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MKN-45 Cells (mkn-45 + cell)
Selected AbstractsModulation of Activation-Induced Cytidine Deaminase by Curcumin in Helicobacter pylori -Infected Gastric Epithelial CellsHELICOBACTER, Issue 6 2009Syed Faisal Haider Zaidi Abstract Background:, Anomalous expression of activation-induced cytidine deaminase (AID) in Helicobacter pylori -infected gastric epithelial cells has been postulated as one of the key mechanisms in the development of gastric cancer. AID is overexpressed in the cells through nuclear factor (NF)-,B activation by H. pylori and hence, inhibition of NF-,B pathway can downregulate the expression of AID. Curcumin, a spice-derived polyphenol, is known for its anti-inflammatory activity via NF-,B inhibition. Therefore, it was hypothesized that curcumin might suppress AID overexpression via NF-,B inhibitory activity in H. pylori -infected gastric epithelial cells. Materials and Methods:, MKN-28 or MKN-45 cells and H. pylori strain 193C isolated from gastric cancer patient were used for co-culture experiments. Cells were pretreated with or without nonbactericidal concentrations of curcumin. Apoptosis was determined by DNA fragmentation assay. Enzyme-linked immunosorbent assay was performed to evaluate the anti-adhesion activity of curcumin. Real-time polymerase chain reaction was employed to evaluate the expression of AID mRNA. Immunoblot assay was performed for the analysis of AID, NF-,B, inhibitors of NF-,B (I,B), and I,B kinase (IKK) complex regulation with or without curcumin. Results:, The adhesion of H. pylori to gastric epithelial cells was not inhibited by curcumin pretreatment at nonbactericidal concentrations (,10 ,mol/L). Pretreatment with nonbactericidal concentration of curcumin downregulated the expression of AID induced by H. pylori. Similarly, NF-,B activation inhibitor (SN-50) and proteasome inhibitor (MG-132) also downregulated the mRNA expression of AID. Moreover, curcumin (,10 ,mol/L) has suppressed H. pylori -induced NF-,B activation via inhibition of IKK activation and I,B degradation. Conclusion:, Nonbactericidal concentrations of curcumin downregulated H. pylori -induced AID expression in gastric epithelial cells, probably via the inhibition of NF-,B pathway. Hence, curcumin can be considered as a potential chemopreventive candidate against H. pylori -related gastric carcinogenesis. [source] Mechanisms involved in hydroxycamptothecin-induced apoptosis of gastric cancer cellsJOURNAL OF DIGESTIVE DISEASES, Issue 1 2002Shui Ping TU OBJECTIVE: Hydroxycamptothecin (HCPT) is a unique antitumor drug that acts directly on topoisomerase I and inhibits its activity. However, the mechanism of HCPT-induced apoptosis is unclear. In the present study, the mechanism of HCPT-induced apoptosis in gastric cancer cells was investigated by detecting the expression of p53, c - myc, bcl-2, bcl-xl and bcl-xs genes in gastric cancer cells. METHODS: Apoptosis of gastric cancer cells (SGC-7901, MKN-45) was determined by terminal deoxyribonucleotidyl transferase-mediated dUTP, digoxigenin nick-end labeling (TUNEL) and flow cytometry. The mRNA and protein levels of the p53, c-myc, bcl-2, bcl-xl and bcl-xs genes were tested by reverse transcription,polymerase chain reaction analysis and immunocytochemical stain, respectively. RESULTS: Hydroxycamptothecin may induce apoptosis in different differentiated gastric cancer cells. The effect of HCPT-induced apoptosis on gastric cancer cells was dependent on the dose of HCPT used and the time of exposure to HCPT. Both SGC-7901 and MKN-45 cells manifested some morphological features of apoptosis after 12 h exposure to HCPT, including cell shrinkage, nuclear condensation, DNA fragmentation and formation of apoptotic bodies. Some typical subdiploid peaks before the G0/G1 phase were observed. The apoptotic rates induced by 10 ,g/mL HCPT in SGC-7901 and MKN-45 cells were 21.88 and 12.34%, respectively. The mRNA and protein levels of p53 and bcl-2 were downregulated after treatment with HCPT in SGC-7901 cells. However, the c-myc, bcl-xl and bcl-xs protein levels were unchanged in SGC-7901 cells. In MKN-45 cells, the mRNA and protein levels of p53 increased after treatment with HCPT, whereas the protein levels of bcl-2, c-myc, bcl-xl and bcl-xs remained unchanged. CONCLUSIONS: Our results indicate that HCPT-induced apoptosis in gastric cancer cells may be regulated through modulation of the expression of p53 and bcl-2 genes. [source] Docetaxel enhances the cytotoxicity of cisplatin to gastric cancer cells by modification of intracellular platinum metabolismCANCER SCIENCE, Issue 8 2004Shingo Maeda We have examined the combined anticancer effects of docetaxel (DOC) and cisplatin (CDDP) in vitro using the gastric cancer cell lines MKN-45, MKN-74, and TMK-1. Treatment of the cell lines with 30 ,g/ml of DOC for 24 h followed by incubation with 3 or 10 ,g/ml of CDDP for 24 h showed a clear synergistic effect. Sequence dependency of the agents was observed in these cell lines: DOC followed by CDDP (DC) showed a stronger antitumor effect than CDDP followed by DOC (CD) in all cell lines. To clarify the mechanism of action of the DC combination, total intracellular platinum (Pt) levels were evaluated after treatment with CDDP alone or combined with DC. For the MKN-45 and -74 cell lines, cells treated with DOC (10 ,g/ml for 12 h) and then CDDP showed significantly increased intracellular Pt accumulation compared to cells treated with CDDP alone. We also investigated alterations in intracellular glutathione (GSH) concentration in response to DOC and CDDP. MKN-45 and -74 cells pretreated with DOC (10 ,g/ml for 12 h) showed significantly increased intracellular GSH levels compared to cells administered CDDP only. To explain these findings, messenger RNA (mRNA) levels for multidrug resistance-associated protein-1 (MRP-1), the ATP-dependent pump for Pt-GSH complexes, were quantified in CDDP-treated MKN-45 cells with and without DOC pretreatment. While CDDP administration increased MRP-1 mRNA expression in MKN-45 cells, MRP-1 was not up-regulated after CDDP administration in DOC pretreated MKN-45 cells. Our results suggested that the enhanced CDDP toxicity due to DOC pretreatment may be related to the accumulation of intracellular Pt-GSH complexes, because DOC appears to suppress the MRP-1 up-regulation induced by CDDP exposure in gastric cancer cells. [source] | ||||||||||