Defective transport as a mechanism of acquired resistance to methotrexate in patients with acute lymphocytic leukemia

摘要: Although the mechanisms of resistance to methotrexate (MTX) are known in experimental tumors made resistant this drug, little information is available regarding acquired MTX patients. A competitive displacement assay using fluorescent lysine analogue MTX, N-(4-amino-4-deoxy-N10-methylpteroyl)-N epsilon-(4′-fluorescein- thiocarbamyl)-L-lysine (PT430), was developed as a sensitive method detection transport cell lines, well blast cells from patients with leukemia. Rapid uptake PT430 at high concentrations (20 mumol/L) leukemic blasts resulted achievement steady-state levels within 2 hours. Subsequent incubation folate antagonists, and trimetrexate (TMTX), which differ mode carrier transport, produced characteristic patterns displacement. Flow cytometric analysis mean fluorescence intensity human CCRF-CEM T-cell lymphoblastic leukemia line its MTX-resistant subline clearly identified presence deficiency subline. Analysis 17 leukemia, nine no prior chemotherapy eight previously treated chemotherapy, found evidence two four who were considered be clinically drug. The finding that some due decreased has important implications for clinical use drug new development.