Stahnke K, Fulda S, Friesen C, Strauss G, Debatin K M
Department of Pediatrics, University Children's Hospital, Ulm, Germany.
Blood. 2001 Nov 15;98(10):3066-73. doi: 10.1182/blood.v98.10.3066.
In addition to myelosuppression, anticancer drugs cause rapid and persistent depletion of lymphocytes, possibly by direct apoptosis induction in mature T and B cells. Induction of apoptosis regulators was analyzed in peripheral blood lymphocytes from pediatric patients undergoing first-cycle chemotherapy for solid tumors. In vivo chemotherapy induced a significant increase in lymphocyte apoptosis ex vivo. The activation of initiator caspase-8 and effector caspase-3 and the cleavage of caspase substrates was detected 12 to 48 hours after the onset of therapy. Caspase inhibition by Z-VAD-fmk did not reduce ex vivo lymphocyte apoptosis in all patients, indicating the additional involvement of caspase-independent cell death. No evidence for the involvement of activation-induced cell death was found in the acute phase of lymphocyte depletion as analyzed by activation marker expression and sensitivity for CD95 signaling. Lymphocyte apoptosis in vivo appeared to be predominantly mediated by the mitochondrial pathway because a marked decrease of mitochondrial membrane potential (DeltaPsi(M)) was detected after 24 to 72 hours of treatment, preceded by the increased expression of Bax. Interestingly, despite the use of DNA-damaging agents, p53 remained completely undetectable throughout treatment. In contrast, in vitro treatment with cytarabine and etoposide induced p53 protein, CD95 receptor expression, CD95 sensitivity, and CD95 receptor-ligand interaction in stimulated cycling lymphocytes, but no such induction was seen in resting cells. These data suggest that chemotherapy-induced lymphocyte depletion involves distinct mechanisms of apoptosis induction, such as direct mitochondrial and caspase-dependent pathways in resting cells and p53-dependent pathways in cycling lymphocytes.
除骨髓抑制外，抗癌药物还会导致淋巴细胞迅速且持续减少，可能是通过直接诱导成熟T细胞和B细胞凋亡。对接受实体瘤首轮化疗的儿科患者外周血淋巴细胞中的凋亡调节因子进行了分析。体内化疗在体外诱导淋巴细胞凋亡显著增加。治疗开始后12至48小时检测到起始半胱天冬酶-8和效应半胱天冬酶-3的激活以及半胱天冬酶底物的切割。Z-VAD-fmk对半胱天冬酶的抑制并未降低所有患者的体外淋巴细胞凋亡，表明存在半胱天冬酶非依赖性细胞死亡的额外参与。通过激活标志物表达和对CD95信号的敏感性分析，在淋巴细胞减少的急性期未发现激活诱导的细胞死亡参与的证据。体内淋巴细胞凋亡似乎主要由线粒体途径介导，因为在治疗24至72小时后检测到线粒体膜电位（ΔΨm）显著降低，之前Bax表达增加。有趣的是，尽管使用了DNA损伤剂，但在整个治疗过程中p53仍完全检测不到。相比之下，体外使用阿糖胞苷和依托泊苷处理可诱导受刺激的循环淋巴细胞中的p53蛋白、CD95受体表达、CD95敏感性以及CD95受体-配体相互作用，但在静止细胞中未观察到此类诱导。这些数据表明，化疗诱导的淋巴细胞减少涉及不同的凋亡诱导机制，如静止细胞中的直接线粒体和半胱天冬酶依赖性途径以及循环淋巴细胞中的p53依赖性途径。
