All five implanted GBM cultures adapted their phenotype to the brain environment (Fig. 4d; Supplementary Fig. 6E, F, Supplementary Data 1F, G) with a strong tendency toward the enrichment of CD133−CD44− cells (P9–P12) and depletion of CD133 + CD44 + (P5–P8) and CD133−CD44 + (P13–P16) cells. This evidence concerns the gene CD44 and glioblastoma.