Primary Gastric Cancer Tissues Research Articles

MiR-508-5p acts as an anti-oncogene by targeting MESDC1 in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer associated mortality. Accumulating evidence has shown that microRNAs (miRNAs) act as critical factors for tumor recurrence and metastasis. MiR-508-5p has been reported as a down-regulated miRNA in the primary gastric cancer tissues. However, the role of miR-508-5p on HCC has not been well elucidated. In this study, we observed that miR-508-5p was downregulated in HCC tissues when compared to the non-tumorous tissues. We then demonstrated that overexpression of miR-508-5p attenuated HepG2 cells proliferation and invasion and induced cell apoptosis in vitro. Furthermore, our further investigations revealed that mesoderm development candidate 1 (MESDC1) is a potential target of miR-508-5p, as well as miR-508-5p overexpression downregulated MESDC1 expression. Overexpression of MESDC1 promoted HepG2 cells migration, invasion and proliferation in vitro. In addition, miR-508-5p markedly suppressed the tumor growth in xenograft model, while MESDC1 promoted the tumor growth in xenograft model. This study provides new insight into molecular mechanisms that miR-508-5p acts as a tumor suppressor by targeting MESDC1 in HCC progression.

CXCR7/CXCL12 axis is involved in lymph node and liver metastasis of gastric carcinoma.

AIMTo investigate the role of CXC chemokine receptor (CXCR)-7 and CXCL12 in lymph node and liver metastasis of gastric carcinoma.METHODSIn 160 cases of gastric cancer, the expression of CXCR7 and CXCL12 in tumor and matched tumor-adjacent non-cancer tissues, in the lymph nodes around the stomach and in the liver was detected using immunohistochemistry to analyze the relationship between CXCR7/CXCL12 expression and clinicopathological features and to determine whether CXCR7 and CXCL12 constitute a biological axis to promote lymph node and liver metastasis of gastric cancer. Furthermore, the CXCR7 gene was silenced and overexpressed in human gastric cancer SGC-7901 cells, and cell proliferation, migration and invasiveness were measured by the MTT, wound healing and Transwell assays, respectively.RESULTSCXCR7 expression was up-regulated in gastric cancer tissues (P = 0.011). CXCR7/CXCL12 expression was significantly related to high tumor stage and lymph node (r = 0.338, P = 0.000) and liver metastasis (r = 0.629, P = 0.000). The expression of CXCL12 in lymph node and liver metastasis was higher than that in primary gastric cancer tissues (χ2 = 6.669, P = 0.010; χ2 = 25379, P = 0.000), and the expression of CXCL12 in lymph node and liver metastasis of gastric cancer was consistent with the positive expression of CXCR7 in primary gastric cancer (r = 0.338, P = 0.000; r = 0.629, P = 0.000). Overexpression of the CXCR7 gene promoted cell proliferation, migration and invasion. Silencing of the CXCR7 gene suppressed SGC-7901 cell proliferation, migration and invasion. Human gastric cancer cell lines expressed CXCR7 and showed vigorous proliferation and migratory responses to CXCL12.CONCLUSIONThe CXCR7/CXCL12 axis is involved in lymph node and liver metastasis of gastric cancer. CXCR7 is considered a potential therapeutic target for the treatment of gastric cancer.

Mast Cells Density Positive to Tryptase Correlate with Microvascular Density in both Primary Gastric Cancer Tissue and Loco-Regional Lymph Node Metastases from Patients That Have Undergone Radical Surgery.

Mast Cells (MCs) play a role in immune responses and more recently MCs have been involved in tumoral angiogenesis. In particular MCs can release tryptase, a potent in vivo and in vitro pro-angiogenic factor via proteinase-activated receptor-2 (PAR-2) activation and mitogen-activated protein kinase (MAPK) phosphorylation. MCs can release tryptase following c-Kit receptor activation. Nevertheless, no data are available concerning the relationship among MCs Density Positive to Tryptase (MCDPT) and Microvascular Density (MVD) in both primary gastric cancer tissue and loco-regional lymph node metastases. A series of 75 GC patients with stage T2–3N2–3M0 (by AJCC for Gastric Cancer Seventh Edition) undergone to radical surgery were selected for the study. MCDPT and MVD were evaluated by immunohistochemistry and by image analysis system and results were correlated each to other in primary tumor tissue and in metastatic lymph nodes harvested. Furthermore, tissue parameters were correlated with important clinico-pathological features. A significant correlation between MCDPT and MVD was found in primary gastric cancer tissue and lymph node metastases. Pearson t-test analysis (r ranged from 0.74 to 0.79; p-value ranged from 0.001 to 0.003). These preliminary data suggest that MCDPT play a role in angiogenesis in both primary tumor and in lymph node metastases from GC. We suggest that MCs and tryptase could be further evaluated as novel targets for anti-angiogenic therapies.

