Regulation of macromolecular synthesis in Morris hepatomas

In this review, some studies are discussed in which an attempt has been made to determine the nature of changes in macromolecular synthesis in Morris hepatomas. The incorporation of isotope labeled precursors into nucleic acids and proteins has suggested greatly increased rates of DNA synthesis in comparison with rat liver of normal and tumor bearing rats, but for RNA and proteins the changes may be impressive for individual macromolecular species but total synthesis is not greatly changed. Fractionation of nuclear proteins has indicated altered patterns of synthesis which are related to the growth rates of the tumors and are much more pronounced than in regenerating liver despite a growth rate similar to that of the most rapidly growing hepatomas. Investigations with drugs which inhibit synthesis of macromolecules has suggested that liver neoplasia may be accompanied by changes in response which may make the tumor less sensitive or more sensitive to regulation than the tissue of origin.