Reversal of resistance to methotrexate in L1210 murine leukemia by uracil.

Cytotoxicity of 5-fluoro-2'-deoxyuridine: requirement for reduced folate cofactors and antagonism by methotrexate.

Protein in vitro inhibition of thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45) by 5-fluoro-2'-deoxyuridylate requires 5,10-methylenetetrahydrofolate. The cytoxicity of 5-fluoro-2'-deoxyuridine towards cultured L1210 mouse leukemia cells is reduced when intracellular reduced folates are depleted, either by limiting the source in media or by inhibition ...

Biochemical correlates of responsiveness and collateral sensitivity of some methotrexate-resistant murine tumors to the lipophilic antifolate, metoprine.

The M5076 murine "ovarian" tumor which is naturally refractive to methotrexate was found to be highly responsive to the lipophilic antifolate, metoprine. M5076 cells were markedly deficient in mediated entry of methotrexate. This was in contrast to the L1210 leukemia, a tumor highly responsive to methotrexate but poorly responsive to metoprine. Two L1210 leukemia sublines, with acquired resista...

Evaluation of ribonucleoside and deoxyribonucleoside triphosphate pools in cultured leukemia cells during exposure to methotrexate or methotrexate plus thymidine.

Continuous exposure to inhibitory concentrations of methotrexate produces distinct rates of steady-state growth of murine leukemia L1210 and human leukemia CCRF-CEM cells in culture. Addition of thymidine to the medium produces reversal (6 to 40%) of this steady-state growth rate inhibition. This study utilized combinations of methotrexate and thymidine for an evaluation of the accompanying rel...

The effects of antibiotics and cancer chemotherapeutic agents on the cellular transport and antitumor activity of methotrexate in L1210 murine leukemia.

The effect of the simultaneous addition of a number of clinically useful antibiotics and cancer chemotherapeutic agents on the transport of 2 x 10~6 M methotrexate (4-amino-lO-methylpteroyl-glutamic acid; MTX) was stud ied in L1210 murine leukemia cells in vitro. The results were correlated with the effects of these agents on the antitumor activity of MTX in BALB/cAnN x C57BL/KaLwN F, mice bear...

Reversibility of high-affinity binding of methotrexate in L1210 murine leukemia cells.