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

A global DNA hypomethylation might activate oncogene transcription, thus promoting carcinogenesis and tumor development. S-Adenosylmethionine (SAM) serves as a major methyl donor in biological transmethylation events. The object of this study is to explore the influence of SAM on the status of methylation at the promoter of the oncogenes c-myc, H-ras and tumor-suppressor gene p16 (INK4a), as well as its inhibitory effect on cancer cells. The results indicated that SAM treatment inhibited cell growth in gastric cancer cells and colon cancer cells, and the inhibition efficiency was significantly higher than that in the normal cells. Under standard growth conditions, C-myc and H-ras promoters were hypomethylated in gastric cancer cells and colon cancer cells. SAM treatment resulted in a heavy methylation of these promoters, which consequently downregulated mRNA and protein levels. In contrast, there was no significant difference in mRNA and protein levels of p16 (INK4a) with and without SAM treatment. SAM can effectively inhibit the tumor cells growth by reversing the DNA hypomethylation on promoters of oncogenes, thus down-regulating their expression. With no influence on the expression of the tumor suppressor genes, such as P16, SAM could be used as a potential drug for cancer therapy.
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PMID:S-adenosylmethionine inhibits the growth of cancer cells by reversing the hypomethylation status of c-myc and H-ras in human gastric cancer and colon cancer. 2115 19

PURPOSE : Treatment effects of advanced gastric cancer (AGC) are unsatisfactory, and novel therapeutic approaches are much needed. The epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab inhibits the growth of several human cancer cells but has been tested rarely for the treatment of GC. The synergy between cetuximab and irinotecan has been reported in colorectal cancer, but the mechanisms are still not fully clarified. Consequently, we hypothesized cetuximab/irinotecan combination should enhance the antitumor activity of irinotecan in GC cells. METHODS : The in vitro antiproliferative, pro-apoptotic, cell cycle arrest effects and induction of senescence were examined in SGC-7901 and MKN-45 GC cell lines. The effects of cetuximab or irinotecan as single agents or the combination on the expression of p53, p16, and EGFR signaling pathways were also studied. RESULTS : The study revealed that cetuximab alone did not show any antiproliferative, pro-apoptotic, cell cycle arrest or cellular senescence effect on GC cells but when combined with irinotecan synergistically inhibits GC cell proliferation and induces apoptosis and G2/M phase arrest. Irinotecan increases phosphorylation of EGFR, MAPK, and AKT and decreases the expression of P27(Kip1), which could be all abrogated by its combination with cetuximab. The combination could also inhibit the expression of Cyclin D1 and phosphorylated mTOR while had no impact on p53, p16, PTEN, and HIF-1alpha. CONCLUSIONS : Cetuximab enhances the activities of irinotecan on GC cells via the downregulation of the EGFR pathway upregulated by irinotecan. Combination therapy with cetuximab and irinotecan, a novel therapeutic approach, warrants further study in GC.
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PMID:Cetuximab enhances the activities of irinotecan on gastric cancer cell lines through downregulating the EGFR pathway upregulated by irinotecan. 2128 18

The tumor suppressor p16 is a negative regulator of the cell cycle, commonly believed to act in the nucleus. We recently found that p16 protein is expressed in the cytoplasm of gastric cancer cells, concomitantly with anion exchanger 1 (AE1). The aim of this study was to analyze the significance of cytoplasmic p16 and its relationship to AE1 in the progression of gastric cancer. Expression of p16 and AE1 was examined by immunohistochemical analysis in 196 patients; 98 with early gastric cancer and 98 with advanced gastric cancer. The relationship between cytoplasmic p16 and clinicopathological features, and the relationship between cytoplasmic p16 and AE1, were analyzed statistically. Expression of p16 was observed in the nucleus in early stage gastric cancer, but was located mainly in the cytoplasm in advanced cancer cells. Furthermore, cytoplasmic expression of p16 was correlated with AE1 expression, and both were associated with the absence of lymph metastasis in gastric cancer. In conclusion, cytoplasmic immunoreactivity of p16 appears to be a good prognostic indicator in advanced gastric cancer. Co-localization of p16 and AE1 predicts a lack of metastasis in gastric cancer. The role of cytoplasmic p16 and AE1, and the mechanisms involved in the progression of gastric cancer, warrant further investigation.
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PMID:Expression of cytoplasmic p16 and anion exchanger 1 is associated with the invasion and absence of lymph metastasis in gastric carcinoma. 2147 8

We analyzed gastric cancers for p16 gene alterations. Homozygous deletion of the p16 gene was found in 1 of 8 gastric cancer cell lines and none of 20 primary gastric cancers. Mutations of the p16 gene were not detected in exon 1-3. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed decreased or no expression of the p16 gene in 1 of 8 cell lines (12.5%) and in 8 of 20 tumors (40%), although no homozygous deletions or mutations within exon 1-3 were detected. These results suggest that the p16 gene may correlate to tumorigenesis due to decrease or loss of gene products in gastric cancers.
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PMID:Decreased expression of p16 gene in gastric cancer. 2154 52

