Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0024623 (gastric cancer)
 36,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Genetic and epigenetic alterations of multiple cancer-related genes and molecules are implicated in the development and progression of human gastric carcinomas. Reactivation of telomerase, inactivation of p53 tumor suppressor gene, overexpression of cyclin E, and reduced expression of p27 KIP1 by disorganized degradation in proteasome are common events of both well-differentiated and poorly differentiated gastric adenocarcinomas. Inactivation of hMLH1 mismatch repair gene by CpG hypermethylation resulting in microsatellite instability, amplification of c-erbB2 oncogene, inactivation of APC tumor suppressor gene, and K-ras mutations are preferentially associated with well-differentiated gastric cancer. Conversely, reduction or loss of E-cadherin and catenins by both mutation and CpG hypermethylation and K-sam and c-met oncogene amplification are necessary for the development and progression of poorly differentiated or scirrhous gastric carcinomas. Interaction between cancer cells expressing c-met and hepatocyte growth factor from stromal cells is implicated in morphogenesis of gastric cancer.
 ...
PMID:Genetic and epigenetic changes in stomach cancer. 1124 97

The intramuscular ATP-dependent ubiquitin (Ub)-proteasome proteolytic system is hyperactivated in experimental cancer cachexia. The present study aimed at verifying whether the expression of the muscle Ub mRNA is altered in patients with cancer. Total muscle RNA was extracted using the guanidinium isothiocyanate/phenol/chloroform method from rectus abdominis biopsies obtained intraoperatively from 20 gastric cancer (GC) patients and 10 subjects with benign abdominal diseases (CON) undergoing surgery. Ub mRNA levels were measured by northern blot analysis. Serum soluble tumor necrosis factor receptor (sTNFR) was measured by ELISA. Ub mRNA levels (arbitrary units, means +/- SD) were 2,345 +/- 195 in GC and 1,162 +/- 132 in CON (P = 0.0005). Ub mRNA levels directly correlated with disease stage (r = 0.608, P = 0.005), being 1,945 +/- 786 in stages I and II, 2,480 +/- 650 in stage III, and 3,799 +/- 66 in stage IV. Ub mRNA and sTNFR did not correlate with age and nutritional parameters. This study confirms experimental data indicating an overexpression of muscle Ub mRNA in cancer cachexia. Lack of correlation with nutritional status suggests that Ub activation in human cancer is an early feature that precedes any clinical sign of cachexia.
 ...
PMID:Increased muscle ubiquitin mRNA levels in gastric cancer patients. 1129 77

E2F-1 regulates the transcription of genes required for DNA synthesis. Previously, we have reported that UCN-01 suppresses E2F-1 protein expression without any noticeable effect on its mRNA level in gastric cancer cell line SK-GT5 (Clin. Cancer Res., 4: 2201-2206, 1998). In this study, we investigated the mechanism responsible for the suppression of E2F-1 expression by UCN-01 in SK-GT5 cells. After 24-h exposure to 1 microM UCN-01, E2F-1 protein expression was decreased by >99%. The suppressive effect of UCN-01 could be reversed by ubiquitin-dependent proteasome inhibitors such as calpain inhibitor I and lactacystin. Transfection experiments using expression plasmids encoding full-length E2F-1 or truncated E2F-1 with deletion of the COOH-terminal region (which is required for eliciting ubiquitination and protein degradation) revealed that the expression of truncated E2F-1 was not affected by UCN-01. Other cell-cycle-related and ubiquitin-proteasome-regulated proteins such as p21, p27, and cyclin B1 were not repressed by UCN-01 in E2F-1-overexpressing cells. In vitro-translated, full-length E2F-1 degraded more rapidly upon incubation with extracts from UCN-01-treated cells when compared with truncated E2F-1. Taken together, these data indicate that UCN-01 suppresses E2F-1 protein expression mediated by the ubiquitin-proteasome pathway in a specific manner.
 ...
PMID:UCN-01 suppresses E2F-1 mediated by ubiquitin-proteasome-dependent degradation. 1129 63

