Authors' Affiliations: Laboratory of Cellular & Molecular Radiation Oncology, Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Charlestown; Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston; and Center for Cancer Research, Massachusetts General Hospital Cancer Center, Charlestown, Massachusetts; Research Oncology, Genentech, Inc., South San Francisco, California; Department of Pharmaceutical Biology, Ludwig Maximilian University of Munich, Munich; and Center for Oncology, University Medical Center Hamburg-Eppendorf, University of Hamburg, Hamburg, Germany.
Cancer Res. 2013 Oct 15;73(20):6254-63. doi: 10.1158/0008-5472.CAN-13-0044. Epub 2013 Aug 21.
In patients with lung cancer whose tumors harbor activating mutations in the EGF receptor (EGFR), increased responses to platinum-based chemotherapies are seen compared with wild-type cancers. However, the mechanisms underlying this association have remained elusive. Here, we describe a cellular phenotype of cross-linker sensitivity in a subset of EGFR-mutant lung cancer cell lines that is reminiscent of the defects seen in cells impaired in the Fanconi anemia pathway, including a pronounced G2-M cell-cycle arrest and chromosomal radial formation. We identified a defect downstream of FANCD2 at the level of recruitment of FAN1 nuclease and DNA interstrand cross-link (ICL) unhooking. The effect of EGFR mutation was epistatic with FANCD2. Consistent with the known role of FANCD2 in promoting RAD51 foci formation and homologous recombination repair (HRR), EGFR-mutant cells also exhibited an impaired RAD51 foci response to ICLs, but not to DNA double-strand breaks. EGFR kinase inhibition affected RAD51 foci formation neither in EGFR-mutant nor wild-type cells. In contrast, EGFR depletion or overexpression of mutant EGFR in wild-type cells suppressed RAD51 foci, suggesting an EGFR kinase-independent regulation of DNA repair. Interestingly, EGFR-mutant cells treated with the PARP inhibitor olaparib also displayed decreased FAN1 foci induction, coupled with a putative block in a late HRR step. As a result, EGFR-mutant lung cancer cells exhibited olaparib sensitivity in vitro and in vivo. Our findings provide insight into the mechanisms of cisplatin and PARP inhibitor sensitivity of EGFR-mutant cells, yielding potential therapeutic opportunities for further treatment individualization in this genetically defined subset of lung cancer.
在肿瘤携带有表皮生长因子受体（EGFR）激活突变的肺癌患者中，与野生型癌症相比，铂类化疗药物的反应增加。然而，这种关联的机制仍然难以捉摸。在这里，我们描述了 EGFR 突变型肺癌细胞系中存在交联剂敏感性的细胞表型，这与在范可尼贫血途径受损的细胞中观察到的缺陷相似，包括明显的 G2-M 细胞周期阻滞和染色体放射状形成。我们在 FANCD2 下游鉴定了 FAN1 核酸内切酶和 DNA 链间交联（ICL）解钩的募集缺陷。EGFR 突变的作用与 FANCD2 是上位的。与 FANCD2 促进 RAD51 焦点形成和同源重组修复（HRR）的已知作用一致，EGFR 突变细胞对 ICL 的 RAD51 焦点反应也受损，但对 DNA 双链断裂无影响。EGFR 激酶抑制对 EGFR 突变和野生型细胞中的 RAD51 焦点形成均无影响。相比之下，EGFR 突变细胞中 EGFR 激酶的抑制或野生型细胞中突变 EGFR 的过表达均抑制了 RAD51 焦点的形成，这表明 DNA 修复存在 EGFR 激酶独立调控。有趣的是，用 PARP 抑制剂奥拉帕利处理的 EGFR 突变细胞也显示出 FAN1 焦点诱导减少，同时可能存在 HRR 后期步骤的阻断。结果，EGFR 突变型肺癌细胞在体外和体内均表现出奥拉帕利敏感性。我们的发现为 EGFR 突变细胞对顺铂和 PARP 抑制剂敏感性的机制提供了深入了解，为这一遗传定义的肺癌亚组的进一步个体化治疗提供了潜在的治疗机会。
