Proliferation inhibition, cell cycle arrest and apoptosis induced in HL-60 cells by a natural diterpene ester from Daphne mucronata

ABSTRACT

Gnidilatimonoein [Gn], a new diterpene ester from Daphne mucronata, possesses strong anti-metastasis and anti-tumor activities. In this study, its apoptosis and differentiation capabilities were evaluated by using the leukemia HL-60 cell line. Cell prolifaration inhibition was estimated by MTT assay. The occurrence of apoptosis was evaluated by EtBr/AO double staining technique, cell cycle analyses and detection of apoptotic cells by Annexin V-FITC and propodium iodide [PI]. Differentiation of the cells was determined by NBT reduction assay and the expression of specific cell surface markers such as CD 14 and CD1 Ib, were analyzed by flow cytometry. The drug decreased the growth of the cells dose- and time-dependently and the IC[50] was found to be 1.3 microM. Our data suggested that Gn induced both monocytic differentiation and apoptosis among HL-60 cells. In addition, cell cycle analyses showed an increase in Gl phase population by 24 hrs, which was gradually replaced by Sub-Gl cell population [apoptotic cells] by 72 hrs. Based on these data, the Gn-treated HL-60 cells displayed differentiation-dependent apoptosis. Thus, Gn might be a good candidate for differentiation therapy of leukemia, pending full biological evaluation of the compound among the wide array of leukemia cells