As an alternative target to surgically resected tissue specimens, liquid biopsy has gained much attention over the past decade. Of the various circulating biomarkers, circulating tumor cells (CTCs) have particularly opened new windows into the metastatic cascade, with their functional, biochemical, and biophysical properties. Given the extreme rarity of intact CTCs and the associated technical challenges, however, analyses have been limited to bulk-cell strategies, missing out on clinically significant sources of information from cellular heterogeneity. With recent technological developments, it is now possible to probe genetic material of CTCs at the single-cell resolution to study spatial and temporal dynamics in circulation. Here, we discuss recent transcriptomic profiling efforts that enabled single-cell characterization of patient-derived CTCs spanning diverse cancer types. We further highlight how expression data of these putative biomarkers have advanced our understanding of metastatic spectrum and provided a basis for the development of CTC-based liquid biopsies to track, monitor, and predict the efficacy of therapy and any emergent resistance.

作为手术切除的组织标本的替代目标，在过去的十年中，液体活检受到了广泛的关注。在各种循环生物标志物中，循环肿瘤细胞（CTC）凭借其功能，生化和生物物理特性，特别为转移级联打开了新窗口。鉴于完整的四氯化碳极为稀少，并且伴随着相关的技术挑战，因此，分析仅限于大细胞策略，而缺少细胞异质性在临床上具有重要意义的信息资源。随着最新技术的发展，现在有可能以单细胞分辨率探测CTC的遗传物质，以研究循环中的时空动态。这里，我们讨论了最近的转录组谱分析工作，这些工作使得能够对跨越多种癌症类型的患者来源的四氯化碳进行单细胞表征。我们进一步强调这些表达数据如何推定的生物标志物已加深了我们对转移谱的理解，并为开发基于CTC的液体活检样品以追踪，监测和预测治疗效果及任何新出现的耐药性提供了基础。