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)

Flavopiridol (L86-8275) is a synthetic flavone currently undergoing Phase I clinical trials. It is active against a series of human cancer cell lines and has been shown to inhibit a broad range of protein kinases, including cyclin-dependent kinases and protein kinase C (PKC). Previous studies have shown that the PKC-specific inhibitor safingol significantly enhances the induction of apoptosis by mitomycin-C (MMC) in gastric cancer cells. Because flavopiridol can potentially inhibit PKC, we elected to determine the extent to which flavopiridol would promote MMC-induced apoptosis in both gastric and breast cancer cells. For these studies, MKN-74 gastric cancer cells and MDA-MB-468 breast cancer cells were exposed to either no drug, 1 microgram/ml MMC alone, 300 nM flavopiridol alone, or a combination of chemotherapy with flavopiridol for 24 h. Sequence specificity was also examined by first exposing cells to MMC for 24 h followed by flavopiridol for 24 h or to the same drugs in the reverse order. Apoptosis was measured by quantitative fluorescence microscopy of nuclear chromatin condensation in cells stained with the dye, bisbenzimide trihydrochloride. Exposure of MKN-74 cells to flavopiridol alone induced apoptosis in 12 +/- 1% of the cells, and exposure to MMC alone induced apoptosis in 10 +/- 1%. However, the combination of flavopiridol and MMC increased the induction of apoptosis to 55 +/- 3% of the cells (P < 0.005 for the drug combination versus flavopiridol alone). Pretreatment with the PKC activator 3-phorbol 12-myristate 13-acetate only partially reversed this effect (43 +/- 1%; P < 0.025). In MDA-MB-468 cells, flavopiridol alone induced apoptosis in 17 +/- 1% of the cells, and MMC alone induced apoptosis in 10 +/- 1% of the cells. The combination of flavopiridol and MMC increased the percentage of MDA-MB-468 cells undergoing apoptosis to 58 +/- 4% (P < 0.005 for the drug combination versus flavopiridol alone). Sequential treatment with MMC followed by flavopiridol induced apoptosis in 63 +/- 2% of the MKN-74 cells (P < 0.05 versus the concomitant drug combination) and in 76 +/- 2% of the MDA-MB-468 cells (P < 0.025 versus the concomitant drug combination), whereas flavopiridol followed by MMC did not increase the induction of apoptosis in either cell line. As determined by the terminal deoxynucleotidyl transferase labeling of the 3' ends of DNA fragments produced in apoptotic cells, the induction of apoptosis with the combination of flavopiridol and MMC occurred to MKN-74 cells in all phases of the cell cycle (i.e., G0-G1, S, and G2-M). These results indicate that flavopiridol potentiates the cytotoxic effect of the chemotherapeutic agent MMC by promoting drug-induced apoptosis in tumor cells. Sequencing studies suggest that MMC followed by flavopiridol or simultaneous treatment is superior to flavopiridol followed by MMC. The enhancement of MMC-induced apoptosis by flavopiridol may be partially PKC dependent and is not associated with one specific region of the cell cycle.
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PMID:Potentiation of apoptosis by flavopiridol in mitomycin-C-treated gastric and breast cancer cells. 981 32

Apoptosis plays a major role in gastrointestinal epithelial cell turnover, ulcerogenesis and tumorigenesis. We have examined apoptosis induction by non-steroidal anti-inflammatory drugs (NSAIDs) in human gastric (AGS) cancer cells and the role of protein kinase C (PKC) and apoptosis-related oncogenes. After treatment with aspirin or indomethacin, cell growth was quantified by MTT assay, and apoptosis was determined by acridine orange staining, DNA fragmentation and flow cytometry. The mRNA and protein of p53, p21waf1/cip1 and c-myc was detected by Northern and Western blotting respectively. The influence of PKC on indomethacin-induced apoptosis was determined by co-incubation of 12-O-tetradecanoylphorbol 13-acetate (TPA). The role of c-myc was determined using its antisense oligonucleotides. The results showed that both aspirin and indomethacin inhibited cell growth and induced apoptosis of AGS cells in a dose- and time-dependent manner, without altering the cell cycle. Indomethacin increased c-myc mRNA and protein, whereas p53 and p21wafl/cip1 were unchanged. Down-regulation of c-myc by its antisense oligonucleotides reduced apoptosis induction by indomethacin. TPA could inhibit indomethacin-induced apoptosis and accumulate cells in G2/M. Overexpression of c-myc was inhibited by TPA and p21waf1/cip1 mRNA increased. In conclusion, NSAIDs induce apoptosis in gastric cancer cells which may be mediated by up-regulation of c-myc proto-oncogene. PKC activation can abrogate the effects of NSAIDs by decreasing c-myc expression.
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PMID:Non-steroidal anti-inflammatory drug-induced apoptosis in gastric cancer cells is blocked by protein kinase C activation through inhibition of c-myc. 1002 4