Promoter methylation acts as an important alternative to genetic alterations for gene inactivation in gastric carcinogenesis. Although a number of gastric cancer-associated genes have been found to be methylated in gastric cancer, valuable methylation markers for early diagnosis and prognostic evaluation of this cancer remain largely unknown. In the present study, we used methylation-specific PCR (MSP) to analyze promoter methylation of 9 gastric cancer-associated genes, including MLF1, MGMT, p16, RASSF2, hMLH1, HAND1, HRASLS, TM, and FLNc, and their association with clinicopathological characteristics and clinical outcome in a large cohort of gastric cancers. Our data showed that all of these genes were aberrantly methylated in gastric cancer, ranging from 8% to 51%. Moreover, gene methylation was strongly associated with certain clinicopathological characteristics, such as tumor differentiation, lymph node metastasis, and cancer-related death. Of interest, methylation of MGMT, p16, RASSF2, hMLH1, HAND1, and FLNc was closely associated with poor survival in gastric cancer, particularly MGMT, p16, RASSF2 and FLNc. Thus, our findings suggested these epigenetic events may contribute to the initiation and progression of gastric cancer. Importantly, methylation of some genes were closely relevant to poor prognosis in gastric cancer, providing the strong evidences that these hypermethylated genes may be served as valuable biomarkers for prognostic evaluation in this cancer.
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PMID:Prognostic significance of aberrant gene methylation in gastric cancer. 2220 50

Abnormalities in signal transducer and activator of transcription (STAT) signaling, especially STAT3 and STAT5, are involved in the oncogenesis of several human cancers, including gastric cancer (GC). However, the downstream targets of STAT3 and STAT5 are not fully identified, and the precise roles and the prognostic value of STAT3 and STAT5 in GC have not been fully characterized. In this study, we used ChIP-on-chip to identify STAT3 and STAT5 target genes on a whole genome scale in AGS cells, a human GC cell line. A total of 2,514 and 1,314 genes were identified as STAT3 and STAT5 target genes, which were mainly related to cell growth, metabolism, differentiation, adhesion, immune response, and stress response. Furthermore, we depleted STAT3 and STAT5 with a small interfering RNA, respectively. Our results demonstrate that STAT3, but not STAT5, is involved in GC cell growth and cell cycle progression through regulation of gene expression, such as Bcl-2, p16(ink4a) and p21(waf1/cip1). Moreover, expression of pSTAT3(Tyr705) correlates with TNM stage, differentiation and survival, and is a significant prognostic factor in GC. Therefore, our findings provide novel evidence that STAT3 may be a potential therapeutic target for GC treatment and pSTAT3(Tyr705) expression can predict prognosis in GC.
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PMID:Constitutive activation of STAT3 is predictive of poor prognosis in human gastric cancer. 2232 12

The aim of this study was to evaluate the methylation status of three important cancer related genes viz. p16, E-cadherin and hMLH1 promoters and to associate the findings with specific dietary habits in Kashmiris, a culturally distinct population in India, with gastric cancer. The study subjects were divided into three age groups viz. 0-30 yrs (1st), 31-60 yrs (2nd) and 61-90 yrs (3rd). A highly significant association between the intake of local hot salted tea in 2nd (p=0.001) and 3rd (p=0.009) age groups was observed with the promoter hypermethylation of E cadherin. Again a highly significant association between the aberrant methylation of hMLH1 (p=0.000) and p16 (p=0.000) promoters and the intake of local hot salted tea was observed in the 2nd age group of gastric cancer patients. The intake of sun-dried food was also significantly associated with the promoter hypermethylation of E cadherin (p=0.003) and p16 (p=0.015) genes in 3rd age group. The results of the present study suggest a close association between the aberrant methylation of p16, E-cadherin and hMLH1 promoters and the intake of local hot salted tea and sun-dried foods in Kashmiri population.
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PMID:Association between p16, hMLH1 and E-cadherin promoter hypermethylation and intake of local hot salted tea and sun-dried foods in Kashmiris with gastric tumors. 2250 64

