UCN-01 (7-hydroxystaurosporine) enhances 5-fluorouracil cytotoxicity through down-regulation of thymidylate synthetase messenger RNA.
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.
Abe
S
S
Department of Surgery, School of Medicine, Keio University, Shinjuku-ku, Tokyo 160-8582, Japan.
Kubota
T
T
Otani
Y
Y
Furukawa
T
T
Watanabe
M
M
Kumai
K
K
Kitajima
M
M
D000470:Alkaloids / Q000008:administration & dosage / Q000494:pharmacology*; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D002277:Carcinoma / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005472:Fluorouracil / Q000008:administration & dosage / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019311:Staurosporine / Q000031:analogs & derivatives; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000470:Alkaloids; D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C054852:7-hydroxystaurosporine; D013940:Thymidylate Synthase; D019311:Staurosporine; D005472:Fluorouracil