ALDH1A1 and cancer: Up to now, Wnt/β-catenin signaling has been considered as the key factor in regulating cancer stem cells, and masses of cancer stemness-related genes (OCT4, ALDH1A1, LGR5, CD44, c-Myc, SOX2, and so on) are regulated by Wnt/β-catenin signaling [43, 44].