Enhanced expression of alkaline phosphatase in hybrids between neuroblastoma and embryonal carcinoma

Three independent hybrid cell lines were isolated from the fusion of clonal lines of embryonal carcinoma and neuroblastoma. A series of subclones was subsequently derived from the original hybrid clones. In early hybrid generations all hybrid lines showed enhancement of alkaline phosphatase activity, expressing 2--8 times the activity of the teratoma parental line. The overexpression of APase appears to take place in the stationary phase of the growth cycle. Segregation for very high levels of APase activity was observed among subclones of one hybrid line. Specific activities of the segregants ranged from 0.1 to 133. Results of heat denaturation studies are consistent with the hypothesis that it is the embryonal carcinoma APase that is being expressed in the hybrids.