Epigenetic alterations of CYLD promoter modulate its expression in gastric adenocarcinoma: A footprint of infections.

Gastric cancer (GC) is one of the most common causes of cancer-related death in the world, with multiple genetic and epigenetic alterations involved in disease development. CYLD tumor suppressor gene encodes a multifunctional deubiquitinase which negatively regulates various signaling pathways. Deregulation of this gene has been found in different types of cancer. This study aimed to evaluate for the first time the CpG island methylation pattern of CYLD gene promoter, and its expression level in gastric adenocarcinoma. CYLD messenger RNA expression and promoter methylation in 53 tumoral and their non-neoplastic counterpart tissues were assessed using quantitative polymerase chain reaction and bisulfite sequencing. Also, we investigated the impacts of the infectious agents including Helicobacter pylori (H. pylori), EBV, and CMV on CYLD expression and promoter methylation in GC. Results showed that the expression level of CYLD was downregulated in GC, and was significantly associated with gender (female), patient's age (<60), high grade, and no lymph-node metastasis (p = 0.001, 0.002, 0.03, and 0.003, respectively). Among the 31 analyzed CpG sites located in about 600 bp region within the promoter, two CpG sites were hypermethylated in GC tissues. We also found a significant inverse association between DNA promoter methylation and CYLD expression (p = 0.02). Furthermore, a direct association between H. pylori, EBV, and CMV infections with hypermethylation and reduced CYLD expression was observed (p = 0.04, 0.03, and 0.03, respectively). Our findings indicate that CYLD is downregulated in GC. Infectious agents may influence CYLD expression.

CTNNBIP1 downregulation is associated with tumor grade and viral infections in gastric adenocarcinoma.

Gastric cancer is a life-threatening disease; resulting from interaction among genetic, epigenetic, and environmental factors. Aberrant dysregulation and methylation changes in Wnt/ß-catenin signaling downstream elements are a prevalent phenomenon encountered in gastric tumorigenesis. Also, viral infections play a role in gastric cancer development. CTNNBIP1 (ß-catenin interacting protein 1) gene is an antagonist of Wnt signaling which binds to the ß-catenin molecules. The CTNNBIP1 function as tumor suppressor gene or oncogene in different types of cancer is controversial. Moreover, its function and regulatory mechanisms in gastric cancer progression is unknown. In the present study, we examined CTNNBIP1 gene expression, the methylation status of the regulatory region of the gene, and their association with Epstein-Barr virus (EBV), and cytomegalovirus (CMV) and Helicobacter pylori infections in human gastric adenocarcinoma tissues in comparison with their adjacent nontumoral tissues. Our data revealed a significant downregulation of CTNNBIP1 in gastric tumors. Female patients showed lower level of CTNNBIP1 than males (p < 0.05). Also, decreased expression of CTNNBIP1 was markedly associated with well-differentiated tumor grades (p < 0.05). No methylation change was observed between tumoral and nontumoral tissues. Additionally, CTNNBIP1 down regulation was significantly associated with CMV infection (p < 0.05). In the absence of EBV infection, lower expression of CTNNBIP1 was observed. There was no association between H. pylori infection and CTNNBIP1 expression. Our findings revealed the tumor suppressor role for CTNNBIP1 in gastric adenocarcinoma. Interestingly, EBV and CMV infections modulate CTNNBIP1 expression.

FAT4 hypermethylation and grade dependent downregulation in gastric adenocarcinoma.

Gastric cancer is one of the major causes of death due to cancer in the world. It is a multi-factorial disease with epigenetic factors being also involved in its development. FAT4 is a tumor suppressor gene exerting an important role in cell adhesion. This study aimed at analyzing FAT4 expression and promoter methylation in gastric cancer. FAT4 expression was studied in 30 tumoral tissues and their non-tumoral counterparts using Taqman real time PCR method. Promoter methylation was assessed using bisulfite conversion method followed by sequencing. Tumor tissues showed reduced FAT4 expression (P = 0.04). FAT4 downregulation was associated with tumor grade, with higher repression at advanced grades. Significant increase of promoter methylation was observed in tumoral tissues. Reduced expression of FAT4 and increased methylation of its promoter may be one of the effective processes in turning a healthy stomach tissue into a tumor tissue.

Myofibroblast stromal presence and distribution in squamous epithelial carcinomas, oral dysplasia and hyperkeratosis.

PURPOSE: Stromal elements play a key role in growth and development of different neoplasms. Myofibroblasts are the major components and occur in stromal tissue during carcinogenesis processes. The purpose of this study was to review the frequency and the distribution pattern of myofibroblasts(αSMA-positive) in the stroma of squamous epithelial carcinoma and to compare values with those for with oral dysplasia and hyperkeratosis. METHODS: we evaluated αSMA protein frequency in hyperkeratosis (N =18), oral epithelial dysplasia (N=18) and oral squamous cell carcinoma (N=18) using immunohistochemistry. RESULTS: αSMA-positive expression was observed in 67% of OSCC tissue samples with network and spindle patterns, whereas it was seen in 22% with a focal pattern in dysplasia and in 6% with a scanty pattern in hyperkeratosis cases. CONCLUSION: These findings suggest that an increase in number of myofibroblasts and change in their distribution pattern occurs during carcinogenesis which can be an expression of their role in tumor invasive characteristics.