Abnormal Size Profiles of Soluble Macromolecules From Azo-Dye Liver Tumors

In a search for aberrations associated with neoplasms resulting from chemical carcinogens, the soluble macromolecules of primary liver tumors were extensively resolved according to molecular size, and the resultant profiles were compared with those from normal and preneoplastic livers. Primary liver tumors were obtained from male rats after long-term ingestion of the liver azocarcinogen 3′-methyl-4-dimethylaminoazobenzene (3′-Me-DAB). Sieving of the soluble tumor macromolecules through long gel columns yielded molecular size distributions containing at least 7 sizes. Six tumor pools gave remarkably similar profiles, which were then compared with those previously obtained from normal, control, and preneoplastic livers of rats fed 3′-Me-DAB or N-2-fluorenylacetamide (2-acetyl-aminofluorene). In contrast to segregation of the soluble macromolecules of all these livers into fairly discrete and ordered size classes, the macromolecules of the primary liver tumors were distributed in markedly diffuse profiles. Among other differences, the relative amount of 15–20S macromolecules in the tumor extracts was double that in the liver extracts, while that of 6–7.5S macromolecules was half. A multitude of cellular proteins changed in amount as a result of the overall transformation of liver cells to overt tumors.