Integrated Bioinformatics Analysis for Identifying the Significant Genes as Poor Prognostic Markers in Gastric Adenocarcinoma.

Gastric adenocarcinoma (GAC) is the most common histological type of gastric cancer and imposes a considerable health burden globally. The purpose of this study was to identify significant genes and key pathways participated in the initiation and progression of GAC. Four datasets (GSE13911, GSE19826, GSE54129, and GSE79973) including 171 GAC and 77 normal tissues from Gene Expression Omnibus (GEO) database were collected and analyzed. Through integrated bioinformatics analysis, we obtained 69 commonly differentially expressed genes (DEGs) among the four datasets, including 20 upregulated and 49 downregulated genes. The prime module in protein-protein interaction network of DEGs, including ADAMTS2, COL10A1, COL1A1, COL1A2, COL8A1, BGN, and SPP1, was enriched in protein digestion and absorption, ECM-receptor interaction, focal adhesion, PI3K-Akt signaling pathway, and amoebiasis. Furthermore, expression and survival analysis found that all seven hub genes were highly expressed in GAC tissues and 6 of them (except for SPP1) were able to predict poor prognosis of GAC. Finally, we verified the 6 high-expressed hub genes in GAC tissues via immunohistochemistry, Western blot, and RNA quantification analysis. Altogether, we identified six significantly upregulated DEGs as poor prognostic markers in GAC based on integrated bioinformatical methods, which could be potential molecular markers and therapeutic targets for GAC patients.

STAT1ß enhances STAT1 function by protecting STAT1α from degradation in esophageal squamous cell carcinoma.

STAT1, which carries tumor suppressor functions in several models, consists of two isoforms, namely STAT1α and STAT1ß. The biological function and significance of STAT1ß has never been examined in human cancer. We examined STAT1ß function in esophageal squamous cell carcinoma (ESCC) by transfecting a STAT1ß gene into various ESCC cell lines. The interaction between STAT1α and STAT1ß was examined by using co-immunoprecipitation and confocal microscopy. The prognostic significance of STAT1ß expression, detectable by immunohistochemistry and western blot, was evaluated in a large cohort of ESCC patients. Enforced expression of STAT1ß induced and prolonged the expression and phosphorylation of STAT1α in ESCC cells, and these effects were amplified by gamma-interferon (IFN-γ). We also found that STAT1ß interacts with STAT1α and decreases STAT1α degradation by the proteasome. Moreover, STAT1ß substantially increased the DNA binding and transcription activity of STAT1. STAT1ß also sensitized ESCC cells to chemotherapeutic agents, including cisplatin and 5-flurouracil. Using western blot and immunohistochemistry, we found that STAT1ß was frequently decreased in esophageal cancer, as compared to their adjacent benign esophageal epithelial tissue. Loss of STAT1ß significantly correlated with lymph node metastasis, invasion and shorter overall survival in ESCC patients. Therefore, STAT1ß plays a key role in enhancing the tumor suppressor function of STAT1α, in ESCC, in a manner that can be amplified by IFN-γ.

ERK expression and its correlation with STAT1 in esophageal squamous cell carcinoma.

BACKGROUND: Esophageal squamous cell carcinoma is one of leading causes of cancer-related deaths in Chaoshan region a high-risk region for esophageal cancer. Extracellular regulated protein kinases (ERK) usually play an important role in cell proliferation and differentiation. However, accumulating evidence has shown that the ERK was aberrantly expressed in cancers and correlated with STAT1 depression. RESULTS: The activated ERK downregulates STAT1 expression in ESCC cell lines and U0126 increases expression of STAT1. Our immunohistochemistry result also confirms that the expression of ERK inversely correlated with that of STAT1 in ESCC tumors. In addition, a significantly higher expression of ERK/p-ERK was found in ESCC tissues in comparison with case-matched normal esophageal tissues (p < 0.05). Moreover, the immunohistochemical analysis demonstrated that ERK expression was paralleled with the differentiation and clinical stage. In 74 patients with follow-up data, those with ERKlow tumors survived significantly longer than those with ERKhigh tumors (p = 0.04); patients with ERKlow/STAT1high tumors had the longest survival (p = 0.001). MATERIALS AND METHODS: To investigate whether ERK can mediated STAT1 expression in ESCC, we used the MEK plasmid and U0126, a MEK inhibitor, to treat the cell. To further confirm our in-vitro study, we detected the ERK, p-ERK and STAT1 expression in 131 ESCC cases and 22 case-matched normal esophageal tissues adjacent to the tumors specimens. CONCLUSIONS: These findings provide pathological evidence that ERK/p-ERK is negatively correlated with STAT1 in ESCC. Our data suggests that inhibition of ERK and/or restoration of STAT1 expression maybe useful therapeutic strategies for ESCC.

