When tumor cells acquire the capacity to move around and invade other tissues, there is a risk of metastases and cancer treatment becomes more difficult. The basement membrane around the mammary gland is a barrier to the spread of cancer cells. Three proteins in the tumor cells transport enzymes needed to perforate this barrier, and another protein puts these enzymes in the right place. Tissues are generally formed by cells arranged side by side. Epithelial cells cover an outer surface, such as the skin or an organ such as the mammary gland, and remain tightly bound together. This cohesion is vital to the body’s functioning, and the epithelial cells remain in position in their original tissue until they die. Sometimes, though, they detach and move away, and while such migration is essential during embryonic development as cells give rise to new tissues, when tumor cells break loose this often heralds the formation of metastases. |
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