Originally, CD133 was known as a surface marker of hematopoietic stem cells and progenitor cells, but CD133 has also recently been reported as a marker of CSCs in solid cancers such as brain tumors [2], lung cancer [3], liver cancer [4], colon cancer [5, 6], pancreatic cancer [7], and prostate cancer [8]. Here, PROM1 is linked to liver cancer.