TY - JOUR
T1 - Limited effectiveness of in vitro high-dose methotrexate and leucovorin to overcome resistance in L1210 leukemia cells with elevations of dihydrofolate reductase
AU - Bruckner, H.
AU - Runinoff, M.
AU - Waxman, S.
N1 - Funding Information:
METHOTREXATE (MTX) given in various dosages and schedules has a wide spectrum of antitumor activity \[1 \]. New treatment schedules designed to be used with N-5 formyltetrahydrofolic acid \[leucovorin (LV)\] permit 10-1000 times larger than the conventional amounts of MTX to be used to preferentially inhibit tumor growth and rescue normal tissue from MTX \[2, 3\]. Treatment with high-dose MTX-LV regimens may be superior to conventional treatment in some clinical situations such as osteogenic sarcoma \[4\], leukemia resistant to conventional doses Accepted 25 September 1979. *This work was supported by the Chemotherapy Foundation, Inc., NCI Contract NO1-CM 43703 and NIH Grant No. 1 RO1-AM16690-03. Requests for reprints should be addressed to Dr. Samuel Waxman, Division of Medical Oncology, Fifth Avenue and 100th Street, New York, NY 10029, U.S.A.
PY - 1980
Y1 - 1980
N2 - Two L1210 cell lines, one sensitive to methotrexate (MTX) (L1210S) and the other resistant (L1210/740R) due to high dihydrofolate reductase were exposed to MTX in serial log concentrations from 10-3 M MTX. Maximal (90%) inhibition of de novo DNA synthesis was produced by 10-6 M MTX in L1210/S. 10-4 MTX produced no more than 40% inhibition in the L1210/740R line. Leucovorin [N-5-formyltetrahydrofolic acid (LV)] 10-4 M completely rescued L1210S from 10-7 M MTX and L1210/740R from 10-5 M MTX. There was a partial rescue by LV of L1210/740T but none in L1210S from 10-4 M MTX. LV completely corrected the metabolic defect produced by 10-4 M MTX when the cells were washed in MTX free media following exposure to 10-4 M MTX. Thus, high-dose MTX has no apparent major advantage when MTX resistance is due to high dihydrofolate reductase. High-dose MTX can produce a defect involving a low affinity (reversible) site which is not corrected by LV and a high affinity site defect which is completely corrected by LV. LV rescue is not directly dependent on the concentration of free MTX alone in extracellular media. The measurement of the antimetabolic effect of different simulated MTX treatment programs in cell lines with different defined mechanisms of resistance to MTX may serve as a method for identifying the biochemical parameters of cells and optimum conditions, if any, for treatment with high-dose MTX and LV.
AB - Two L1210 cell lines, one sensitive to methotrexate (MTX) (L1210S) and the other resistant (L1210/740R) due to high dihydrofolate reductase were exposed to MTX in serial log concentrations from 10-3 M MTX. Maximal (90%) inhibition of de novo DNA synthesis was produced by 10-6 M MTX in L1210/S. 10-4 MTX produced no more than 40% inhibition in the L1210/740R line. Leucovorin [N-5-formyltetrahydrofolic acid (LV)] 10-4 M completely rescued L1210S from 10-7 M MTX and L1210/740R from 10-5 M MTX. There was a partial rescue by LV of L1210/740T but none in L1210S from 10-4 M MTX. LV completely corrected the metabolic defect produced by 10-4 M MTX when the cells were washed in MTX free media following exposure to 10-4 M MTX. Thus, high-dose MTX has no apparent major advantage when MTX resistance is due to high dihydrofolate reductase. High-dose MTX can produce a defect involving a low affinity (reversible) site which is not corrected by LV and a high affinity site defect which is completely corrected by LV. LV rescue is not directly dependent on the concentration of free MTX alone in extracellular media. The measurement of the antimetabolic effect of different simulated MTX treatment programs in cell lines with different defined mechanisms of resistance to MTX may serve as a method for identifying the biochemical parameters of cells and optimum conditions, if any, for treatment with high-dose MTX and LV.
UR - https://www.scopus.com/pages/publications/0018950727
U2 - 10.1016/0014-2964(80)90253-4
DO - 10.1016/0014-2964(80)90253-4
M3 - Article
C2 - 6969180
AN - SCOPUS:0018950727
SN - 0277-5379
VL - 16
SP - 1057
EP - 1063
JO - European Journal of Cancer and Clinical Oncology
JF - European Journal of Cancer and Clinical Oncology
IS - 8
ER -