Abstract
PURPOSE: Blasts isolated from bone marrow aspirates or blood samples of patients with acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML) were compared for uptake of methotrexate (MTX) and formation of MTX polyglutamates (MTX-Glu(n)). Red blood cells (RBC) from the same patient samples were also analyzed. METHODS: Blasts were isolated by standard density centrifugation. RBC were prepared from the pellet of the same centrifugation. MTX-Glu(n) were analyzed by means of HPLC and radiochemical quantification. RESULTS: In lymphoblasts isolated from blood, the distribution patterns of MTX-Glu(n) were the same as in bone marrow lymphoblasts, but the total amount of MTX-Glu(n) accumulated in blood lymphoblasts was reduced by 41% 51% when compared to the same number of bone marrow lymphoblasts of the same patient. RBC accumulated MTX but no formation of MTX-Glu(n) occurred. CONCLUSIONS: The determination of MTX and MTX-Glu(n) in lymphoblasts isolated from blood samples of patients with common ALL provides qualitative information on the capacity of the blasts to form MTX-Glu(n) since distribution patterns of MTX and MTX-Glu(n) parallel that of bone marrow lymphoblasts. The amounts of MTX-Glu(n) accumulated, however, were much lower in blood lymphoblasts. Blood lymphoblasts are therefore not useful for a quantitative analysis of MTX-Glu(n). The contribution of RBC to MTX and MTX-Glu(n) in vitro is only marginal and residual RBC in lymphoblast preparations from bone marrow can therefore be ignored.