Metastasis involves several key mechanisms: 1. Intravasation: Cancer cells enter the bloodstream or lymphatic vessels. This involves breaking through the vessel walls, often facilitated by the degradation of basement membrane components. 2. Survival in Circulation: Cancer cells must survive the hostile environment of the bloodstream, where they face immune attacks and hemodynamic forces. 3. Extravasation: Cancer cells exit the bloodstream at distant sites by adhering to the vascular endothelium and migrating through the vessel walls. 4. Colonization: Once at a new site, cancer cells must adapt to the local microenvironment to establish new tumors. This involves interactions with stromal cells and the formation of a supportive niche.
