Stadheim T A, Xiao H, Eastman A
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Cancer Res. 2001 Feb 15;61(4):1533-40.
Chemotherapeutic agents induce alterations in intracellular signal transduction cascades that culminate in the initiation of the apoptotic program. Here, the relationship between the mitogen-activated protein kinase (MAPK) response and apoptosis in ML-1 cells treated with vinblastine and paclitaxel was investigated. We show that these compounds elicit different effects on MAPKs with vinblastine, but not paclitaxel, increasing both c-Jun-NH2-terminal kinase (JNK) and p38 activity. However, vinblastine and paclitaxel both induced apoptosis with similar kinetics, suggesting that increased JNK and p38 activity is not required for apoptosis that is induced by microtubule interfering agents. Strikingly, the abrogation of extracellular signal-regulated kinase (ERK)-signaling by the MAPK/ERK kinase (MEK)1/2 inhibitor PD098059 in combination with vinblastine robustly induced apoptosis in ML-1 cells at a rate much faster than treatment with vinblastine alone and occurred at all phases of the cell cycle. This apoptotic induction was attributed to JNK activation because: (a) non-JNK-activating concentrations of vinblastine failed to increase apoptosis in the presence of PD098059; (b) apoptosis induced by paclitaxel, which did not activate JNK, was not potentiated by PD098059; and (c) transduction of an inhibitor of JNK activity partially suppressed both JNK activity and apoptosis induced by vinblastine plus PD098059. Additionally, we found that the activation of JNK by vinblastine occurred upstream of effector caspase activation because treatment with a pan-specific caspase inhibitor (valine-alanine-aspartate-fluoromethylketone) resulted in complete abrogation of apoptosis with no effect on MAPK signaling. Taken together, these data suggest that inhibition of the MEK-->ERK signal transduction cascade alleviates cell cycle dependence for vinblastine-induced apoptosis by a mechanism that requires JNK activation.
化疗药物会诱导细胞内信号转导级联反应发生改变，最终引发凋亡程序。在此，研究了长春碱和紫杉醇处理的ML-1细胞中丝裂原活化蛋白激酶（MAPK）反应与凋亡之间的关系。我们发现，这些化合物对MAPK产生不同影响，长春碱可增加c-Jun氨基末端激酶（JNK）和p38活性，而紫杉醇则无此作用。然而，长春碱和紫杉醇均以相似的动力学诱导凋亡，这表明微管干扰剂诱导的凋亡并不需要JNK和p38活性增加。令人惊讶的是，MAPK/ERK激酶（MEK）1/2抑制剂PD098059与长春碱联合使用可消除细胞外信号调节激酶（ERK）信号，在ML-1细胞中强力诱导凋亡，其速率比单独使用长春碱快得多，且在细胞周期的所有阶段均会发生。这种凋亡诱导归因于JNK激活，原因如下：（a）在存在PD098059的情况下，非JNK激活浓度的长春碱无法增加凋亡；（b）未激活JNK的紫杉醇诱导的凋亡未被PD098059增强；（c）JNK活性抑制剂的转导部分抑制了长春碱加PD098059诱导的JNK活性和凋亡。此外，我们发现长春碱对JNK的激活发生在效应半胱天冬酶激活的上游，因为用泛特异性半胱天冬酶抑制剂（缬氨酸-丙氨酸-天冬氨酸-氟甲基酮）处理可完全消除凋亡，而对MAPK信号无影响。综上所述，这些数据表明，抑制MEK→ERK信号转导级联可通过一种需要JNK激活的机制减轻长春碱诱导凋亡对细胞周期的依赖性。
