Analysis of chromosomal proteins of fractionated chromatin from rat liver and transplantable hepatocellular carcinomas.

The chromosomal proteins from a number of transplantable hepatocellular carcinomas (THC) induced by a single carcinogen or its derivatives and varying greatly in their growth rates were examined by sodium dodecyl sulfate (SDS) polyarcylamide gel electrophoresis. Before extraction and analysis of proteins, chromatin from hepatomas, as well as from normal and regenerating liver was fractionated into rapidly and slowly sedimenting gradient components. Ten non-histone chromosomal proteins (NHCP) present in the tumors and ranging in molecular weight from 220,000 to 55,000, were absent from normal liver. Further, each rapidly growing tumor possessed more non-histone protein bands in the most rapidly sedimenting chromatin fractions than did corresponding, slowly growing tumor fractions. A number of single protein occurrences common only to normal liver and/or rapidly or slowly growing tumors were also found. In contrast, NHCP banding patterns of rapidly growing 70% hepatectomized rat liver were identical to those of non-dividing liver. Of particular interest was the finding that the prototypic "minimal deviation tumor" 9618A varied more in its NHCP-banding pattern when compared to liver than did those tumors which were rapidly growing and poorly differentiated. These studies represent an initial attempt at seeking NHCP which might be uniquely related to the malignant process.