In Helicobacter pylori-associated gastric mucosal injury, interleukin (IL) -8, a potent leukocyte chemoattractant, is produced by epithelial cells infected by H. pylori and directs neutrophils to the gastric mucosa. According to previous studies, the IL-8 production requires direct contact between the bacteria and epithelial cells. The aims of the present study were to determine whether an H. pylori water extract (HPE) induces IL-8 production by gastric epithelial cells and to characterize IL-8-inducing substances in HPE. Extracts were prepared from a standard strain and from strains obtained from patients with gastric ulcers. After addition of HPE to MKN 45 cells, a gastric cancer cell line, IL-8 in supernatants and IL-8 mRNA were measured by immunoassay and reverse transcription-polymerase chain reaction, respectively. For characterization, active fractions obtained by gel filtration of standard-strain HPE were treated by heating or trypsinization. To study the signal pathway leading to IL-8 production, inhibitors for protein kinase A (PKA), protein kinase C (PKC), or protein tyrosine kinase (PTK) were incubated with MKN45 cells before HPE stimulation. HPE from the standard strain and one of these clinical strains induced IL-8 production. Lipopolysaccharide or cagA in the strains showed no correlation with IL-8 concentration. Standard-strain HPE induced IL-8 mRNA expression in MKN 45 cells. Gel filtration localized activity to a low-molecular-weight fraction of about 7 kDa, which was resistant to heat and trypsin digestion. PKC inhibitors significantly blocked HPE-induced IL-8 production by MKN 45 cells; however, the PKA inhibitor or PTK inhibitors showed a partial inhibitory effect. HPE contains a nonprotein substance of low molecular weight that is responsible for IL-8 induction in gastric epithelial cells. This induction is mainly dependent on the activation of PKC but partially also dependent on PKA or PTK.
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PMID:Helicobacter pylori water extract induces interleukin-8 production by gastric epithelial cells. 1006 6

Disruption of interactions between epithelial cells and extracellular matrix proteins leads to apoptosis of the cells, a phenomenon termed anoikis. Anoikis seems to play important roles in control of cellular positioning and inhibition of inappropriate cell growth. Here we found that a protein kinase C (PKC) activator phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) promoted cell death in human gastric cancer cell lines MKN45 and MKN74 only when they lost anchorage. Loss of anchorage slightly increased enzymatic activity of PKCalpha, and an addition of TPA promoted cell death with further increase of PKCalpha activity, but not PKCbeta in MKN45 cells, implicating an involvement of PKCalpha in anoikis. Furthermore, vaccinia virus-mediated overexpression of PKCalpha strongly increased CPP32 activity in the detached MKN45 and MKN74 cells, and augmented anoikis, however it had little effect on viability and CPP32 activity in the attached cells. Taken together, PKCalpha promotes apoptotic cell death in gastric cancer cells depending upon loss of anchorage, thereby may be a modulator of anoikis.
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PMID:Protein kinase Calpha promotes apoptotic cell death in gastric cancer cells depending upon loss of anchorage. 1052 38

The protein kinase C (PKC) signaling pathway plays a key role in tumor cell proliferation, differentiation, and apoptosis. Gastric cancer usually possesses a higher level of PKC activity than normal tissue. We evaluated inhibition of PKC activity in apoptosis induction of gastric cancer cells and the expression profile of apoptosis-related genes. Gastric cancer cells (AGS) were incubated with two highly specific PKC inhibitors (RO-31-8220 and chelerythrine). Cell viability and cell cycle were determined by methyl-tetrazolium (MTT) assay and flow cytometry, respectively. Apoptosis was characterized by acridine orange staining, DNA gel electrophoresis, and flow cytometry. The expression of p53, p21(waf/cip1), c-myc, bcl-2, and bax was determined by western blot. The results showed that both PKC inhibitors hindered cell growth, arrested cells at G0/G1 phase and induced apoptosis. The protein level of p53, p21(waf/cip1), c-myc, and bax was elevated while bcl-2 kept unchanged following drug exposure. In conclusion, PKC inhibitors suppress growth of gastric cancer cells through apoptosis induction and cell cycle quiescence, which may be regulated by differential expression of apoptosis-related genes.
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PMID:Pharmacological inhibition of protein kinase C activity could induce apoptosis in gastric cancer cells by differential regulation of apoptosis-related genes. 1054 53

