PROM1 and neoplasm: CD133 has been reported to be a presumed colon cancer stem cell marker (O’Brien et al, 2007; Ricci-Vitiani et al, 2007; Todaro et al, 2008), even if this function is now challenged (LaBarge and Bissell, 2008; Shmelkov et al, 2008), and CD44 has been more convincingly described as an informative marker of colon cancer stem cells in both primary tumours and xenografts (Dalerba et al, 2007; Subramaniam et al, 2007; Du et al, 2008).