In Vitro and In Vivo Apoptosis-Inducing Antileukemic Effects of Mucuna macrocarpa Stem Extract on HL-60 Human Leukemia Cells

Mucuna macrocarpa Wallich (Leguminosae) is believed to hold blood circulation activating effects, and has been used as a folk remedy in Southeast Asia for the treatment of various hematologic and circulatory-related ailments. The objective of this study was to investigate whether crude methanolic extract of M macrocarpa (CMEMM) possessed antileukemic effects on HL-60, human leukemia cells. CMEMM was prepared from dried stems of this plant, and its apoptosis-inducing effects were investigated using HL-60 cells in vitro and in vivo. With treatment of 25 to 75 mu g/mL CMEMM, the in vitro antiproliferative effect on HL-60 cells increased in a dose-and time-dependent manner during the 72-hour treatment period. The concentration of CMEMM that exhibited a 50% growth inhibition (IC50) for 72-hour exposure was 36.4 mu g/mL. Apoptosis triggered by CMEMM in HL-60 cells was confirmed by the following observations: (a) characteristic apoptotic nuclear fragmentation, (b) dose-dependent accumulation of sub-G(1) phase in cell cycle analyses, (c) increased percentages of annexin V-positive apoptotic cells, and (d) dose-dependent elevation of active caspase-3. Furthermore, an in vivo tumor growth suppression effect by CMEMM (500 mg/kg/d intraperitoneally) was observed in mouse xenografts. The results suggest that CMEMM exerts antileukemic effects via an apoptotic pathway in HL-60 cells, and could be a candidate for developing antileukemic agents in the future.