MiRNA-194 activates the Wnt/β-catenin signaling pathway in gastric cancer by targeting the negative Wnt regulator, SUFU

Emerging evidence has shown that miRNA-194 is aberrantly upregulated in gastric cancer (GC); however, the biological mechanisms underlying its involvement are largely unknown. Wnt/β-catenin signaling has been implicated in gastric tumorigenesis; we therefore hypothesized that miRNA-194 promotes gastric carcinogenesis by activating Wnt/β-catenin signaling. MiRNA-194 was found to be overexpressed in GC cell lines and 43 paired GC tissues. Overexpression of miRNA-194 promoted cell proliferation and migration, while inhibition of miRNA-194 blocked these processes. Inhibition of miRNA-194 decreased tumor volumes in nude mice. Furthermore, miRNA-194 inhibitors promoted cytoplasmic localization of β-catenin, leading to repression of Wnt signaling. We also discovered that SUFU, a known negative regulator of Hedgehog and Wnt signaling, was a target of miRNA-194. Anti-SUFU siRNAs rescued the inhibitory effects of miRNA-194 antagonists on cell proliferation and migration and on colony formation. We also found that SUFU expression was downregulated in GC tissues and cell lines and negatively correlated with miRNA-194 expression in primary GC tissues. Moreover, SUFU expression was negatively correlated with tumor stage, supporting its potential as a diagnostic or prognostic marker in GC. Taken together, these findings suggest that miRNA-194 is oncogenic and promotes GC cell proliferation and migration by activating Wnt signaling, at least in part, via suppression of SUFU.

FAM46C Serves as a Predictor of Hepatic Recurrence in Patients with Resectable Gastric Cancer.

Gastric cancer (GC) relapse can occur even if curative resection is achieved. Biomarkers predicting recurrence are needed to provide appropriate postoperative surveillance and perioperative therapeutic strategy. A global expression profiling was performed using tissues from GC patients with synchronous liver-confined metastasis. Family with sequence similarity 46, member C (FAM46C), was identified as a candidate biomarker. mRNA expression analysis, direct nucleotide sequencing, bisulfite sequencing and copy number assays for FAM46C were performed with eleven GC cell lines. Expression levels of FAM46C in primary GC tissues from 129 patients who underwent curative GC resection were determined and correlated with clinicopathological factors, including postoperative outcome. Levels of FAM46C mRNA differed among GC cell lines. Point mutations in FAM46C were detected in five GC cell lines accompanied with reduced FAM46C transcription. No hypermethylation was found in the promoter region of FAM46C. Copy number alterations were found in six GC cell lines with differing FAM46C transcription levels. Reduced FAM46C mRNA expression levels were detected in 117 (91%) GC specimens compared with adjacent noncancerous tissues. Low FAM46C expression levels were significantly associated with larger macroscopic GC tumor sizes. The low FAM46C expression group was likely to have shorter disease-free survival than the high group and low FAM46C level was identified as an independent risk factor for recurrence after curative resection. FAM46C expression levels were low in all cases that were later found to have hepatic recurrence. Reduced GC expression of FAM46C is a potential biomarker to predict hepatic recurrence after curative gastrectomy.

The roles of HOXB7 in promoting migration, invasion, and anti-apoptosis in gastric cancer.

