Growth and differentiation of an embryonal carcinoma cell line (C145b).

Several cell and tumour lines were isolated from a single-embryo-derived teratocarcinoma and their karyotypes and differentiation in adult hosts recorded. The majority of cells contained normal karyotypes by banding. The cells were injected into blastocysts and although they sometimes colonized the yolk sac, they never colonized the embryo. Thus the possession of a normal karyotype is not a sufficient condition for embryo colonization. The loss of growth capacity was investigated by studying differentiation and tumourigenicity in a variety of circumstances. The change in appearance from an EC cell morphology to a big flat cell in culture leads to retardation of growth in adult hosts. When EC cells are injected into a blastocyst, the ability to grow progressively both in culture and in adult hosts is lost.