Co-expression of the toleragenic glycoprotein, CD200, with markers for cancer stem cells.

Tumor immunology fundamentals suggest immunological surveillance has the ability to recognize malignant cells and kill them before a tumor develops. However, cancer cells employ evasion mechanisms whereby the immune system may be actively suppressed or even tolerized to the tumor. Recently cancer stem cells were linked to tumor initiation and formation. However, no reports have addressed whether these cells participate in a tumor's ability to evade immune surveillance. Recently the glycoprotein CD200, expressed within the innate immune system and other tissues and cells, was shown to be involved in tolerance. Here we describe CD200 co-expression with stem cell markers found on prostate, breast, brain, and colon cancers. This is the first report describing an immunomodulatory molecule on epithelial cancer stem cells. This important finding suggests a mechanism by which a tumor might evades immune system detection.