POU5F1 and cancer: Furthermore, simultaneous expressions of YB-1 and the other four (SOX2, POU3F2, OCT-4, and OLIG1) or five (SOX2, SALL2, OCT-4, POU3F2, and Bmi-1) transcription factors in YB-1 knockout cancer stem cells restored the stemness of YB-1 knockout cancer stem cells.