We propose to isolate and study mammalian gene sequences which play a role in the initiation and maintenance of the malignant phenotype. Using cell hybridization and chromatin or DNA mediated transfer systems we will establish which tumor derived cell lines can donate their malignant phenotype to an appropriate "normal" recipient cell type. The DNA from the tumor line will be digested with each of a large number of restriction endonucleases to determine which enzymes would fail to destroy the gene activity. The DNA that is digested with one or a combination of enzymes which do not cleave within the gene will be ligated to bacterial plasmid pBR322. The DNA from this library will be used for transformation of the normal cells. Cells forming foci will be isolated and tested for tumor related phenotypes and pBR322 sequences. The tumor related phenotypes we will examine include anchorage independence, tumor formation in nude mice and production and secretion of plasminogen activator. The sequence(s) responsible for transformation are expected to be adjacent to pBR322 sequences. The DNA from such cell line will be digested with an enzyme which does not cleave pBR322, circularized and used for transformation of an appropriate bacterial host. Selection for markers on pBR322 (plasmid rescue) would permit isolation of the mammalian gene involved in conferring tumor phenotypes. The DNA sequences thus isolated will be used in structural and functional studies.