Open AccessAZT: A Biochemical Response Modifier of Methotrexate and 5-Fluorouracil Cytotoxicity in Human Ovarian and Pancreatic Carcinoma Cells
Author(s) -
George Weber,
Masami Nagai,
Noémi Prajda,
Hiroyuki Nakamura,
Thomas Szekeres,
Edith Oláh
Publication year - 1991
Publication title -
cancer communications
Language(s) - English
Resource type - Journals
ISSN - 0955-3541
DOI - 10.3727/095535491820873407
Subject(s) - thymidylate synthase , clonogenic assay , cytotoxicity , thymidine kinase , thymidine , cell culture , biology , cancer research , microbiology and biotechnology , biochemistry , chemistry , cell , fluorouracil , in vitro , immunology , chemotherapy , genetics , virus , herpes simplex virus
In ovarian and pancreatic carcinoma cell lines, the activity of the salvage enzyme, thymidine kinase (EC 2.7.1.21), was 2- to 13-fold higher than that of the key enzyme of thymidylate de novo biosynthesis, thymidylate synthase (dTMP synthase, EC 2.1.1.45). AZT (3'-azido-3'-deoxythymidine, zidovudine) competitively inhibited thymidine kinase activity in extracts of human ovarian and pancreatic carcinoma cells, with Dixon plots yielding Ki = 1.1 microM in both cell lines. AZT (20 microM) yielded synergistic cytotoxicity with methotrexate (0.4 microM) in human pancreatic carcinoma cells in clonogenic assay and also with methotrexate (0.02 microM) in human ovarian carcinoma cells, as measured by cell counts. Thymidine (10 microM) and hypoxanthine (100 microM) reversed these inhibitions. AZT (20 or 40 microM) also provided synergistic cytotoxicity with 5-fluorouracil (0.5 and 1.0 microM) in human pancreatic carcinoma cells in clonogenic assay. These studies suggest a new role for AZT, which, as an inhibitor of thymidine salvage, should be useful as a biochemical response modifier to provide a synergistic clinical anticancer impact on de novo biosynthesis of thymidylates in conjunction with methotrexate or 5-fluorouracil.