Epidermal growth factor stimulates colony formation and non-neuronal marker protein expression by human neuroblastoma...

Growth of the human neuroblastoma IMR-32 in methylcellulose culture was studied. The number of colonies was proportional to the number of seeded cells in all conditions tested: control cultures (CT) and test cultures with epidermal growth factor (EGF), hydrocortisone (HC), combined EGF/HC, fibroblast growth factor (FGF) or nerve growth factor (NGF). A portion of IMR-32 cells formed colonies and all factors were without effect when tested individually. In contrast, the combination of EGF/HC at low cell densities enhanced the number of colonies two-fold as compared to controls. Differentiation in IMR-32 colonies was examined by immunocytochemical detection of cell specific marker proteins. As determined by staining with different markers, at least two cells subpopulations could be established within the same colony. One of them expressed NSE (neuron specific enolase) and was designated as neuronal. The other subpopulation was called non-neuronal since it consisted of vimentin and S-100 protein positive cells which were considerably enhanced in the presence of EGF or EGF/HC. In vitro, the IMR-32 neuroblastoma cell line contains pluripotent stem cells from which are derived distinct phenotypes sensitive to different extrinsic factors. Increasing time in culture enhanced neuronal differentiation. EGF, on the other hand, targeted preferentially the non-neuronal phenotype, and stimulated colony formation and its differentiation.