title: Post-translational modifications of eukaryotic initiation factor-5A (eIF-5A) as a new target for anti-cancer therapy.
abstract: Eukaryotic translation initiation factor 5A (eIF-5A) is the only cell protein that contains the unusual basic amino acid hypusine [N epsilon-(4-amino-2-hydroxybutyl)lysine]. Hypusine is formed by the transfer of the butylamine portion from spermidine to the epsilon-amino group of a specific lysine residue of eIF-5A precursor and the subsequent hydroxylation at carbon 2 of the incoming 4-aminobutyl moiety. Agents that reduce cell hypusine levels inhibit the growth of mammalian cells. These observations suggest that hypusine is crucial for proliferation and transformation of eukaryotic cells. Here we have studied whether the inhibition of hypusine synthesis can potentiate the anti-cancer activity of the anti-tumour agents interferon-alpha (IFN alpha) and cytosine arabinoside (ara-C). We have found that IFN alpha increased epidermal growth factor receptor (EGF-R) expression, but reduced S phase and proliferative marker expression in human epidermoid KB cells and that this effect was antagonised by epidermal growth factor (EGF). Growth inhibition induced by IFN alpha was paralleled by decreased hypusine synthesis and, when EGF counteracted anti-proliferative effects, a reconstitution of hypusine levels was recorded. We also studied the effects of IFN alpha on the cytotoxicity of the recombinant toxin TP40 which inhibits elongation factor 2, another step of protein synthesis, through EGF-R binding and internalisation; IFN alpha induced an about 27-fold increase of TP40 cytotoxicity in KB cells. Ara-C, another antineoplastic agent commonly used in haematologic malignancies, induced both apoptosis and iron depletion in human acute myeloid leukaemic cells. The combination of ara-C and of the iron chelator desferioxamine, a strong inhibitor of hypusine synthesis, had a synergistic activity on apoptosis in these cells. The data strongly suggest that the post-translational modifications of eIF-5A could be a suitable target for the potentiation of the activity of anti-cancer agents.
authors.affiliation: Department of Biochemistry and Biophysics F. Cedrangolo, Second University of Naples, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Caraglia
authors.forename: P
authors.initials: P
authors.lastname: Tagliaferri
authors.forename: A
authors.initials: A
authors.lastname: Budillon
authors.forename: A
authors.initials: A
authors.lastname: Abbruzzese
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D003676:Deferoxamine / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000187:drug effects; D005098:Exotoxins / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D007938:Leukemia; D008239:Lysine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism; D009959:Oropharyngeal Neoplasms; D010448:Peptide Initiation Factors / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D016601:RNA-Binding Proteins; D016211:Transforming Growth Factor alpha / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000097574:Eukaryotic Translation Initiation Factor 5A
chemical_list: D000970:Antineoplastic Agents; D002614:Chelating Agents; D003561:Cytarabine; D003676:Deferoxamine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D005098:Exotoxins; D007371:Interferon-gamma; D007501:Iron; D008239:Lysine; D010448:Peptide Initiation Factors; D016601:RNA-Binding Proteins; D016211:Transforming Growth Factor alpha; D000097574:Eukaryotic Translation Initiation Factor 5A; C083452:transforming growth factor alpha-Pseudomonas exotoxin A (40); C100028:hypusine