Division of Hematology-Oncology, University of California San Diego, La Jolla, 1200 Garden View Road, Encinitas, CA, 92024, USA.
Medical College of Wisconsin Cancer Center, Milwaukee, WI, USA.
J Hematol Oncol. 2022 Sep 12;15(1):131. doi: 10.1186/s13045-022-01351-y.
Liquid biopsies are increasingly used for cancer molecular profiling that enables a precision oncology approach. Circulating extracellular nucleic acids (cell-free DNA; cfDNA), circulating tumor DNA (ctDNA), and circulating tumor cells (CTCs) can be isolated from the blood and other body fluids. This review will focus on current technologies and clinical applications for liquid biopsies. ctDNA/cfDNA has been isolated and analyzed using many techniques, e.g., droplet digital polymerase chain reaction, beads, emulsion, amplification, and magnetics (BEAMing), tagged-amplicon deep sequencing (TAm-Seq), cancer personalized profiling by deep sequencing (CAPP-Seq), whole genome bisulfite sequencing (WGBS-Seq), whole exome sequencing (WES), and whole genome sequencing (WGS). CTCs have been isolated using biomarker-based cell capture, and positive or negative enrichment based on biophysical and other properties. ctDNA/cfDNA and CTCs are being exploited in a variety of clinical applications: differentiating unique immune checkpoint blockade response patterns using serial samples; predicting immune checkpoint blockade response based on baseline liquid biopsy characteristics; predicting response and resistance to targeted therapy and chemotherapy as well as immunotherapy, including CAR-T cells, based on serial sampling; assessing shed DNA from multiple metastatic sites; assessing potentially actionable alterations; analyzing prognosis and tumor burden, including after surgery; interrogating difficult-to biopsy tumors; and detecting cancer at early stages. The latter can be limited by the small amounts of tumor-derived components shed into the circulation; furthermore, cfDNA assessment in all cancers can be confounded by clonal hematopoeisis of indeterminate potential, especially in the elderly. CTCs can be technically more difficult to isolate that cfDNA, but permit functional assays, as well as evaluation of CTC-derived DNA, RNA and proteins, including single-cell analysis. Blood biopsies are less invasive than tissue biopsies and hence amenable to serial collection, which can provide critical molecular information in real time. In conclusion, liquid biopsy is a powerful tool, and remarkable advances in this technology have impacted multiple aspects of precision oncology, from early diagnosis to management of refractory metastatic disease. Future research may focus on fluids beyond blood, such as ascites, effusions, urine, and cerebrospinal fluid, as well as methylation patterns and elements such as exosomes.
液体活检越来越多地用于癌症分子谱分析，从而实现精准肿瘤学方法。可以从血液和其他体液中分离出循环细胞外核酸（游离 DNA；cfDNA）、循环肿瘤 DNA（ctDNA）和循环肿瘤细胞（CTC）。本综述将重点介绍液体活检的当前技术和临床应用。已经使用多种技术分离和分析了 ctDNA/cfDNA，例如液滴数字聚合酶链反应、珠子、乳液、扩增和磁珠（BEAMing）、标记扩增子深度测序（TAm-Seq）、通过深度测序进行癌症个体化特征分析（CAPP-Seq）、全基因组亚硫酸氢盐测序（WGBS-Seq）、全外显子组测序（WES）和全基因组测序（WGS）。CTC 是通过基于生物标志物的细胞捕获，以及基于生物物理和其他特性的阳性或阴性富集来分离的。ctDNA/cfDNA 和 CTC 正在各种临床应用中得到利用：使用连续样本区分独特的免疫检查点阻断反应模式；基于基线液体活检特征预测免疫检查点阻断反应；基于连续采样预测靶向治疗和化疗以及免疫治疗（包括 CAR-T 细胞）的反应和耐药性；评估来自多个转移部位的脱落 DNA；评估潜在的可操作改变；分析预后和肿瘤负担，包括手术后；探索难以活检的肿瘤；以及在早期阶段检测癌症。后者可能受到进入循环系统的肿瘤衍生成分数量较少的限制；此外，所有癌症的 cfDNA 评估都可能受到不确定潜能的克隆造血的干扰，尤其是在老年人中。CTC 比 cfDNA 更难分离，但允许进行功能测定，以及评估 CTC 衍生的 DNA、RNA 和蛋白质，包括单细胞分析。血液活检比组织活检侵入性更小，因此适合进行连续采集，可以实时提供关键的分子信息。总之，液体活检是一种强大的工具，该技术的显著进步已经影响了精准肿瘤学的多个方面，从早期诊断到难治性转移性疾病的管理。未来的研究可能集中在血液以外的液体上，如腹水、渗出液、尿液和脑脊液，以及甲基化模式和外泌体等元素。
