title: Histone deacetylase inhibition modulates deoxyribonucleotide pools and enhances the antitumor effects of the ribonucleotide reductase inhibitor 3'-C-methyladenosine in leukaemia cells.
abstract: Histone deacetylase (HDAC) inhibitors are a new class of epigenetic agents that were reported to enhance the cytotoxic effects of classical anticancer drugs through multiple mechanisms. However, which of the possible drug combinations would be the most effective and clinically useful are to be determined. We treated the HL60 and NB4 promyelocytic leukaemia cells with a combination of the ribonucleotide reductase (RR) inhibitor 3'-C-methyladenosine (3'-Me-Ado) and several hydroxamic acid-derived HDAC inhibitors, including two recently synthesized molecules, MC1864 and MC1879, and the reference compound trichostatin A (TSA). The results showed significant growth inhibitory and apoptotic synergistic effects with the combinations. Hence, we evaluated the effects of the combinations on cell cycle distribution and on the level of several proteins involved in the apoptotic process (p21, caspase-3, Bcl-2, Bax, AIF). Since HDAC inhibitors increased the G1-S transition block induced by 3'-Me-Ado, an effect on RR activity was hypothesized. Indeed, the HPLC evaluation of intracellular deoxyribonucleotide (dNTP) pools showed that both TSA and MC1864 induced a decrease in dNTPs, even if with a somewhat different pattern, suggesting that RR inhibition contributes to the observed synergism. Furthermore, while TSA was shown to activate the intrinsic apoptotic pathway, MC1864 induced a dose-dependent increase in ROS and AIF levels. Moreover, the treatment with the radical scavenger N-acetylcysteine determined a significant inhibition of MC1864- but not TSA-mediated synergistic effects. Hence, our findings are consistent with a possible role of HDAC inhibitor mediated-ROS induction in RR inhibition and in the potentiation of RR inhibitor-mediated apoptosis.
authors.affiliation: Dipartimento di Scienze per Promozione della Salute G. D'Alessandro- Sezione di Farmacologia, Policlinico P. Giaccone, via del Vespro 129, 90127 Palermo, Italy. mmeli@unipa.it
authors.forename: Maria
authors.initials: M
authors.lastname: Meli
authors.forename: Manlio
authors.initials: M
authors.lastname: Tolomeo
authors.forename: Mario
authors.initials: M
authors.lastname: Grifantini
authors.forename: Antonello
authors.initials: A
authors.lastname: Mai
authors.forename: Loredana
authors.initials: L
authors.lastname: Cappellacci
authors.forename: Riccardo
authors.initials: R
authors.lastname: Petrelli
authors.forename: Dante
authors.initials: D
authors.lastname: Rotili
authors.forename: Arianna
authors.initials: A
authors.lastname: Ferro
authors.forename: Philipp
authors.initials: P
authors.lastname: Saiko
authors.forename: Thomas
authors.initials: T
authors.lastname: Szekeres
authors.forename: Luisa
authors.initials: L
authors.lastname: Dusonchet
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003854:Deoxyribonucleotides / Q000032:analysis*; D016193:G1 Phase / Q000187:drug effects; D018922:HL-60 Cells; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007938:Leukemia / Q000188:drug therapy*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors*
chemical_list: C502992:3'-C-methyladenosine; D000970:Antineoplastic Agents; D003854:Deoxyribonucleotides; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D017382:Reactive Oxygen Species; C012589:trichostatin A; D012264:Ribonucleotide Reductases; D000241:Adenosine