Fig. 2. Schematic drawing of the development of Cancer-inducing niche and stem cell alternation.

Against invaders, resident tissue macrophages start the attack while other immune cells infiltrate into the tissue from the blood vessels. These cells secrete cytokines and chemokines killing the invaders and damaging tissues in the microenvironment of inflammation, after which wound healing by activated cell growth occurs. Chronic inflammation results from a continuous immune response that keeps the microenvironment filled with pro-inflammatory mediators and growth factors, which in turn initiate cancer converting stem cells or progenitors into cancer stem cells.