The aim of this study was to compare HOXB7 expression level between gastric cancer and non-cancerous gastric tissues. Additionally, the functional effects of HOXB7, including its pro-migration or invasion and anti-apoptosis roles, were evaluated in gastric cancer cells. Both gene and protein expression levels of HOXB7 were examined in gastric cancer cell lines, and HOXB7 expression was compared between primary or metastatic gastric cancer tissues and chronic gastritis or intestinal metaplasia tissues. Functional studies included a wound healing assay, a Matrigel invasion assay, and an Annexin-V assay were performed, and Akt/PTEN activity was measured by western blotting. Both gene and protein expression levels of HOXB7 could be clearly detected in various gastric cancer cell lines except MKN-28 cell. HOXB7 expression was significantly higher in primary or metastatic gastric cancer tissues than in chronic gastritis or intestinal metaplasia tissues. HOXB7 knockdown led to inhibition of cell invasion and migration, had an apoptotic effect, downregulated phosphor-Akt, and upregulated PTEN in AGS and SNU-638 cells. Reinforced expression of HOXB7 caused the opposite effects in MKN-28 and MKN-45 cells. Our study suggests that HOXB7 has an oncogenic role in gastric cancer, which might be related to the modulation of Akt/PTEN activity to induce cell migration/invasion and anti-apoptotic effects.

FGFR2 in gastric cancer: protein overexpression predicts gene amplification and high H-index predicts poor survival

AbstractFGFR2 gene amplification, and resulting FGFR2 protein overexpression, is rare in gastric cancer patients, and development of an accurate and widely available method for mass screening to identify patients who may respond to treatment with fibroblast growth factor receptor (FGFR) inhibitors is important. We first screened 312 gastric cancer patients with known copy number variations by FGFR2b immunohistochemistry using FPR2-D, an isoform-specific antibody. Next, we performed immunohistochemistry on tissue microarrays from 1574 gastric cancer patients. Selected cases were analyzed for FGFR2 amplification by FISH. In addition, FGFR2b overexpression was studied in 88 matched primary and metastatic gastric cancers. In the first cohort, FGFR2b immunohistochemistry results correlated very well with those of copy number variation (r=0.79) and FISH (r=1.0). In total, FGFR2b overexpression was identified in 73 of 1974 gastric cancers (4%). The concordance between immunohistochemistry and FISH was extremely high; all 2+ and 3+ cases identified by immunohistochemistry were FGFR2 amplified. In the matched primary and metastatic gastric cancer pairs, the positivity and percentage of positive tumor cells were significantly higher in metastatic gastric cancers than in primary gastric cancers (8% vs 3% and 75% vs 47%, respectively; P<0.001). FGFR2b overexpression was significantly more frequent in gastric cancers with diffuse subtype (P=0.01) and higher N stage (P=0.006). FGFR2b overexpression with H-score ≥150 were independent prognostic factors for overall survival with hazard ratio of 1.836 (95% confidence interval, 1.034–3.261; P=0.038). FGFR2b positivity in immunohistochemistry was strongly correlated with FGFR2 amplification. Given the low frequency of FGFR2 amplification in gastric cancers, FGFRb2 immunohistochemistry is an accurate screening tool to detect FGFR2 amplification, and both primary and metastatic gastric cancer tissues should be tested to select gastric cancer patients for treatment with FGFR2 inhibitors.

Epigenetic suppression of the immunoregulator MZB1 is associated with the malignant phenotype of gastric cancer.

Prediction of tumor recurrence after curative resection is critical for determining the prognosis of patients with gastric cancer (GC). The initiation and progression of GC are associated with inappropriate immune responses caused by chronic inflammation of the gastric mucosa. To identify immunoregulatory molecules involved in GC progression, GC cell lines and 200 pairs of tumor and normal tissues from patients with GC were analyzed for gene expression, amplification and methylation as well as function of a differentially expressed gene. The transcriptome analysis revealed that marginal zone B and B1 cell specific protein (MZB1) was expressed at significantly decreased levels in primary GC tissues when compared with the corresponding normal gastric mucosa. PCR array analysis exploring genes expressed cooperatively with MZB1 revealed that differential expression of MZB1 mRNA in GC cell lines correlated positively with the levels of the mRNAs encoding estrogen receptor 1 and desumoylating isopeptidase 1. Hypermethylation of the MZB1 promoter was frequent in cell lines with decreased levels of MZB1 mRNA. siRNA-mediated knockdown of MZB1 significantly increased proliferation, invasion and migration of GC cell lines. Low MZB1 expression was an independent prognostic factor for recurrence after curative gastrectomy and was associated significantly with increased hematogenous recurrence. MZB1 acts as a suppressor of GC. Low MZB1 expression in the primary GC tissue is predictive of recurrence after curative resection.

