Despite the lack of direct evidence for colon cancer, the correlation of elevated CD133 cancer populations in tumour spheres with enriched epithelial–mesenchymal transition and stem cell marker properties is consistent with observations in high-grade brain tumours that elevated CD133 expression correlates with poor prognosis (Beier et al, 2008; Rebetz et al, 2008). This evidence concerns the gene PROM1 and brain neoplasm.