It appears that the level of CD133 protein expression does not alter upon cell differentiation; however, tertiary conformational changes in differentiated colon cancer cells block the binding of an anti-CD133 antibody, suggesting that the expression of the CD133 epitope is restricted to undifferentiated stem cells (Grosse-Gehling et al., 2013). This evidence concerns the gene PROM1 and malignant colon neoplasm.