Increased expression of S100A6 promotes cell proliferation in gastric cancer cells.

S100A6 is involved in regulating the progression of cancer. S100A6 can regulate the dynamics of cytoskeletal constituents, cell growth and differentiation by interacting with binding or target proteins. The present study investigated whether S100A6 affects cell proliferation in gastric cancer cells by stimulating several downstream factors. Firstly, the expression and localization of S100A6 were investigated using immunohistochemical staining, an immunoelectron microscopy and laser confocal scanning. A ChIP-Chip assay was performed to determine the downstream factors of S100A6 using promoter Chip analysis, including approximately the -800 to +200 regions around the transcription starting point. Polymerase chain reaction analysis was performed to confirm this. It was found that the intensity of S100A6 staining was markedly higher in the cytoplasm and nucleus, and its expression level correlated with that of the Ki67 protein. The overexpression of S100A6 also promoted cell proliferation in AGS and BGC823 cell lines, detected using a Cell Counting-Kit 8 assay. In cells overexpressing S100A6, the expression levels of interleukin (IL)-8, cyclin-dependent kinase (CDK)5, CDK4, minichromosome maintenance complex component 7 (MCM7) and B-cell lymphoma 2 (Bcl2) were noticeably increased. In conclusion, the increased expression of S100A6 promoted cell proliferation by regulating the expression levels of IL-8, CDK5, CDK4, MCM7 and Bcl2 in gastric cancer cells.

Presence of S100A9-positive inflammatory cells in cancer tissues correlates with an early stage cancer and a better prognosis in patients with gastric cancer.

BACKGROUND: S100A9 was originally discovered as a factor secreted by inflammatory cells. Recently, S100A9 was found to be associated with several human malignancies. The purpose of this study is to investigate S100A9 expression in gastric cancer and explore its role in cancer progression. METHODS: S100A9 expression in gastric tissue samples from 177 gastric cancer patients was assessed by immunohistochemistry. The expression of its dimerization partner S100A8 and the S100A8/A9 heterodimer were also assessed by the same method. The effect of exogenous S100A9 on motility of gastric cancer cells AGS and BGC-823 was then investigated. RESULTS: S100A9 was specifically expressed by inflammatory cells such as macrophages and neutrophils in human gastric cancer and gastritis tissues. Statistical analysis showed that a high S100A9 cell count (> = 200) per 200x magnification microscopic field in cancer tissues was predictive of early stage gastric cancer. High S100A9-positive cell count was negatively correlated with lymph node metastasis (P = 0.009) and tumor invasion (P = 0.011). S100A9 was identified as an independent prognostic predictor of overall survival of patients with gastric cancer (P = 0.04). Patients with high S100A9 cell count were with favorable prognosis (P = 0.021). Further investigation found that S100A8 distribution in human gastric cancer tissues was similar to S100A9. However, the number of S100A8-positive cells did not positively correlate with patient survival. The inflammatory cells infiltrating cancer were S100A8/A9 negative, while those in gastritis were positive. Furthermore, exogenous S100A9 protein inhibited migration and invasion of gastric cancer cells. CONCLUSIONS: Our results suggested S100A9-positive inflammatory cells in gastric cancer tissues are associated with early stage of gastric cancer and good prognosis.

Phospholipase A2 group IIA expression correlates with prolonged survival in gastric cancer.

AIMS: The secreted phospholipase A2 type IIA (PLA2G2A) gene has been identified as a modifier of intestinal adenoma multiplicity in Apc(Min/+) mice. The aim of the present study was to analyse the clinical significance of PLA2G2A expression in human gastric cancer. METHODS AND RESULTS: Using immunohistochemistry, cytoplasmic immunoreactivity of PLA2G2A was observed in 27% (40 of 149) of gastric cancer tissues compared with negative staining in normal mucosa. The PLA2G2A expression rate in well-differentiated carcinoma was elevated significantly compared with that in poorly differentiated carcinoma (46% versus 19%, P = 0.001). Statistical analysis also revealed that PLA2G2A expression correlated negatively with depth of mural invasion, lymph node metastasis and tumour-node-metastasis (TNM) stage (P < 0.05). Patients with positive PLA2G2A expression showed higher 5-year overall survival than those with negative expression (P = 0.0004). In intestinal metaplasia, PLA2G2A was found to be abundant in Paneth cells. The coexistence of PLA2G2A and lysozyme was observed in Paneth cell-rich gastric cancer (P < 0.0001). CONCLUSIONS: PLA2G2A may predict survival and might be a potential biomarker for early detection and individualized therapy.

