Effects of A-methopterin on formate incorporation into the nucleic acids of susceptible and resistant leukemic cells.

Abstract

It has been demonstrated that A-methopterin inhibits formate incorporation into nucleic acid purines and thymine in leukemic cells which are sensitive to this compound and also in viscera of mice bearing these susceptible leukemic cells. A-methopterin, however, causes a significant increase in formate incorporation into the nucleic acids of leukemic cells which have become dependent on A-methopterin for optimal growth while inhibiting formate incorporation in the visceral nucleic acids of mice bearing the dependent strain of leukemia. Possible mechanisms involved are discussed.