Establishment and characterization of a tumorigenic trophoblast-like cell line from a human placenta.

A trophoblast-like cell line, TL, was established from a normal-term human placenta. The TL cells were epithelial in morphology with relatively large vesicular nuclei, prominent nucleoli, and numerous microvilli on the cell surface. Cytoplasmic organelles were generally sparse but mitochondria and polysomes were abundant. The cells grew as compact sheets with close membrane approximation interconnected occasionally by desmosome-like junctions. TL cells contained placental alkaline phosphatase, a placenta-associated antigen, cytokeratin, and prekeratin, but not keratin. In parallel, they were negative for factor VIII, vimentin, and fibronectin. Population doubling time was estimated to be about 34 h. TL cells were tumorigenic in nude mice and an increase in tumorigenicity was observed after a certain number of passages in vitro. Chromosome analysis revealed that TL cells were highly heterogenous and had a female aneuploid karyotype with a hypotriploid mode. Unlike trophoblastic cell lines established from neoplastic tissues, TL cells did not synthesize human chorionic gonadotropin or other gonadal hormones, and only a small amount of ferritin (40.3 ng/10(6) cells) could be detected in the cell supernatant and cell extract. Based on various morphological and histochemical criteria, we suggest that the TL cells are derived from the Langhans cells (villous cytotrophoblast), and due to their special features, the cells may be valuable for the study of the differentiation and tumorigenesis of trophoblastic cells.