Overexpression of cancer cell-derived immunoglobulin G correlates with poor prognosis in gastric cancer patients

Background: Various human epithelial origin cancers produce cytoplasmic immunoglobulin (Ig) G. Recent studies have elucidated that it was related with the tumorigenesis. This study was aimed to identify relationship between the cancer cell-derived IgG expression level and clinical parameters in gastric cancer (GC). Methods: Cancer cell-derived IgG expression was assessed using immunohistochemistry analysis in 231 primary GC tissues. The role of cancer cell-derived IgG on cell proliferation, migration and invasion were assessed. Results: Our results indicated that IgG was overexpressed in GC tissues (42.2%, 46/109) than in adjacent tissues (11.0%, 12/109, P vs. 37.2%, respectively). Upon univariate analysis, IgG positive group had significantly lower 5-year overall survival than the negative group (P=0.0361). Multivariate analysis showed IgG expression was an independent prognostic indicator for 5-year overall survival of patients with GC (P=0.018). Furthermore, knockdown of IgG by short interfering RNA (siRNA) resulted in reducing proliferation, migration and invasion of GC cell. Conclusions: Our results showed that cancer cell-derived IgG overexpression might be correlated with GC progression, and would be a novel biomarker to predict the prognosis of patients with GC.

MiR-135a acts as a tumor suppressor in gastric cancer in part by targeting KIFC1

miR-135a was downregulated in the majority of human primary gastric cancer (GC) tissues and GC cell lines. Kinesin family member C1 (KIFC1) was significantly upregulated in GC tissues and cell lines and promoted GC development and progression. We searched for miR-135a targets by using MiRanda, TargetScan, and PicTar tools, and found that KIFC1 was a potential target of miR-135a. Based on these findings, we speculated that miR-135a might target KIFC1 to inhibit GC growth. We determined the expression of miR-135a and KIFC1 by quantitative real-time polymerase chain reaction and Western blot assays, respectively, and found downregulation of miR-135a and upregulation of KIFC1 in GC tissues and cell lines. Cell proliferation and apoptosis assays showed that knockdown of KIFC1 inhibited proliferation and promoted apoptosis of GC cells, and miR-135a mimics had similar effects on GC cell proliferation and apoptosis. Furthermore, we verified that KIFC1 was a direct target of miR-135a, which confirmed our speculation that the functional effect of miR-135a on GC cells, at least, in part, depends on KIFC1. These findings suggest that miR-135a has an important role in the suppression of GC and presents a novel mechanism of miRNA-mediated KIFC1 expression in cancer cells.

Expression of annexin A7 and its clinical significance in gastric carcinoma

To investigate the expression of annexin A7 (ANXA7) in the differentiation and lymphatic metastasis of gastric cancer (GC), and to investigate the relationship between ANXA7 and biological characteristics of GC. The clinicopathological data of 124 patients with gastric cancer who underwent surgical treatment in our hospital were retrospectively reviewed and analyzed. Immunohistochemical staining and Western blot were performed to analyze the expression of ANXA 7 in primary GC tissues. Logistic regression analysis was conducted to evaluate the association between ANXA7 expression level and differentiation of the GC. A total of 124 GC patients were enrolled in this study, and the expression rate of ANXA7 was 65.3% in the GC. The survival rate of ANXA7-positive patients was significantly lower than that in the patients with negative expression (P<0.001). The results of Cox regression analysis showed that the positive expression of ANXA7, submucosal confinement and pathological stage of GC were associated with poor clinical outcomes. The ratio of pixel density value of primary GC tissues with lymph node metastasis was significantly higher than those in the tissues without lymph node metastasis (0.51±0.07 vs. 0.39±0.06, P<0.001). ROC analysis showed a high area under the curve for the ratio of pixel density value of annexin A7 in the primary GC tissues. At a cut-off level of >0.419, the ratio of pixel density value of ANXA7 exhibited a sensitivity of 91.2% and a specificity of 72.7% for detecting lymph node metastasis of GC. High annexin A7 expression is associated with poor differentiation of gastric cancer, and it may become a predictor for lymphatic metastasis of GC.

Stem Cells Antigen-1 Enriches for a Cancer Stem Cell-Like Subpopulation in Mouse Gastric Cancer.

