King D, Pringle J H, Hutchinson M, Cohen G M
Department of Pathology, MRC Toxicology Unit, University of Leicester, UK.
Leukemia. 1998 Oct;12(10):1553-60. doi: 10.1038/sj.leu.2401153.
Chlorambucil and prednisolone, two commonly used drugs in the treatment of chronic lymphocytic leukemia (CLL), induce apoptosis in CLL cells. We have investigated the involvement in this apoptotic cell death of caspases, which cleave critical cellular substrates thereby acting as the executioners of the apoptotic process. Induction of spontaneous or chlorambucil/prednisolone-induced apoptosis of freshly isolated B-CLL cells in culture resulted in the activation of the 'effector' caspases, -3 and -7, but generally not of caspase-2. Activation of caspases-3 and -7 was accompanied by the proteolysis of the DNA repair enzyme, poly (ADP-ribose) polymerase. Induction of apoptosis was also accompanied by the processing of caspase-8, the extent of which varied between patients. Induction of apoptosis and processing of all the caspases was inhibited by the cell permeable caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone (Z-VAD.fmk). Our results demonstrate a key role for the activation and processing of caspases in the execution phase of apoptosis in CLL cells. Apoptosis of CLL cells resulted in the selective activation of some but not all caspases. Our results suggest that the dysregulation of apoptosis observed in CLL may be due to the signalling leading to the activation of caspases rather than a deletion of pro-caspases. High levels of caspase-8 in CLL cells in conjunction with low levels of CD95 receptor may offer new therapeutic opportunities for the treatment of CLL.
苯丁酸氮芥和泼尼松龙是治疗慢性淋巴细胞白血病（CLL）常用的两种药物，可诱导CLL细胞凋亡。我们研究了半胱天冬酶在这种凋亡性细胞死亡中的作用，半胱天冬酶可切割关键的细胞底物，从而充当凋亡过程的执行者。培养中新鲜分离的B-CLL细胞自发凋亡或苯丁酸氮芥/泼尼松龙诱导的凋亡导致“效应”半胱天冬酶-3和-7的激活，但一般不会激活半胱天冬酶-2。半胱天冬酶-3和-7的激活伴随着DNA修复酶聚（ADP-核糖）聚合酶的蛋白水解。凋亡的诱导还伴随着半胱天冬酶-8的加工，其程度在患者之间有所不同。细胞可渗透的半胱天冬酶抑制剂苄氧羰基-Val-Ala-Asp（OMe）氟甲基酮（Z-VAD.fmk）可抑制凋亡的诱导和所有半胱天冬酶的加工。我们的结果表明，半胱天冬酶的激活和加工在CLL细胞凋亡的执行阶段起关键作用。CLL细胞凋亡导致部分而非全部半胱天冬酶的选择性激活。我们的结果表明，CLL中观察到的凋亡失调可能是由于导致半胱天冬酶激活的信号传导，而不是前半胱天冬酶的缺失。CLL细胞中高水平的半胱天冬酶-8与低水平的CD95受体可能为CLL的治疗提供新的治疗机会。
