Division of Cancer Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Cancer Research Centre, Oglesby Cancer Research Building, 555 Wilmslow Road, Manchester, M20 4GJ, UK.
Department of Medical Oncology, The Christie NHS Foundation Trust, Wilmslow Rd, Manchester, M20 4BX, UK.
J Exp Clin Cancer Res. 2021 Oct 16;40(1):323. doi: 10.1186/s13046-021-02124-0.
Patients with ovarian cancer often present at advanced stage and, following initial treatment success, develop recurrent drug-resistant disease. PARP inhibitors (PARPi) are yielding unprecedented survival benefits for women with BRCA-deficient disease. However, options remain limited for disease that is platinum-resistant and/or has inherent or acquired PARPi-resistance. PARG, the PAR glycohydrolase that counterbalances PARP activity, is an emerging target with potential to selectively kill tumour cells harbouring oncogene-induced DNA replication and metabolic vulnerabilities. Clinical development of PARG inhibitors (PARGi) will however require predictive biomarkers, in turn requiring an understanding of their mode of action. Furthermore, differential sensitivity to PARPi is key for expanding treatment options available for patients.
A panel of 10 ovarian cancer cell lines and a living biobank of patient-derived ovarian cancer models (OCMs) were screened for PARGi-sensitivity using short- and long-term growth assays. PARGi-sensitivity was characterized using established markers for DNA replication stress, namely replication fibre asymmetry, RPA foci, KAP1 and Chk1 phosphorylation, and pan-nuclear γH2AX, indicating DNA replication catastrophe. Finally, gene expression in sensitive and resistant cells was also examined using NanoString or RNAseq.
PARGi sensitivity was identified in both ovarian cancer cell lines and patient-derived OCMs, with sensitivity accompanied by markers of persistent replication stress, and a pre-mitotic cell cycle block. Moreover, DNA replication genes are down-regulated in PARGi-sensitive cell lines consistent with an inherent DNA replication vulnerability. However, DNA replication gene expression did not predict PARGi-sensitivity in OCMs. The subset of patient-derived OCMs that are sensitive to single-agent PARG inhibition, includes models that are PARPi- and/or platinum-resistant, indicating that PARG inhibitors may represent an alternative treatment strategy for women with otherwise limited therapeutic options.
We discover that a subset of ovarian cancers are intrinsically sensitive to pharmacological PARG blockade, including drug-resistant disease, underpinned by a common mechanism of replication catastrophe. We explore the use of a transcript-based biomarker, and provide insight into the design of future clinical trials of PARGi in patients with ovarian cancer. However, our results highlight the complexity of developing a predictive biomarker for PARGi sensitivity.
卵巢癌患者常处于晚期，在初始治疗成功后，会发展出复发性耐药疾病。PARP 抑制剂（PARPi）为 BRCA 缺陷疾病的女性带来了前所未有的生存获益。然而，对于铂耐药和/或固有或获得性 PARPi 耐药的疾病，选择仍然有限。PARG 是一种 PAR 糖基水解酶，可平衡 PARP 活性，是一种新兴的靶标，具有选择性杀死携带致癌基因诱导的 DNA 复制和代谢脆弱性的肿瘤细胞的潜力。然而，PARG 抑制剂（PARGi）的临床开发需要预测性生物标志物，这反过来又需要了解其作用模式。此外，对 PARPi 的不同敏感性是为患者扩大可用治疗选择的关键。
使用短期和长期生长测定法，对 10 种卵巢癌细胞系和患者来源的卵巢癌模型（OCM）的活体生物库进行了 PARGi 敏感性筛选。使用 DNA 复制应激的既定标志物，即复制纤维不对称性、RPA 焦点、KAP1 和 Chk1 磷酸化以及全核 γH2AX，来描述 PARGi 敏感性，这表明存在 DNA 复制灾难。最后，还使用 NanoString 或 RNAseq 检查了敏感和耐药细胞中的基因表达。
在卵巢癌细胞系和患者来源的 OCM 中均发现了 PARGi 敏感性，敏感性伴随着持续的复制应激标志物和有丝分裂前细胞周期阻滞。此外，PARGi 敏感细胞系中 DNA 复制基因下调，与固有 DNA 复制脆弱性一致。然而，DNA 复制基因表达并不能预测 OCM 中的 PARGi 敏感性。对单一 PARG 抑制敏感的患者来源 OCM 亚组，包括 PARPi 和/或铂耐药模型，表明 PARG 抑制剂可能代表其他治疗选择有限的女性的另一种治疗策略。
我们发现，一部分卵巢癌固有地对药理学 PARG 阻断敏感，包括耐药疾病，其基础是复制灾难的共同机制。我们探讨了使用基于转录的生物标志物，并为未来 PARGi 在卵巢癌患者中的临床试验设计提供了见解。然而，我们的结果强调了开发 PARGi 敏感性预测性生物标志物的复杂性。
