PROM1 and neoplasm: To determine whether CD133-expressing tumour cells are present in the Hep3B tumours that developed after treatment with AC133-vcMMAF, immunohistochemical analysis was performed using a rabbit MAb that binds to the third extracellular domain of CD133 (Figure 4B) and a rabbit polyclonal Ab generated against a different epitope within the intracellular C terminus (data not shown).