Pretreatment of tumor cells with the protein kinase C (PKC) inhibitor bryostatin-1 enhances the cytotoxicity of most chemotherapeutic agents. However, in the case of paclitaxel, this effect has been shown in vitro to be best achieved when bryostatin-1 follows (rather than precedes) paclitaxel treatment. With combination trials of bryostatin-1 and paclitaxel planned for clinical trials and with only in vitro data available regarding drug sequence, we elected to undertake an in vivo study evaluating the effect of sequential bryostatin-1 and paclitaxel in a tumor-bearing mouse model and to correlate this effect to cell cycle events, tumor metabolism, and tumor blood flow. At the maximum tolerated i.p. dose, bryostatin-1 at 80 microg/kg resulted in a small but significant increase in tumor doubling time (4.2 +/- 0.3 days) compared with control tumors (3.0 +/- 0.3 days; P < 0.01). Mice treated with i.v. paclitaxel, administered at a dose of 12 mg/kg every 12 h for three doses, weekly for 3 weeks, had a tumor doubling time of 23.4 +/- 1.7 days. Mice pretreated with i.p. bryostatin-1 (80 microg/kg) followed 12 h later by i.v. paclitaxel (12 mg/kg every 12h for three doses) weekly for 3 weeks had a tumor doubling time of 9.7 +/- 1.1 days. This was significantly less (P < .001) than paclitaxel alone, which indicated an inhibitory effect by bryostatin-1 on paclitaxel therapy. In comparison, tumor-bearing mice that were treated with the same dose but with the sequence of paclitaxel followed by bryostatin-1 had a tumor doubling time of 29.6 +/- 0.6 days. This was significantly greater than the tumor doubling times for any condition tested (P < 0.01), demonstrating the sequence dependence of this combination. The efficacy of paclitaxel is dependent on mitotic entry, a step that requires activation of p34cdc2 kinase activity. Treatment with paclitaxel in vivo increased p34 cdc2 kinase activity in the mouse mammary tumors, whereas administration of bryostatin-1 before paclitaxel prevented the p34cdc2 kinase activation by paclitaxel. This was further evaluated in vitro by flow cytometry in MKN-74 human gastric cancer cells. As determined by MPM-2 labeling, which identifies cells in mitosis, pretreatment with bryostatin-1 prevented paclitaxel-treated cells from entering mitosis. Bryostatin-1 has been reported to induce changes in muscle metabolism and to decrease muscle blood flow. These events could impact on the interaction of bryostatin-1 with paclitaxel. Using proton-decoupled phosphorus nuclear magnetic resonance (31P-NMR) spectroscopy in vivo, bryostatin-1 at 80 micro1g/kg induced a decrease in both intratumoral pH and high-energy phosphates. In vivo perfusion studies, using dynamic enhanced NMR imaging with gadolinium diethylenetriamine pentaacetic acid, also demonstrated decreased tumor blood flow. These studies suggest that the inhibition of tumor response to paclitaxel by bryostatin-1 is multifactorial and includes such diverse factors as inhibition of cell entry into mitosis, a decrease in pH and energy metabolism, and a decrease in tumor blood flow. These results indicate that, as this combination enters Phase I clinical trials, the sequence of paclitaxel followed by bryostatin-1 will be critical in the clinical trial design.
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PMID:The in vivo effect of bryostatin-1 on paclitaxel-induced tumor growth, mitotic entry, and blood flow. 1077 82

The hormone bombesin (BBS) and its mammalian equivalent gastrin-releasing peptide (GRP) act through specific GRP receptors (GRP-R) to affect multiple cellular functions in the gastrointestinal tract; the intracellular signaling pathways leading to these effects are not clearly defined. Previously, we demonstrated that the human gastric cancer SIIA possesses GRP-R and that BBS stimulates activator protein-1 (AP-1) gene expression. The purpose of our present study was to determine the signaling pathways leading to AP-1 induction in SIIA cells. A rapid induction of c-jun and jun-B gene expression was noted after BBS treatment; this effect was blocked by specific GRP-R antagonists, indicating that BBS is acting through the GRP-R. The signaling pathways leading to increased AP-1 gene expression were delineated using phorbol 12-myristate 13-acetate (PMA), which stimulates protein kinase C (PKC)-dependent pathways, by forskolin (FSK), which stimulates protein kinase A (PKA)-dependent pathways, and by the use of various protein kinase inhibitors. Treatment with PMA stimulated AP-1 gene expression and DNA binding activity similar to the effects noted with BBS; FSK stimulated jun-B expression but produced only minimal increases of c-jun mRNA and AP-1 binding activity. Pretreatment of SIIA cells with either H-7 or H-8 (primarily PKC inhibitors) inhibited the induction of c-jun and jun-B mRNAs in response to BBS, whereas H-89 (PKA inhibitor) exhibited only minimal effects. Pretreatment with tyrphostin-25, a protein tyrosine kinase (PTK) inhibitor, attenuated the BBS-mediated induction of c-jun and jun-B, but the effect was not as pronounced as with H-7. Collectively, our results demonstrate that BBS acts through its receptor to produce a rapid induction of both c-jun and jun-B mRNA and AP-1 DNA binding activity in the SIIA human gastric cancer. Moreover, this induction of AP-1, in response to BBS, is mediated through both PKC- and PTK-dependent signal transduction pathways with only minimal involvement of PKA.
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PMID:Signaling mechanisms regulating bombesin-mediated AP-1 gene induction in the human gastric cancer SIIA. 1091 98

