Indoleacetic Acid Falcarindiol Ester Induces Granulocytic Differentiation of the Human Leukemia Cell Line HL-60

Indoleacetic acid falcarindiol ester (Compound 1 has previously been isolated, and purified using an SiO2 column and ODS HPLC from an acetone extract of Japanese ivy (Hedera rhombea). Here we investigate the differentiation-inducing activity of compound I using the human promyelocytic leukemia HL-60 cell line. The effect of compound 1 on HL-60 cell viability and proliferation was determined at different treatment times using the 3-(4,5-dimethythiazol-2-yl)-2,5-diohenyl-2H-tetrazolium bromide (MTT) assay and flow cytometry analysis. Also cell cycle kinetics were examined using propidium iodide staining of DNA. Cell differentiation was assessed by specific and non-specific esterase double staining assays, and by detection of the cell surface differentiation markers CD11b and CD14 using flow cytometry. The results showed HL-60 cell growth inhibition at 0.1 and 1.0 mu g/mL compound 1, whereas 10 mu g/mL was cytotoxic. The growth suppression induced by compound 1 was accompanied by G(0)/G(1) phase arrest in the cell cycle at 1.0 mu g/mL. Moreover, staining and immunochemical analysis indicated that compound 1 induced granulocytic differentiation in HL-60 cells. This is the first report describing granulocytic differentiation activity of a falcarindiol derived polyacetylenic compound on leukemia cells.