Engert Florian, Schneider Cornelius, Weiβ Lilly Magdalena, Probst Marie, Fulda Simone
Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany.
Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Frankfurt, Germany. German Cancer Consortium (DKTK), Heidelberg, Germany. German Cancer Research Center (DKFZ), Heidelberg, Germany.
Mol Cancer Ther. 2015 Dec;14(12):2818-30. doi: 10.1158/1535-7163.MCT-15-0587. Epub 2015 Oct 5.
Ewing sarcoma has recently been reported to be sensitive to poly(ADP)-ribose polymerase (PARP) inhibitors. Searching for synergistic drug combinations, we tested several PARP inhibitors (talazoparib, niraparib, olaparib, veliparib) together with chemotherapeutics. Here, we report that PARP inhibitors synergize with temozolomide (TMZ) or SN-38 to induce apoptosis and also somewhat enhance the cytotoxicity of doxorubicin, etoposide, or ifosfamide, whereas actinomycin D and vincristine show little synergism. Furthermore, triple therapy of olaparib, TMZ, and SN-38 is significantly more effective compared with double or monotherapy. Mechanistic studies revealed that the mitochondrial pathway of apoptosis plays a critical role in mediating the synergy of PARP inhibition and TMZ. We show that subsequent to DNA damage-imposed checkpoint activation and G2 cell-cycle arrest, olaparib/TMZ cotreatment causes downregulation of the antiapoptotic protein MCL-1, followed by activation of the proapoptotic proteins BAX and BAK, mitochondrial outer membrane permeabilization (MOMP), activation of caspases, and caspase-dependent cell death. Overexpression of a nondegradable MCL-1 mutant or BCL-2, knockdown of NOXA or BAX and BAK, or the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) all significantly reduce olaparib/TMZ-mediated apoptosis. These findings emphasize the role of PARP inhibitors for chemosensitization of Ewing sarcoma with important implications for further (pre)clinical studies.
最近有报道称尤因肉瘤对聚（ADP）-核糖聚合酶（PARP）抑制剂敏感。为寻找协同药物组合，我们测试了几种PARP抑制剂（他拉唑帕尼、尼拉帕尼、奥拉帕尼、维利帕尼）与化疗药物联合使用的效果。在此，我们报告PARP抑制剂与替莫唑胺（TMZ）或SN-38协同诱导细胞凋亡，并且在一定程度上还增强了阿霉素、依托泊苷或异环磷酰胺的细胞毒性，而放线菌素D和长春新碱则几乎没有协同作用。此外，与双联或单药治疗相比，奥拉帕尼、TMZ和SN-38三联疗法显著更有效。机制研究表明，凋亡的线粒体途径在介导PARP抑制与TMZ的协同作用中起关键作用。我们发现，在DNA损伤引发的检查点激活和G2期细胞周期停滞之后，奥拉帕尼/TMZ联合治疗导致抗凋亡蛋白MCL-1下调，随后促凋亡蛋白BAX和BAK激活、线粒体外膜通透性增加（MOMP）、半胱天冬酶激活以及半胱天冬酶依赖性细胞死亡。不可降解的MCL-1突变体或BCL-2的过表达、NOXA或BAX和BAK的敲低，或半胱天冬酶抑制剂N-苄氧羰基-Val-Ala-Asp-氟甲基酮（zVAD.fmk）均显著降低奥拉帕尼/TMZ介导的细胞凋亡。这些发现强调了PARP抑制剂在尤因肉瘤化疗增敏中的作用，对进一步的（临床前）临床研究具有重要意义。