There is a strong need to identify markers to enrich gastric cancer stem cells (CSCs). However, CSC enrichment markers for mouse gastric cancers have not yet been determined. In our previous study, we generated primary mouse gastric cancer cell line NCC-S1 (S1) established from a Villin-cre;Smad4(F/F) ;Trp53(F/F) ;Cdh1(F/wt) mouse and its metastatic variant cell line NCC-S1M (S1M). Interestingly, S1M cells exhibited CSC-like features, such as increased tumorigenic potential and chemoresistance. By comparing gene expression profiles between S1 and S1M cells, we identified Stem Cells Antigen-1 (Sca-1) as a cell surface marker, which was mostly upregulated in S1M. Sca-1 was upregulated in tumorspheres from S1 cells or after cisplatin treatment in S1 cells. Immunofluorescence (IF) analysis showed that approximately 7% of cancer cells exhibited positivity for Sca-1 in primary mouse gastric cancer tissues. An in vivo-limiting dilution assay showed that Sca-1(high) mouse gastric cancer cells demonstrated increased tumorigenicity compared with Sca-1(negative) cells. The Sca-1 expression was downregulated by TGF-β pathway activation and Wnt pathway inhibition in mouse gastric cancer cells. Sca-1(high) cells showed relatively low TGF-β reporter activity and high TCF/LEF1 reporter activity compared with Sca-1(negative) cells. A chromatin immunoprecipitation analysis demonstrated that Sca-1 was a β-catenin/LEF1 target gene. Sca-1(high) allografts were more resistant to cisplatin/fluorouracil chemotherapy than Sca-1(negative) allografts, and overexpressed Bcl-xL. Eighty-five mouse genes overexpressed in Sca-1(high) S1 cells compared with Sca-1(negative) cells clustered 123 pretreatment gastric cancer patient samples according to survival following chemotherapy. Taken together, Sca-1 is a novel CSC enrichment marker that mediates TGF-β and Wnt/β-catenin signaling in mouse gastric cancer. Stem Cells 2016;34:1177-1187.

MicroRNA-145-5p inhibits gastric cancer invasiveness through targeting N-cadherin and ZEB2 to suppress epithelial-mesenchymal transition.

MicroRNA (miR)-145-5p has been reported to function as a suppressor of cancer and plays an important role in cancer invasiveness. Epithelial–mesenchymal transition (EMT) is an important process in cancer invasion and migration. However, the involvement of miR-145-5p in EMT in human gastric cancer (GC) remains unclear. In this study, we aimed to investigate the molecular mechanisms by which miR-145-5p regulates EMT in GC invasiveness. We used quantitative real-time polymerase chain reaction to investigate the miR-145-5p expression level in GC and matched normal tissues. The effects of miR-145-5p on GC cell invasion and migration abilities were evaluated using Transwell models. The relationships among miR-145-5p and zinc-finger E-box binding homeobox 2 (ZEB2), E-cadherin, and N-cadherin were analyzed by quantitative real-time polymerase chain reaction and Western blot analyses. miR-145-5p levels in primary GC tissues obtained from 60 patients were significantly downregulated, compared to those in paired normal tissues. Lauren classification, depth of tumor invasion, lymph node metastasis, lymphatic invasion, and tumor–node–metastasis stage were associated with miR-145-5p expression. miR-145-5p inhibits the expression of the candidate target gene ZEB2 to delay the invasion and migration of GC cells. ZEB2 acts as transcriptional repressor of E-cadherin, while miR-145-5p is known to suppress N-cadherin directly to regulate EMT. Therefore, we concluded that miR-145-5p may target N-cadherin and ZEB2 directly to influence EMT.

Metastatic pathway-specific transcriptome analysis identifies MFSD4 as a putative tumor suppressor and biomarker for hepatic metastasis in patients with gastric cancer.

