The Tumor Microenvironment

In recent years, the cancer research community has become increasingly aware of the critical role of the tumor microenvironment in promoting cancer progression.  The microenvironment consists of the cells and factors surrounding a tumor, and these components can promote tumor cell growth. 

1. Cancer cell: Cancer cells are like rogue agents, once a cooperative part of the body but now working for themselves. The tumors are not just passive recipients of beneficial information, they secrete their own factors to modulate their environment and influence the activity of their surrounding cells.

2. Angiogenesis: Tumors can promote the formation of new blood vessels, which then deliver nutrients to the growing tumor.

3. Stroma: Influenced by the tumor-secreted factors and unaware that the cancer is no longer cooperative, these surrounding cells secrete growth factors to help it.

4. Immune cells: Similarly, immune cells secrete cytokines, proteins that help create an inflammatory and potentially growth-promoting environment.

5. Immune system: The immune system usually recognizes signals from foreign invaders and eliminates them to protect the body.  However, because the tumor is derived from the body’s own cells, the immune system can be fooled into protecting it from elimination. 

Read more: Douglas Hanahan and Lisa Coussens. Accessories to the Crime: Functions of cells recruited to the tumor microenvironment, Cancer Cell, March 20, 2012.