Although all over-expressed antigens might not be strong immunotherapeutic targets, certain other types of overexpressed antigens have been studied, such as ALDH1A1 and hTERT in CD44+ breast cancer CSCs[97], HER2 proto-oncogene in glioma CSCs[98], and CEP55 and COA-1[99] in colon CSCs. Here, CD44 is linked to central nervous system cancer.