PROM1 and sarcoma: Subsequent work by numerous investigators have identified several other candidate CSC cell surface markers (e.g., CD34, CD44, CD90, CD117, CD133, CD20) in a variety of different solid tumors including brain, breast, prostate, melanoma, colon, lung, liver, and sarcomas (Al-Hajj et al., 2003; Singh et al., 2003; Collins et al., 2005; Fang et al., 2005; Eramo et al., 2008; Tirino et al., 2008).