KLF4 and glioblastoma: Although it has been shown that stem cell markers such as CD133 and CD44 persist on genetically diverse clones (53), the presence of more primitive markers, such as OCT-4, SALL4, NANOG, SOX2, c-Myc, KLF4, and pSTAT3, on different GBM or GBCSC subtypes has not been defined.