UCN-01 (7-hydroxystaurosporine) enhances 5-fluorouracil cytotoxicity through down-regulation of thymidylate synthetase messenger RNA

S. Abe, T. Kubota, Y. Otani, T. Furukawa, M. Watanabe, K. Kumai, M. Kitajima

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Abstract

UCN-01 (7-hydroxystaurosporine) is a newly developed cell cycle inhibitor known to have several modes of action, including inhibition of cyclin-dependent kinase, induction of p21 and suppression of pRb phosphorylation. In order to test a combination therapy of UCN-01 and 5-fluorouracil (5-FU), growth inhibition of CRL 1420 (MIA PaCa-2; undifferentiated pancreatic carcinoma) by four different treatments was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5 -diphenyl-2H-tetrazolium bromide (MTT) assay. The treatments used were UCN-01 alone, 5-FU alone, 5-FU followed by UCN-01 (5-FU/UCN-01) and UCN- 01 followed by 5-FU (UCN-01/5-FU). We also assessed changes in thymidylate synthetase (TS) mRNA levels, TS activity, and 5-FU incorporation by RNA (FRNA) for each treatment. Although treatment with UCN-01 alone, 5-FU alone, and 5-FU/UCN-01 inhibited CRL 1420 growth in a concentration-dependent manner, treatment with UCN-01/5-FU inhibited the growth of CRL 1420 synergistically at less than 1 μg/ml drug concentration. The down-regulation of TS mRNA by UCN-01 resulted in stable total TS and decreased free TS, and UCN-01/5-FU resulted in enhanced thymidylate synthetase inhibition rate (TSIR) compared to UCN-01 alone and 5-FU/UCN-01. This increased TSIR due to UCN-01 pretreatment was accompanied by elevated F-RNA concentrations in the UCN-01/5-FU treatment. The suppression of TS mRNA and TS activity by UCN-01 may lead to higher sensitivity of tumor cells to 5-FU and may explain the synergistic antitumor effect of UCN-01/5-FU. In conclusion, low concentrations of UCN-01 (from 0.01 to 1 μg/ml) may be clinically useful, affording low cytotoxicity of UCN-01, while enhancing the antitumor effect of 5-FU.

Original languageEnglish
Pages (from-to)1192-1198
Number of pages7
JournalJapanese Journal of Cancer Research
Volume91
Issue number11
DOIs
Publication statusPublished - 2000 Jan 1

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Keywords

  • 5-Fluorouracil
  • Pancreatic cancer
  • Thymidylate synthetase
  • UCN-01
  • mRNA

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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