The prognosis of hepatocellular carcinoma (HCC) is closely linked to the occurrence of recurrent, metastatic disease. Metastasis has been proposed to be initiated by circulating tumor cells (CTCs); however, the transcriptomic plasticity and adaptive mechanisms of CTCs in systemic circulation are not well defined. Here, we established single-cell RNA-sequencing profiles of 113 CTCs isolated from four key vascular sites along the dissemination route in ten HCC patients. In our study, we found that single CTCs displayed profound spatial transcriptional heterogeneity within the circulatory system, which is associated with increased transcriptional activity, cell cycle progression, and chemokine-induced immune escape programs. In particular, CTCs dynamically drove chemokine (C-C motif) ligand 5 (CCL5) expression over the course of circulation. We demonstrated that increased CCL5 expression in turn recruited regulatory T cells to facilitate immune evasion and metastatic progression, as rigorously validated by our in vitro and in vivo models. Finally, we identified an inherently dormant CTC subset with an epithelial-mesenchymal transition and immune-evasive phenotype, and demonstrated its potential prognostic implications. Collectively, our results reveal the previously unappreciated spatial heterogeneity of CTCs, and define its role in diverse regulatory programs and cellular states. Our study offers new insight into metastatic mechanisms, highlighting the potential utility of anti-CTC therapeutic strategies.

Citation Format: Liang Wu, Miaomiao Jiang, Yunfan Sun, Xinrong Yang, Yong Hou, Jia Fan, Shiping Liu. Dissecting the spatial heterogeneity of circulating tumor cells reveals CCL5-Treg-mediated immune evasion in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4601.