RESUMO
<p><b>OBJECTIVE</b>To study the effect of astragalus injection on U937 leukemia cells proliferation and apoptosis and relevant molecular mechanisms.</p><p><b>METHODS</b>Leukemia cell line U937 cells were treated with different concentrations of astragalus (62.5, 125, 250, 500, 1 000 μg/mL). The U937 cells without astragalus treatment were used as the control group. The ability of cell proliferation was measured by MTT method. Flow cytometry was used to explore cell apoptosis. The cell morphology changes were observed under a fluorescent microscope by dyeing Hoechst33258. mRNA expression of c-myc and p27 in U937 cells which was exposed in 1 000 μg/mL astragalus after 0, 12, 24 and 48 hours was detected by reverse transcription polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>Various concentrations of astragalus injection inhibited U937 cell proliferation effectively compared with the control group (P<0.05). They also induced U937 cells apoptosis and the apoptosis rate reached to (63 ± 4)% in the 1 000 μg/mL astragalus treatment group. mRNA expression level of c-myc was gradually declined and p27 mRNA expression was gradually increased with astragalus treatment time (P<0.01).</p><p><b>CONCLUSIONS</b>Astragalus injection may inhibit proliferation and induce apoptosis of leukemia cell line U937 in vitro. This contributes to down-regulation of c-myc expression and up-regulation of p27 expression.</p>