Epithelial cell growth in suspension enriched for progenitors in different lineages. (A) Colonies from epithelial cells that grew in suspension in non-adherent culture (mammospheres) expressed both cytokeratin 8 (CK8+; luminal) and CK14 (basal). Colonies that grew in suspension over adherent plates (floating colonies) were CK8+ but were negative for CK14. (B) Epithelial cells formed characteristic colonies on adherent plates that were CK8+, CK14+, or CK8/14+ (bi-potent). (C) When grown on adherent plates, CD10+ cell populations formed bi-potent and basal colonies, while EpCAM+ cell populations formed bi-potent and luminal colonies. Epithelial cells were sorted based on cell surface markers EpCAM and CD10, grown in adherent culture, stained for CK8/14, and colonies were quantified. Scale bar = 100 μm.