Cancer chemoprevention locks onto a new polyamine metabolic target

Abstract

Ornithine decarboxylase has a relatively long history as a target for cancer chemoprevention and chemotherapy. Plym Forshell et al. report new evidence (beginning on p. 140 in this issue of the journal) indicating that spermidine synthase, a fellow enzyme of ornithine decarboxylase in polyamine metabolism, is transactivated in part by the MYC gene and is a potential target for chemoprevention of B-cell lymphomas.

Fig. 1

MYC target genes in the polyamine pathway. Polyamines derive from the amino acid arginine through ornithine. Putrescine is the decarboxylation product of ornithine. S-Adenosylmethionine (SAM) is decarboxylated by adenosylmethionine decarboxylase (AMD1). Decarboxylated SAM (dcSAM) is the propyl amine donor for the formation of spermidine by SRM. Spermidine is the substrate for the posttranslational modification, which converts a lysine residue to the novel amino acid hypusine in the eukaryotic translation initiation factor 5A (eIF5A) protein. Two unique chromosomal loci encode related forms of eIF5A (eIF5A1 and eIF5A2). MYC target genes in the polyamine pathway include ODC, AMD1, SRM, and eIF5A2. These genes may mediate MYC-dependent oncogenesis.