To investigate whether tumour spheroid cells retain tumourigenic potential upon prolonged passaging, 100 spheres (containing ∼5 × 104 viable cells or 4.5 × 104 CD133+ cells) from tumour spheres cultured for over 6 months were injected subcutaneously into the flank of SCID-Beige mice. This evidence concerns the gene PROM1 and neoplasm.