> 37.2% and 17.7%, down-regulated. The positive rates of Fas-mRNA and Fas in patients with Undifferentiated and poorly differentiated cancer were significantly lower than that in well differentiated cancer (p<0.05). Fas-mRNA and Fas protein in patients without lymph node metastasis were significantly enhanced compared with that in patients with positive lymph node metastasis (p<0.05). No significant relationship was identified between Fas-mRNA, Fas protein and the invasive depth (p>0.05). No correlation was found between the expression of Fas-mRNA and Fas protein and metastasis in gastric cancer patients (p>0.05).3 Association of expression levels of Fas with HP infectionThere was a positive relation between the expression of Fas-mRNA, Fas protein and HP infection rates in patients with chronic superficial gastritis, atrophic gastritiswith atypical hyperplasia (p<0.05).No association were found between the expression of Fas-mRNA, Fas protein and HP infection rates in in patients with chronic atrophic gastritis with intestinal metaplasia and gastric cancer (p>0.05). Conclusions:The development of gastric cancer is a multi-step process featuring the accumulation of several genetic alterations; not only including the activation of oncogenes and the inactivation of tumor suppress genes, but also involving the inhibition of apoptosis genes. Evading apoptosis is critical for the expansion of gastric neoplasms. Our research has found that the expression and activity of Survivin was gradually up-regulated and conversely the expression and activity of Fas was progressively down-regulated during the course of gastric cancer progression. Our results suggest that alterations in Survivin and Fas genes have occurred at the early stage of gastric neoplasm and the precancerous stage. The imbalance between apoptosis genes Fas and Survivin plays a important role through the inhibition of apoptosis during the carcinogenesis and tumor progression of gastric cancer. In the present study, we also demonstrated that there was a positive correlation between the expression of Survivin-mRNA, Fas-mRNA and HP infection positive rates in patients with precancerous lesions such as chronic superficial gastritis, atrophic gastritis with atypical hyperplasia. Our data suggest that HP infection can promote the expression of Survivin and Fas in gastric epithelial cells. But on the other hand, expression of Survivin in non-neoplastic tissues is closely associated with HP infection and gastric inflammation, Why this happened may require further studies. There was a negative relation between the expression of survivin-mRNA and Fas-mRNA in patients with gastric carcinoma. The survivin positive cancer patients showed a significantly decreased Fas expression. Survivin enables cancer cells not only to suppress immune cell attack by inhabiting Fas-mediated apoptotic signaling, but also attack immune cells by induction of FasL. Co-expression of Survivin and Fas may suggest multiple pathways contributing to the inhabition of apoptosis in gastric cancer. Collectively, these abnormal expressions of Survivin and Fas in carcinogenesis of gastric mucosa must be involved in the pathogenesis and differentiation of gastric cancer. Detection of Survivin and Fas genes has positive effects on early diagnosis, malignancy determination, prognosis and treatment of gastric carcinoma. Apoptosis inhibition may be a general feature of neoplasia and identify Survivin and Fas as potential newtargets for apoptosis-based therapy in gastric cancer.