It has been recognized that an established tumor is able to shut down immune rejection cells so they cannot work. A glycoprotein called CD200 appears to be very important in this shut down process. CD200 suppresses NK cells, promotes the generation of regulatory T cells, and is expressed on stem cells. All tissues in the body develop from stem cells. When a genetic change occurs in a stem cell, it may become malignant and give rise to a collection of more developed cells recognized as a cancer, and many of these cells do not express CD200. However, as long as CD200 is present, the stem cell can evade rejection. Chemotherapy is most effective when aided by an immune response, but killing the last cell requires eradicating cancer stem cells. Over time, more and more genetic changes in stem cells enable the tumor to metastasize to different organs and resist chemotherapy.
In this project, tumor tissue from 30 breast cancer patients who had undergone surgery was stained for CD200. 80% of the samples were positive for CD200. There was greater CD200 staining with larger tumours. CD200 staining did not correlate with the presence of lymph node metastases. The study results were published in the American Journal of Reproductive Immunology in 2014.
It is interesting that for many years, breast cancers were not particularly sensitive to immunotherapy. Recent research has shown that the natural history of triple negative breast cancer may be related to immune function of tumor infiltrating lymphocytes. It may be that CD200 may play a role in immunotherapy of triple negative breast cancer.