Interestingly, the recoveries of HeLa and A549 cells from anti-cancer drug treatments (Fig. 7A, B), were accompanied by enhanced expression of the stem cell markers ALDH1, Sox2 and Nanog (Fig. 7C, D), which suggests a possible relationship between non-mitotic division and cancer stem cells in tumor recurrence [32–34]. This evidence concerns the gene ALDH1A1 and cancer.