Nucleotide Sequences Homologous to Mammalian Proto-oncogenes and Their Expression in Fish Cell Lines

Abstract

It has been shown that mammalian proto-oncogenes may be centrally involved in cell transformation in vitro and the formation of tumors in vivo. As part of a study on the evolutionary aspects of tumor formation, we have screened cell lines derived from brown bullhead Ictalurus nebulosus (BB), rainbow trout Oncorhynchus mykiss (RTG-2), common carp Cyprinus carpio (EPC), and chinook salmon Oncorhynchus tshawytscha (CHSE-214) for the presence or expression of sequences homologous to the mammalian proto-oncogenes. Southern blotting of DNA isolated from the fish cell lines showed multiple fragments having homology to v-src, v-raf, v-ras ^h, and v-erb-b DNA probes. In addition, monoclonal antibodies against the viral or cellular oncogenes of mammalian cells were able to recognize fish proteins that may be related to the myc, abl, fos, ras ^k, and p53 gene products. This study shows that proto-oncogenes are well conserved evolutionarily in vertebrates and may be factors involved in the acquisition of the transformed phenotype in fish.