Immunological Probes in the Analysis of myc Protein Expression

Abstract

Three well-defined genes have been identified within the human genome, c-myc, N-myc and L-myc (Alt et al., 1986). c-myc is the proto-oncogene homologue of the retroviral v-myc genes found in avian myelocytic leukemia viruses and feline leukaemia viruses. It is expressed in many tissues during embryogenesis (Ohlsson et al., 1986; Zimmerman et al., 1986; Ruppert et al., 1986) and is a mitogen response gene in many, perhaps all, adult cell types (Kelly et al., 1983; Rabbitts et al., 1985). c-myc has also been found amplified in transformed cell lines derived from several lineages (Little et al., 1983; Alitalo et al., 1987; Dalla Favera et al., 1982). In contrast to c-myc, both N-myc and L-myc show a much more restricted pattern of expression (Alt et al., 1986). Both are expressed during embryogenesis in certain tissues. N-myc is also expressed in certain lineage cells in the adult, and is found amplified in more serious childhood neuroblastomas. It is not known which, if any, cells in the adult express L-myc, but the gene is found amplified in some small cell lung carcinomas. c-myc, N-myc and L-myc genes are related by sequence homology which is particularly marked in certain regions (Figure 1) — the so-called “myc boxes” (Schwab, 1985; Alt et al., 1986). The three genes also share a similar structural organisation within the genome, and all are active in transformation assay when co-transfected with the ras oncogene (Alt et al., 1986).