Yang Meng, Topaloglu Umit, Petty W Jeffrey, Pagni Matthew, Foley Kristie L, Grant Stefan C, Robinson Mac, Bitting Rhonda L, Thomas Alexandra, Alistar Angela T, Desnoyers Rodwige J, Goodman Michael, Albright Carol, Porosnicu Mercedes, Vatca Mihaela, Qasem Shadi A, DeYoung Barry, Kytola Ville, Nykter Matti, Chen Kexin, Levine Edward A, Staren Edgar D, D'Agostino Ralph B, Petro Robin M, Blackstock William, Powell Bayard L, Abraham Edward, Pasche Boris, Zhang Wei
Wake Forest Baptist Comprehensive Cancer Center, Wake Forest Baptist Medical Center, Medical Center Blvd., Winston-Salem, NC, 27157, USA.
Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, NC, 27157, USA.
J Hematol Oncol. 2017 May 4;10(1):100. doi: 10.1186/s13045-017-0468-1.
Solid tumors residing in tissues and organs leave footprints in circulation through circulating tumor cells (CTCs) and circulating tumor DNAs (ctDNA). Characterization of the ctDNA portraits and comparison with tumor DNA mutational portraits may reveal clinically actionable information on solid tumors that is traditionally achieved through more invasive approaches.
We isolated ctDNAs from plasma of patients of 103 lung cancer and 74 other solid tumors of different tissue origins. Deep sequencing using the Guardant360 test was performed to identify mutations in 73 clinically actionable genes, and the results were associated with clinical characteristics of the patient. The mutation profiles of 37 lung cancer cases with paired ctDNA and tumor genomic DNA sequencing were used to evaluate clonal representation of tumor in circulation. Five lung cancer cases with longitudinal ctDNA sampling were monitored for cancer progression or response to treatments.
Mutations in TP53, EGFR, and KRAS genes are most prevalent in our cohort. Mutation rates of ctDNA are similar in early (I and II) and late stage (III and IV) cancers. Mutation in DNA repair genes BRCA1, BRCA2, and ATM are found in 18.1% (32/177) of cases. Patients with higher mutation rates had significantly higher mortality rates. Lung cancer of never smokers exhibited significantly higher ctDNA mutation rates as well as higher EGFR and ERBB2 mutations than ever smokers. Comparative analysis of ctDNA and tumor DNA mutation data from the same patients showed that key driver mutations could be detected in plasma even when they were present at a minor clonal population in the tumor. Mutations of key genes found in the tumor tissue could remain in circulation even after frontline radiotherapy and chemotherapy suggesting these mutations represented resistance mechanisms. Longitudinal sampling of five lung cancer cases showed distinct changes in ctDNA mutation portraits that are consistent with cancer progression or response to EGFR drug treatment.
This study demonstrates that ctDNA mutation rates in the key tumor-associated genes are clinical parameters relevant to smoking status and mortality. Mutations in ctDNA may serve as an early detection tool for cancer. This study quantitatively confirms the hypothesis that ctDNAs in circulation is the result of dissemination of aggressive tumor clones and survival of resistant clones. This study supports the use of ctDNA profiling as a less-invasive approach to monitor cancer progression and selection of appropriate drugs during cancer evolution.
存在于组织和器官中的实体瘤通过循环肿瘤细胞（CTC）和循环肿瘤DNA（ctDNA）在血液循环中留下痕迹。对ctDNA图谱进行表征并与肿瘤DNA突变图谱进行比较，可能会揭示实体瘤的临床可操作信息，而这些信息传统上是通过更具侵入性的方法获得的。
我们从103例肺癌患者和74例其他不同组织来源的实体瘤患者的血浆中分离出ctDNA。使用Guardant360检测进行深度测序，以鉴定73个临床可操作基因中的突变，并将结果与患者的临床特征相关联。利用37例配对ctDNA和肿瘤基因组DNA测序的肺癌病例的突变谱，评估肿瘤在循环中的克隆代表性。对5例进行纵向ctDNA采样的肺癌病例进行癌症进展或治疗反应监测。
TP53、EGFR和KRAS基因的突变在我们的队列中最为常见。ctDNA的突变率在早期（I期和II期）和晚期（III期和IV期）癌症中相似。在18.1%（32/177）的病例中发现了DNA修复基因BRCA1、BRCA2和ATM的突变。突变率较高的患者死亡率显著更高。从不吸烟者的肺癌显示出比曾经吸烟者显著更高的ctDNA突变率以及更高的EGFR和ERBB2突变。对同一患者的ctDNA和肿瘤DNA突变数据进行比较分析表明，即使关键驱动突变在肿瘤中以较小的克隆群体存在，也能在血浆中检测到。在肿瘤组织中发现的关键基因的突变即使在一线放疗和化疗后仍可留在循环中，这表明这些突变代表了耐药机制。对5例肺癌病例的纵向采样显示，ctDNA突变图谱存在明显变化，这与癌症进展或对EGFR药物治疗的反应一致。
本研究表明，关键肿瘤相关基因中的ctDNA突变率是与吸烟状态和死亡率相关的临床参数。ctDNA中的突变可能作为癌症的早期检测工具。本研究定量证实了循环中的ctDNA是侵袭性肿瘤克隆播散和耐药克隆存活的结果这一假设。本研究支持将ctDNA分析作为一种侵入性较小的方法，用于监测癌症进展以及在癌症演变过程中选择合适的药物。
