September 17, 2008, Cambridge, UK – Knee scrapes and tumor growth might have more in common than you think. The idea that tumor growth triggers the same immune response as a cut or wound was once a highly controversial notion. However, increasing evidence supports the idea that the same cellular mechanisms which heal a skinned knee might also have a role in preventing the growth of tumors. A report published today in Disease Models & Mechanisms (DMM), dmm.biologists.org, now reveals more details about the common links between tumor growth and tissue damage in flies. Tian Xu and colleagues at the Yale University School of Medicine examined the activity of hemocytes, a type of immune cell, in response to genetically-induced tumor growth in the fruit fly Drosophila. They found that tumors caused circulating hemocytes to replicate and adhere to the tumor surface, thereby limiting tumor growth. They compared this hemocyte response to cell activity in normal flies which were wounded and had tissue damage. Hemocyte profileration in these flies occurred just as in the tumor-producing fly. Furthermore, by examining the molecular signals triggered in the immune response, Xu's team discovered that the tumor's physical disruption and damage of nearby tissues at least in part triggered the hemocyte response. This study not only supports previously reported links between immune responses and cancer, but also identifies key pathways in the fly's immune response to tumor growth and tissue disruption. These pathways are likewise shared in humans, demonstrating that the fly can be used to study potential drug targets which could enhance the body's natural immune response against cancer.