At present, it is unknown whether the subcellular localization of CD133 glycoprotein may affect CD133 function, or its involvement in cancer stem biology, although it has been hypothesized that the apical/endoluminal staining represents a particular step in cellular differentiation, while the less frequently represented cytoplasmic staining would more likely characterize cells with stemness features [24]. This evidence concerns the gene PROM1 and cancer.