JD 77 Gene Expression

The passing of human tumour tissue through a series of immunodeficient nude mice (“serial passaging”) has been an important model system in cancer research for more than 40 years (Rygaard & Povlsen, 1969). Such xenograft models have the advantage of unlimited availability of live tumour tissue, allowing for repeated experiments on the same tumour. It has been shown by various techniques, including histology and DNA ploidy, that the transplants are stable over many passages and for several years (Povlsen et al., 1980). For most practical purposes it has been assumed that multiple xenografts, derived from a single xenograft sample, are more or less identical within a limited number of passages. Limitations of the system may be due to selection bias of tumour lines by their transplantability, the replacement of the human stroma by murine stroma cells and altered host/graft interaction as for example regarding drug metabolism and immunology. These limitations have to be addressed when interpreting the results of xenograft experiments. At our institution xenograft models are used in a Scand. J. Lab. Anim. Sci. 2006 Vol. 33 No. 1