KLF4 and central nervous system cancer: Many additional surface markers have been described that might be used to identify GSCs, such as the cell surface gangliosides GFAP, KLF4, SALL4, ALDH1, L1CAM, SOX2, CD90, and A2B5, and the cell surface glycoprotein CD44.34, 35, 36, 37, 38, 39, 40 Although CD133 is a cell surface marker that enriches GSCs, the use of CD133 as a unique glioma stem cell marker is likely not enough to tag the whole self-renewing cancer cell reservoir and additional research is needed to identify more markers for GBM stem cells.41, 42, 43 The main biomarkers of glioma stem cells are illustrated in Figure 2.