Purine biosynthesis in L1210 leukemia cells is inhibited by 7-hydroxymethotrexate (7-OH-MTX) polyglutamates (PGS)

Journal Article · Thu May 01 04:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5145232

Seither, R L; Matherly, L H; Goldman, I D

The biochemical basis for 7-OH-MTX cytotoxicity was examined in L1210 tumor cells. Cells were exposed to 100 ..mu..M 7-OH-MTX (approx. 50% growth inhibition) or 10 ..mu..M methotrexate (MTX) (approx. 95% growth inhibition) for 6 hrs to allow high levels of PGS to accumulate. Dihydrofolate reductase (DHFR) activity was assessed by dihydrofolate (FH/sub 2/) pools labeled with 5-formyl-(/sup 3/H)-tetrahydrofolate (5..mu..M) or /sup 3/H-folic acid (1 ..mu..M). FH/sub 2/ was not elevated above control levels in 7-OH-MTX treated cells, in contrast to MTX treated cells in which FH/sub 2/ increased 4- to 7-fold. /sup 3/H-Deoxyuridine incorporation into DNA was not inhibited in cells containing high levels (11.5 nmol/g dry wt.) of 7-OH-MTX tetraglutamate (7-OH-4-NH/sub 2/-10-CH/sub 3/-PteGlu/sub 4/), well in excess of the DHFR-binding capacity (7.3 +/- 0.9 nmol/g), indicating a normal rate of thymidylate synthesis. Although small amounts of 7-OH-MTX and its PGS were bound to DHFR in L1210 cells, as assessed by gel filtration, there was evidence for the preferential binding of 7-OH-MTX tetraglutamate. In all cases this was well below the DHFR binding capacity, consistent with normal rates of deoxyuridine metabolism and FH/sub 2/ levels in the cell. Incorporation of /sup 14/C-formate (60 min) into thymidylate and amino acids was unaffected by 7-OH-MTX, yet incorporation into purines was inhibited over 50%, supporting a block(s) in de novo purine biosynthesis.

• Research Organization: Medical College of Virginia, Richmond
• OSTI ID: 5145232
• Report Number(s): CONF-8606151-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
• Country of Publication: United States
• Language: English

Related Subjects

550201 -- Biochemistry-- Tracer Techniques
560301* -- Chemicals Metabolism & Toxicology-- Cells-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
ANIMAL CELLS
ANTIMETABOLITES
AROMATICS
AZAARENES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
DISEASES
DRUGS
ENZYMES
FOLIC ACID
FORMIC ACID
GROWTH
HEMATINICS
HEMATOLOGIC AGENTS
HEMIC DISEASES
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INHIBITION
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LEUKEMIA
METHOTREXATE
MONOCARBOXYLIC ACIDS
NEOPLASMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
PTERIDINES
PURINES
REACTION KINETICS
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
TUMOR CELLS
VITAMIN B GROUP
VITAMINS