Human yolk sac tumor serially transplanted in nude mice: its morphologic and functional properties

Three human yolk sac tumors (TE, OE, and TT-1) were serially transplanted into nude mice. The histology of the transplanted tumors is moderately different from that of the original tumor; the transplants had mainly a tubular structure with an inconspicuous endodermal sinus structure due to a decreased mesenchymal element surrounding the vascular core. Ultrastructural features of the transplanted tumor cells, however, were identical to those of the original tumor. Immunochemical survey of the blood plasma of nude mice bearing these tumors demonstrated the production of adult type human plasma proteins including prealbumin, albumin (Alb), alpha 1-antitrypsin (alpha AT), transferrin (Tf), hemopexin, and alpha 1-fetoprotein (AFP). The types of adult plasma proteins that were produced varied, depending on the tumor line but were the same between serial passages within the same tumor line. The intracellular localization of AFP, alpha AT, Tf, and Alb was also investigated by immunoelectron microscopy. Plasma proteins of the adult type and AFP were localized mainly within the membrane systems of the endoplasmic reticulum and Golgi complex and occasionally on the microvilli. These results suggest that transplanted human yolk sac tumors have almost all of the protein-producing function possessed by their normal counterparts.