The ubiquitin-proteasome pathway plays a critical role in the degradation of cellular proteins and cell cycle control. Dysregulating the degradation of such proteins should have profound effects on tumor growth and causes cells to undergo apoptosis. The aims of this study are to evaluate the ubiquitin-proteasome pathway in gastric cancer and the potential role of pharmacological inhibition of proteasome on induction of apoptosis in gastric cancer cells. Gastric cancer cell lines AGS (p53 wild-type) and MKN-28 (p53 mutant) were treated with proteasome inhibitor MG132. The results showed that MG132 inhibited cell proliferation in AGS and MKN-28 cells in a time- and dose-dependent manner. The inhibition of cell proliferation was caused by apoptosis which was also time- and dose-dependent. AGS cells were more responsive to MG132 than MKN-28 cells. Induction of apoptosis was preceded by the activation of caspase-3, as measured by a colorimetric caspase-3 cellular activity and Western blotting of the cleavage of caspase-3 and its substrate PARP. Activation of caspase-7 was also exhibited. In addition, z-VAD-fmk, a broad spectrum caspase inhibitor, reversed apoptosis induced by MG132 in AGS and MKN28 cells. Although z-DEVD-fmk, a specific caspase-3 inhibitor, suppressed MG132-induced apoptosis in MKN28 cells, it only partially rescued the apoptotic effect in AGS cells. Caspase-3 activation was the result of release of cytochrome c from mitochondria into the cytosol, as a consequence of upregulation of bax. There were overexpressions of all the proteasome-related proteins p53, p21(waf1) and p27(kip1) at 4 hr after proteasome inhibition which was identified by the accumulation of ubiquitin-tagged proteins. This was accompanied by accumulation of cells at G(1) phase. Our present study suggests that inhibition of proteasome function in gastric cancer cells induces apoptosis and proteasomal inhibitors have potential use as novel anticancer drugs in gastric cancer.
 ...
PMID:Inhibition of proteasome function induced apoptosis in gastric cancer. 1147 51

We examined in the present study whether human gastric cancer cells express peroxisome proliferator-activated receptor gamma (PPARgamma), the effect of PPARgamma activation by troglitazone, a selective ligand, on cellular growth, and the mechanism of the growth arrest by troglitazone in gastric cancer cells. RT-PCR, northern blot and western blot analysis demonstrated that all four tested human gastric cancer cell lines, MKN-28, MKN-45, MKN-74 and KATO-III, expressed PPARgamma mRNA and protein. WST-1 assay and flow cytometric analysis revealed that troglitazone inhibited the growth and induced G1 arrest in all four gastric cancer cell lines. To examine the role of p27(Kip1), a cyclin-dependent kinase inhibitor, in the G1 arrest by troglitazone, we determined p27(Kip1) protein expression by western blot analysis in gastric cancer cells that had been treated with troglitazone. Troglitazone increased p27(Kip1) in all four gastric cancer cell lines. Since it has been reported that the ubiquitin-proteasome system plays a vital role in the degradation of p27(Kip1) protein, we evaluated the hypothesis that inhibition of proteasome mediates the troglitazone-induced p27(Kip1) accumulation. Lactacystin, a proteasome inhibitor, inhibited cell growth and increased p27(Kip1) expression in MKN-74 cells. It was further demonstrated that troglitazone inhibited proteasome activity in a dose-dependent manner in MKN-74 cells. All these results suggest that troglitazone inhibited proteasome activity, followed by induction of p27(Kip1), which arrests cells at the G1 phase of the cell cycle in gastric cancer cells. The troglitazone-mediated inhibition of the proteasome suggests a novel mechanism for the anti-proliferative effect of this agent in cancer cells.
 ...
PMID:Troglitazone induces G1 arrest by p27(Kip1) induction that is mediated by inhibition of proteasome in human gastric cancer cells. 1214 43

The transcription factor NF-kappaB is constitutively activated in many human cancers and induces the expression of multiple genes, including those of anti-apoptotic proteins. This study investigated the mechanism by which human gastric cancer cells (MKN45) are resistant to apoptosis induced by tumor necrosis factor alpha (TNF-alpha). Confluent monolayers of MKN45 cells were either pretreated or not for 60 min with PSI, a peptide aldehyde known to specifically inhibit the chymotrypsin-like activity of 26S proteasome. Cells were subsequently stimulated with recombinant human TNF-alpha, and cell viabilities were determined by the WST-1 assay. Apoptosis was confirmed by fluorescence microscopy after staining with Hoechst 33342, and DNA fragmentation was determined by a DNA fragmentation detection kit. A 24-h incubation with either TNF-alpha or PSI alone did not affect cell viabilities; however, pretreatment with PSI significantly enhanced the level of apoptosis induced by TNF-alpha. Therefore, this study suggests the possibility that blocking of NF-kappaB activity renders gastric cancer cells susceptible to the apoptosis induced by TNF-alpha.
 ...
PMID:Blocking of NF-kappaB activation enhances the tumor necrosis factor alpha-induced apoptosis of a human gastric cancer cell line. 1270 75

