abstract
- 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.