Elevated activity of additional ALDH isoforms, namely ALDH1A2, ALDH1A3, ALDH1A7, ALDH2*2, ALDH3A1, ALDH4A1, ALDH5A1, ALDH6, and ALDH9A1, has been observed in normal and cancer stem cells (10, 20–25). This evidence concerns the gene ALDH1A3 and cancer.