Helicobacter pylori infection is associated with increased gastric epithelial cell turnover and is a risk factor for noncardia gastric cancer. H. pylori reduces the expression of p27 protein, a cyclin-dependent kinase inhibitor of the G(1) to S-phase cell cycle transition and gastric tumor suppressor gene. Although cell cycle dysregulation associated with decreased p27 may contribute to gastric carcinogenesis, how H. pylori reduces p27 in gastric epithelial cells remains unknown. In the present study, we investigated the mechanisms of the p27 decrease, using AGS and MKN28 gastric epithelial cells cocultured with H. pylori strains under conditions of defined cell cycle distribution. The expression of p27 protein was reduced by H. pylori in a dose- and time-dependent manner. Northern blot and pulse-chase analyses revealed that this reduction was not regulated at a transcriptional level but by accelerated p27 degradation via a proteasome-dependent pathway. Despite up-regulation of the proteasome-dependent degradation of p27 protein, neither threonine 187-phosphorylated p27 nor skp2 (the ubiquitin ligase for p27) were increased. Furthermore, H. pylori impaired p27 ubiquitination and did not increase global proteasomal function. These results indicate that H. pylori increases the degradation of p27 through a proteasomal pathway distinct from the physiological pathway that degrades p27 during cell cycle progression. Putative virulence genes of H. pylori (cagA, cagE, or vacA) played no role in reducing p27 expression. Increased degradation of p27 by H. pylori through a proteasome-dependent, ubiquitin-independent pathway may contribute to the increased risk of gastric cancer associated with chronic H. pylori infection.
 ...
PMID:Helicobacter pylori increases proteasome-mediated degradation of p27(kip1) in gastric epithelial cells. 1290 57

Retinoic acid receptor alpha (RARalpha) plays an important role in mediating all-trans retinoic acid (ATRA) signals. In this study, we found that ATRA up-regulated RARalpha mRNA and protein expression in gastric cancer BGC-823 cells. However, in breast cancer MCF-7 cells it down-regulated RARalpha protein expression with no effect on its RARalpha mRNA. Immunoprecipitation/Western blot analysis showed that, although sumoylated and ubiquitinated RARalpha existed simultaneously in both cancer cell lines, ATRA exerted different regulatory effects on sumoylation and ubiquitination of RARalpha. In MCF-7 cells, ATRA treatment enhanced the ubiquitination of RARalpha and the subsequent degradation of RARalpha through the ubiquitin/proteasome pathway. This resulted in a reduction in the DNA binding activity of RARalpha/retinoid X receptor alpha (RXRalpha) heterodimer, the separation of RXRalpha from RARalpha and the translocation of RXRalpha from the nucleus to the cytoplasm. By contrast, in BGC-823 cells, ATRA augmented sumoylation, not ubiquitination, of RARalpha. The stability of sumoylated RARalpha was significantly stronger than in non-sumoylated RARalpha. These results also showed an increase in the DNA binding activity of the RARalpha/RXRalpha heterodimer and the stability of nuclear localization of this heterodimer, which normally facilitates the ATRA signal transduction. In conclusion, our results reveal a novel mechanism for the regulation of RARalpha-dependent signal transduction through the ubiquitin/proteasome pathway in breast cancer cells and the sumoylation pathway in gastric cancer cells.
 ...
PMID:Ubiquitinated or sumoylated retinoic acid receptor alpha determines its characteristic and interacting model with retinoid X receptor alpha in gastric and breast cancer cells. 1517 3

By comparative proteome analysis we searched for characteristic alterations of human stomach adenocarcinoma tissue and paired surrounding normal tissue. Selected differential protein spots were identified with peptide mass fingerprinting based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and database searching. We identified protein alterations in 18 stomach cancer tissues compared with normal controls, comprising elevated levels of eight proteins, including 14-3-3 zeta, calcyclin, keratin, apolipoprotein A-1 precursor, proteasome activator complex subunit, nucleoside diphosphate kinase, nicotinamide N-methyltransferase, and pyridoxal kinase. Five proteins (CA11, prohibitin, peroxiredoxin 4, serum amyloid P component, and NADH-ubiquinone oxidoreductase 23 kDa subunit) were decreased. These data are valuable for identification of differentially expressed proteins involved in stomach cancer carcinogenesis, providing biomarker candidates to develop diagnostic and therapeutic tools.
 ...
PMID:The differential proteome profile of stomach cancer: identification of the biomarker candidates. 1555 63

Rebamipide accelerates healing of gastric ulcers and gastritis but its actions on gastric cancer are not known. Survivin, an anti-apoptosis protein, is overexpressed in stem, progenitor, and cancer cells. In gastric cancer, increased and sustained survivin expression provides survival advantage and facilitates tumor progression and resistance to anti-cancer drugs. Aurora-B kinase is essential for chromosome alignment and mitosis progression but surprisingly its role in gastric cancer has not been explored. We examined in human gastric cancer AGS cells: (1) survivin expression, (2) localization of survivin and Aurora-B, (3) cell proliferation, and (4) effects of specific survivin siRNA and/or rebamipide (free radical scavenging drug) on survivin and Aurora-B expression and cell proliferation. Survivin and Aurora-B are strongly expressed in human AGS gastric cancer cells and co-localize during mitosis. Survivin siRNA significantly reduces AGS cell viability. Rebamipide significantly downregulates in AGS cell survivin expression, its association with Aurora-B and cell proliferation. Rebamipide-induced downregulation of survivin is at the transcription level and does not involve ubiquitin-proteasome pathway.
 ...
PMID:Rebamipide inhibits gastric cancer growth by targeting survivin and Aurora-B. 1599 41


1 2 3 4 5 6 7 8 Next >>