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Fig. 3 | Molecular Cancer

Fig. 3

From: Circulating tumor cells in cancer patients: developments and clinical applications for immunotherapy

Fig. 3

The metastatic cascade: The main steps of tumor spread. a. Intravasation: Tumor cells are first released from the primary tumor microenvironment, then traverse the interstitial connective tissue, and ultimately gain access to the circulation by penetrating the vascular basement membrane. b. CTCs escape from immune surveillance in the circulation: CTCs encounter immune cells through direct cell–cell interactions and are subject to immune-mediated elimination. Escape mechanisms involving the expression of CD47, PD-L1 and FASL, as well as alterations in MHC molecules, promote the survival of CTCs in the circulation. c. Extravasation: In the process of extravasating to secondary locations, CTCs can directly interact with immune cells, supporting the formation of metastases

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