Common single-nucleotide polymorphisms (SNPs) in microRNAs (miRNAs) have been shown to be associated with susceptibility to several types of human cancer. We evaluated the association between three SNPs (rs11614913, rs2910164 and rs3746444) in pre-miRNAs (miR-196a2, miR-146a and miR-499) and various clinicopathological characteristics, including CpG island hypermethylation (CIHM) status and overall survival in gastric cancer (GC) patients. rs11614913 (T>C), rs2910164 (C>G) and rs3746444 (A>G) SNPs were genotyped in 127 GC patients. CIHM of p14, p16, DAP-kinase and CDH1 genes was determined by methylation-specific polymerase chain reaction in the cancer tissues. A significant marginal association was found between the rs11614913 CC genotype and polypoid or elevated type morphology in early-stage GC (OR=6.29, 95% CI 1.18-33.47, p=0.03). The rs2910164 CC and CG genotypes were associated with increased susceptibility to CIHM of DAP-kinase (CC+CG, OR=5.48, 95% CI 1.30-23.10, p=0.02; CC, OR=6.93, 95% CI 1.37-35.02, p=0.02; CG, OR=4.24, 95% CI 0.87-20.78, p=0.07). The 11614913 TT and TC genotypes were associated with a higher number of CIHM (no. of CIHM 0-1 vs. 2-4; TT+TC, OR=3.67, 95% CI 0.98-13.72, p=0.05; TC, OR=4.08, 95% CI 1.04-15.97, p=0.04). When the subjects were divided according to age group, the combined rs11614913 TT+TC genotype tended to be associated with worse overall survival than the CC genotype in patients younger than 65 years of age (p=0.05). The combined rs2910164 CG+GG genotype also tended to be associated with worse overall survival than the CC genotype in the same age group (p=0.09). It appears that rs11614913 and rs2910164 SNPs in pre-miRNAs (miR-196a2 and miR-146a) affect the clinicopathological characteristics of GC, including its morphological appearance, CIHM status and overall survival.
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PMID:Association between common genetic variants in pre-microRNAs and the clinicopathological characteristics and survival of gastric cancer patients. 2299 37

Aberrant regulation of histone deacetylase 2 (HDAC2) was reported for gastric cancers. However, responsive cancer genes in disease onset and progression are less understood. HDAC2 expression was studied by quantitative RT-PCR and Western blotting. The functional consequences of HDAC2 knockdown on cell-cycle regulation, programmed cell death, and gene target identification was investigated by flow cytometry, Western blotting, electron microscopy, anchorage-independent colony formation, and cell migration assay and by whole-genome microarray. Therapeutic efficacy of HDAC2 knockdown was determined in nude mice with small hairpin expressing human gastric cancer cells. Epigenetic regulation of p16(INK4a) was studied by methylation-specific PCR and chromatin-IP to evidence HDAC2 or acetylated-histone-H4 binding at gene specific promoter sequences. HDAC2 gene and protein expression was significantly upregulated in different histopathologic grades of human gastric cancers and cancer cell lines. HDAC2 inactivation significantly reduced cell motility, cell invasion, clonal expansion, and tumor growth. HDAC2 knockdown-induced G(1)-S cell cycle arrest and restored activity of p16(INK4a) and the proapoptotic factors. This treatment caused PARP cleavage and hypophosphorylation of the Rb-protein, repressed cyclinD1, CDK4, and Bcl-2 expression and induced autophagic phenotype, that is, LC3B-II conversion. Some gastric tumors and cancer cells displayed p16(INK4a) promoter hypermethylation but treatment with 5-aza-deoxycitidine restored activity. With others the methylation status was unchanged. Here, chromatin-IP evidenced HDAC2 binding. Nonetheless, expression of p16(INK4a) was restored by HDAC2 knockdown with notable histone-H4-acetylation, as determined by chromatin-IP. Thus, p16(INK4a) is regulated by HDAC2. HDAC2 is a bona fide target for novel molecular therapies in gastric cancers.
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PMID:Targeted inactivation of HDAC2 restores p16INK4a activity and exerts antitumor effects on human gastric cancer. 2317 21

2-Amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP) is one of the most abundant heterocyclic amines (HCAs) generated from overcooking meat at high temperatures. To understand the possible mechanism of PhIP-associated stomach cancer, the effects of PhIP on morphology, oxidative stress, gene expression of c-fos, c-jun and p16 in rat stomachs were investigated. The results showed that (1) 15mg/kg body weight PhIP induced obvious histopathological changes in gastric mucosa; (2) PhIP (10 and/or 15mg/kg) significantly decreased superoxide dismutase (SOD) and glutathioneperoxidase (GPx) activities, while increased catalase (CAT) activity compared with the control. With the elevated doses of PhIP, malondialdehyde (MDA) contents, protein carbonyl (PCO) contents and DNA-protein crosslinks (DPC) coefficients were significantly raised in a dose-dependent manner; (3) PhIP at the doses of 10mg/kg and/or 15mg/kg significantly inhibited p16 mRNA and protein expression, whereas enhanced c-fos and c-jun expression relative to control. The data indicated that PhIP could cause stomach injury, oxidative stress in rat stomachs as well as the activation of c-fos and c-jun and inactivation of p16, which may play a role in the pathogenesis of PhIP-associated stomach cancer.
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PMID:Effects of 2-amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP) on histopathology, oxidative stress, and expression of c-fos, c-jun and p16 in rat stomachs. 2331 94


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