In gastric cancer, altered expression of MUC1, MUC2, MUC5AC, and MUC6 mucin genes has already been described. We show in this report by the means of in situ hybridization, reverse transcriptase-polymerase chain reaction, and transfection assays that MUC5B is also abnormally expressed in gastric carcinomatous tissues and cell lines. We thus undertook to elucidate the molecular mechanisms that regulate the transcription of MUC5B in gastric cancer cells. To this end, high expressing (KATO-III) and low expressing (AGS) gastric cancer cell lines were chosen to study human mucin gene MUC5B expression and promoter activity. Sequencing of the promoter region revealed a distal TATA box located 1 kilobase upstream of the proximal TATA box. Functional activity of the promoter was addressed by using deletion mutants covering 2044 nucleotides upstream of the MUC5B transcription start site. We identified a distal promoter 10 times more active than the proximal promoter in KATO-III cells. In AGS cells, both promoters, much less active, showed the same range of activity. Binding assays allowed us to show that the transcription factor ATF-1 binds to a cis-element present in the distal promoter. Sp1, which binds to both promoters specifically transactivates the proximal promoter. Treatment of transfected cells with PMA, cholera toxin A subunit, and calcium ionophore showed that only PMA led to a substantial activation of the distal promoter. MUC5B 5'-flanking region having a high GC content, influence of methylation on the MUC5B expression was assessed. Our results indicate that repression of MUC5B expression visualized in AGS cells is due in part to the presence of numerous methylated cytosine residues throughout the 5'-flanking region. Altogether these results demonstrate that MUC5B expression in gastric cancer cells is governed by a highly active distal promoter that is up-regulated by protein kinase C and that repression is under the influence of methylation.
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PMID:Aberrant expression of human mucin gene MUC5B in gastric carcinoma and cancer cells. Identification and regulation of a distal promoter. 1127 96

Phorbol 12-myristate 13-acetate (PMA) rapidly induced cell death in SNU-16 gastric adenocarcinoma cells. DNA ladder formation and caspase-3/CPP32 activation were observed in PMA treated cells indicating that PMA induces apoptosis. z-DEVD-fmk, specific inhibitor of caspase-3/CPP32, inhibited the induction of apoptosis by PMA, demonstrating that caspase/CPP32 are critically involved in PMA-induced apoptosis. The serine protein inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride effectively blocked apoptosis, and also prevented caspase-3/CPP32 activation. Go6983, a specific inhibitor of PKC, almost completely suppressed apoptosis and caspase-3/CPP32 activation. Furthermore, 1,2-dihexanoyl-sn-glycerol, an endogenous activator of PKC, induced apoptosis detected by DNA fragmentation and Hoechst 33258 nuclear staining. From these results, we conclude that PMA is not only a tumor promoter, but can also induce apoptosis in gastric cancer cells. PMA-induced apoptosis appears to be mediated through activation of protein kinase C, and the activation of serine protease(s) and caspase-3/CPP32 may be the molecular mechanisms by which PMA induces apoptosis.
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PMID:Protein kinase C activation by PMA rapidly induces apoptosis through caspase-3/CPP32 and serine protease(s) in a gastric cancer cell line. 1129 59

Although apoptosis-dependent involution of malignant tumors is associated with a number of non-surgical treatments including chemotherapy, most solid tumors, including gastric cancers, respond poorly to these therapies. In the hope of overcoming the resistance mechanism against non-surgical therapies, we studied the apoptosis-resistance mechanism in cells of gastric cancers as a model system. During the course of our study on apoptotic machinery in human gastric cancer cell lines, we previously found a rapid and efficient induction of apoptosis by sorbitol. In the present study, we demonstrated that the down-regulation of PKC activity in response to sorbitol is a major factor in the induction of apoptotic cell death in gastric cancer cells.
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PMID:Down-regulation of protein kinase C activity by sorbitol rapidly induces apoptosis in human gastric cancer cell lines. 1148 59


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