Expression of cancer-testis antigens in stem cells: is it a potential drawback or an advantage in cancer immunotherapy.

Cancer-testis antigens (CTAs) are a group of tumor associated antigens with a restricted expression pattern in normal gametogenic tissues but expression in a broad range of malignancies. Their expression pattern has made them potential targets for immunotherapy. However, expression of some of these antigens has been demonstrated in normal stem cells as well as cancer stem cells (CSCs). As CSCs have been shown to be sources of metastasis and tumor recurrence, novel therapies are being focused on their eradication. On the other hand, CTA expression in normal stem cells raises the possibility that CTA based immunotherapies cause side effects in normal tissues.