Antigenic similarity of nonhistone chromosomal proteins in cultured rat liver epithelial cells, fetal liver, and transplantable tumors.

The cell and tissue specificity of antisera prepared to chromatin fractions from a nontumorigenic adult rat liver-derived clonal epithelial cell line (ARL-15Cl1) was characterized with immunotransfer analysis and immunoabsorption experiments. These antisera reacted with a range of high-molecular-weight chromosomal proteins greater than Mr 100,000. Extensive immunoabsorption-immunoblocking studies indicated antigenic homologies between the chromatins of the nontumorigenic ARL-15Cl1 cell line, a transformed, tumorigenic cell line (ARL-16T2), fetal liver, and several transplantable malignant tumors. Considerably less homology was observed for normal adult and regenerating liver chromatins. The antigenic similarity between the ARL-15Cl1 line and fetal rat liver was confirmed by immunoabsorption experiments with antisera to fetal rat liver chromatin fractions. The apparent changes in antigenic specificity suggest that retrodifferentiation occurred in the cultured liver cells, and our findings identify several high-molecular-weight nonhistone proteins which may be useful markers of developmental expression.