肿瘤坏死因子凋亡诱导配体诱导白血病细胞凋亡中抵抗机制的初步探讨

目的初步探讨肿瘤坏死因子凋亡诱导配体(TRAIL)诱导白血病细胞发生凋亡过程中可能存在的抵抗机制。方法用流式细胞仪检测经 TRAIL 处理后,白血病细胞系 K562、CEM 凋亡情况及线粒体跨膜电位的改变;采用 Western blot 检测 TRAIL 处理后细胞凋亡相关蛋白 Bcl-xL、Bax 及内源性半胱天冬酶(caspase)-8表达情况;并用 ELISA 法检测核转录因子(NF)-kB 活性变化。结果经TRAIL 处理后,K562、CEM 细胞出现不同程度的凋亡,其凋亡指数分别为29.98%、14.1%,后者显著低于前者(P<0.001);线粒体跨膜电位下降,分别为73.25%、25.4%(P<0.01);CEM 细胞中内源性caspase-8的表达水平低于 K562细胞,并且两者均表现出 Bcl-xL 表达上升、Bax 表达下降,在 CEM 细胞中 Bcl-xL/Bax 比例为18.8,显著高于 K562细胞 Bcl-xL/Bax 的比值(5.1);并且在 TRAIL 处理 CEM细胞后早期(2 h)即表现出 NF-kB 活性增加(0.48 μmol·L~(-1)·mg~(-1)蛋白),高于 K562细胞(0.326μmol·L~(-1)·mg~(-1)蛋白(P<0.001)。结论 TRAIL 诱导白血病细胞凋亡过程中,CEM 细胞对药物抵抗原因可能与 CEM 细胞内源性 caspase-8表达水平较低、线粒体内膜敏感程度降低、NF-kB 活性早期增加以及 Bcl-2家族蛋白的表达变化有关。

Study on the potential mechanisms of leukemia cell resistance to TRAIL-induced apoptosis

OBJECTIVE: To explore the potential mechanisms of leukemia cell resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) -induced apoptosis. METHODS: Cells apoptosis, changes of mitochondrial membrane potential, activity of NF-kappaB, activity of caspase-8 and expressions of apoptosis-related proteins in TRAIL treated K562 and CEM cells, were detected by flowcytometry, ELISA and Western blotting methods, respectively. RESULTS: After treated with TRAIL, the apoptosis indexes were 29.98% and 14.1%, and mitochondrial membrane potential were decreased to 73.25% and 25.4% in K562 and CEM cells respectively. Constitutive level of caspase-8 expression in CEM was lower than that in K562 cells. Both cells became over-expressed Bcl-xL and down-regulated Bax. The ratio of Bcl-xL/Bax in CEM cells was higher than that in K562 cells. Compared with that in K562, the NF-kappaB activity increased significantly in CEM after treatment with TRAIL in early stage. CONCLUSION: CEM cells were more resistant to TRAIL-induced apoptosis than K562 cells did. The potential mechanisms associated with CEM drug resistance might be the lower expression of the constitutive level of caspase-8, lower sensitivity of mitochondrial inner membrane, early increase in NF-KB activity and altered expression of Bcl-2 proteins family.