SV40 T Antigen Transgenic Mice: Cytotoxic T Lymphocytes as a Selective Force in Tumor Progression
The specific immune response to some antigenic determinants expressed on the initiated cell can be a contributing factor to the prevention of tumor appearance. Indeed, one aspect of tumor progression may be the evolution and selection of tumor cell variants capable of avoiding the immune response of the host. The oncogenic virus-induced tumors have provided the most direct evidence for these points; viral gene products elicit specific immune responses, and the normal cell-virus infected cell-virally transformed cell praxis provides an experimental system to test these concepts. However, in vivo tumorigenicity testing of cells transformed by viruses in vitro does not provide proof for these hypotheses since the characteristics of these cells following growth in vitro cannot reflect those of the analogous tumor cells arising in the selective environment of the intact organism. The development of the simian virus (SV40) tumor (T) antigen (ag) transgenic mouse1 has provided a model system in which the specific contribution, if any, of host immunity to the control of these endogenous tumors can be evaluated. Moreover, because expression of the viral transforming gene can be targeted to different tissues, by linking the sequences encoding the SV40 T/t antigens to those controlling transcription of other genes in specific cell types, a wide range of tumor types are available for comparison2–5. Expression of sufficient levels of the viral oncogene potentiates tumor formation but their appearance is controlled by subsequent events which may vary depending on the cell type and on the developmental time in which SV40 Tag is expressed.
KeywordsPermanent Cell Line Viral Gene Product Tumor Appearance Thymic Stromal Cell Hyperplastic Cell
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