Efficient utilization of the reduced folate carrier in CCRF-CEM human leukemic lymphoblasts by the potent antifolate Nα-(4-amino-4-deoxypteroyl)- Nδ-hemiphthaloyl- l-ornithine (PT523) and its B-ring analogues

• Published in: Biochemical pharmacology Vol. 60; no. 1; pp. 41 - 46
• Main Authors: Wright, Joel E, Vaidya, Chitra M, Chen, Ying-Nan, Rosowsky, Andre
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.07.2000; Elsevier Science
• Subjects: Antineoplastic agents; Biological and medical sciences; dihydrofolate reductase; General aspects; Medical sciences; Nα-(4-amino-4-deoxypteroyl)- Nδ-hemiphthaloyl- l-ornithine (PT523) analogues; Pharmacology. Drug treatments; reduced folate carrier; N α-(4-amino-4-deoxypteroyl)- N δ-hemiphthaloyl- l-ornithine (PT523) analogues; dihydrofolate reductase; reduced folate carrier; Antineoplastic agent; Human; Cell proliferation; Enzyme; Acute; Enzyme inhibitor; Cytotoxicity; Malignant hemopathy; In vitro; Folate; Structure activity relation; Lymphoproliferative syndrome; Analog; Established cell line; Oxidoreductases; Dihydrofolate reductase; Acute lymphocytic leukemia; Methotrexate; Ornithine; Tumor cell
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/S0006-2952(00)00294-X

The potent nonpolyglutamatable dihydrofolate reductase inhibitor N α-(4-amino-4-deoxypteroyl)- N δ-hemiphthaloyl- l-ornithine (PT523) and six of its B-ring (5-deaza, 8-deaza, and 5,8-dideaza) analogues were compared in terms of their ability to: (a) inhibit the growth of CCRF-CEM human leukemic lymphoblasts, and (b) utilize the reduced folate carrier (RFC) in these cells as measured in a competition assay of [ 3H]methotrexate ([ 3H]MTX) influx. The ic 50 values of the hemiphthaloylornithine derivatives against CCRF-CEM cells after 72 hr of drug exposure varied from 0.64 to 1.3 nM as compared with 14 nM for MTX and 4.4 nM for aminopterin (AMT). The K i values of these compounds in the [ 3H]MTX influx assay were in the 0.3 to 0.7 μM range as compared with a K i of 5.4 μM for AMT and a K t of 7.1 μM for MTX. As a group, the affinities of these compounds for the RFC were approximately 10-fold greater than those of their respective glutamate analogues. These results indicate that, in addition to their previously reported tight binding to dihydrofolate reductase, a property contributing to the high potency of PT523 and its B-ring analogs as inhibitors of tumor cell growth is their strong affinity for the RFC.