PROM1 and neoplasm: Research in brain tumors, followed by subsequent work in other solid tumors, revealed that the CD133+ subpopulation of cells were capable of recapitulating the parental tumor when the CD133+ cells were transplanted into immunodeficient mice (Singh et al., 2003, 2004; Suetsugu et al., 2006; Hermann et al., 2007; Klein et al., 2007; Monzani et al., 2007; Ricci-Vitiani et al., 2007; Eramo et al., 2008).