Abstract: Objective To explore the mechanism of Shuanghuanglian（SHL）freeze-dried powder induced apoptosis of acute B lymphocytic leukemia cells (Nalm6). Methods SHL was used to treat acute lymphoblastic leukemia cell lines (Nalm6, Jurkat, Molt4 and KG1a) at 0, 0.025, 0.05, 0.1, 0.2, 0.4 and 0.8 g/L. The cell proliferation activity was detected by the CCK-8 method and the half inhibitory concentration (IC50) was calculated. Nalm6 cells were divided into the blank control group (RPMI 1640 medium containing 10% fetal bovine serum) and the SHL treatment groups (0.1, 0.2, and 0.4 g/L). Flow cytometry was used to detect cell cycle distribution and apoptosis in each group. The morphological changes of cell apoptosis were observed after Hoechst 33342 staining. Western blot assay was used to detect the expression levels of MEKERK-c-Myc signaling pathway proteins and apoptosis proteins in Nalm6 cells of each group. Results SHL had the lowest IC 50 for Nalm6, which was (0.11±0.01) g/L. After treatment with 0.1-0.4 g/L SHL, flow cytometry analysis showed that the cell cycle distribution of Nalm6 cells had no obvious changes. However, with the SHL concentration increasing, the apoptotic cell number and the total apoptotic rate of Nalm6 increased. In addition, the expression levels of tBid, cleaved Caspase-9, cleaved Caspase-3 and cleaved PARP increased. While the expression levels of MEK/ERK pathway related proteins decreased, including p-MEK/MEK, p-ERK/ERK and c-Myc (all P＜0.05). After pretreatment with the apoptosis inhibitor Z-VAD-FMK, the pro-apoptotic effect of SHL on Nalm6 cells was inhibited. Conclusion SHL can induce Nalm6 cell apoptosis by inhibiting the MEK-ERK signaling pathway.

Key words: leukemia, lymphoid, leukemia, myeloid, cell line, tumor, Shuanghuanglian injection, apoptosis, MAP kinase signaling system, Nalm6 cell