Lymphatic system is the mainstream for breast cancer dissemination and metastasis revealed by single-cell lineage tracing

Abstract Cancer metastasis is the primary cause of cancer-related death, yet the forces that drive cancer cells through various steps and different routes to distinct target organs/tissues remain elusive. In this study, we applied a CellTag system-based single-cell lineage tracing approach to show the metastasis rate and route of breast cancer cells and their interactions with the tumour microenvironment (TME) during metastasis. The results indicate that only a small fraction of cells can intravasate from the primary site into the blood circulation, whereas more cells disseminate through the lymphatic system to different organs. Tumour cells derived from the same progenitor cell exhibit different gene expression patterns in different soils, and the cancer cell-TME communication paradigm varies significantly between primary and metastatic tumours. Furthermore, metastable cells require a prewired IL-2 expression ability to migrate in vivo. In summary, leveraging a single-cell lineage tracing system, we demonstrate that the crosstalk between tumour cells and the TME is the driving force controlling the preferential metastatic fate of cancer cells through the lymphatic system and that this metastasis can be suppressed by knockdown of IL-2.