Morphology of colonies generated from AC133-derived cells.

In parallel experiments, cells cultured for 8 days (day 8 cells, A and B) and 14 days (day 14 cells, C and D) in liquid cultures with stem cell growth factor (SCGF) and vascular endothelial growth factor (VEGF) were transferred to methylcellulose and stimulated either with the hematopoietic growth factor combination SCF, interleukin 3 (IL-3), IL-6, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor plus erythropoietin, or with the combination of SCGF and VEGF. In response to the hematopoietic growth factors, day 8 cells formed multilineage colonies, including the formation of burst-forming unit erythroid (A); whereas under the same culture conditions, day 14 cells produced colonies that were restricted to the granulocyte-macrophage lineage (C). Colonies grown from day 8 cells and day 14 cells, respectively, under the influence of SCGF and VEGF displayed a morphology that was different of the hematopoietic colonies and were assumed to represent endothelial colonies. Original magnification ×100.