Similar to these observations, cell sorting experiments demonstrated that only pan-CD44-positive GBM cells were capable of forming neurospheres in the CD44high GBM samples (GBM107 and 1600) (Figure S 2, left panel), whereas no significant difference in neurosphere-forming potential was exhibited between equal numbers of pan-CD44-positive and -negative cells seeded in serum-free media from the CD44low GBM sample (GBM157) (Figure S2, right panel). Here, CD44 is linked to glioblastoma.