The overall goal of this proposed research is to assign a role in hepatocarcinogenesis of each of severalgenetic changes commonly identified in human and/or mouse liver tumors. To accomplish this objective, anewly developed, novel in vivo assay system is employed, the comparative hepatocyte growth assay. Asstarting material, this assay uses rodents that have been genetically modified to reflect activation ofproposed carcinogenic pathways. Hepatocytes are isolated from these animals, and then transplanted intoliver of specially designed recipient mice with liver disease that support transient replication of donorhepatocytes: Evaluation of the subsequent clonal growth of donor cells in the new host environment allowsquantification of the influence of single or combined genetic modifications on (1) the rate at whichhepatocytes proliferate under growth stimulatory conditions; (2) the capacity for sustained hepatocyte growthin a quiescent liver environment; and (3) the risk for hepatocyte progression to malignant transformation.Each measure reflects an important characteristic of neoplastic cells. The quantitative nature of the data.provides a more refined understanding of the specific contribution of each genetic change, alone and incombination with others, to hepatocarcinogenesis. The final objective is to use this system as a tool forcancer gene discovery, by correlating changes in patterns of gene expression with the changes inhepatocyte clonal growth that will be identified. The proposal has the following specific aims.
Aim 1 : Definethe effects of specified combinations of gene changes on mouse hepatocarcinogenesis.
Aim 2 : Quantifyeffects of defined gene changes on hepatocyte growth and transformation frequency in vivo.
Aim 3 : Identifygrowth characteristics and changes in the pattern of gene expression of transformed hepatocytes in vivo.Successful completion of these experiments will (1) define specific interactions between several highlyrelevant genetic changes (synergistic or additive complementation, or no complementation) during hepaticcarcinogenesis; (2) provide a systematic and comparative evaluation of the influence of genetic andenvironmental alterations, selected for their relevance to liver cancer, on hepatocyte growth potential; and (3)will identify gene sets that cooperate with oncogenes during tumor progression.
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