KLF4 and glioblastoma: FACS–sorted Fluo+ cells from three tested human primary GBM cultures demonstrated significantly increased mRNA expression levels of a variety of pluripotency-associated genes, including BMI1, KLF4, NANOG, NESTIN, OCT3/4, and SOX2, which are frequently reported to be overexpressed in CSCs [24,25,26,27], as compared to their Fluo− counterparts (Figure 2A).