[Cellular mechanism of the antileukemic action of quinoline dibromide]

Autoradiography (3H-thymidine) and DNA-cytofluorometry were used to study the effect of quinoline dibromide (QD), a potential inhibitor of cobalamine-dependent methionine synthetase, on the kinetics of cell proliferation of L-1210 mouse leukemia. QD was found to produce the secondary blockade of leukemic cells in the late S-phase of the mitotic cycle. Such a mechanism of QD action promoted the potentiation of antitumor activity of the antimetabolites methotrexate, cytosine arabinoside and 5-fluorouracil during combined chemotherapy.