Abstract: OBJECTIVE: To study cellular changes during induction of differentiation of human acute promyelocytic leukemia cells (NB4) by an alcohol extract from Herba Saginae Japonicae (HSJ). METHODS: NB4 cells in culture were were organized into four groups:HSJ low dose (30 μg/mL), HSJ middle dose (60 μg/mL), HSJ high dose (120 μg/mL) and negative control groups. Cells in the experimental groups were treated with HSJ for 48 h and their cellular morphology was observed by transmission electron microscopy. nitrotriazole nitrogen (NBT) reduction test was used to detect the differentiation ability of NB4 cells. The distribution of NB4 cell cycles and expression rates of CD14 and CD11b cells were detected using flow cytometry. Expression of c-fos mRNA was detected using quantitative real-time PCR(qPCR). Expression of cfos protein was detected using the Western blot method. RESULTS: Compared with the control group, the nuclei of HSJ-treated cells, in the three different doses, were reduced and changed into kidney-shape, and the cytoplasm was vacuolated. The NBT test showed that the reduction rate of the treated cells were significantly higher than that in the control group (P < 0.05). The proportions of G2 phase cells in the treated groups were significantly higher than that in the control group, while the proportion of S phase cells were significantly lower (P < 0.05). The expression rates of CD14 and CD11b positive cells in the treated groups were significantly higher than that in the control group (P < 0.05). In addition, expression rates of c-fos mRNA and c-fos proteins in the middleand the high-dose groups were significantly higher than that in the control group (P < 0.05) but no difference for the low-dose group. CONCLUSION: HSJ may induce NB4 cells to differentiate into mature granulocytes.

Key words: Herba Saginae Japonicae, flow cytometry, NB4 cells, differentiation, acute promyelocytic leukemia