POU5F1 and neoplasm: To understand the biological functions of the two OCT3/4 isoforms in CC cells, Li et al. (46) evaluated sphere formation efficiency in stable cell lines: SiHa-OCT3/4A and SiHa-OCT3/4B and showed that SiHa-OCT3/4A cells had increased sphere formation capacity, whereas SiHa-OCT3/4B generated few or even no tumor spheres.