Biological nature of the effect of ascorbic acids on the growth of human leukemic cells.

The effects of L-ascorbic acid (LAA) on the in vitro growth of human leukemic colony-forming cells (L-CFC) were analyzed for all acute nonlymphocytic leukemia patients from whom bone marrow aspirates were received by this laboratory for cell culture study. Among 259 cases, 163 could be directly evaluated for LAA effect. L-CFC growth enhancement was noted in 53 (33%) and suppression in 28 (17%), with overall 50% of patients affected by LAA. Among 34 normal bone marrows tested, none were enhanced by LAA while 8 (24%) were suppressed. While caution is needed in interpreting L-CFC suppression by LAA, L-CFC enhancement is clearly significant. Two isomers of LAA, D-isoascorbic acid and D-ascorbic acid, which have weaker antiscorbutic activity than that of LAA, also produced the L-CFC growth-enhancing effect, but to a lesser degree than that of LAA. A dose-response study also substantiated that D-ascorbic acid was definitely less effective than was LAA. Since D-ascorbic acid is the true optical isomer of LAA and has identical physicochemical properties as does LAA, this differential effect is clearly of biological nature. This study indicates that L-CFC growth suppression by LAA is observed in one-sixth of leukemic patients, L-CFC enhancement in one-third of patients, and that L-CFC growth enhancement is a clearly significant finding with a biological mechanism as the basis.