Fig. 2
From: The functional and clinical roles of liquid biopsy in patient-derived models
Key stages of metastasis relating to CTC generation and colonization. In the primary tumor site, tumor cells undergo EMT triggered by extracellular molecules and tumor microenvironment stimuli such as hypoxia. EMT promotes CTC shedding and intravasation. In circulation, only a small proportion of CTCs can survive shear stress. CTCs can form CTC clusters with each other or with other immune cells or cancer-associated fibroblasts, which enhances their metastatic potential, proliferation ability, stemness, and immune escape. Eventually, tumor cells form a pre-metastatic niche and colonization at a distant site after CTC extravasation. EVs also play an important role in these stages, mediating cell-to-cell communication and shaping the pre-metastatic niche. However, more research is needed to understand the interaction between EVs and CTC. CTC: circulating tumor cells; EMT: epithelial-mesenchymal transition; EVs: extracellular vesicles; HSP: heat shock protein. By Figdraw