SOX2 and glioblastoma: In addition to inhibiting well-accepted biomarkers33,34 of “stemness” in breast cancer and glioblastoma (ALDH and Sox-2, respectively: Supplementary Fig. 6), both markers that are associated with a poor prognosis in these two malignancies, we assessed the frequency (f) of sphere formation in vitro using an extreme limited dilution analysis (ELDA) which indicated the number of tumor cells capable of forming a single sphere29.