CD44 and glioblastoma: The glioblastoma antigens currently targeted in the clinic, often in combination, are Cluster of Differentiation proteins (CD133, CD44 & CD70), IL receptors (IL-13Ra2), EGFR and EGFRvIII, ephrin receptor A2 (EphA2), human epidermal growth factor receptor 2 (HER2) and B7-H3 (Table 2).