© 1996 Oxford University Press
research-article |
Transformation of immortalized woodchuck hepatic cell lines with the c-Ha-ras proto-oncogene
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University Ithaca, NY 14853, USA
Woodchuck hepatocytes were immortalized with the simian virus 40 T antigen (SV40 T-ag) oncogene and utilized in an oncogenic transformation assay. Transfection of these cell lines with an activated c-Ha-ras oncogene (EJ6.6) resulted in the transformation of cells to a phenotype characterized by anchorage-independent growth in soft agar. Colonies of transformed cells were subcloned and up to 80% were positive for oncoprotein expression detected by immunoblotand Northern blot procedures. When compared with the parental cell lines, ras-transformed derivatives were altered both morphologically and in growth rate. The tumorigenic potential of c-Ha-ras transformed cells was demonstrated in severe combined immunodeficient (SCID) mice. There was a latency period of 1 to 4 weeks before tumors were detectable and a period of over 7 weeks was required for tumors to reach a diameter of 1 cm. Histologically, tumorsderived from cell lines fully transformed by the SV40 T-ag had the appearance of well differentiated hepatocellular carcinoma (HCC) while tumors derived from c-Ha-ras transformed cell lines had the appearance of poorly differentiated HCC. The capacity to induce oncogenic transformation events in immortalized woodchuck hepatic cell lines should provide the opportunity to study the cooperative effects of hepadnaviral genes in hepatocarcinogenesis in vitro.