HRAS1-selected, chromosome mediated gene transfer; in situ hybridization with combined biotin and tritium label localizes the oncogene and reveals duplications of the human transgenome

Chromosomes isolated from a human bladder carcinoma cell line which contains the actively transforming oncogene HRAS1 on chromosome 11 can be used to transform mouse cells. We have analyzed these chromosome mediated gene transformants by in situ hybridization techniques using biotinylated human DNA and a double antibody detection system to visualize the whole of the transgenome in a number of cell lines. In some transformants, where the amount of the transgenome was below the level of detection by the simple biotin system, we used a gold-silver enhancement technique. We have developed a combined in situ hybridization procedure using biotinylated human DNA plus antibodies and 3H-labeled HRAS1 DNA plus autoradiography to locate the actively transforming oncogene within the human transgenome in a selection of these transformants. In each of these there were complex insertions of the transgenome, either at multiple sites or with duplicated inserts at a single site. Each insertion contained a copy of HRAS1. The double in situ hybridization analysis helps define the types of arrangement and rearrangement which can accompany the chromosome mediated gene transfer process and, consequently, the potentials and limitations of the technique as a somatic cell and molecular genetic tool. Our analysis also suggests that multiple copies of the HRAS1 gene may be needed for stable transformation.