sc-236 and Stomach-Neoplasms

Inhibition of cyclooxygenase-2 has been proposed to be a potential mechanism for the chemoprevention of gastrointestinal tumors by nonsteroidal anti-inflammatory drugs. This study investigates the mechanisms by which the cyclooxygenase-2 inhibitor SC236 induces apoptosis of gastric cancer cell lines and its downstream signaling pathway.. Two gastric cancer cell lines, AGS and MKN28, were treated with SC236 and assessed for cell growth and apoptosis. The involvement of mitogen-activated protein kinase and Akt kinase/protein kinase B (Akt/PKB) pathways and their downstream signalings were studied in the AGS cell line.. SC236 treatment induced apoptosis in gastric cancer cells and caused activation of p38 and stress-activated protein kinase/jun kinase, but down-regulated Akt/PKB. The specific p38 inhibitor SB203580 and the dominant-negative stress-activated protein kinase/jun kinase both failed, while the constitutively active form of Akt/PKB was able to block SC236-induced apoptosis. SC236-induced apoptosis was coupled with release of cytochrome c and activation of caspases.. One of the pathways involved in SC-236-induced apoptosis in gastric cancer cells is through downregulation of Akt and then release of cytochrome c.

Topics: Acridine Orange; Adenocarcinoma; Apoptosis; Blotting, Western; Caspases; Cyclooxygenase 2 Inhibitors; Cytochromes c; Down-Regulation; Enzyme Activation; Humans; Mitogen-Activated Protein Kinases; Proto-Oncogene Proteins c-akt; Pyrazoles; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Stomach Neoplasms; Sulfonamides; Transfection; Tumor Cells, Cultured

To investigate the underlying mechanism of apoptosis-inducing effect of a specific COX-2 inhibitor SC236 in gastric cancer cells.. Western blot analysis was used to measure apoptosis-related proteins, cytochrome c, and caspase-3. The catalytic activity of the caspases was measured using a colorimetric assay.. Treatment of AGS gastric cancer cells with SC236 caused a significant elevation of the pro-apoptotic protein Bak, release of cytochrome c to the cytosol, and activation of caspase-3. A specific caspase-3 inhibitor, z-DEVD-fmk, blocked SC236-induced apoptosis.. SC236 inhibits cell growth and induces apoptosis in gastric cancer cells at least partly through the up-regulation of Bak, stimulation of cytochrome c release, and activation of caspase-3.

Topics: Adenocarcinoma; Apoptosis; bcl-2 Homologous Antagonist-Killer Protein; Caspase 3; Caspases; Cell Line, Tumor; Cyclooxygenase 2 Inhibitors; Cytochromes c; Humans; Oligopeptides; Poly(ADP-ribose) Polymerases; Pyrazoles; Stomach Neoplasms; Sulfonamides

Aspirin exerts antitumor effect partly through blocking tumor promoter-induced activator protein-1 (AP-1) activation. The aim of this study is to determine how specific COX-2 inhibitor SC-236 mediates antitumor effect by modulation of AP-1-signaling pathway.. AP-1 transcriptional activity and DNA-binding activity were detected by luciferase reporter assay and gel shift assay, separately. Mitogen-activated protein kinase (MAPK) activation was determined by Western blot and in vitro kinase assay. Antisense oligonucleotide against c-Jun-N-terminal kinase (JNK) was used to suppress JNK expression.. We showed that SC-236 inhibited 12-O-tetradecanoylphorbol-13-acetate (PMA)-induced cell transformation in a dose-dependent manner in JB6 cells. At a dose range (12.5-50 micromol/L) that inhibited cell transformation, SC-236 also inhibited anchorage-independent cell growth and AP-1-activation in 3 gastric cancer cells, independent of COX-prostaglandin synthesis. SC-236 down-regulated c-Jun-NH2-terminal kinase phosphorylation and activity. Suppression of JNK activity reversed the inhibitory effect on AP-1 activity by SC-236 and suppressed gastric cancer cell growth, indicating that the inhibitory effect of SC-236 on AP-1 activation and cell growth was through interaction with JNK.. The inhibitory effect on JNK-c-Jun/AP-1 activation contributes to the antitumor effect of COX-2-specific inhibitor, and inhibition of JNK activation may have a therapeutic benefit against gastric cancer.

Topics: Cell Division; Cell Line, Tumor; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Dinoprostone; Dose-Response Relationship, Drug; Enzyme Activation; Humans; Isoenzymes; JNK Mitogen-Activated Protein Kinases; Membrane Proteins; Mitogen-Activated Protein Kinases; Phosphorylation; Prostaglandin-Endoperoxide Synthases; Pyrazoles; Stomach Neoplasms; Sulfonamides; Tetradecanoylphorbol Acetate; Transcription Factor AP-1

It has been found that expression of 15-lipoxygenase-1 (15-LOX-1) and its main product, 13-S-hydroxyoctadecadienoic acid (13-S-HODE), are decreased in human colorectal and esophageal cancers and that non-steroidal anti-inflammatory drugs (NSAIDs) can therapeutically induce 15-LOX-1 expression to trigger apoptosis in those cancer cells. We found that a specific cyclooxygenase-2 (COX-2) inhibitor SC-236 similarly induced apoptosis in gastric cancer cells. In the present study, we tested whether SC-236 induced apoptosis through up-regulation of 15-LOX-1 in gastric cancer. We found that: (i) SC-236 inhibited growth of gastric cancer cells mainly by inducing apoptosis; (ii) SC-236 induced 15-LOX-1 expression and increased endogenous 13-S-HODE product, instead of 15-S-HETE during apoptosis; (iii) SC-236 did not affect expression of COX-1, COX-2, 5-LOX and 12-LOX; and (iv) 15-LOX-1 inhibition suppressed SC-236 induced apoptosis. These findings demonstrated that SC-236 induced apoptosis in gastric cancer cells via up-regulation of 15-LOX-1, and 13-S-HODE. These are potential and new targets for prevention and treatment of gastric cancer.

