Inhibition of [3H]dUrd incorporation into DNA in L1210 leukemic cells by MTX and Ara-C alone and in (1:0.782) combination L1210 murine leukemic cells (8 × 106 cells) were incubated in Eagle's basal medium in the presence and absence of various concentrations of MTX and Ara-C and their mixture (molar ratio, 1:0.782) at 37°C for 20 min and then incubated with 0.5 μM (1 μCi) of [6-3H]dUrd at 37°C for 30 min. Fractional inhibition (fi or fa) of [6-3H]dUrd incorporation into perchloric acid-insoluble DNA fraction was then measured. All measurements were made in duplicate. Modified from “Quantitative Analysis of Dose-Effect Relationships: The Combined Effects of Multiple Drugs or Enzyme Inhibitors,” Advances in Enzyme Regulation, volume 22, pp 27-55. Copyright 1984 with permission from Elsevier.
MTX | Fractional Inhibition (fa) at [Ara-C] of: | |||||||
---|---|---|---|---|---|---|---|---|
0 | 0.0782 | 0.156 | 0.313 | 0.625 | 1.25 | 2.5 | 5.0 | |
μM | ||||||||
0 | 0 | 0.582 | 0.715 | 0.860 | 0.926 | 0.955 | 0.980 | 0.993 |
0.1 μM | 0.0348 | 0.405 | ||||||
0.2 μM | N.D.a | 0.587 | ||||||
0.4 μM | N.D. | 0.775 | ||||||
0.8 μM | 0.140 | 0.878 | ||||||
1.6 μM | 0.415 | 0.943 | ||||||
3.2 μM | 0.573 | 0.970 | ||||||
6.4 μM | 0.755 | N.D. |
↵ a Result not used because of large variation between duplicates