循环肿瘤DNA在乳腺癌中的研究进展

乳腺癌在中国的发病率和病死率呈逐渐上升的趋势,因此,对乳腺癌的早期诊断、预测复发以及延长患者的生存期至关重要。活体组织检查作为一种侵入性的操作并非总是可行的,影像学检查和肿瘤标志物检测均无法提供足够的肿瘤特征信息以指导进一步的治疗。因此,近年来,液体活体组织检查已经逐渐取代肿瘤活体组织检查。循环肿瘤DNA(ctDNA)存在于肿瘤患者的血液循环中,在血浆游离的DNA中,ctDNA所占的比例极小,因此,ctDNA的检测成为一项难题。基因测序技术的发展使DNA的定性和定量检测成为可能,对肿瘤患者的ctDNA进行基因分析受到越来越多的关注。ctDNA因其具有侵害性小、简便易行等优点而成为一种新型的循环肿瘤标志物,ctDNA检测也成为了目前最重要的液体活体组织检查手段,在乳腺癌的精准治疗领域具有广阔的应用前景,可用于乳腺癌的早期诊断、监测疗效、探索耐药机制、预测疾病复发和判断预后等诸多方面,可为乳腺癌治疗方法的选择提供有利的依据,为乳腺癌更加精准化的治疗提供契机,从而真正实现乳腺癌患者的个体化治疗。     

肿瘤循环DNA的研究进展

肿瘤分子生物学的研究进展,为分析和最终阐明肿瘤的发生开辟了新的天地,血循环游离DNA的检测及其生物学指标的研究,将有可能为临床肿瘤的早期诊断、预后监测及跟踪随访等提供一系列方便、快捷、特异、无创或微创和分子生物学检测手段。以血循环DNA为研究目标的科学探索,已在世界各地蓬蓬勃勃地开展起来,尤以最近的10年最为突出。     

肿瘤DNA甲基化的临床应用进展

肿瘤表观遗传学是一门新兴学科，主要包括DNA甲基化、组蛋白修饰、染色质重塑、基因组印记和非编码RNA调控等几个方面。其中，DNA甲基化与肿瘤的关系是研究的热点。近年来，肿瘤DNA甲基化的研究逐渐向临床应用方面过渡，已展现出可喜的前景。     

DNA低甲基化及其与肿瘤关系的研究进展

DNA甲基化是DNA的一种表观遗传学修饰方式,是基因表达调控的一种重要机制,现已用于研究非遗传毒物的致癌机制。在人类肿瘤中存在的DNA甲基化异常既包括局部的DNA甲基化水平降低或升高,也包括全基因组的DNA甲基化水平降低,而基因组DNA甲基化水平降低是较早被发现的DNA甲基化改变形式之一。本文简要综述DNA低甲基化及其与肿瘤关系的研究进展。     

DNA甲基化在肿瘤无创性分子诊断中的研究进展

DNA甲基化是真核细胞基因组最常见的一种表观遗传学修饰.DNA甲基化异常在肿瘤的发生、发展过程中扮演重要角色.研究显示DNA甲基化是一类潜力很大的肿瘤标志物.肿瘤特异性的DNA甲基化标志物可从肿瘤患者血清/血浆、尿液、粪便和支气管肺泡灌洗液中检出,为进行肿瘤无创性诊断DNA甲基化检测提供了新思路.本文对DNA甲基化在恶性肿瘤早期诊断的研究进展作一综述.     

循环肿瘤DNA在结直肠癌临床诊疗中的应用及价值

循环肿瘤DNA(circulating tumor DNA,ctDNA)是由实体肿瘤细胞释放到循环系统中的基因组小片段,来源于机体内所有肿瘤部位,其携带的基因组信息与肿瘤组织具有良好的一致性,能克服常规肿瘤组织活检所无法突破的肿瘤异质性问题.通过外周血ctDNA检测可以进行肿瘤相关基因的遗传学和表观遗传学研究,如基因突变、异常扩增、杂合性缺失等,还可以进行定量,追踪机体内特异性基因的状态变化.ctDNA检测是一种新兴技术,相对于传统的肿瘤组织活检具有简单、易行、高重复性等优点,更易被患者接受.目前主要的技术及平台包括PCR技术和二代测序法,两者各有所长,根据不同时期不同需求可以进行调整.ctDNA检测在结直肠癌的早期诊断、疗效评估、动态监测、耐药评估以及个体化精准治疗中具有深远意义及临床价值.     

肿瘤循环DNA的临床研究

随着生物技术的迅猛发展,当今肿瘤临床的早期诊断、鉴别诊断、疗效观察及预后监测越来越受益于分子标志物的发现及其检测方法学的完善[1].鉴于手术切除肿瘤标本的分子生物学检测存在一定的局限性(如标本来源的限制、无法连续检测及随访追踪等),肿瘤患者外周血循环DNA分子生物学检测现正以其日益明显的优点逐渐被人们所重视.     

