Vaccine, Immunity and Cancer Directorate, Frederick National Laboratory for Cancer Research, Frederick, MD, USA.
Division of Cancer Prevention, National Cancer Institute, Bethesda, MD, USA.
J Natl Cancer Inst. 2024 Jun 7;116(6):957-965. doi: 10.1093/jnci/djae060.
Lynch syndrome is a hereditary cancer predisposition syndrome caused by germline mutations in DNA mismatch repair genes, which lead to high microsatellite instability and frameshift mutations at coding mononucleotide repeats in the genome. Recurrent frameshift mutations in these regions are thought to play a central role in the increased risk of various cancers, but no biomarkers are currently available for the surveillance of high microsatellite instability-associated cancers.
A frameshift mutation-based biomarker panel was developed and validated by targeted next-generation sequencing of supernatant DNA from cultured high microsatellite instability colorectal cancer cells. This panel supported selection of 122 frameshift mutation targets as potential biomarkers. This biomarker panel was then tested using matched tumor, adjacent normal tissue, and buffy coat samples (53 samples) and blood-derived cell-free DNA (cfDNA) (38 samples) obtained from 45 high microsatellite instability and mismatch repair-deficient patients. We also sequenced cfDNA from 84 healthy participants to assess background noise.
Recurrent frameshift mutations at coding mononucleotide repeats were detectable not only in tumors but also in cfDNA from high microsatellite instability and mismatch repair-deficient patients, including a Lynch syndrome carrier, with a varying range of target detection (up to 85.2%), whereas they were virtually undetectable in healthy participants. Receiver operating characteristic curve analysis showed high sensitivity and specificity (area under the curve = 0.94) of the investigated panel.
We demonstrated that frameshift mutations can be detected in cfDNA from high microsatellite instability and mismatch repair-deficient patients and asymptomatic carriers. The 122-target frameshift mutation panel described here has promise as a tool for improved surveillance of high microsatellite instability and mismatch repair-deficient patients, with the potential to reduce the frequency of invasive screening methods for this high-cancer-risk cohort.
林奇综合征是一种遗传性癌症易感性综合征，由 DNA 错配修复基因的种系突变引起，导致基因组中编码单核苷酸重复的微卫星高度不稳定和移码突变。这些区域的反复移码突变被认为在增加各种癌症的风险中起核心作用，但目前尚无用于监测高微卫星不稳定性相关癌症的生物标志物。
通过对培养的高微卫星不稳定性结直肠癌细胞上清液 DNA 进行靶向下一代测序，开发并验证了基于移码突变的生物标志物面板。该面板支持选择 122 个移码突变靶标作为潜在的生物标志物。然后，使用来自 45 名高微卫星不稳定性和错配修复缺陷患者的匹配肿瘤、相邻正常组织和白细胞层样本（53 个样本）以及血液衍生的无细胞 DNA（cfDNA）（38 个样本）测试了该生物标志物面板。我们还对 84 名健康参与者的 cfDNA 进行了测序，以评估背景噪声。
不仅在肿瘤中，而且在高微卫星不稳定性和错配修复缺陷患者的 cfDNA 中也可检测到编码单核苷酸重复的反复移码突变，其靶标检测范围各不相同（高达 85.2%），而在健康参与者中几乎无法检测到。受试者工作特征曲线分析显示，所研究的面板具有较高的灵敏度和特异性（曲线下面积=0.94）。
我们证明了 cfDNA 中可以检测到高微卫星不稳定性和错配修复缺陷患者和无症状携带者的移码突变。这里描述的 122 个靶标移码突变面板有望成为改善高微卫星不稳定性和错配修复缺陷患者监测的工具，有可能减少对这一高癌症风险队列进行侵入性筛查方法的频率。
