Inhibition by methotrexate (MTX) polyglutamates (PGS) of folate-dependent biosyntheses in L1210 Leukemia cells

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

OSTI ID:5090149

Matherly, L H; Barlowe, C K; Goldman, I D

The inhibition of folate-dependent pathways by MTX PGS was evaluated in folate-depleted L1210 cells incubated with (6S)5-formyl(CHO)tetrahydrofolate(FH/sub 4/)(5..mu..M). The accumulation of MTX PGS during exposure to MTX (10..mu..M;3h) inhibited cell growth (>70%) under these conditions. In the presence of 5-CHO-FH/sub 4/, carbon transfer from /sup 14/C-formate or 3-/sup 14/C-serine into purines, dTMP, and amino acids was suppressed following MTX-pretreatment, suggesting the formation of only low levels of FH/sub 4/ to drive these reactions. In cells treated with MTX (6S)5-CHO-(/sup 3/H)-FH/sub 4/ was metabolized predominantly to 10-CHO-(/sup 3/H)-FH/sub 4/. While intracellular dihydrofolate (FH/sub 2/) increased 10-fold, indicating a block at FH/sub 2/ reductase by MTX PGS, FH/sub 2/ represented only 20% of the total metabolites of 5-CHO-FH/sub 4/. The incorporation of /sup 14/C from 5-(/sup 14/C)-CHO-FH/sub 4/ into serine and methionine was not affected by the presence of intracellular MTX PGS, however, carbon transfer into dTMP and purine nucleotides was reduced (50-60%). These findings demonstrate that MTX pretreatment inhibits de novo nucleotide and amino acid biosynthetic pathways even when high levels of reduced folates are present. The data suggest a suppression of dTMP synthase and the purine transformylase(s) by MTX and/or FH/sub 2/ PGS that accumulate in drug-treated cells. Inhibition of the purine biosynthetic steps appears to trap 10-CHO-FH/sub 4/, limiting FH/sub 4/ for the synthesis of dTMP, serine, and methionine.

• Research Organization: Medical College of Virginia, Richmond
• OSTI ID: 5090149
• 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
BIOLOGICAL EFFECTS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
DISEASES
DRUGS
FORMIC ACID
GLUTAMIC ACID
GROWTH
HEMIC DISEASES
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
INHIBITION
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEUKEMIA
LIPOTROPIC FACTORS
METABOLISM
METABOLITES
METHIONINE
METHOTREXATE
MONOCARBOXYLIC ACIDS
NEOPLASMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PURINES
SERINE
SYNTHESIS
TRACER TECHNIQUES
TUMOR CELLS