循环肿瘤DNA甲基化在卵巢癌中的研究进展

卵巢癌是最致命的妇科恶性肿瘤,对卵巢癌的早期诊断、治疗监测和预后判断尤为重要。越来越多的证据表明DNA甲基化在致癌过程中发挥重要的作用。肿瘤中发现的基因启动子异常甲基化,可以反映在从肿瘤释放到外周血的循环肿瘤DNA（circulating tumor DNA,ctDNA）,与原发肿瘤有一致性改变,从而使ctDNA甲基化成为基于血液检测的非侵入性分子标志物。本文将介绍ctDNA甲基化及其检测方法,卵巢癌中常见的ctDNA甲基化标志物,并重点阐述ctDNA甲基化在卵巢癌中的研究进展。     

非小细胞肺癌患者循环肿瘤DNA的研究进展

摘 要：循环游离DNA以细胞外游离形式存在于血液中,可由正常细胞和癌细胞释放。非小细胞肺癌（NSCLC）患者血液中游离DNA水平高于正常人,且循环游离DNA可以反映癌组织的基因突变,甲基化状态,拷贝数改变,杂合子丢失等特征,是肺癌诊断、治疗、预后检测中具有巨大潜力的生物学指标。本综述简要介绍了循环游离DNA的生物学特性,并对近年来循环游离DNA基因改变检测在NSCLC中的临床应用进行阐述。     

Recent advances in circulating tumor cells and cell-free DNA in metastatic prostate cancer: a review

Introduction: The treatment landscape of metastatic prostate cancer has changed dramatically over the past five years. As new discoveries are made and further novel therapies become available, there is a heightened urgency to develop biomarkers that can guide prognoses and predict therapy responses. Circulating tumor cells (CTCs) and cell-free circulating tumor DNA (ctDNA) in the blood have emerged as potential promising tumor avatars.

Areas covered: In this review, we describe technological breakthroughs and clinical implementation of the CTCs and ctDNA. We also discuss the key challenges that must be overcome before circulating blood-based biomarkers can be universally adopted into the management of patients with metastatic prostate cancer.

Expert commentary: Both CTCs and ctDNA have the potential to be incorporated into routine patient care, with increasing numbers of prospective trials incorporating them into clinical designs. CTCs and ctDNA will thus have an increasingly valuable role in augmenting our understanding of prostate cancer at a molecular level, aiding in prognostication of prostate cancer patients, acting as a surrogate for OS in clinical trials, and helping us prioritize our treatment selections by elucidating resistance mechanisms.     

Genotyping of circulating cell-free DNA enables noninvasive tumor detection in myxoid liposarcomas

Soft tissue sarcomas (STS) are rare tumors of mesenchymal origin. About 50% of patients with STS experience relapse and more than 30% will die within 10 years after diagnosis. In this study we investigated circulating free DNA (cfDNA) and tumor-specific genetic alterations therein (circulating tumor DNA, ctDNA) as diagnostic biomarkers. Plasma concentrations and fragmentation of cfDNA was analyzed with quantitative PCR. Patients with STS (n = 64) had significantly higher plasma concentrations and increased fragmentation of cfDNA when compared to patients in complete remission (n = 19) and healthy controls (n = 41) (p < 0.01 and p < 0.001). Due to overlapping values between patients with STS and controls, the sensitivity and specificity of these assays is limited. Sensitive assays to detect genomic alterations in cfDNA of synovial sarcomas (t(X;18)), myxoid liposarcomas (t(12;16) and TERT C228T promoter mutation) and well-differentiated/de-differentiated liposarcomas (MDM2 amplifications) were established. ctDNA was quantified in nine liposarcoma patients during the course of their treatment. Levels of breakpoint t(12;16) and TERT C228T ctDNA correlated with the clinical course and tumor burden in patients with myxoid liposarcomas (n = 4). ctDNA could detect minimal residual disease and tumor recurrence. In contrast, detection of MDM2 amplifications was not sensitive enough to detect tumors in patients with well-differentiated/de-differentiated liposarcomas (n = 5). Genotyping of cfDNA for tumor specific genetic alterations is a feasible and promising approach for monitoring tumor activity in patients with myxoid liposarcomas. Detection of ctDNA during follow-up examinations despite negative standard imaging studies might warrant more sensitive imaging (e.g. PET-CT) or closer follow-up intervals to timely localize and treat recurrences.     

