[08]Do We Know What Causes Metastatic Cancer?
Step 3 is the growth of the more malignant cells that tend to spread. Normal
cells that form organs such as the lungs and liver are held in place by a
substance called extracellular matrix, or ECM. This is like the mortar holding
bricks together to form the walls of buildings. For cancers to spread, their
cells must break loose from the ECM. Cancer cells may do this by producing
enzymes that break down the ECM. However, breaking loose from a tumor is only
the first of many steps a cancer cell must take before it can spread. Cancer
cells also undergo changes that enable them to break through the walls of blood
vessels or lymphatic vessels and get into other tissues.
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