Cell surface antigen of human neuroblastomas is related to nuclear antigen of normal cells

The localization of MC25, an antigen first detected on the surface of human neuroblastoma cells, was determined in cultured cells and tissues. Neuroblastoma cell lines (15/17) express the antigen on the surface and in the cytoplasm (scMC25+), whereas 156/160 cell lines derived from other normal and malignant human cell types are scMC25-. However, MC25 is found in the nucleus of scMC25- cells (nMC25+), presenting a discrete granular pattern. In scMC25+/nMC25- neuroblastoma lines, apparent antigen shifting from the cell surface/cytoplasm to the nucleus accompanies variant formation, which represents a transition in the neuronal differentiation program of these cells. Results of immunohistochemical studies with human tissues parallel the findings with cultured cells. Almost all cell types are scMC25-/nMC25+; basal cells of the epidermis are the only cells constitutively expressing cMC25; and a population of neurons are the only scMC25-/nMC25- cells. Alternative localization of MC25 to different cellular compartments and antigen shifting are reminiscent of the behavior of certain developmentally regulated antigens in Drosophila and Xenopus.