Down-regulation of thymidylate synthase expression and its steady-state mRNA by oxaliplatin in colon cancer cells
Journal
Anti-Cancer Drugs
Journal Volume
15
Journal Issue
4
Pages
371-376
Date Issued
2004
Author(s)
Abstract
Recently, evidence has accumulated that weekly 24-h infusion of high-dose 5-fluorouracil (5-FU) with leucovorin (LV, folinic acid) biochemical modulation may improve the response rates compared with the bolus 5-FU regimens in colorectal cancer (CRC). Combining the infusional 5-FU/LV (iFL) regimens with oxaliplatin or irinotecan is widely adopted to further improve treatment efficacy. Either oxaliplatin-iFL or irinotecan-iFL may achieve an overall response rate of more than 50% in the first-line treatment. Intriguingly, in the salvage treatment for metastatic CRC patients who had failed iFL, only oxaliplatin-iFL may achieve a response rate of about 13-25%. In contrast, oxaliplatin alone or irinotecan-iFL had a very low response rate of 5% or less. To test if the oxaliplatin may reverse the iFL-related 5-FU resistance in CRC, we used DLD-1 colon adenocarcinoma cells as the in vitro study model. First, we revealed that oxaliplatin and 5-FU act synergistically on DLD-1 cells by MTT cytotoxicity assay and median drug effect analysis. Second, we treated the DLD-1 cells with serial concentrations of oxaliplatin (0.1-10 μM). Oxaliplatin treatment results in down-regulation of free thymidylate synthase (TS) protein expression by Western blotting. Further, we analyzed the TS mRNA level by reverse transcription and real-time quantitative polymerase chain reaction assay. Oxaliplatin treatment results in down-regulation of the TS mRNA level up to 40% (mean ± SD of ratio to reference control=0.60 ± 0.21, range 0.42-0.84). In this study, our data provide important information explaining the reason why the combination of oxaliplatin and 5-FU results in a better objective response in 5-FU-resistant patients than oxaliplatin alone does. Our data also suggest that TS down-regulation happens at the transcriptional level. TS modulation and down-regulation had, thus, shed light on the useful potential strategy to achieve objective responses in 5-FU-resistant CRC patients. ? 2004 Lippincott Williams & Wilkins.
SDGs
Other Subjects
fluorouracil; messenger RNA; oxaliplatin; thymidylate synthase; article; cancer cell culture; cell strain; colon adenocarcinoma; colon carcinoma; controlled study; cytotoxicity test; down regulation; drug effect; drug potentiation; human; human cell; in vitro study; messenger RNA synthesis; nitroblue tetrazolium test; priority journal; protein blood level; protein expression; real time polymerase chain reaction; reverse transcription polymerase chain reaction; steady state; Western blotting; Adenocarcinoma; Antimetabolites, Antineoplastic; Antineoplastic Agents; Blotting, Western; Calorimetry; Colonic Neoplasms; Down-Regulation; Drug Resistance, Neoplasm; Drug Synergism; Fluorouracil; Humans; Inhibitory Concentration 50; Organoplatinum Compounds; RNA, Messenger; Thymidylate Synthase; Tumor Cells, Cultured
Type
journal article