C-myc as a Tumor Marker for Primary Human Cancers

Abstract

Activated proto-oncogenes play an important role in the development and progression of human cancers. C-myc, one of these protooncogenes, was first identified through its homology to the cancer inducing oncogene present in avian myelocytoma virus MC29 (Duesberg et al., 1977). Molecular studies have revealed that c-myc protein is one of the essential proteins for cellular DNA replication and enhancement of mRNA transcription. Both c-myc messenger RNA and protein have very short half-lives (<30 min) (Dani et al., 1984; Rabbitts et al., 1985; Jones and Cole, 1987). C-myc protein is phosphorylated at serine and threonine, and binds to specific sequences of genomic DNA in a manner analogous to c-fos and c-jun (Ariga et al., 1989; reviewed by Cole, 1986). However, actual functions and regulatory mechanisms of its expression have not been fully clarified. Recently, Max and DMax, two proteins that can form heterodimers with c-myc protein, were discovered (Makela et al., 1992). Studies on these proteins may further clarify the precise actions of c-myc.