MacKeigan J P, Collins T S, Ting J P
Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, Department of Surgery, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
J Biol Chem. 2000 Dec 15;275(50):38953-6. doi: 10.1074/jbc.C000684200.
The anti-cancer drug paclitaxel (Taxol) alters microtubule assembly and activates pro-apoptotic signaling pathways. Previously, we and others found that paclitaxel activates endogenous JNK in tumor cells, and the activation of JNK contributes to tumor cell apoptosis. Here we find that paclitaxel activates the prosurvival MEK/ERK pathway, which conversely may compromise the efficacy of paclitaxel. Hence, a combination treatment of paclitaxel and MEK inhibitors was pursued to determine whether this treatment could lead to enhanced apoptosis. The inhibition of MEK/ERK with a pharmacologic inhibitor, U0126, together with paclitaxel resulted in a dramatic enhancement of apoptosis that is four times more than the additive value of the two drugs alone. Enhanced apoptosis was verified by the terminal transferase-mediated dUTP nick end labeling assay, by an enzyme-linked immunosorbent assay for histone-associated DNA fragments, and by flow cytometric analysis for DNA content. Specificity of the pharmacologic inhibitor was confirmed by the use of (a) a second MEK/ERK inhibitor and (b) a transdominant-negative MEK. Enhanced apoptosis was verified in breast, ovarian, and lung tumor cell lines, suggesting this effect is not cell type-specific. This is the first report of enhanced apoptosis detected in the presence of paclitaxel and MEK inhibition and suggests a new anticancer strategy.
抗癌药物紫杉醇（泰素）可改变微管组装并激活促凋亡信号通路。此前，我们及其他研究人员发现紫杉醇可激活肿瘤细胞中的内源性JNK，且JNK的激活有助于肿瘤细胞凋亡。在此我们发现，紫杉醇可激活促生存的MEK/ERK通路，而这反过来可能会削弱紫杉醇的疗效。因此，我们采用紫杉醇与MEK抑制剂联合治疗，以确定这种治疗是否能增强细胞凋亡。使用药理学抑制剂U0126抑制MEK/ERK，并联合紫杉醇，可使细胞凋亡显著增强，比单独使用两种药物的累加值高出四倍。通过末端转移酶介导的dUTP缺口末端标记试验、组蛋白相关DNA片段的酶联免疫吸附测定以及DNA含量的流式细胞术分析，证实了细胞凋亡的增强。通过使用（a）第二种MEK/ERK抑制剂和（b）一种显性负性MEK，证实了药理学抑制剂的特异性。在乳腺、卵巢和肺癌细胞系中均证实了细胞凋亡的增强，表明这种效应并非细胞类型特异性的。这是在紫杉醇和MEK抑制作用下检测到细胞凋亡增强的首篇报道，并提示了一种新的抗癌策略。
