Tumorigenic cell lines altered by genetic engineering and their use for

Abstract

The invention describes a novel method for determining the mass of vital tumor cells of xenotransplants in animal models. Cells altered by genetic engineering which form a tumor after transplantation synthesize an excreted reporter gene. This is shown by way of example for a secreted form of human placenta-specific, alkaline phosphate (SEAP). The latter can be demonstrated in the serum of test animals or in culture supernatants. The activity of SEAP in the serum correlates with the number of vital tumor cells in the animal and can be measured prior to the formation of a palpable tumor. The invention shows the use of cell lines altered by genetic engineering in such a manner in subcutaneous and orthotopic tumor models. Dicistronic, eukaryotic expression vectors are used for the stable transfection of the mammalian cell lines or tumor cells used. These vectors contain, under the control of a constitutive or inducible promotor element, the gene coding for SEAP, coupled with a second gene. This latter gene codes e.g. for a receptor tyrosine kinase such as erbB2/HER2 which transforms during overexpression.