Chronic inflammation-related DNA damage response: a driving force of gastric cardia carcinogenesis.

Gastric cardia cancer (GCC) is a highly aggressive disease associated with chronic inflammation. To investigate the relationship between DNA damage response (DDR) and chronic inflammation, we collected 100 non-tumor gastric cardia specimens of Chaoshan littoral, a high-risk region for esophageal and gastric cardia cancer. A significantly higher proportion of severe chronic inflammation was found in dysplastic epithelia (80.9%) in comparison with that in non-dysplastic tissues (40.7%) (P<0.001). Immunohistochemical analysis demonstrated that DNA damage response was parallel with the chronic inflammation degrees from normal to severe inflammation (P<0.05). We found that DNA damage response was progressively increased with the progression of precancerous lesions (P<0.05). These findings provide pathological evidence that persistent chronic inflammation-related DNA damage response may be a driving force of gastric cardia carcinogenesis. Based on these findings, DNA damage response in non-malignant tissues may become a promising biomedical marker for predicting malignant transformation in the gastric cardia.

Correlation of STAT1 with apoptosis and cell-cycle markers in esophageal squamous cell carcinoma.

We recently found evidence that STAT1 in esophageal squamous carcinoma (ESCC) cells exerts tumor suppressor function, and it regulates five key regulators of apoptosis or cell-cycle progression, including Bcl-2, Bcl-xL, survivin, cyclin D1 and p21. In this study, we confirmed these findings in four ESCC cell lines. Using immunohistochemistry, we also assessed the expression of these proteins in 62 primary tumors. The expression of these markers was heterogeneous, ranging 39 to 69% of the cohort. Significant correlation was found between STAT1 and three proteins (p21, Bcl-xL and survivin), whereas only a trend was identified for cyclin D1 and Bcl-2. We then correlated the expression of these proteins with several clinicopathologic parameters including lymph node metastasis, depth of invasion, clinical stage and overall survival. Significant correlations were found between Bcl-2 and deep invasion (p = 0.033), survivin and lymph node metastasis (p = 0.006), as well as cyclin D1 and clinical stage (p = 0.014). Patients with p21-positive tumors had a significantly longer survival compared to those with p21-negative tumors (p = 0.031). To conclude, our findings support the concept that STAT1 exerts its tumor suppressor effects in ESCC via modulating the expression of key regulators of apoptosis and cell-cycle progression.

Esophageal intraepithelial invasion of Helicobacter pylori correlates with atypical hyperplasia.

Helicobacter pylori (H. pylori), a common pathogen residing in the gastrointestinal tract, has been well characterized in stomach cancer,while its correlation with esophageal cancer remains poorly understood. In this study, we aim to assess the relationship between esophageal intraepithelial H. pylori invasion and inflammation as well as atypical hyperplasia in esophageal squamous epithelial tissues. Esophageal squamous cell carcinoma (ESCC) tissue samples from 196 individuals from both southern and northern esophageal carcinoma high-risk areas in China were examined (125 from northern high-risk areas, 71 from southern high-risk area), while additional 30 samples were collected adjacent to the esophageal squamous cell carcinoma (A-ESCC). H. pylori infection was identified by Giemsa staining, immuno-histochemical staining, and H. pylori 16S rRNA-based PCR. A significant increase of H. pylori infection was found in tumor tissues (including ESCC and A-ESCC samples) compared to that of non-tumor tissues (p < 0.05). The positive rate of H. pylori 16S rRNA in ESCC, A-ESCC, and normal groups were 62.5, 74.1, and 26.7%, respectively. The PCR results showed that the positive incidence of the H. pylori virulence factor CagA gene in tumor (ESCC and A-ESCC) and normal groups was 54.9 and 20%, respectively (p < 0.05). To explore the possible causes of CagA+ H. pylori infection leading to carcinogenesis, we found that CagA+ H. pylori filtrate induced DNA strand breaks in esophageal epithelial NE3 cells, suggesting that H. pylori infection may be an original cause leading to atypical hyperplasia of esophageal squamous epithelial tissues and contributed to pathological carcinogenesis of ESCC.