Frequent amplification of PTP1B is associated with poor survival of gastric cancer patients

The protein tyrosine phosphatase 1B (PTP1B), a non-transmembrane protein tyrosine phosphatase, has been implicated in gastric pathogenesis. Several lines of recent evidences have shown that PTP1B is highly amplified in breast and prostate cancers. The aim of this study was to investigate PTP1B amplification in gastric cancer and its association with poor prognosis of gastric cancer patients, and further determine the role of PTP1B in gastric tumorigenesis. Our data demonstrated that PTP1B was significantly up-regulated in gastric cancer tissues as compared with matched normal gastric tissues by using quantitative RT-PCR (qRT-PCR) assay. In addition, copy number analysis showed that PTP1B was amplified in 68/131 (51.9%) gastric cancer cases, whereas no amplification was found in the control subjects. Notably, PTP1B amplification was positively associated with its protein expression, and was significantly related to poor survival of gastric cancer patients. Knocking down PTP1B expression in gastric cancer cells significantly inhibited cell proliferation, colony formation, migration and invasion, and induced cell cycle arrested and apoptosis. Mechanically, PTP1B promotes gastric cancer cell proliferation, survival and invasiveness through modulating Src-related signaling pathways, such as Src/Ras/MAPK and Src/phosphatidylinositol-3-kinase (PI3K)/Akt pathways. Collectively, our data demonstrated frequent overexpression and amplification PTP1B in gastric cancer, and further determined the oncogenic role of PTP1B in gastric carcinogenesis. Importantly, PTP1B amplification predicts poor survival of gastric cancer patients.     

Heat shock factor 1 (HSF1) specifically potentiates c-MYC-mediated transcription independently of the canonical heat shock response

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Decreased expression of the ARID1A gene is associated with poor prognosis in primary gastric cancer

Background

The ARID1A gene encodes adenine-thymine (AT)-rich interactive domain-containing protein 1A, which participates in chromatin remodeling. ARID1A has been showed to function as a tumor suppressor in various cancer types. In the current study, we investigated the expression and prognosis value of ARID1A in primary gastric cancer. Meanwhile, the biological role of ARID1A was further investigated using cell model in vitro.

Methodology/Principal Findings

To investigate the role of ARID1A gene in primary gastric cancer pathogenesis, real-time quantitative PCR and western blotting were used to examine the ARID1A expression in paired cancerous and noncancerous tissues. Results revealed decreased ARID1A mRNA (P = 0.0029) and protein (P = 0.0015) expression in most tumor-bearing tissues compared with the matched adjacent non-tumor tissues, and in gastric cancer cell lines. To further investigate the clinicopathological and prognostic roles of ARID1A expression, we performed immunohistochemical analyses of the 224 paraffin-embedded gastric cancer tissue blocks. Data revealed that the loss of ARID1A expression was significantly correlated with T stage (P = 0.001) and grade (P = 0.006). Consistent with these results, we found that loss of ARID1A expression was significantly correlated with poor survival in gastric cancer patients (P = 0.003). Cox regression analyses showed that ARID1A expression was an independent predictor of overall survival (P = 0.029). Furthermore, the functions of ARID1A in the proliferation and colony formation of gastric cell lines were analyzed by transfecting cells with full-length ARID1A expression vector or siRNA targeting ARID1A. Restoring ARID1A expression in gastric cancer cells significantly inhibited cell proliferation and colony formation. Silencing ARID1A expression in gastric epithelial cell line significantly enhanced cell growth rate.

Conclusions/Significance

Our data suggest that ARID1A may play an important role in gastric cancer and may serve as a valuable prognostic marker and potential target for gene therapy in the treatment of gastric cancer.     

Neuroprotective drug riluzole amplifies the heat shock factor 1 (HSF1)- and glutamate transporter 1 (GLT1)-dependent cytoprotective mechanisms for neuronal survival

