Purpose: Genomic instability is a hallmark of cancer and targeting DNA damage response (DDR) is emerging as a promising therapeutic strategy in different solid tumors. The effectiveness of targeting DDR in colorectal cancer has not been extensively explored. Experimental Design: We challenged 112 cell models recapitulating the genomic landscape of metastatic colorectal cancer with ATM, ATR, CHK1, WEE1, and DNA-PK inhibitors, in parallel with chemotherapeutic agents. We focused then on ATR inhibitors (ATRi) and, to identify putative biomarkers of response and resistance, we analyzed at multiple levels colorectal cancer models highly sensitive or resistant to these drugs. Results: We found that around 30% of colorectal cancers, including those carrying KRAS and BRAF mutations and unresponsive to targeted agents, are sensitive to at least one DDR inhibitor. By investigating potential biomarkers of response to ATRi, we found that ATRi-sensitive cells displayed reduced phospho-RPA32 foci at basal level, while ATRi-resistant cells showed increased RAD51 foci formation in response to replication stress. Lack of ATM and RAD51C expression was associated with ATRi sensitivity. Analysis of mutational signatures and HRDetect score identified a subgroup of ATRi-sensitive models. Organoids derived from patients with metastatic colorectal cancer recapitulated findings obtained in cell lines. Conclusions: In conclusion, a subset of colorectal cancers refractory to current therapies could benefit from inhibitors of DDR pathways and replication stress. A composite biomarker involving phospho-RPA32 and RAD51 foci, lack of ATM and RAD51C expression, as well as analysis of mutational signatures could be used to identify colorectal cancers likely to respond to ATRi.

中文翻译：

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靶向结直肠癌中的 DNA 损伤反应途径和复制应激

目的：基因组不稳定是癌症的一个标志，靶向 DNA 损伤反应 (DDR) 正在成为不同实体瘤的一种有前景的治疗策略。靶向 DDR 在结直肠癌中的有效性尚未得到广泛探索。实验设计：我们使用 ATM、ATR、CHK1、WEE1 和 DNA-PK 抑制剂，同时使用化疗药物，对 112 个细胞模型进行了挑战，以概括转移性结直肠癌的基因组图谱。然后，我们将重点放在 ATR 抑制剂 (ATRi) 上，为了确定反应和耐药的假定生物标志物，我们在多个水平上分析了对这些药物高度敏感或耐药的结直肠癌模型。结果：我们发现约 30% 的结直肠癌，包括携带 KRAS 和 BRAF 突变且对靶向药物无反应的结直肠癌，对至少一种 DDR 抑制剂敏感。通过研究对 ATRi 反应的潜在生物标志物，我们发现 ATRi 敏感细胞在基础水平上表现出磷酸化 RPA32 焦点减少，而 ATRi 抗性细胞在复制应激时表现出 RAD51 焦点形成增加。ATM 和 RAD51C 表达的缺乏与 ATRi 敏感性相关。对突变特征和 HRDetect 评分的分析确定了 ATRi 敏感模型的一个亚组。来自转移性结直肠癌患者的类器官概括了在细胞系中获得的发现。结论：总而言之，对当前疗法难治的一部分结直肠癌可能受益于 DDR 通路和复制应激抑制剂。一种复合生物标志物，涉及磷酸化 RPA32 和 RAD51 病灶，缺乏 ATM 和 RAD51C 表达，