The Aldefluor assay is one of the most commonly used techniques for enriching the CSC population, based on the finding that cells which exhibit high ALDH enzymatic activity (ALDHhigh cells) have enhanced tumorigenicity in various malignancies, including breast [139,140,141,142], liver [143,144], colorectal [145,146,147,148], lung [149,150], prostate [151,152], pancreatic [153,154], ovarian [155], esophageal [156,157], nasopharyngeal [158], gastric [159,160], bone [103,161,162], neuroblastoma [163], skin [164], and blood [165,166] cancer. The gene discussed is LDHA; the disease is cancer.