POU5F1 and neoplasm: Quantification of the fraction of RFP positive cells before and after GCV treatment demonstrated an increase in the proportion of CD133 (P = 0.0003) and OCT4/SOX2 (P = 0.0002) positive cells relative to the total tumor cell population (Fig. 1G,H), a fact that was also accompanied by an increase in the RLuc/PLuc ratio (P = 0.05 and P = 0.0022, respectively) (Fig. S1).