Gastric cancer (GC) with hepatic metastasis remains a fatal disease. Global expression profiling was conducted using tissues from patients who had GC with synchronous hepatic metastasis, and major facilitator superfamily domain containing 4 (MFSD4) was identified as a candidate biomarker for hepatic metastasis in GC. Functional and expression analyses of this molecule in GC cell lines and clinical samples were conducted. We analyzed MFSD4 expression, DNA methylation, and copy number. RNA interference experiments evaluated the effects of MFSD4 expression on cell phenotype and apoptosis. We analyzed tissues of 200 patients with GC to assess the diagnostic performance of MFSD4 levels for predicting hepatic recurrence, metastasis, or both. Differential expression of MFSD4 mRNA by GC cell lines correlated positively with the levels of NUDT13 and OCLN mRNAs and inversely with those of BMP2. Hypermethylation of the MFSD4 promoter was detected in cells with lower levels of MFSD4 mRNA. Inhibition of MFSD4 expression significantly increased the invasiveness and motility of GC cells but did not influence cell proliferation or apoptosis. MFSD4 mRNA levels in primary GC tissues were reduced in patients with concomitant hepatic metastasis or recurrence compared with those without. Low levels of MFSD4 mRNA in primary GC tissues were an independent risk factor of hepatic recurrence and metastasis. MFSD4 expression in gastric tissues may represent a useful biomarker for identification of patients at high risk for hepatic recurrence, metastasis, or both.

Dysregulation of MicroRNA-196b-5p and MicroRNA-375 in Gastric Cancer.

PurposeDysregulated microRNAs (miRNAs) can contribute to cancer development by leading to abnormal proliferation of cells, apoptosis, and differentiation. Although several miRNAs that are related to gastric cancer have been identified, the reported results have been inconsistent. The aim of this study was to determine miRNA expression profiles and validate miRNAs up- and down-regulated in gastric cancer.Materials and MethodsWe evaluated 34 primary gastric cancer tissues and paired adjacent nontumorous gastric tissues. Total RNA was extracted, and low-molecular-weight RNAs (<200 nucleotides) were isolated for further analysis. Two pairs of tissues were processed for GeneChip microarray analysis, and the identified up- and down-regulated miRNAs were validated by real-time quantitative polymerase chain reaction (qPCR).ResultsIn the set of differentially expressed miRNAs, 5 were overexpressed by more than 2 fold, and 5 were reduced by 2 fold or less in gastric cancer tissues compared with normal gastric tissues. Four of these miRNAs (miR-196b-5p, miR-375, miR-483-5p, and miR-486-5p) were then validated by qPCR, and the relative expression levels of 2 miRNAs (miR-196b-5p and miR-375) were significantly different between cancer and normal tissues.ConclusionsOur results revealed that the expression of miR-196b-5p and miR-375 significantly correlates with gastric cancer. These miRNAs could therefore serve as diagnostic biomarkers of gastric cancer.

TBL1XR1 Is Highly Expressed in Gastric Cancer and Predicts Poor Prognosis.

Objective. To investigate the expression of transducin- (β-) like 1 X-linked receptor 1 (TBL1XR1) in human gastric cancer (GC) and its correlation with prognostic and biologic significance. Methods. TBL1XR1 mRNA expression was analyzed in gastric cancer using a microarray dataset (GSE2701) from the Gene Expression Omnibus (GEO). Immunohistochemistry (IHC) analysis of TBL1XR1 was performed on GC tissue microarray (TMA) to assess its prognostic and biological significance in 334 patients of GC. Results. Analysis of GSE2701 showed that the mRNA levels of TBL1XR1 were significantly elevated in primary gastric tumor and lymph node tissues than normal gastric tissues (P < 0.05). The same results of TBL1XR1 protein level were observed by IHC staining in 334 GC tissues. 204 of 334 (60.1%) primary gastric cancer tissues showed high expression of TBL1XR1 protein. TBL1XR1 overexpression was significantly correlated with lymph node metastasis (P = 0.000) and advanced TNM stage (P = 0.001). Moreover, high levels of TBL1XR1 predicted worse overall survival (P = 0.015). Multivariate Cox regression analysis indicated that high expression of TBL1XR1 was an independent prognostic factor for poor overall survival (HR, 0.525; 95% confidence interval, 0.367–0.752; P = 0.005). Conclusion. This present study demonstrates that TBL1XR1 is overexpressed in gastric cancer and may be a potential predictor and therapeutic target for GC patients.

