PCSCs exhibit self-renewal ability and can regenerate tumorigenic progeny by regulating a number of developmental signaling pathways including PTEN/PI3K/Akt [5], p53 [6] and NF-κB [7] pathways as well as by expressing stemness-related genes such as c-Myc [8], aldehyde dehydrogenase 1A1 (ALDH1A1) [9], CD44 [10], NANOG [11] and SOX-2 [12], which participate in maintaining the stem cell characteristics of cancer cells. Here, ALDH1A1 is linked to cancer.