ABCG2 and neoplasm: We subsequently demonstrated increased expression of ABCG2 (Figure 4C) and recognised embryonic/pluripotent stem cell markers Nanog, Notch1 and SOX2 (Figure 4D–F), which have been associated with tumorigenesis [30], using real time PCR in the tumours formed following the injection of ABCG2hi SP cells compared with the residual cell pellets harvested from mice injected with ABCG2low NSP cells.