S100A6 overexpression is associated with poor prognosis and is epigenetically up-regulated in gastric cancer.

S100A6 has been implicated in a variety of biological functions as well as tumorigenesis. In this study, we investigated the expression status of S100A6 in relation to the clinicopathological features and prognosis of patients with gastric cancer and further explored a possible association of its expression with epigenetic regulation. S100A6 expression was remarkably increased in 67.5% of gastric cancer tissues as compared with matched noncancerous tissues. Statistical analysis demonstrated a clear correlation between high S100A6 expression and various clinicopathological features, such as depth of wall invasion, positive lymph node involvement, liver metastasis, vascular invasion, and tumor-node metastasis stage (P < 0.05 in all cases), as well as revealed that S100A6 is an independent prognostic predictor (P = 0.026) significantly related to poor prognosis (P = 0.0004). Further exploration found an inverse relationship between S100A6 expression and the methylation status of the seventh and eighth CpG sites in the promoter/first exon and the second to fifth sites in the second exon/second intron. In addition, the level of histone H3 acetylation was found to be significantly higher in S100A6-expressing cancer cells. After 5-azacytidine or trichostatin A treatment, S100A6 expression was clearly increased in S100A6 low-expressing cells. In conclusion, our results suggested that S100A6 plays an important role in the progression of gastric cancer, affecting patient prognosis, and is up-regulated by epigenetic regulation.

Identification of prognosis-related proteins in advanced gastric cancer by mass spectrometry-based comparative proteomics.

PURPOSE: The objective of this study was to identify differentially expressed proteins of advanced gastric cancer from patients with different prognosis using NanoLC-MS/MS (LTQ) (nanoflow liquid chromatography system interfaced with a linear ion trap LTQ mass spectrometer). METHODS: Eight gastric cancer patients with relatively early TNM stage and survival time >34 months were identified as good survival (group G), while the other eight with late stage and survival time <15 months as poor survival (group P). The total protein of the tissue samples from each group was extracted and pooled together respectively. The resulting two protein mixtures were trypsin-digested and analyzed using NanoLC-MS/MS (LTQ). Database searches were done against NCBI non-redundant database and SWISS-PROT database and the identified proteins were classified through an online Web Gene Ontology Annotation Plot tool. Immunohistochemistry was used to verify candidate prognosis-related proteins. RESULTS: There were 284 and 213 proteins identified for group G and group P respectively. And 117 proteins were detected exclusively in group G and 46 proteins exclusively in group P. These protein markers function in calcium ion signaling pathway, cellular metabolism, cytoskeleton formation, stress reaction, etc. Among those, the down-regulated expression of S100P was verified to claim a poor clinical outcome of gastric cancer patients (P = 0.0375). CONCLUSION: The MS-based proteomics approach is efficient in identifying differentially expressed proteins in relation to prognosis of advanced gastric cancer patients. These differentially expressed proteins could be potential prognosis-related cancer markers and deserve further validation and functional study.

[Nuclear expression of S100A4 is associated with lymph node metastasis in gastric carcinoma].

OBJECTIVE: To investigate the intracellular localization of S100A4 in gastric carcinoma cells and the relationship between S100A4 expression status and lymph node metastasis of gastric carcinoma. METHODS: Western blotting analysis was performed to locate the expression of S100A4 protein in sub-fraction components of frozen tissues. S100A4 protein expression was also determined by immunohistochemical method in 131 samples of gastric cancer and 20 samples of matched metastatic lymph nodes. RESULTS: Thirty-two of 131 (24.4%) gastric carcinoma showed positive S100A4 nuclear expression and 50/131 (38.2%) carcinoma showed positive cytoplasmic expression. In 32 samples with positive S100A4 nuclear expression, 30 (93.8%) carcinomas had positive lymph node metastases. S100A4 nuclear expression level was higher in gastric carcinoma with lymph node metastasis (29.1%) than that without lymph node metastasis (7.1%) (P=0.016). CONCLUSION: Nuclear expression of S100A4 is associated with lymph node metastasis of gastric carcinoma.