ALDH1A1 and neoplasm: Chen et al. (2009) demonstrated that EMT-related genes were upregulated in both ALDH1+ and CD44+/CD24-/ALDH1+ cells; further, the knockdown of Snail significantly reduced sphere formation, tumorigenicity in vivo, and colony formation in vitro in both ALDH1+ and CD44+/CD24-/ALDH1+ cells, suggesting that Snail expression plays a key role in the regulation of self-renewal, tumorigenesis, and cancer stem properties in malignant HNSCC tumours [11].