Carcinomas induced by cell lines cultivated from normal mouse placentas.

Cell lines have been established from placentas of various strains of mice by in vitro cultivation. The established lines appear to be trophoblast cells as judged from their production of gonadotropin-like substance and their production of gonadotropin-like substance and steroid hormones. The cell lines lack detectable H-2 antigen, Fc receptor sites, Thy 1 and antigen and surface immunoglobulin determinants. In addition, the cells are resistant to murine type-C RNA tumor virus infection. The resistance is due to a block of viral replication after the stages of viral adsorption and penetration. The cell lines induced carcinomas after injection into adult mice of original host strains. Usually at least 2 x 10(6) cells are required to induce tumors by i.p. or s.c. injection. Transplantation of the tumor cells to various strains of mice revealed that some strains accepted and some strains rejected the transplant. Genetic crossings between susceptible and resistant mouse strains indicate that susceptibility to transplantation of tumor is determined by a single pair of dominant autosomal genes.