Summary of antifolate resistance parameters in 7-OHMTX–resistant and MTX-resistant CCRF-CEM and MOLT-4 cells compared with their parental cells
Cell line . | RFC-mediated transport*(fold change) . | FPGS activity†(fold change) . | FPGH activity‡(fold change) . | TS activity§(fold change) . |
|---|---|---|---|---|
| CCRF-CEM/MTX | ↓ ↓ (13) | ↑ (1.3) | No change | ↑ (1.7) |
| CCRF-CEM/7-OHMTX | ↓ (1.4) | ↓ ↓ (56) | ↑ (1.7) | No change |
| MOLT-4/MTX | ↓ ↓ (11) | ↑ (1.5) | No change | ↑ (2.4) |
| MOLT-4/7-OHMTX | No change | ↓ ↓ (92) | No change | No change |
Cell line . | RFC-mediated transport*(fold change) . | FPGS activity†(fold change) . | FPGH activity‡(fold change) . | TS activity§(fold change) . |
|---|---|---|---|---|
| CCRF-CEM/MTX | ↓ ↓ (13) | ↑ (1.3) | No change | ↑ (1.7) |
| CCRF-CEM/7-OHMTX | ↓ (1.4) | ↓ ↓ (56) | ↑ (1.7) | No change |
| MOLT-4/MTX | ↓ ↓ (11) | ↑ (1.5) | No change | ↑ (2.4) |
| MOLT-4/7-OHMTX | No change | ↓ ↓ (92) | No change | No change |
MRP1 through MRP4 mRNA and protein levels were assayed by RT-PCR and Western blotting; no change was observed in any cell line.
RFC transport is depicted as [3H]MTX influx rates at an extracellular concentration of 1 μM [3H]MTX. Control values for parental CCRF-CEM and MOLT-4 cells were 0.87 ± 0.13 pmol [3H]-MTX/min/107 cells and 0.34 ± 0.05 [3H]-MTX/min/107 cells, respectively
FPGS activity was determined at substrate concentrations of 250 μM MTX and 4 mM [3H]-L-glutamic acid. Control values for parental CCRF-CEM and Molt-4 cells were 958 ± 478 and 739 ± 171 pmol [3H]-glutamate incorporated/h/mg protein, respectively
FPGH activity was determined at substrate concentration of 100 μM MTX-Glu2. Control values for parental CCRF-CEM and MOLT-4 cells were 8460 ± 374 and 2658 ± 42 pmol MTX-Glu2 breakdown/h/mg protein, respectively
TS activity was measured either in cell extracts or in intact cells in situ. Control values for parental CCRF-CEM and Molt-4 cells were 4.8 ± 0.23 and 2.7 ± 0.24 nmol/h/mg protein, respectively