Biomaterial Database

Novel mechanism(s) of resistance to 5-fluorouracil in human colon cancer (HCT-8) sublines following exposure to two different clinically relevant dose schedules. 1992

C Aschele, and A Sobrero, and M A Faderan, and J R Bertino

Department of Molecular Pharmacology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.

Mechanisms of resistance to 5-fluorouracil (FUra) were compared between a cell line resistant to a short-term exposure (4 h) to this agent (HCT-8/FU4hR) and a cell line resistant to a prolonged exposure (7 days) to the fluoropyrimidine (HCT-8/FU7dR). The two cell lines were obtained by repeatedly exposing 2 x 10(5) cells to a constant concentration of FUra (1000 microM for 4 h or 15 microM for 7 days), able to produce 3-4 logs of cell kill. HCT-8/FU4hR cells were still sensitive to FUra given as a 7-day exposure, suggesting different mechanisms of resistance. In addition, HCT-8/FU7dR cells were cross-resistant to fluorodeoxyuridine and, to a lesser degree, methotrexate; while HCT-8/FU4dR cells were not. Both HCT-8/FU4hR and HCT-8/FU7dR cells were similar to parental HCT-8 cells with regard to uptake of FUra as well as the pattern of FUra-metabolizing and FUra target enzymes. Although neither in situ thymidylate synthase (TS) activity nor the degree of its inhibition by FUra showed any evidence of alteration in HCT-8/FU7dR cells, a rapid recovery of TS activity after drug removal was evident in this cell line. The addition of as much as 100 microM leucovorin did not completely inhibit the recovery of thymidylate synthesis after FUra exposure. No differences were detected in the kinetic properties (Km for 2'-deoxyuridylate and 5,10-methylenetetrahydrofolate, concentration producing 50% inhibition for fluorodeoxyuridylate) or TS from HCT-8/FU7dR cells as compared to parental HCT-8 TS. Baseline levels of 5,10 methylenetetrahydrofolate were decreased in HCT-8/FU7dR cells, and analysis of the chain length distribution of the polyglutamylated form of the folate cofactor showed that in this cell line the defect in 5,10-methylenetetrahydrofolate levels is accompanied by, and possibly due to, a defect in the polyglutamylation of this cofactor. In contrast, HCT-8/FU4hR cells were similar to the parental cell line with regard to both the degree of in situ TS inhibition by FUra and duration of inhibition after FUra removal. Labeling studies with [3H-6]FUra (4 h exposure, 100 microM) showed that the incorporation of the fluoropyrimidine into RNA is significantly decreased in HCT-8/FU4hR cells as compared to parental HCT-8 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008727	Methotrexate	An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA.	Amethopterin,Methotrexate Hydrate,Methotrexate Sodium,Methotrexate, (D)-Isomer,Methotrexate, (DL)-Isomer,Methotrexate, Dicesium Salt,Methotrexate, Disodium Salt,Methotrexate, Sodium Salt,Mexate,Dicesium Salt Methotrexate,Hydrate, Methotrexate,Sodium, Methotrexate
D011624	Pteroylpolyglutamic Acids	Derivatives of folic acid (pteroylglutamic acid). In gamma-glutamyl linkage they are found in many tissues. They are converted to folic acid by the action of pteroylpolyglutamate hydrolase or synthesized from folic acid by the action of folate polyglutamate synthetase. Synthetic pteroylpolyglutamic acids, which are in alpha-glutamyl linkage, are active in bacterial growth assays.	Folate Polyglutamates,Polyglutamate Folates,Pteroylpolyglutamates,Acids, Pteroylpolyglutamic,Folates, Polyglutamate,Polyglutamates, Folate
D011743	Pyrimidines	A family of 6-membered heterocyclic compounds occurring in nature in a wide variety of forms. They include several nucleic acid constituents (CYTOSINE; THYMINE; and URACIL) and form the basic structure of the barbiturates.
D002460	Cell Line	Established cell cultures that have the potential to propagate indefinitely.	Cell Lines,Line, Cell,Lines, Cell
D002470	Cell Survival	The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability.	Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D003110	Colonic Neoplasms	Tumors or cancer of the COLON.	Cancer of Colon,Colon Adenocarcinoma,Colon Cancer,Cancer of the Colon,Colon Neoplasms,Colonic Cancer,Neoplasms, Colonic,Adenocarcinoma, Colon,Adenocarcinomas, Colon,Cancer, Colon,Cancer, Colonic,Cancers, Colon,Cancers, Colonic,Colon Adenocarcinomas,Colon Cancers,Colon Neoplasm,Colonic Cancers,Colonic Neoplasm,Neoplasm, Colon,Neoplasm, Colonic,Neoplasms, Colon
D004351	Drug Resistance	Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.	Resistance, Drug
D005467	Floxuridine	An antineoplastic antimetabolite that is metabolized to fluorouracil when administered by rapid injection; when administered by slow, continuous, intra-arterial infusion, it is converted to floxuridine monophosphate. It has been used to treat hepatic metastases of gastrointestinal adenocarcinomas and for palliation in malignant neoplasms of the liver and gastrointestinal tract.	FUdR,Fluorodeoxyuridine,5-FUdR,5-Fluorodeoxyuridine,5 Fluorodeoxyuridine
D005472	Fluorouracil	A pyrimidine analog that is an antineoplastic antimetabolite. It interferes with DNA synthesis by blocking the THYMIDYLATE SYNTHETASE conversion of deoxyuridylic acid to thymidylic acid.	5-FU,5-FU Lederle,5-FU Medac,5-Fluorouracil,5-Fluorouracil-Biosyn,5-HU Hexal,5FU,Adrucil,Carac,Efudex,Efudix,Fluoro-Uracile ICN,Fluoroplex,Fluorouracil Mononitrate,Fluorouracil Monopotassium Salt,Fluorouracil Monosodium Salt,Fluorouracil Potassium Salt,Fluorouracil-GRY,Fluorouracile Dakota,Fluorouracilo Ferrer Far,Fluoruracil,Fluracedyl,Flurodex,Haemato-FU,Neofluor,Onkofluor,Ribofluor,5 FU Lederle,5 FU Medac,5 Fluorouracil,5 Fluorouracil Biosyn,5 HU Hexal,Dakota, Fluorouracile,Fluoro Uracile ICN,Fluorouracil GRY,Haemato FU