Akpinar Birce, Bracht Ethiene V, Reijnders Dorin, Safarikova Barbora, Jelinkova Iva, Grandien Alf, Vaculova Alena Hyrslova, Zhivotovsky Boris, Olsson Magnus
Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Department of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic.
Oncotarget. 2015 Dec 22;6(41):43679-97. doi: 10.18632/oncotarget.6030.
Despite recent advances in targeted therapeutics, administration of 5-fluorouracil (5-FU) remains a common clinical strategy for post-surgical treatment of solid tumors. Although it has been proposed that RNA metabolism is disturbed by 5-FU treatment, the key cytotoxic response is believed to be enzymatic inhibition of thymidylate synthase resulting in nucleotide pool disproportions. An operating p53 tumor suppressor signaling network is in many cases essential for the efficiency of chemotherapy, and malfunctions within this system remain a clinical obstacle. Since the fate of chemotherapy-insensitive tumor cells is rarely described, we performed a comparative analysis of 5-FU toxicity in p53-deficient cells and conclude that p53 acts as a facilitator rather than a gatekeeper of cell death. Although p53 can act as a regulator of several cellular stress responses, no rerouting of cell death mode was observed in absence of the tumor suppressor. Thus, the final death outcome of 5-FU-treated p53-/- cells is demonstrated to be caspase-dependent, but due to a slow pace, accumulation of mitochondrial reactive oxygen species contributes to necrotic characteristics. The oligomerization status of the p53 target gene DR5 is determined as a significant limiting factor for the initiation of caspase activity in an intracellular TRAIL-dependent manner. Using several experimental approaches, we further conclude that RNA-rather than DNA-related stress follows by caspase activation irrespectively of p53 status. A distinct 5-FU-induced stress mechanism is thereby functionally connected to a successive and discrete cell death signaling pathway. Finally, we provide evidence that silencing of PARP-1 function may be an approach to specifically target p53-deficient cells in 5-FU combinatorial treatment strategies. Together, our results disclose details of impaired cell death signaling engaged as a consequence of 5-FU chemotherapy. Obtained data will contribute to the comprehension of factors restraining 5-FU efficiency, and by excluding DNA as the main stress target in some cell types they propose alternatives to currently used and suggested synergistic treatment regimens.
尽管靶向治疗最近取得了进展，但5-氟尿嘧啶（5-FU）给药仍然是实体瘤术后治疗的常见临床策略。虽然有人提出RNA代谢会受到5-FU治疗的干扰，但关键的细胞毒性反应被认为是胸苷酸合成酶的酶抑制作用，导致核苷酸库失衡。在许多情况下，正常运作的p53肿瘤抑制信号网络对于化疗的有效性至关重要，而该系统内的功能障碍仍然是一个临床障碍。由于很少描述化疗不敏感肿瘤细胞的命运，我们对p53缺陷细胞中的5-FU毒性进行了比较分析，并得出结论：p53作为细胞死亡的促进者而非守门人。尽管p53可以作为几种细胞应激反应的调节因子，但在缺乏肿瘤抑制因子的情况下未观察到细胞死亡模式的重新定向。因此，5-FU处理的p53-/-细胞的最终死亡结果被证明是半胱天冬酶依赖性的，但由于速度缓慢，线粒体活性氧的积累导致坏死特征。p53靶基因DR5的寡聚化状态被确定为以细胞内TRAIL依赖性方式启动半胱天冬酶活性的重要限制因素。使用几种实验方法，我们进一步得出结论：无论p53状态如何，RNA而非DNA相关应激会导致半胱天冬酶激活。由此，一种独特的5-FU诱导应激机制在功能上与连续且离散的细胞死亡信号通路相连。最后，我们提供证据表明，沉默PARP-1功能可能是在5-FU联合治疗策略中特异性靶向p53缺陷细胞的一种方法。总之，我们的结果揭示了5-FU化疗导致的细胞死亡信号受损的细节。获得的数据将有助于理解限制5-FU疗效的因素，并且通过排除某些细胞类型中DNA作为主要应激靶点，它们为当前使用的和建议的联合治疗方案提出了替代方案。
