Expression Pattern of EphB2 in Gastric Cancer

PURPOSE: The EphB2 receptor, a member of the receptor tyrosine kinase family, is a target gene of the Wnt signaling pathway and may achieve a tumor suppressor function through regulation of cell growth and migration. Our aim was to determine whether an altered expression of EphB2 might be associated with gastric cancer development and, if so, to determine to which pathologic parameter it is linked. MATERIALS AND METHODS: For the construction of the gastric cancer tissue microarray, 83 paraffin-embedded tissues containing gastric cancer areas were cored 3 times and transferred to the recipient master block. The expression patterns of EphB2 were examined on tissue microarray slides by using immunohistochemistry and were compared using pathologic parameters, including histological type, depth of invasion, lymph node metastatsis, and peritoneal dissemination. RESULTS: The EphB2 protein was expressed in the normal gastric mucosal epithelium, especially in the bottom of the mucosa. We found loss of EphB2 expression in 30 (36.1%) of the 83 gastric cancer tissues. Statistically, loss of EphB2 expression was more common in gastric cancer with lymph-node metastasis. There was no significant correlation between EphB2 expression and depth of invasion, histologic type, or peritoneal dissemination. CONCLUSION: Our findings suggest that loss of EphB2 expression may represent a critical step in gastric carcinogenesis.

Mutation of the Chk1 Gene in Gastric Cancers with Microsatellite Instability

PURPOSE: The protein kinase Chk1 is required for cell cycle arrest in response to DNA damage and is shown to play an important role in the G2/M checkpoint. The aim of this study was to investigate the relationship between microsatellite instability and frameshift mutation of the Chk1 gene in gastric cancers. MATERIALS AND METHODS: The microsatellite instability was analyzed in 95 primary gastric carcinomas by using microdissection and 6 microsatellite markers. We also performed single strand conformational polymorphism and sequencing to detect frameshift mutation of the Chk1 gene. RESULTS: We found positive microsatellite instability in 19 (20%) of the 95 gastric cancers, 13 high- and 6 low-frequency microsatellite instability cases. The frameshift mutation of Chk1, which resulted in a truncated Chk1 protein, was detected in two high-frequency microsatellite instability cases. CONCLUSION: These data suggest that the microsatellite instability may contribute to the development of gastric carcinomas through inactivation of Chk1.

Expression Pattern of KLF6 in Korean Gastric Cancers

PURPOSE: KLF6, a member of the KLF family, is a ubiquitous zinc finger tumor suppressor protein that is mutated in several human cancers. Our aim was to determine whether the expression pattern of KLF6 might be associated with gastric cancer development and, if so, to determine to which pathologic parameter it is linked. MATERIALS AND METHODS: For the construction of the gastric cancer tissue microarray, 85 paraffin-embedded tissues containing gastric cancer areas were cored 3 times and transferred to the recipient master block. The expression pattern of KLF6 was examined on tissue microarray slides by using immunohistochemistry and was compared with pathologic parameters, including histologic type, depth of invasion, lymph node metastasis, and peritoneal dissemination. RESULTS: The KLF6 protein was expressed on superficial and foveolar epithelial cells in the gastric mucosa. We found loss of KLF6 expression in 28 (32.9%) of the 85 gastric cancer tissues. There was a significant correlation between loss of KLF6 expression and lymph-node metastasis. However, other pathologic parameters, such as histologic type, depth of invasion, and peritoneal dissemination, were not statistically associated with loss of KLF6 expression. CONCLUSION: Our findings suggest that loss of KLF6 expression may contribute to abnormal regulation of gastrointestinal epithelial cell growth and differentiation and to the development and/or progression of Korean gastric cancer.

Functional Defect of the Fas Mutants Detected in Gastric Cancers

PURPOSE: The balance between cell proliferation and apoptosis is crucial for homeostatic maintenance in a cell population. Decreased apoptosis or uncontrolled proliferation can lead to cancer. The Fas receptor signal through a cytoplasmic death domain is very important in the apoptotic pathway. To identify the effect of the death domain of the Fas gene in the development and/or progression of gastric cancer, we examined the apoptotic potential of five known Fas mutants detected in gastric cancers. MATENRIALS AND METHODS: A wild-type Fas gene was cloned with cDNA from normal liver tissue and full length Fas was sequenced. Mutants of the gene were generated with site- directed mutagenesis by using the wild-type gene and specific primers. Wild- and mutant-type genes were transfected to HEK293 cells. Forty-eight hours after transfection the cells were stained with DAPI and cell death was counted under fluorescent microscopy. RESULTS: In wild-type Fas-transfected cells, the percentage of apoptotic cells was 85.9+/-3.6%, and significant cell death and classic morphologic signs of apoptosis were observed. However, the percentages of apoptotic cells transfected with N239D, E240G, D244V, and R263H of tumor-derived mutant Fas were 29.5+/-2.08%, 28.5+/-3.34%, 25.225+/-2.06%, and 36.625+/-4.49%, respectively. CONCLUSION: These results suggest that inactivation of Fas caused by mutations in the death domain of the Fas gene may be one of the possible escape mechanisms against Fas-mediated apoptosis and that inactivating mutation of the Fas may contribute to the development or progression of gastric cancers.

