phenylalanine-methyl-ester and perfosfamide

The antileukemic activities of the lysosomotropic compounds, such as phenylalanine methyl ester (PME), have received little attention. In this study, a 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was used to investigate the antileukemic activity of PME. Leukemic specimens from untreated patients that contained greater than or equal to 75% blasts were used. Leukemic cells were treated with PME at 37 degrees C and 22 degrees C in concentrations ranging from 0.5 to 50 mM. Normal blood mononuclear cells served as controls. At both 37 degrees C and 22 degrees C, the recovery of normal peripheral blood cells was approximately 28% following incubation with 50 mM PME. At 37 degrees C, 50 mM PME caused greater than one log reduction of leukemic cells in 13/16 acute myelogenous leukemia (AML), 7/9 acute lymphocytic leukemia (ALL), and 8/8 in blast crisis of chronic myelogenous leukemia (CML-BC) specimens. PME had less activity at 22 degrees C than at 37 degrees C. PME was compared with 100 micrograms/ml 4-hydroperoxycyclophosphamide (4HC). In contrast to PME, 4HC was associated with a greater than one log reduction of leukemic cells in only 1/13 AML, 1/3 ALL and 0/6 CML-BC specimens. 4HC activity exceeded PME activity in only one case each of ALL and prolymphocytic leukemia (PLL). In a case of CD34+ B cell ALL, synergy of PME and 4HC was demonstrated. These studies indicate 1) PME has antileukemic activity and 2) 4HC has less antileukemic activity than PME.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antineoplastic Agents; Blast Crisis; Child; Cyclophosphamide; Drug Screening Assays, Antitumor; Drug Synergism; Female; Humans; Leukemia; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Male; Middle Aged; Monocytes; Phenylalanine; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Temperature; Tumor Cells, Cultured

Phenylalanine methylester (PME), a lysosomotropic compound can be used to deplete monocytes and myeloid cells from peripheral blood and bone marrow (BM). The potential of PME for purging leukemic cells from BM was investigated using U937 and HL-60 cell lines as models. Optimal purging conditions for U937 cells were determined using an MTT assay (3-4, 5-dimethylthiazol-2, 5-diphenyl tetrazolium biomide; Sigma). Elimination of U937 cells was time-, temperature-, and dose-dependent. PME activity was optimal at 37 degrees C for 45 minutes. Depletion of U937 was > 2.8 logs for 50 mmol/L PME. Compared with another purging agent, 100 micrograms/mL 4-hydroperoxycyclophosphamide had activity comparable to 40 mmol/L PME. HL-60 cells were even more sensitive to PME than U937 cells. To support observations made with the MTT assay, clonogenic assays were performed. PME, 50 mmol/L at 37 degrees C resulted in total depletion (> 5 logs) of U937 colonies. Progressive depletion of normal progenitor cells occurred when BM was incubated with PME at concentrations from 5 to 100 mmol/L. At 37 degrees C, 50 mmol/L PME reduced colony-forming units-granulocyte-macrophage and burst-forming units-erythroid (BFU-E) recovery by 98%. Recombinant human mast cell factor augmented BFU-E after PME treatment but had no effect on HL-60 or U937. These studies suggest that PME deserves further study as an agent for ex vivo marrow purging.

Topics: Bone Marrow; Bone Marrow Purging; Colony-Forming Units Assay; Cyclophosphamide; Erythropoietin; Hematopoietic Cell Growth Factors; Humans; Kinetics; Leukemia, Myeloid; Leukemia, Promyelocytic, Acute; Phenylalanine; Recombinant Proteins; Stem Cell Factor; Time Factors; Tumor Cells, Cultured