CD44 and cancer: Furthermore, some stemness regulators representing stem cell characteristics – including NES, NANOG, and POU5F1 – were all more highly expressed in CD24− 3AO cells and CD44+ SKOV3 cells than in parental cells, suggesting that induction of sphere formation by serum-free suspension culture of 3AO and SKOV3 does indeed enrich cancer stem cells, which can be further studied.