Heat shock factor 1 (HSF1) mediates the cellular response to stress to increase the production of heat shock protein (HSP) chaperones for proper protein folding, trafficking, and degradation; failure of this homeostatic mechanism likely contributes to neurodegeneration. We show that the neuroprotective drug riluzole increased the amount of HSF1 in NG108-15 neuroprogenitor cells by slowing the specific turnover of HSF1 and supporting a more robust and sustained activation of HSF1. Using Hsp70-luciferase as a functional readout of the activity of HSF1, we show that riluzole amplified the heat shock induction of the reporter gene with an optimal increase at 1 μM. Immunocytochemical staining and Western blot quantitation of HSP70 in NG108-15 neuroprogenitor cells and embryonic spinal cord neurons provided corroborative evidence that riluzole amplified the HSF1-dependent regulation of HSP70 expression. Parallel studies on the GLT1 glutamate transporter showed that riluzole increased GLT1-reporter and GLT1 protein expression and that the increase was enhanced by heat shock and coincident with the increased expression of HSP70 and HSP90. This result is consistent with the anti-glutamatergic profile of riluzole and the presence of multiple heat shock elements on the GLT1 gene promoter, suggesting that riluzole may modulate GLT1 expression through HSF1. The increased HSP chaperones and GLT1 transporter blunted glutamate-induced and N-methyl D-aspartate receptor-mediated excitotoxic death. In summary, we show that riluzole increased the amount and activity of HSF1 to boost the expression of HSPs and GLT1 for neuroprotection under stress.     

Perioperative blood transfusion is associated with poorer survival in patients with gastric cancer

The putative prognostic significance of perioperative blood transfusions on gastric cancers is controversial and the published results are contradictory. The aim of this study was to evaluate the prognostic influence of transfusion on Chinese gastric cancer surgery. Six hundreds and seventy-six patients who underwent curative gastrectomy for gastric cancer from 2000 to 2004 were retrospectively reviewed. Uni- and multivariate analyses of the incidence and amount of transfusion, and a comparison of the clinicopathological features were performed. Subgroup analyses of prognosis according to stage, tumor size, and pretreatment anemia were carried out. Blood transfusion was significantly associated with older age (>60 year), larger tumor (>6 cm), upper and middle location, surgical margin status, and pretreatment anemia. In addition, tumors in the transfused group were more advanced in depth of invasion, nodal stage, and TNM stage. No significant relationship was found between the amount of transfused blood and prognosis. Subgroup analyses of prognosis according to stage showed significant differences in stages II and III, between the transfused and nontransfused groups. Significant difference between the transfused and nontransfused groups could be observed in two subgroups of tumor size. Patients with or without anemia in the nontransfused group both had a longer survival time than those in the transfused group. On multivariate analysis, transfusion was shown to be an independent risk factor for poor prognosis. This study suggests that perioperative blood transfusion is associated with a significantly worse prognosis following gastric cancer surgery. The parameters such as advanced stage, tumor size, and anemia do not affect its prognostic value.     

Virulence of Yersinia ruckeri serotype I strains is associated with a heat sensitive factor (HSF) in cell extracts

Cell extracts of Yersinia ruckeri (serotype I) were examined by SDS-PAGE and Western blotting. An unusual band, termed heat-sensitive factor (HSF) was observed in extracts of virulent strains only. It is thought to be lipid in nature; no differences could be detected in the region of the band in protein profiles of virulent and avirulent strains. When trout were infected either by intraperitoneal injection or bath immersion, mortalities occurred only with HSF+ strains. The HSF appears to be an important virulence determinant of Y. ruckeri.     

Heat and chemical shock potentiation of glucocorticoid receptor transactivation requires heat shock factor (HSF) activity. Modulation of HSF by vanadate and wortmannin

Heat shock and other forms of stress increase glucocorticoid receptor (GR) activity in cells, suggesting cross-talk between the heat shock and GR signal pathways. An unresolved question concerning this cross-talk is whether heat shock factor (HSF1) activity is required for this response. We addressed this issue by modulating HSF1 activity with compounds acting by distinct mechanisms: sodium vanadate (SV), an inhibitor of protein phosphatases; and wortmannin, an inhibitor of DNA-dependent protein kinase. Using HSF1- and GR-responsive CAT reporters, we demonstrate that SV inhibits both HSF1 activity and the stress potentiation of GR, while having no effect on the hormone-free GR or HSF1. Paradoxically, SV increased hormone-induced GR activity in the absence of stress. In contrast, wortmannin increased HSF1 activity in stressed cells and had no effect on HSF1 in the absence of stress. Using the pMMTV-CAT reporter containing the negative regulatory element 1 site for DNA-dependent protein kinase, wortmannin was found to increase the GR response. However, in cells expressing a minimal promoter lacking negative regulatory element 1 sites, wortmannin had no effect on the GR in the absence of stress but increased the stress potentiation of GR. Our results show that the mechanism by which GR activity is increased in stressed cells requires intrinsic HSF1 activity.