INCREASED METHOTREXATE POLYGLUTAMYLATION IN ACUTE MEGAKARYOCYTIC LEUKEMIA (M7) COMPARED TO OTHER SUBTYPES OF ACUTE MYELOCYTIC-LEUKEMIA

Acute myelocytic leukemia (AML) is a malignancy that is intrinsically resistant to methotrexate (MTX). AML blasts, when incubated with radio labeled MTX, form lower amounts of long chain polyglutamates compared to acute lymphocytic leukemia (ALL) blasts, thus providing an explanat ion far their lack of responsiveness to MTX. Leukemic blasts obtained from two children with acute megakaryocytic leukemia (M7 subtype) when incubated with radiolabeled MTX showed increased accumulation ai tota l as well as long chain MTX polyglutamates, comparable to levels previ ously demonstrated in another subtype of AML, acute monocytic leukemia (M5), as well as in blasts from patients with pre-B ALL. We suggest t hat M7-AML patients with blasts showing increased MTX polyglutamylatio n might benefit from treatment with MTX.