Cell renewing in neuroblastoma: Electrophysiological and immunocytochemical characterization of stem cells and derivatives

We explored the stem cell compartment of the SH-SY5Y neuroblastoma (NB) clone and its development by a novel approach, integrating clonal and immunocytochemical investigations with patch-clamp measurements of ion currents simultaneously expressed on single cells. The currents selected were the triad I-HERG, I-KDR, I-NA, normally expressed at varying mutual ratios during development of neural crest stem cells, from which NB derives upon neoplastic transformation. These ratios could be used as electrophysiological clusters of differentiation (ECDs), identifying otherwise indistinguishable stages in maturation. Subcloning procedures allowed the isolation of highly clonogenic substrate-adherent (S-type) cells that proved to be p75- and nestin-positive and were characterized by a nude electrophysiological profile (ECDS0). These cells expressed negligible levels of the triad and manifested the capacity of generating the two following lineages: first, a terminally differentiating, smooth muscular lineage, positive for calponin and smooth muscle actin, whose electrophysiological profile is characterized by a progressive diminution of I-HERG the increase of I-KDR and I-Na, and the acquisition of (ECDS2); second, a neuronal abortive pathway (NF-68 positive), characterized by a variable expression of I-HERG and I-KDR and a low expression of IN. (ECDNs). This population manifested a vigorous amplification, monopolizing the stem cell compartment at the expense of the smooth muscular lineage to such an extent that neuronal-like (N-type) cells must be continuously removed if the latter are to develop.