title: Basis for natural resistance to methotrexate in human acute non-lymphocytic leukemia.
abstract: The basis of intrinsic resistance of blasts from patients with acute non-lymphocytic leukemia (ANLL) to methotrexate was studied. MTX polyglutamate formation was measured in blast cells from 19 patients with ANLL and in 7 pediatric patients with acute lymphocytic leukemia (ALL), after in vitro incubation for 24 h with 3H-methotrexate. There was no significant differences seen in the total amount of MTX plus polyglutamates measured between ANLL and ALL blasts, indicating that transport defects do not account for intrinsic MTX resistance in ANLL. However, there were significant differences between the amounts of long chain MTX polyglutamates found in ANLL cells as compared to ALL cells. Most, but not all, ANLL blasts were unable to form long chain polyglutamates. In as much as the level of MTX polyglutamates found in blast cells after MTX administration allows for retention of this drug, this property may explain, at least in part, the refractoriness of most patients with ANLL to methotrexate.
authors.affiliation: Department of Molecular Pharmacology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
authors.forename: J T
authors.initials: JT
authors.lastname: Lin
authors.forename: W P
authors.initials: WP
authors.lastname: Tong
authors.forename: T M
authors.initials: TM
authors.lastname: Trippett
authors.forename: D
authors.initials: D
authors.lastname: Niedzwiecki
authors.forename: Y
authors.initials: Y
authors.lastname: Tao
authors.forename: C
authors.initials: C
authors.lastname: Tan
authors.forename: P
authors.initials: P
authors.lastname: Steinherz
authors.forename: B I
authors.initials: BI
authors.lastname: Schweitzer
authors.forename: J R
authors.initials: JR
authors.lastname: Bertino
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004351:Drug Resistance; D006801:Humans; D007223:Infant; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism / Q000473:pathology*; D008727:Methotrexate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D008875:Middle Aged; D011099:Polyglutamic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism / Q000473:pathology; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
chemical_list: D011099:Polyglutamic Acid; C014085:methotrexate polyglutamate; D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate