For example, CD133 (prominin-1), an apical plasma membrane protein predominantly on embryonic epithelial structures, has been reported to be an important CSC marker in a number of solid malignancies, including brain tumor [10], prostate carcinoma [11], ovarian carcinoma [12], colorectal cancer [13], osteosarcoma [14] and lung cancer [15]. Here, PROM1 is linked to osteosarcoma.