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  • Title: Administration sequence-dependent antitumor effects of paclitaxel and 5-fluorouracil in the human gastric cancer cell line MKN45.
    Author: Toiyama Y, Tanaka K, Konishi N, Mohri Y, Tonouchi H, Miki C, Kusunoki M.
    Journal: Cancer Chemother Pharmacol; 2006 Feb; 57(3):368-75. PubMed ID: 16075279.
    Abstract:
    BACKGROUND: The clinical outcome of gastric cancer patients has been improved by combination of 5-fluorouracil (5-FU) and paclitaxel (PXL). However, the optimal schedule of this combination has not been determined. METHODS: The efficacies of sequential administrations of 5-FU and PXL on the gastric cancer cell line MKN45 were investigated using a WST-8 colorimetric assay. The cell cycle distribution of each drug was evaluated by flow-cytometry. Furthermore, the mechanism of antitumor activity enhancement by the administration sequence was investigated by western blotting. RESULTS: MKN45 cell growth was significantly inhibited by each drug in a dose- and time-dependent manner. The cytotoxicities of PXL followed by 5-FU were significantly greater than those of 5-FU followed by PXL. The flow-cytometric analysis revealed that PXL exposure caused viable cell accumulation in G2/M phase in a dose-dependent manner. Western blotting showed that PXL exposure followed by 5-FU up-regulated Chk1 and Wee1 protein expressions until PXL removal and 5-FU exposure, when these expressions gradually decreased to their basal levels. 14-3-3sigma protein expression was significantly up-regulated upon PXL treatment followed by 5-FU. Interestingly, Mad2 protein expression with PXL treatment followed by 5-FU gradually increased after the PXL removal and 5-FU exposure. CONCLUSIONS: PXL followed by 5-FU administration may be the optimal sequence for treatment of gastric cancer. The enhanced viable cell accumulation after PXL pretreatment may be related to G2 arrest. After PXL removal and 5-FU exposure, the cells progressing to M phase may undergo cell death by mitotic catastrophe due to DNA damage caused by 5-FU exposure.
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