Loss of Heterozygosity and Microsatellite Instability at Multiple Tumor Suppressor Genes in Gastric Carcinomas

PURPOSE: The aim of this study was to investigate the frequency of loss of heterozygosity and the microsatellite instability at multiple tumor suppressor gene loci in gastric adenocarcinomas. MATENRIALS AND METHODS: Loss of heterozygosity and the microsatellite instability at several tumor suppressor gene loci were analyzed in 29 primary gastric carcinomas by using microdissection and the polymerase chain reaction. RESULTS: Twenty-three (79%) of the 29 cases demonstrated loss of heterozygosity at one or more loci. The frequency of loss of heterozygosity at the p53 locus was the highest (63%) and those at the VHL, APC, p16, Rb, MEN1, BRCA1, DPC4, 3p21, and 16p13 region were 41%, 36%, 19%, 29%, 33%, 26%, 21%, 32%, and 11%, respectively. Compared with histological type, loss of heterozygosity was more common in diffuse-type gastric cancer (P<0.01). Interestingly, 9 of 10 tumors with allelic deletion at the p53 locus showed loss of heterozygosity at other tumor suppressor gene loci. The microsatellite instability was also detected in 6 (20%) of the 29 cases at one or more loci. CONCLUSION: These data suggest that frequent loss of heterozygosity and the microsatellite instability at multiple tumor suppressor genes might be required for the development and the progression of gastric carcinomas and that p53 allelic loss may be the most frequent event in the development of gastric carcinomas.

Expression Pattern of Caspase 2 in Korean Gastric Cancers

PURPOSE: Caspase 2, a member of the family of ICE-like proteases, is activated by the Fas pathway and induces apoptosis by triggering the caspase cascade. The purpose of this study was to determine whether the expression pattern of caspase 2 might be associated with gastric cancer development and if so, to determine to which pathologic parameter it is linked. MATENRIALS AND METHODS: For the construction of the gastric cancer tissue microarray, 78 paraffin-embedded tissues containing gastric cancer areas were cored 3 times and transferred to the recipient master block. The expression pattern of caspase 2 was examined on tissue microarray slides by using immunohistochemistry and was compared with pathologic parameters, including histologic type, depth of invasion, lymph node metastasis, and peritoneal dissemination. RESULTS: Caspase 2 was expressed on superficial and foveolar epithelial cells and lymphocytes in the gastric mucosa, mainly in cytoplasm. We found loss of caspase 2 expression in 41 (52.6%) of the 78 gastric cancer tissues. Statistically, histologic type and other pathologic parameters were not related with loss of caspase 2 expression. CONCLUSION: Our findings provide enough evidence that loss of caspase 2 expression may contribute to the development of Korean gastric cancer and that it might be one of the possible escape mechanisms from apoptosis in gastric cancer.

Association of the Interleukin-1beta and Interleukin-1 Receptor Antagonist Genetic Polymorphism and Korean Gastric Cancer

PURPOSE: Interleukin 1beta (IL-1beta) polymorphisms are associated with hypochlorhydria, atrophic gastritis, and increased risk of gastric cancer in Caucasians. We tried to determine whether the IL-1beta and IL-1 receptor antagonist (IL-1 RN) genetic polymorphisms contribute to the development of gastric cancer and the specific type of gastritis in Korean. MATENRIALS AND METHODS: The study population was comprised of 128 gastric cancer patients with histologically proven carcinoma and 63 normal healthy individuals. Sixty-eight carcinomas were of intestinal-type and sixty tumors were of diffuse-type. No patient had a familial gastric cancer history. The 511 bp and 31 bp polymorphisms in the IL-1beta were genotyped by polymerase chain reaction (PCR)-restriction fragment length polymorphism. The polymorphism of the IL-1 RN was analyzed with variable number tandem repeat after PCR. RESULTS: The genotype of 511C/-31T of IL-1beta and allele 1 of IL-1 RN was dominant in the present subjects. The allelic frequencies of the C allele IL-1beta, which is a high risk genotype for gastric cancer, were 0.551 and 0.429 in gastric cancer and normal controls, respectively. Statistically, significant difference in allelic frequencies of three polymorphic sites between gastric cancer patients and normal controls, and between intestinal-type and diffuse-type was not observed. CONCLUSION: These results suggest that the polymorphisms of IL-1beta and IL-1 RN may not contribute to the development of Korean gastric caner and that other endogenous or exogenous factors will be important for gastric carcinogenesis.