DIFFERENTIATION OF NEUROBLASTOMA, GLIOMA, AND HYBRID CELLS IN CULTURE AS MEASURED BY THE SYNTHESIS OF SPECIFIC PROTEIN SPECIES: EVIDENCE FOR NEUROBLAST‐GLIOBLAST RECIPROCAL GENETIC REGULATION

Abstract— Protein species from differentiating neuroblastoma, glioma, and hybrid neuroblastoma‐glioma cell lines in cell culture were separated and identified initially in the first dimension by the use of isoelectric focusing gels and were further separated in the second dimension by SDS‐acrylamide gels. There were two main classes of proteins identified: proteins which were dominantly expressed in neuroblastoma and also in hybrid cell cultures, and proteins which were expressed in glioma and also hybrid cell cultures. In general, proteins were identified which were significantly expressed in neuroblastoma cells and much reduced in glioma cultures, and also conversely so. The hybrid cell line expressed many of the neuroblastoma‐type proteins and relatively fewer of the glioma type proteins. A specific protein species (2) was identified in hybrid cells and was not present in either parental neuroblastoma or glioma cultures. Protein z was expressed however by the co‐culturing of neuroblastoma and glioma cells suggesting its induction is dependent on a soluble factor. Protein z in hybrid cells was demonstrated in both stained gels and by autoradiography. Chromosome analysis of hybrid cells confirmed the presence of both rat and mouse chromosomes. It is suggested that similar neuronal‐glial interaction may be functional in the intact brain, and that similar reciprocal modulation between neurons and glia may be a central mechanism of differentiation in the nervous system.