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

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 (F-RNA) 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 microg/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 microg/ml) may be clinically useful, affording low cytotoxicity of UCN-01, while enhancing the antitumor effect of 5-FU.

• Authors: S Abe, T Kubota, Y Otani, T Furukawa, M Watanabe, K Kumai, M Kitajima
• Journal: Japanese journal of cancer research : Gann (Jpn J Cancer Res) Vol. 91 Issue 11 Pg. 1192-8 (Nov 2000) ISSN: 0910-5050 [Print] Japan
• PMID: 11092986 (Publication Type: Journal Article)

Chemical References

• Alkaloids
• Antimetabolites, Antineoplastic
• Antineoplastic Agents
• Enzyme Inhibitors
• RNA, Messenger
• RNA, Neoplasm
• 7-hydroxystaurosporine
• Thymidylate Synthase
• Staurosporine
• Fluorouracil

Topics

• Alkaloids (administration & dosage, pharmacology)
• Antimetabolites, Antineoplastic (administration & dosage, pharmacology)
• Antineoplastic Agents (administration & dosage, pharmacology)
• Antineoplastic Combined Chemotherapy Protocols (pharmacology)
• Carcinoma (drug therapy, enzymology, genetics)
• Dose-Response Relationship, Drug
• Down-Regulation (drug effects)
• Drug Synergism
• Enzyme Inhibitors (administration & dosage, pharmacology)
• Fluorouracil (administration & dosage, pharmacology)
• Gene Expression Regulation, Enzymologic (drug effects)
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Pancreatic Neoplasms (drug therapy, enzymology, genetics)
• RNA, Messenger (biosynthesis, genetics, metabolism)
• RNA, Neoplasm (metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Staurosporine (analogs & derivatives)
• Thymidylate Synthase (antagonists & inhibitors, biosynthesis, genetics)
• Tumor Cells, Cultured (drug effects)