Hallmarks of Cancer 6: Tissue Invasion and Metastasis

Sharing another insightful and excellent post from Dr. Buddhini Samarasinghe’s series of guest blog posts on Scientific American. Please give it a read. Here’s a tidbit.

The Hallmarks of Cancer are 10 underlying principles shared by all cancers. You can read the first five Hallmarks of Cancer articles here. The Sixth Hallmark of Cancer is defined as “Tissue Invasion and Metastasis.”

A growing tumor will eventually spawn pioneer cells; these move out of the original clump of mutant cells to invade adjacent tissues and then travel to distant sites where they form new colonies. These distant settlements of cancer cells are named metastases and, with the exception of leukemias and some brain tumors, cause the majority of cancer deaths. Metastasis is bad news, with significantly reduced survival rates and prognosis for patients. The ability to metastasize allows cancer cells to find new areas of the body where space and nutrients are not limiting. How do cancer cells do this?

The Extra Cellular Matrix

In biology, a tissue is an aggregation of cells that performs a specific function. Tissues combine to form organs; organs combine to form a body. Our tissues are composed primarily of two types of cells; epithelial and mesenchymal cells. Epithelial cells adhere to one another to form cell layers, which act as barriers to protect our bodies and organs from the environment. In contrast, mesenchymal cells are solitary and capable of migrating. Our tissues are not made up solely of cells. A large proportion of tissue consists of extracellular space, which is filled with a mixture of carbohydrate and protein molecules; this space is known as the Extracellular Matrix (ECM). The molecules that make up the ECM are secreted by cells embedded in it, and these cells tether themselves to the ECM (and to one another) to form tissues. Metastasis therefore requires the untethering of these bonds, to allow predacious cancer cells to migrate freely.

The complete post is available here.

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