Transgenic animals and the cell lines derived from these Several immortalized cell lines were established from transgenic animals have become important tools in the study the livers of two transgenic rats expressing the simian of many diseases. [1][2][3][4][5][6] The construction of transgenic animals virus protein large T antigen under the control of the involves the introduction of a specific gene into the germ line albumin promoter. Hepatocytes from transgenic rats of an animal, resulting in one or more copies of the transgene were isolated by a two-step perfusion procedure from a in every cell of the adult animal. Expression of the gene may normal-appearing liver and from a liver that contained be regulated through the use of tissue-specific promoters, a single neoplasm. Cells were also isolated from the diswhich allow the gene to be expressed in specific tissues and sociated liver neoplasm. After 5 weeks in culture, cell not to be active in other tissues. colonies were isolated and subcloned as individual cellIn our laboratory, we have developed a line of transgenic lines. Electron microscopy revealed that all cell lines rats to study the process of hepatocellular carcinogenesis in had a high nuclear-to-cytoplasmic ratio compared with this species. 7 These animals were produced by microinjection normal hepatocytes. The cytoplasm contained numerinto fertilized rat eggs of the DNA coding sequence for the ous organelles, including smooth and rough endoplassimian virus large T antigen (SV40) under the control of the mic reticulum, Golgi, mitochondria, peroxisomes, and 5 regulatory region of the mouse albumin gene. 8 These aniannulate lamellae. However, the lines exhibited a varimals develop hepatocellular carcinomas, adenocarcinomas, ety of different cell morphologies. All cell lines, including and hepatoblastomas at about 3 to 5 months of age. Focal those derived from neoplastic cells, exhibited a similar lesions and nodules are observed as early as 2 months, with doubling time of 26 hours and the ability to grow in soft metastases observed in some animals later in life. By 6 to 8 agar. Northern blot analysis revealed that the cell lines months of age, the animals either die of the disease or from differentially expressed hepatocyte markers. Large T other pathological abnormalities that can be attributed to the antigen was expressed in the cultured cell lines at much expression of the transgene. 7 higher levels than was observed in transgenic hepatoThis report presents data characterizing a number of cell cytes in vivo. This suggests that the viral protein is relines derived from isolated alb-SV40 T-antigen transgenic rat quired to maintain cell viability in culture. In addition, hepatocytes. It is important to note that, although the cell the tumor suppressor proteins, p53 and Rbp105, were lines were derived from a single population of isolated hepatodetected in all cultured cell lines. In contrast, these same cytes, the established cell lines exhibit very different cellular proteins were not detected by West...