RT-PCR analysis revealed that the mRNA expressions of Oct-4, Sox-2, and Nanog were significantly increased in the CD133+ tumor spheroid-forming subpopulation of OVCAR3 cells, compared with those in cancer cells from CD133- adherent cultured cells as well as those in the CD133- tumor spheroid-forming subpopulation of OVCAR3 cells (Figure 4). Here, POU5F1 is linked to cancer.