CD44 and central nervous system cancer: A broad mapping of CD44 activities in the various cellular events, including invasion, proliferation, and epithelial-to-mesenchymal transition (EMT), and an understanding of how CD44-activated cellular events can be co-operatively regulated in GBM, particularly glioma stem-like cells, may bring new insight, not only clarifying the molecular mechanisms underlying GBM recurrence but also establishing a therapeutic strategy by effectively targeting CD44 to eradicate GBM.