digitoxigenin and bufalin

We have recently demonstrated that bufalin is a new potent inducer of the differentiation of human myeloid leukemia cells. The present work was carried out to examine further the effect of bufalin on the growth and characteristics of human leukemia-derived cell lines U937, ML1, and HL60. At concentrations of 5-10 nM, bufalin decreased the growth of ML1 cells preferentially at the G2 phase and U937 cells at the S and G2 phases of the cell cycle. Bufalin, under these conditions, induced the differentiation of U937, ML1, and HL60 cells to monocyte/macrophage-like cells by measuring the expression of various differentiation markers, as assessed by morphology and histochemistry, and ability to phagocytose latex particles, to reduce nitroblue tetrazolium, and to develop Fc receptors. U937 and ML1 cells started to differentiate at 4 and 6 h, respectively, after treatment with 10 nM bufalin and showed maximum differentiation 72 h later. At present, a mechanism for the bufalin-mediated induction of the differentiation of these human leukemia cells remains to be determined. The combination of bufalin with all-trans retinoic acid, 1 alpha,25-dihydroxyvitamin D3, 4'-demethylepipodophyllotoxin ethylidene-beta-D-glucoside (VP16), or human gamma-interferon synergistically induced the differentiation of HL60 and U937 cells. A similar effect on ML1 cells was observed with the combination of bufalin with VP16 or human rTNF-alpha. These results suggest that bufalin in combination with VP16, all-trans retinoic acid, 1 alpha,25-dihydroxyvitamin D3, rTNF-alpha, or gamma-interferon may be very useful in the differentiation of human leukemia.

Topics: Antineoplastic Agents; Bufanolides; Cell Differentiation; Cell Division; Cytokines; Digitoxigenin; Drug Administration Schedule; Drug Synergism; Humans; In Vitro Techniques; Leukemia, Myeloid; Macrophages; Monocytes; Ouabain; Sodium-Potassium-Exchanging ATPase; Tumor Cells, Cultured; Vitamins

Bufalin was found to be a potent inducer of differentiation in human erythroleukemia K562 cells by examination of various differentiation markers (as assessed by the morphology, histochemistry, and the abilities to phagocytose latex particles, to reduce nitro-blue tetrazolium and to develop Fc receptors). Bufalin, at a concentration as low as 10 nM, also produced a strong differentiation-inducing activity in three other human leukemia-derived cell lines (human promyelocytic HL60, monoblastic U937 and myeloblastic ML1). Treatment of K562 cells with other cardiotonic steroids, such as cinobufagin, ouabain and digitoxigenin, at the concentration of 10 nM for four days resulted in weak or no effect on the cells. These findings suggest that bufalin might have potentiality as a new agent in the differentiation therapy for human myelogenous leukemia.

Topics: Bufanolides; Cell Differentiation; Cell Line; Digitoxigenin; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Humans; Kinetics; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Materia Medica; Molecular Structure; Ouabain