MiR-101-2, miR-125b-2 and miR-451a act as potential tumor suppressors in gastric cancer through regulation of the PI3K/AKT/mTOR pathway

Gastric cancer (GC) is a deadly malignancy worldwide. In the past, it has been shown that cellular signaling pathway alterations play a crucial role in the development of GC. In particular, deregulation of the PI3K/AKT/mTOR pathway seems to affect multiple GC functions including growth, proliferation, metabolism, motility and angiogenesis. Targeting alterations in this pathway by microRNAs (miRNAs) represents a potential therapeutic strategy, especially in inhibitor-resistant tumors. The objective of this study was to evaluate the expression of 3 pre-selected miRNAs, miR-101-2, miR-125b-2 and miR-451a, in a series of primary GC tissues and matched non-GC tissues and in several GC-derived cell lines, and to subsequently evaluate the functional role of these miRNAs. Twenty-five primary GC samples, 25 matched non-GC samples and 3 GC-derived cell lines, i.e., AGS, MKN28 and MKN45, were included in this study. miRNA and target gene expression levels were assessed by quantitative RT-PCR and western blotting, respectively. Subsequently, cell viability, clone formation, cell death, migration and invasion assays were performed on AGS cells. miR-101-2, miR-125b-2 and miR-451a were found to be down-regulated in the primary GC tissues and the GC-derived cell lines tested. MiRNA mimic transfections significantly reduced cell viability and colony formation, increased cell death and reduced cell migration and invasion in AGS cells. We also found that exogenous expression of miR-101-2, miR-125b-2 and miR-451a decreased the expression of their putative targets MTOR, PIK3CB and TSC1, respectively. Our expression analyses and in vitro functional assays suggest that miR-101-2, miR-125b-2 and miR-451a act as potential tumor suppressors in primary GCs as well as in GC-derived AGS cells.

Abstract PR06: Genomic characterization of immune escape pathways in gastric cancer

Abstract Cancer's evasion of the host immune response has long been recognized for its role in tumorigenesis. Examples such as the immune checkpoint blockade of CTLA-4 and PD-1 have started to be translated into efficacious targeted therapeutics in the clinics. We have recently performed comprehensive molecular profiling of a cohort of 100 patients with gastric cancer, a deadly disease with marked phenotypic diversity that encompasses multiple molecular subtypes. The purposes of the study presented here is to provide a comprehensive catalog of genetic and epigenetic alterations of key immune escape pathways in gastric cancer, and search for novel molecular markers that are associated with gastric tumors likely to be susceptible to immune escape pathway blockage. We obtained fresh frozen primary gastric cancer tissues and matched non-malignant gastric mucosa samples, and molecularly characterized the samples by whole genome sequencing, array-based gene expression, somatic copy number and methylation analysis. Primary tumor tissues are often an admixture of tumor cells as well as surrounding stromal cells and infiltrating immune cells. In order to focus our analysis on tumor-specific alterations and tumor derived factors, we first attempted to infer the fraction of tumor cells in each sample using the DNA sequencing and copy number data from matched tumor-normal pairs, and adjusted the gene expression and methylation profile data based on the samples tumor content. We then characterized each tumor based on their genetic, epigenetic and transcriptomic changes on a panel of key genes known to be involved in various tumor escape mechanisms, including changes in tumor antigenicity, activation of co-inhibitory immune checkpoints, secretion of immunosuppressive cytokines and chemokines, alteration of cell death pathways by tumor, sustained activation of pro-survival, anti-apoptotic signaling pathways, and tumor metabolic changes that facilitate immune evasion. Unsupervised clustering of the tumor samples based on their tumor content adjusted expression of immune escape pathway genes revealed two significant groups. One group of gastric cancers (N=30) showed significant up-regulation of many immune escape pathway genes (thus termed the immune escape high, or IEH group, hereafter), whereas the other group (N=70) displayed relatively low immune escape activity (termed the immune escape low, or IEL group). The IEH tumors included most Epstein-Barr virus (EBV) positive (5 out of 6) or microsatellite instable (MSI, 8 out of 10) gastric cancers, two molecular subtypes of gastric cancer known to be highly immunogenic. Interestingly, the remaining (17 of 30) tumors in this group come from a mixture of other molecular or morphological subtypes not known to be highly immunogenic. Within the IEH group, the EBV positive and MSI tumors had distinct immune escape signatures: the EBV positive tumors displayed relatively high level expression of CD274 (also known as PD-L1, the ligand of co-inhibitory receptor PD-1 on activated cytotoxic T lymphocytes), IDO1 (a key enzyme in tryptophan metabolism whose metabolites can induce T-cell anergy in tumor microenvironment), FASLG (the Fas ligand that may serve as tumors counterattack by triggering apoptosis in Fas-sensitive immune cells), and promoter hypermethylation of TGFB1; whereas the MSI tumors had lower expression and frequent somatic mutation of MHC-I receptor components (which may lead to defects in antigen presentation), down-regulation of CASP8 (a key effector of Fas-mediated apoptosis pathway) and over-expression of TNFRSF6B (a decoy receptor expressed on tumor cells that attenuates Fas-mediated killing by immune cells). Among key drivers of gastric cancers and genomics and clinicopathological parameters, we observed significant enrichment of alterations in ARID1A, a member of the SWI-SNF chromatin remodeling complex and a recently characterized tumor suppressor gene in gastric cancer and other cancer types, in the IEH gastric cancers (16 of 30, p-value = 5.97E-6), which remains to be significant even after EBV positive and MSI gastric tumors were excluded from the analysis. Interestingly, global hyper-methylation level was also significantly higher in IEH gastric cancers. In summary, our study provided a molecular road map of immune escape pathways in gastric cancer, revealed that a subset of gastric cancers are associated with high immune escape activities with diverse underlying mechanisms, and proposed an interesting link between ARID1A alteration and tumor immune escape. This abstract is also presented as Poster A35. Citation Format: Kai Wang, Suet Yi Leung. Genomic characterization of immune escape pathways in gastric cancer. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr PR06.

