Cytotoxicity of Vincristine to Normal and Leukemic Cells

Abstract

The in vitro toxicities of vincristine to non-dividing lymphocytes from normal persons and from patients with chronic lymphocytic leukemia were measured by counts of viable lymphocytes and by the uptake of radioactive uridine. According to both methods, vincristine (0.1 to 10 (µg per ml.) produced in 18 hours a cytotoxic effect on leukemic but not on normal lymphocytes. The sensitivity of the cells was measured by D90, the estimated concentration of vincristine that killed 90% of the cells in seven days. D90’s for lymphocytes from normal persons ranged from 7 to 27 µg. per ml. (median 10). The leukemic lymphocytes were more sensitive than the normal cells, with D90’s 0.1 to 19 (µg. per ml., median 0.8. Vincristine was rapidly toxic to lymphoblasts from two acutely leukemic patients and to myeloblasts from two of eight patients. The data support the hypothesis of Boesen and Davis that the antitumor effect of vincristine is not dependent on metaphase arrest.