PROM1 and neoplasm: There is increasing evidence that CSCs exist in human CRC.5,10 CRC CSC populations have been effectively separated from human colontumors using the CD133 surface marker in studies,10,11 and the tumorigenic potential appeared solely in the CD133+ cell population, whereas the CD133– cells showedno such effect.11 Understanding the roleof colon cancer-forming CSCs in tumor initiation and progression canbe enhanced by correctly characterizing CSCs.