The DNA repair protein PARP-1 emerged as a valuable target in the treatment of tumor entities with deficiencies ofBRCA1/2, such as breast cancer. More recently, the application of PARP inhibitors (PARPi) such as olaparib has been expanded to other cancer entities including colorectal cancer (CRC). We previously demonstrated that PARP-1 is overexpressed in human CRC and promotes CRC progression in a mouse model. However, acquired resistance to PARPi and cytotoxicity-mediated adverse effects limit their clinical applicability. Here, we detailed the role of PARP-1 as a therapeutic target in CRC and studied the efficacy of novel PARPi compounds in wildtype (WT) and DNA repair-deficient CRC cell lines together with the chemotherapeutics irinotecan (IT), 5-fluorouracil (5-FU), and oxaliplatin (OXA). Based on the ComPlat molecule archive, we identified novel PARPi candidates by molecular docking experiments in silico, which were then confirmed by in vitro PARP activity measurements. Two promising candidates (X17613 and X17618) also showed potent PARP-1 inhibition in a CRC cell-based assay. In contrast to olaparib, the PARPi candidates caused no PARP-1 trapping and, consistently, were not or only weakly cytotoxic in WT CRC cells and their BRCA2- or ATR-deficient counterparts. Importantly, both PARPi candidates did not affect the viability of nonmalignant human colonic epithelial cells. While both olaparib and veliparib increased the sensitivity of WT CRC cells towards IT, no synergism was observed for X17613 and X17618. Finally, we provided evidence that all PARPi (olaparib > veliparib > X17613 > X17618) synergize with chemotherapeutic drugs (IT > OXA) in a BRCA2-dependent manner in CRC cells, whereas ATR deficiency had only a minor impact. Collectively, our study identified novel lead structures with potent PARP-1 inhibitory activity in CRC cells but low cytotoxicity due to the lack of PARP-1 trapping, which synergized with IT in homologous recombination deficiency.
DNA修复蛋白PARP-1已成为治疗携带BRCA1/2缺陷的肿瘤（如乳腺癌）的重要靶点。近年来，PARP抑制剂（如奥拉帕尼）的应用已扩展至结直肠癌等其他癌症类型。我们前期研究证实，PARP-1在人类结直肠癌中过度表达，并在小鼠模型中促进结直肠癌进展。然而，PARP抑制剂的获得性耐药及细胞毒性介导的不良反应限制了其临床应用。本研究系统阐述了PARP-1作为结直肠癌治疗靶点的作用机制，并在野生型及DNA修复缺陷型结直肠癌细胞系中，评估了新型PARP抑制剂联合化疗药物伊立替康、5-氟尿嘧啶和奥沙利铂的疗效。基于ComPlat分子数据库，我们通过计算机分子对接实验筛选出新型PARP抑制剂候选化合物，并通过体外PARP活性测定验证其效能。其中两个候选化合物（X17613和X17618）在结直肠癌细胞实验中显示出强效的PARP-1抑制活性。与奥拉帕尼不同，这些候选化合物不会引起PARP-1捕获现象，因此在野生型结直肠癌细胞及其BRCA2或ATR缺陷型细胞中均未产生或仅产生微弱细胞毒性。值得注意的是，两种候选化合物均不影响非恶性人结肠上皮细胞的活力。虽然奥拉帕尼和维利帕尼能增强野生型结直肠癌细胞对伊立替康的敏感性，但X17613和X17618未显示协同作用。最后，我们证实所有PARP抑制剂（奥拉帕尼 > 维利帕尼 > X17613 > X17618）均能以BRCA2依赖的方式与化疗药物（伊立替康 > 奥沙利铂）在结直肠癌细胞中产生协同效应，而ATR缺陷仅产生轻微影响。综上所述，本研究发现了在结直肠癌细胞中具有强效PARP-1抑制活性且因缺乏PARP-1捕获效应而细胞毒性较低的新型先导化合物，这些化合物在同源重组缺陷条件下与伊立替康具有协同作用。
肿瘤(癌症)患者之家