许多癌症携带有丝分裂活化蛋白激酶（MAPK）通路的促增殖突变。在接受 BRAF 抑制剂治疗的 BRAF 驱动型黑色素瘤细胞中，一些细胞亦非遗传性方式通过适应性开始缓慢增殖来逃逸药物诱导的休眠。本研究发现，在响应于多种临床批准的 MAPK 通路抑制剂的情况下，这种现象在许多由 EGFR、KRAS 或 BRAF 突变驱动的癌症类型中普遍存在。在各种癌细胞系的二维培养和三维球体模型中，在 4 天内，一部分细胞逃逸了药物诱导的休眠，并恢复了增殖。这些“逃逸”细胞表现出 DNA 复制缺陷，积累了 DNA 损伤，并启动了依赖于共济失调毛细血管扩张和 RAD3 受体相关（ATR）激酶的应激反应。我们进一步发现，Fanconi 贫血（FA）DNA 修复通路的组分被招募到逃逸细胞有丝分裂 DNA 合成（MiDAS）位点，促使细胞分裂成功地完成。对患者肿瘤样本和临床数据的分析表明，疾病进展与 DNA 复制应激应答因子的增加相关。我们的研究结果表明，许多 MAPK 通路突变的癌症迅速逃逸药物的作用，抑制早期应激耐受通路可能能更持久地实现 MAPK 通路抑制剂的临床有效应答。

Many cancers harbor pro-proliferative mutations of the mitogen-activated protein kinase (MAPK) pathway. In BRAF-driven melanoma cells treated with BRAF inhibitors, subpopulations of cells escape drug-induced quiescence through a nongenetic manner of adaptation and resume slow proliferation. Here, we found that this phenomenon is common to many cancer types driven by EGFR, KRAS, or BRAF mutations in response to multiple, clinically approved MAPK pathway inhibitors. In 2D cultures and 3D spheroid models of various cancer cell lines, a subset of cells escaped drug-induced quiescence within 4 days to resume proliferation. These "escapee" cells exhibited DNA replication deficits, accumulated DNA lesions, and mounted a stress response that depended on the ataxia telangiectasia and RAD3-related (ATR) kinase. We further identified that components of the Fanconi anemia (FA) DNA repair pathway are recruited to sites of mitotic DNA synthesis (MiDAS) in escapee cells, enabling successful completion of cell division. Analysis of patient tumor samples and clinical data correlated disease progression with an increase in DNA replication stress response factors. Our findings suggest that many MAPK pathway-mutant cancers rapidly escape drug action and that suppressing early stress tolerance pathways may achieve more durable clinical responses to MAPK pathway inhibitors.