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Expression of the neuron‐specific protein, 14‐3‐2, and steroid sulfatase in neuroblastoma cell hybrids

Three series of neuroblastoma X fibroblast hybrid clones were isolated from crosses between mouse or human fibroblasts and mouse or human neuroblastoma cell lines by virus‐mediated cell fusion. The expression of 14‐3‐2 protein (an acidic protein specific to neurons) and steroid sulfatase activity was studied in parental and hybrid cell lines. Steroid sulfatase was extinguished in hybrids when only one parent expressed the enzyme, but was expressed in one hybrid combination in which both parents expressed the enzyme. The neuron‐specific 14‐3‐2 protein, on the other hand, continued to be expressed in all three series of neuroblastoma x fibroblast hybrids. In most cases where these pheno‐types were expressed, they also exhibited temporal modulation; that is, specific activity is low during logarithmic growth and increases markedly during stationary phase. The glial‐specific protein S‐100 is absent from all parents and hybrids. The results are discussed in terms of mechanisms of regulation of differentiated phenotypes in mammalian cells.