Studies on the mechanism of antitumor action of 2-desamino-2-methyl-5,8-dideazaisofolic acid.
The new folate analogue, 2-desamino-2-methyl-5,8-dideazaisofolic acid, 2c, was synthesized and evaluated using a variety of biochemical and antitumor assays. For purposes of comparison, its 2-desamino, 2b, and 2-amino, 2a, counterparts, as well as N10-propargly-5,8-dideazafolic acid, 1a, and the corresponding 2-desamino, 1b, and 2-desamino-2-methyl, 1c, modifications were included in these studies. Compound 2c was found to be a potent inhibitor of the growth of L1210 and MCF-7 cells in culture, being only 2-fold and 5-fold less effective than 1c, respectively. However, although analogue 2c was 189-fold less inhibitory toward L1210 thymidylate synthase (TS) than 1c, its cytotoxicity was reversed completely by thymidine alone which suggests that the compound behaves as a TS inhibitor in cells. Enzymatically synthesized polyglutamates of 2c were substantially more inhibitory toward human TS than the parent compound. Compound 2c was the most efficient substrate for mammalian folyl-polyglutamate synthetase of the compounds studied having a Vmax/Km nearly 12-fold larger than 1c. Both 1c and 2c were effective inhibitors of the uptake of [3H]methotrexate into MOLT-4 cells, implying that each is efficiently transported into tumor cells. These results suggest that a weak inhibitor of TS in vitro can be a potent cytotoxic agent if it can readily gain entry into target cells and be converted to polyglutamated metabolites.
Hagan
R L
RL
Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston 29425.
Duch
D S
DS
Smith
G K
GK
Hanlon
M H
MH
Shane
B
B
Freisheim
J H
JH
Hynes
J B
JB
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D058973:Folate Receptors, GPI-Anchored; D005493:Folic Acid Antagonists; D007700:Kinetics; D008727:Methotrexate / Q000378:metabolism; D010453:Peptide Synthases / Q000378:metabolism; D011799:Quinazolines / Q000138:chemical synthesis / Q000494:pharmacology*; D011956:Receptors, Cell Surface; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
D000970:Antineoplastic Agents; D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D005493:Folic Acid Antagonists; D011799:Quinazolines; D011956:Receptors, Cell Surface; C067567:2-desamino-2-methyl-5,8-dideazaisofolic acid; C035530:5,8-dideazaisofolic acid; D013940:Thymidylate Synthase; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase; D008727:Methotrexate