ITGA6 and glioblastoma: We therefore investigated the expression of GSC markers by flow cytometry in cultured GBM cell lines (Fig. 5a and Supplementary Data S5), including the GSC marker CD133, whose protein level is independent of CD133 mRNA expression23, CD15, CD44, CD49f, EphA224 and EphA325, and the progenitor cell markers Sox2 and Nestin7.