Data_Sheet_1_Identification of Germline Mismatch Repair Gene Mutations in Lung Cancer Patients With Paired Tumor-Normal Next Generation Sequencing: A Retrospective Study.docx

Background: Paired tumor-normal targeted next-generation sequencing (NGS) is primarily used to identify actionable somatic mutations, but can also detect germline variants including pathogenic germline mutations in DNA mismatch repair (MMR) genes that underlie Lynch syndrome. In the present study we examined paired NGS data from lung cancer patients to identify germline mutations in MMR genes. As lung cancer is not one of the recognized Lynch syndrome-associated neoplasms, we also investigated whether these lung cancer cases are due to Lynch syndrome or are instead sporadic cancers occurring in Lynch syndrome patients.
Methods: A retrospective study of 1,179 lung cancer patients with available paired NGS data was performed to identify germline mutations in the MMR genes MLH1, MSH2, MSH6, and PMS2, and evaluate tumor mutation burden (TMB). Microsatellite instability (MSI) testing was done on select cases with MMR gene mutations by either NGS or PCR/capillary electrophoresis approach. Immunohistochemistry (IHC) for MMR proteins was performed in select patients.
Results: Pathogenic or likely-pathogenic germline mutations in PMS2, MSH2, or MSH6 were detected in 0.5% (6/1,179) of lung cancer patients; three of the patients had a family history of colon or gastric cancer. The median age at diagnosis of these cases was 68.5 years old. None of these six patients exhibited MSI or loss of MMR protein expression. Among them, no second hit somatic mutations in MMR genes (including single-nucleotide variants, small insertions or deletions and copy number alterations) were detected, and the median TMB was 4.5 muts/MB. Subsequent genetic testing of family members identified new Lynch syndrome cases in two first-degree relatives.
Conclusion: These data imply that lung cancers in Lynch syndrome patients are unrelated to the underlying Lynch syndrome diagnosis and occur spontaneously. Nonetheless, paired tumor-normal NGS can identify germline mutations to help reveal Lynch syndrome in cancer patients. This has important implications for cancer screening and risk reduction in these patients and their families.

【背景】配对肿瘤-正常组织靶向二代测序（NGS）主要用于识别可操作的体细胞突变，同时也可检测种系变异，包括作为林奇综合征（Lynch syndrome）发病基础的DNA错配修复（MMR）基因致病性种系突变。本研究针对肺癌患者的配对NGS数据展开分析，以鉴定MMR基因的种系突变。由于肺癌并非公认的林奇综合征相关肿瘤，我们同时探究此类肺癌究竟由林奇综合征驱动，还是林奇综合征患者所患的散发性肿瘤。
【方法】本研究为回顾性研究，纳入1179例具备配对NGS数据的肺癌患者，旨在鉴定MMR基因MLH1、MSH2、MSH6及PMS2的种系突变，并评估肿瘤突变负荷（TMB）。针对携带MMR基因突变的入选病例，分别采用NGS或聚合酶链反应（PCR）/毛细管电泳法开展微卫星不稳定性（MSI）检测；对部分患者进行MMR蛋白免疫组织化学（IHC）检测。
【结果】在1179例肺癌患者中，共检出0.5%（6/1179）的患者存在PMS2、MSH2或MSH6的致病性或可能致病性种系突变；其中3例患者具备结直肠癌或胃癌家族史，此类病例的诊断中位年龄为68.5岁。6例患者均未表现出MSI或MMR蛋白表达缺失，且未检出MMR基因的二次打击体细胞突变（包括单核苷酸变异、小插入缺失及拷贝数变异），其TMB中位值为4.5突变/MB。对家属的后续基因检测显示，2例一级亲属被确诊为新发林奇综合征病例。
【结论】本研究数据提示，林奇综合征患者所患肺癌与基础的林奇综合征诊断无关，属于自发发生的肿瘤。尽管如此，配对肿瘤-正常组织NGS仍可通过鉴定种系突变，辅助癌症患者的林奇综合征筛查。这一发现对此类患者及其家属的癌症筛查与风险降低具有重要意义。