小檗胺对人慢性粒细胞白血病细胞发生凋亡的诱导机制研究

目的 研究新型p210 bcr/abl抑制剂小檗胺诱导人慢性粒细胞白血病细胞凋亡分子的机制.方法 培养表达内源性p210 bcr/abl蛋白的Ph＋人慢性粒细胞白血病细胞系K562,用小檗胺按指定时间和剂量干预细胞.应用膜联蛋白荧光素（Annexin-V-Fluos）/碘化丙啶（propidium iodide,PI）试剂盒和流式细胞术定量分析凋亡细胞百分比;用cytoperm/cytofix和天冬氨酸特异的半胱氨酸蛋白水解酶-3-McAb-PE定量检测含活化天冬氨酸特异的半胱氨酸蛋白水解酶-3（Caspase-3）细胞百分比;以免疫共沉淀技术（c-abl抗体）和Western印迹p-Tyr（pY99）抗体]定量分析p210 bcr/abl蛋白磷酸化;p210 bcr/abl蛋白总量直接用Western印迹（c-abl抗体）检测;Hsp90和Hsp70等分子伴侣蛋白水平的变化用Western印迹（Hsp90和Hsp70抗体）.结果 48 h IC50浓度小檗胺（8μg/ml）作用48 h后,45.69% K562白血病细胞表达活化的Caspase-3凋亡分子和48.43%白血病细胞发生凋亡.免疫印迹和免疫共沉淀结果显示,低剂量小檗胺可明显抑制白血病细胞内p210 bcr/abl磷酸化：8μg/ml浓度小檗胺处理6 h后,白血病细胞磷酸化p210 bcr/abl蛋白含量仅为对照组的8.41%,而p210 bcr/abl蛋白总量并无变化.小檗胺还能直接下调p210 bcr/abl分子伴侣Hsp90蛋白水平：白血病细胞经8μg/ml浓度小檗胺处理24h时的Hsp90水平只有对照组的18.37%,而且对能诱导白血病细胞产生凋亡抵抗的Hsp70蛋白水平影响不明显.结论 （1）小檗胺是一种新型p210 bcr/abl蛋白磷酸化抑制剂,能通过抑制p210 bcr/abl蛋白磷酸化和诱导Caspase-3通路介导的Ph＋白血病细胞发生凋亡;（2）与已知Hsp90抑制剂格尔德霉素（GA）不同,小檗胺能直接下调Hsp90蛋白水平,而对与肿瘤细胞凋亡抵抗有关的Hsp70蛋白表达影响不大,这提示小檗胺可能还是一种新型蛋白分子伴侣Hsp90抑制剂,值得进一步研究.

The mechanism of apoptosis of chronic myeloid leukemia cells induced by the novel p210 bcr/abl inhibitor berbamine

OBJECTIVE: To investigate the mechanism of apoptosis of chronic myeloid leukemia (CML) cells induced by the novel p210 bcr/abl inhibitor berbamine. METHODS: Human Ph+ CML leukemia K562 cells, which express endogenous p210 bcr/abl protein, were cultured in RPMI 1640 and treated with berbamine as indicated time and dose. Flow cytometry (FCM) and Annexin-V-Fluos/PI staining kit were used to evaluate the apoptosis of leukemic cells; FCM and cytoperm/cytofix plus Caspase-3-McAb-PE were employed to measure the leukemic cells with activated Caspase-3. Phosphorylation of p210 bcr/abl protein in the leukemic cells were assessed by a combination of immunoprecipitation (IP) with c-abl antibody and Western blotting with p-Tyr (pY99) antibody. The protein levels of p210 bcr/abl, Hsp90 and Hsp70 in the leukemic cells were determined by Western blotting with antibodies to c-abl, Hsp90, and Hsp70 respectively. RESULTS: After treatment with berbamine at 8 microg/ml for 48 h, the percentages of leukemic cells expressing activated caspase-3 and apoptotic cells were 45.69% and 48.43% respectively. IP and WB results showed that berbamine at low concentration markedly inhibited phosphorylation of p210 bcr/abl protein in the leukemia cells, and the amount of phosphorylated p210 bcr/abl in the leukemia cells exposed to berbamine at 8 microg/ml for 6 h were only 8.41% of that of untreated leukemia cells without the protein levels of p210 bcr/abl down-regulated. Significantly, berbamine also down-regulated chaperone Hsp90 protein, and the amount of Hsp90 protein in the leukemia cells treated with berbamine at 8 microg/ml for 48 h accounted for 18.37% of that of the untreated leukemia cells. Berbamine at 8 microg/ml had no obvious effect on chaperone Hsp70 protein expression associated with the resistance of leukemia cells to apoptosis. CONCLUSION: (1) Berbamine induces caspase-3-mediated apoptosis of Ph+ leukemia cells through inhibiting phosphorylation of p210 bcr/abl protein and down-regulating its chaperone Hsp90 protein. (2) Unlike Hsp90 inhibitor GA that upregulates Hsp70, berbamine has no obvious effect on chaperone Hsp70 protein expression in leukemia cells, suggesting that berbamine may be a novel class of Hsp90 inhibitor, and further study is required.