Human papilloma virus circulating tumor DNA assay predicts treatment response in recurrent/metastatic head and neck squamous cell carcinoma

Despite the rising incidence of human papillomavirus related (HPV+) oropharyngeal squamous cell carcinoma (OPSCC), treatment of metastatic disease remains palliative. Even with new treatments such as immunotherapy, response rates are low and can be delayed, while even mild tumor progression in the face of an ineffective therapy can lead to rapid death. Real-time biomarkers of response to therapy could improve outcomes by guiding early change of therapy in the metastatic setting. Herein, we developed and analytically validated a new droplet digital PCR (ddPCR)-based assay for HPV16 circulating tumor DNA (ctDNA) and evaluated plasma HPV16 ctDNA for predicting treatment response in metastatic HPV+ OPSCC. We found that longitudinal changes HPV16 ctDNA correlate with treatment response and that ctDNA responses are observed earlier than conventional imaging (average 70 days, range: 35–166). With additional validation in multi-site studies, this assay may enable early identification of treatment failure, allowing patients to be directed promptly toward clinical trials or alternative therapies.     

Detection rate and prognostic value of circulating tumor cells and circulating tumor DNA in metastatic uveal melanoma

Circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) have been recently investigated in several cancer types, but their respective clinical significance remains to be determined. In our prospective study, we compared the detection rate and the prognostic value of these two circulating biomarkers in patients with metastatic uveal melanoma. GNAQ/GNA11 mutations were characterized in archived tumor tissue. Using a highly sensitive and mutation‐specific bidirectional pyrophosphorolysis‐activated polymerization (bi‐PAP) technique, GNAQ c.626A>T, GNAQ c.626A>C and GNA11 c.626A>T copy numbers were quantified in plasma from 12 mL of blood. CTCs were detected at the same time in 7.5 mL of blood by the CellSearch® technique. Patient characteristics and outcome were prospectively collected. CTCs (≥1) were detected in 12 of the 40 included patients (30%, range 1–20). Among the 26 patients with known detectable mutations, ctDNA was detected and quantified in 22 (84%, range 4–11,421 copies/mL). CTC count and ctDNA levels were associated with the presence of miliary hepatic metastasis (p = 0.004 and 0.03, respectively), with metastasis volume (p = 0.005 and 0.004) and with each other (p < 0.0001). CTC count and ctDNA levels were both strongly associated with progression‐free survival (p = 0.003 and 0.001) and overall survival (p = 0.0009 and <0.0001). In multivariate analyses, ctDNA appeared to be a better prognostic marker than CTC. In conclusion, ctDNA and CTC are correlated and both have poor prognostic significance. CTC detection can be performed in every patient but, in patients with detectable mutations, ctDNA was more frequently detected than CTC and has possibly more prognostic value.     

Appropriate use of cancer comprehensive genome profiling assay using circulating tumor DNA

Comprehensive genomic profiling (CGP) is being increasingly used for the routine clinical management of solid cancers. In July 2018, the use of tumor tissue-based CGP assays became available for all solid cancers under the universal health insurance system in Japan. Several restrictions presently exist, such as patient eligibility and limitations on the opportunities to perform such assays. The clinical implementation of CGP based on plasma circulating tumor DNA (ctDNA) is also expected to raise issues regarding the selection and use of tissue DNA and ctDNA CGP. A Joint Task Force for the Promotion of Cancer Genome Medicine comprised of three Japanese cancer-related societies has formulated a policy proposal for the appropriate use of plasma CGP (in Japanese), available at https://www.jca.gr.jp/researcher/topics/2021/files/20210120.pdf , http://www.jsco.or.jp/jpn/user_data/upload/File/20210120.pdf , and https://www.jsmo.or.jp/file/dl/newsj/2765.pdf . Based on these recommendations, the working group has summarized the respective advantages and cautions regarding the use of tissue DNA CGP and ctDNA CGP with reference to the advice of a multidisciplinary expert panel, the preferred use of plasma specimens over tissue, and multiple ctDNA testing. These recommendations have been prepared to maximize the benefits of performing CGP assays and might be applicable in other countries and regions.     

Monitor tumor burden with circulating tumor DNA

There is a need to identify better biomarkers to monitor diseases and/or assess therapeutic responses. For those with cancer, one can identify DNA fragments that contain somatic mutations originating in the tumor DNA in plasma or serum. There have been several early studies suggesting that advances in sequencing technologies will allow identification of somatic genomic alterations that can be used to monitor tumor dynamics. Dawson et al. investigated circulating cell-free DNA carrying tumor specific alterations in patients with breast cancer. The authors compared CT imaging from 30 women with metastatic breast cancer receiving treatment, using two assays for circulating tumor DNA, CA 15-3, and CTCs. Taken the two methods together circulating tumor DNA was detected in 29 or 30 women (97%) and 115 of 141 plasma samples (82%). Circulating tumor DNA levels showed a greater dynamic range and greater correlation with changes in tumor burden than did CA 15-3 or CTC. The relatively small study showed that circulating tumor DNA has a superior sensitivity to other circulating biomarkers and a dynamic range that correlates with tumor burden.