Topics: Apoptosis; Arachidonate 15-Lipoxygenase; Base Sequence; Caffeic Acids; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; DNA Primers; Isoenzymes; Linoleic Acids; Prostaglandin-Endoperoxide Synthases; Pyrazoles; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stomach Neoplasms; Sulfonamides; Tumor Cells, Cultured

Selective cyclooxygenase-2 (COX-2) inhibitors are promising anti-inflammatory drugs with potential antitumor activities. The nuclear factor-kappa B (NF-kappaB) family of proteins is important transcriptional regulators of genes involved in immunity, inflammation, and carcinogenesis. In the present study, we investigated whether and by which molecular mechanism the selective COX-2 inhibitors inhibit NF-kappaB activation in gastric cancer. The effects of SC236 and its derivative, but devoid of COX-2 enzyme inhibition activity on NF-kappaB signaling, were evaluated using electromobility shift, transfection, and reporter gene assay. The translocation of RelA/p65 was investigated using Western blotting and immunocytochemistry. We showed that SC236 suppressed NF-kappaB-mediated gene transcription and binding activity in gastric cancer. This effect occurred through a mechanism independent of cyclooxygenase activity and prostaglandin synthesis. Furthermore, unlike aspirin, SC236 affected neither the phosphorylation, degradation, nor expression of IkappaB-alpha, suggesting that the effects of SC236 are independent of IKK activity and IkappaB-alpha gene transcription. Instead, SC236 worked directly through suppressing nuclear translocation of RelA/p65. It is possible that SC236 directly targets proteins that facilitate the nuclear translocation of NF-kappaB. Our study suggests an important molecular mechanism by which COX-2 inhibitors reduce inflammation and suppress carcinogenesis in gastrointestinal tract.

Topics: Active Transport, Cell Nucleus; Anti-Inflammatory Agents, Non-Steroidal; Anticarcinogenic Agents; Aspirin; Colonic Neoplasms; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; DNA, Neoplasm; Enzyme Activation; Humans; I-kappa B Kinase; I-kappa B Proteins; Isoenzymes; Membrane Proteins; Neoplasm Proteins; NF-kappa B; NF-KappaB Inhibitor alpha; Phosphorylation; Prostaglandin-Endoperoxide Synthases; Protein Binding; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases; Pyrazoles; Stomach Neoplasms; Sulfonamides; Tetradecanoylphorbol Acetate; Transcription Factor RelA; Transcription, Genetic; Transfection; Tumor Necrosis Factor-alpha

Nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of gastrointestinal cancers. Recently, a similar protective effect has been demonstrated by the specific cyclo-oxygenase-2 (COX-2) inhibitors. However, the exact mechanism that accounts for the anti-proliferative effect of specific COX-2 inhibitors is still not fully understood, and it is still controversial whether these protective effects are predominantly mediated through the inhibition of COX-2 activity and prostaglandin synthesis. Identification of molecular targets regulated by COX-2 inhibitors could lead to a better understanding of their pro-apoptotic and anti-neoplastic activities. In the present study, we investigated the effect and the possible molecular target of a COX-2-specific inhibitor SC-236 on gastric cancer. We showed that SC-236 induced apoptosis in gastric cancer cells. However, this effect was not dependent on COX-2 inhibition. SC-236 down-regulated the protein expression and kinase activity of PKC-beta(1), increased the expression of PKCdelta and PKCeta, but did not alter the expression of other PKC isoforms in AGS cells. Moreover, exogenous prostaglandins or PGE(2) receptor antagonists could not reverse the inhibition effect on PKCbeta(1) by SC-236, which suggested that this effect occurred through a mechanism independent of cyclo-oxygenase activity and prostaglandin synthesis. Overexpression of PKCbeta(1) attenuated the apoptotic response of AGS cells to SC-236 and was associated with overexpression of p21(waf1/cip1). Inhibition of PKCbeta(1)-mediated overexpression of p21(waf1/cip1) partially reduced the anti-apoptotic effect of PKCbeta(1). The down-regulation of PKCbeta(1) provides an explanation for COX-independent apoptotic effects of specific COX-2 inhibitor in cultured gastric cancer cells. We also suggest that PKCbeta(1) act as survival mediator in gastric cancer, and its down-regulation by COX-2 inhibitor SC-236 may provide new target for future treatment of gastric cancer.

Topics: Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Cell Cycle Proteins; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Cyclins; Cyclooxygenase Inhibitors; DNA, Antisense; Down-Regulation; Genes, myc; Humans; Isoenzymes; Prostaglandins; Protein Kinase C; Protein Kinase C beta; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Pyrazoles; Receptors, Prostaglandin E; Stomach Neoplasms; Sulfonamides; Transfection; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Tumor Suppressor Proteins