MicroRNA-339, an epigenetic modulating target is involved in human gastric carcinogenesis through targeting NOVA1

The role of miR-339 in human gastric cancer (GC) remains unclear. Here, we found that miR-339 is remarkably decreased in primary GC tissues. Overexpression of miR-339 in GC cells significantly suppressed proliferation, migration, invasion, and tumorigenicity. Furthermore, NOVA1 was confirmed as a target of miR-339. Restoration of NOVA1 in miR-339-overexpressing GC cells partially impaired the inhibitory effects of miR-339. More importantly, epigenetic modification may be involved in the modulation of miR-339 expression. These findings uncover a novel role for miR-339 in gastric carcinogenesis, and restoration of miR-339 could be considered as a potential therapeutic strategy for GC treatment.

Preliminary differential proteome analysis of the human primary or lymph node metastatic gastric adenocarcinoma by two-dimensional differential gel electrophorosis

Objective To establish differential protein expressing profiles of human gastric adenocarcinoma cell in primary or metastatic lymph node tissues by two-dimensional differential gel electrophorosis (2-D DIGE) so as to investigate the metastatic molecular mechanism of the gastric cancer. Methods After obtaining 6 samples of human primary gastric cancer and metastatic lymph node tissues, with manual no-staining frozen sections microdissection, human gastric adenocarcinoma cells from primary or metastatic lymph node tissues were isolated, and then the total proteins were extracted and purified. Highly sensitive 2-D DIGE was used to separate the total protein differentially expressed in the cells. The proteins were visualized by using a fluorescence scanner at appropriate wavelengths for Cy2, Cy3 and Cy5 dyes (Typhoon 9400). Image analysis was carried out with the DeCyder-Differential analysis software (Biological Variation Analysis version 5.0). Results Not only can the study procure defined adenocarcinoma cell populations from gastric primary or metastatic lymph node tissues, but also can resolve the problem of the change in 2-D DIGE patterns because of the varying in protein changes owing to dyeing. All these showed that the technique was simple, easy to perform, versatile and of particular usefulness when laser capture microdissection (LCM) was practically unavailable. The 2-D DIGE patterns with high resolution and reproducibility from adenocarcinoma cells in gastric primary or metastatic lymph node tissues were obtained. The number of spots in Gel1, Gel2 were 1 416 (similar 1 062, decrease 277, increase 77), 1 299 (similar 1 050, decrease 157, increase 92), respectively. A total of 11 differential proteins were acquired by image analysis with DeCyder-Differential analysis software (Biological Variation Analysis version 5.0). Conclusions In this report, a simple, easy to proform method of protein epuration, manual no-staining frozen sections microdissection is described, and have used the highly sensitive 2-D DIGE for the identification of proteins differentially expressing in human gastric adenocarcinoma cells from primary or metastatic lymph node tissues. These results provide a fundamental basis for further study of metastatic mechanism of gastric cancer and screen its specific markers. Key words: Stomach neoplasms; Adenocarcinoma; Primary tissues; Lymphatic metastasis; Manual no-staining frozen sections microdissection; Two-dimensional differential gel electrophorosis; Proteomics