Pro-apoptotic effect of FGVL on NB4 cells and its mechanism

Objective To observe pro-apoptotic effect of flavone from Galium verum L (FGVL) on acute promyelocytic leukemia cells (NB4) and to explore the mechanism of the effect.Methods NB4 cells in culture medium in vitro were treated with different concentrations of FGVL (50,100,and 200 μg/mL).Changes in cell morphological were observed with Hoechst staining and the changes in cell cycle and apoptosis rate were analyzed with flow cytometry.The expression levels of Mel-18,Sall4,and Bmi-1mRNA were assessed with reverse transcriptase PCR(RT-PCR).Results Morphological observations revealed that the percentages of apoptotic cells were significantly enhanced in NB4 cells treated with FGVL for 48 hours,with the percentages of 9.3%,13%,and 20.4% (P<0.05 for all) for the dosages of 50,100,and 200 μg/mL groups,compared with that of in the control group (2.3%);typical apoptotic morphological changes (karyopyknosis,karyorrhexis,and apoptosis bodies) were observed in the NB4 cells.Cell cycle analysis indicated that compared with the control group,the cell ratios in G0/G1 phase (43.92%,37.26%,ans 29.15%) decreased significantly,while the ratios in S phase (54.16%,62.23%,and 70.46%) increased obviously for the NB4 cells treated with 50,100,and 200 μg/mL FGVL.Compared with the control group,the expression level of Mel-18 mRNA increased and Sall4 and Bmi-1mRNA decreased obviously for the NB4 cells treated with 100 and 200 μg/mL FGVL.Conclusion FGVL could inhibit cell proliferation,induce cell apoptosis,and arrest cells in S phase in NB4 cells;the mechanism of the effects is probably through regulating the expressions of Mel-18,Sall4,and Bmi-1 gene.