Collection of a blood sample defined by the term “blood liquid biopsy” is commonly used to detect diagnostic, prognostic, and therapeutic decision‐making markers of metastatic tumors including circulating tumor cells (CTCs). Many tumors also release CTCs and other markers into lymph fluid, but the utility of lymphatic markers largely remains unexplored. Here, we introduce lymph liquid biopsy through collection of peripheral (afferent) and central (thoracic duct [TD]) lymph samples and demonstrates its feasibility for detection of stem‐like CTCs potentially responsible for metastasis development and tumor relapse. Stemness of lymphatic CTCs (L‐CTCs) was determined by spheroid‐forming assay in vitro. Simultaneously, we tested blood CTCs by conventional blood liquid biopsy, and monitored the primary tumor size, early metastasis in a sentinel lymph node (SLN) and distant metastasis in lungs. Using a mouse model at early melanoma stage with no distant metastasis, we identified stem‐like L‐CTCs in lymph samples from afferent lymphatic vessels. Since these vessels transport cells from the primary tumor to SLN, our finding emphasizes the significance of the lymphatic pathway in development of SLN metastasis. Surprisingly, in pre‐metastatic disease, stem‐like L‐CTCs were detected in lymph samples from the TD, which directly empties lymph into blood circulation. This suggests a new contribution of the lymphatic system to initiation of distant metastasis. Integration of lymph and blood liquid biopsies demonstrated that all mice with early melanoma had stem‐like CTCs in at least one of three samples (afferent lymph, TD lymph, and blood). At the stage of distant metastasis, spheroid‐forming L‐CTCs were detected in TD lymph, but not in afferent lymph. Altogether, our results demonstrated that lymph liquid biopsy and testing L‐CTCs holds promise for diagnosis and prognosis of early metastasis. © 2020 International Society for Advancement of Cytometry

中文翻译：

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用于检测癌症干细胞的淋巴液活检

采集由术语“血液活检”定义的血液样本通常用于检测转移性肿瘤（包括循环肿瘤细胞 (CTC)）的诊断、预后和治疗决策标志物。许多肿瘤也会将 CTC 和其他标志物释放到淋巴液中，但淋巴标志物的效用在很大程度上仍未得到探索。在这里，我们通过收集外周（​​传入）和中央（胸导管 [TD]）淋巴样本来介绍淋巴液活检，并证明其检测可能导致转移发展和肿瘤复发的干细胞样 CTC 的可行性。淋巴 CTCs (L-CTCs) 的干度是通过体外球体形成试验确定的。同时，我们通过常规血液活检检测血液 CTC，并监测原发肿瘤大小，前哨淋巴结（SLN）的早期转移和肺的远处转移。使用没有远处转移的早期黑色素瘤阶段的小鼠模型，我们在来自传入淋巴管的淋巴样本中鉴定了干细胞样 L-CTC。由于这些血管将细胞从原发性肿瘤转运到 SLN，我们的发现强调了淋巴通路在 SLN 转移发展中的重要性。令人惊讶的是，在转移前疾病中，在来自 TD 的淋巴样本中检测到了干细胞样 L-CTC，它直接将淋巴排空到血液循环中。这表明淋巴系统对远处转移的开始有新的贡献。淋巴和血液活检的整合表明，所有患有早期黑色素瘤的小鼠在三个样本（传入淋巴、TD 淋巴和血液）中至少有一个具有干细胞样 CTC。在远处转移阶段，在 TD 淋巴液中检测到形成球体的 L-CTC，但在传入淋巴液中未检测到。总之，我们的结果表明，淋巴液活检和检测 L-CTC 对早期转移的诊断和预后有希望。© 2020 国际细胞术进步协会