CD44 and central nervous system cancer: In addition, knocking down CD44 in glioma exosomes impaired the ability of glioma exosomes to induce XBP1s and miR-21 expression in BM-MSCs (Fig. S4N), indicating that glioma exosomal CD44 promoted XBP1s expression and upregulated cellular and exosomal miR-21 expression in MSCs.