Although growing putative GSC markers like CD133, CD90, CD15, A2B5, ALDH1, Label-retention, Nestin, proteasome activity, and ABC transporters (78, 104) have been used to recognize GSCs, and a considerable number of studies have been conducted on these markers to provide compelling and informative evidence that these putative GSC markers are powerful tools to investigate the tumorigenic process in the cerebral nervous system and promote the diagnosis and treatment of GBM (Table 1). This evidence concerns the gene ABCG2 and glioblastoma.