OBJECTIVETo investigate the effect of gambogic acid (GA) on cell proliferation and induction of apoptosis in HL-60 cells in vitro, as well as the regulation of nucleoporin Nup88 to explore the relationship between them.

METHODSThe effect of GA on the growth of HL-60 cells was determined by MTU assay. Apoptosis was detected with Hoechst 33258 staining and annexin-V FITC/PI double-labeled flow cytometry. The influence on cell cycle was studied by a propidium iodide method. Both flow cytometry (FCM) and RT-PCR techniques were applied to assess the expression of Nup88, whereas the localization of Nup88 was determined by confocal laser scanning microscopy.

RESULTSGA presented striking inhibitory effect on proliferation of HL-60 cells in vitro and induction of apoptosis in a time- and dose-dependent manner. However, no obvious influence was found on the cell cycle in HL-60 cells. The IC50 value for 12 h was 1.797 micromol/L. 15.1% of HL-60 cells went apoptosis when treated with 0.4 micromol/L GA for 12 h. When the dose of GA was increased to 1.6 micromol/L, more than half of cells were apoptotic. On the other hand, the expression level of Nup88 was down-regulated in HL-60 cells induced by GA in a dose-dependent manner. The distribution of Nup88 was also changed from widely dispersed in both nucleus and cytoplasm to that only localized at the cytoplasmic side of nuclear membrane, occasionally in the cytoplasm sporadically.

CONCLUSIONGA exhibites remarkable inhibitory effect on cell proliferation in leukemic cells and inducing apoptosis in HL-60 cells in a cell cycle-independent manner, which might correspond to the regulation of the expression as well as the distribution of nucleoporin Nup88. It may become a new remedy for treatment for acute leukemia.