Synergistic Leukemia Eradication by Combined Treatment with Retinoic Acid and HIF Inhibition by EZN-2208 (PEG-SN38) in Preclinical Models of PML-RARα and PLZF-RARα-Driven Leukemia.
OBJECTIVE
Retinoic acid-arsenic trioxide (ATRA-ATO) combination therapy is the current standard of care for patients with acute promyelocytic leukemia (APL) carrying the oncogenic fusion protein PML-RARα. Despite the high cure rates obtained with this drug combination, resistance to arsenic is recently emerging. Moreover, patients with APL carrying the PLZF-RARα fusion protein are partially resistant to ATRA treatment. Hypoxia-inducible factor-1α (HIF-1α) activation has been recently reported in APL, and EZN-2208 (PEG-SN38) is a compound with HIF-1α inhibitory function currently tested in clinical trials. This study investigates the effect of EZN-2208 in different preclinical APL models, either alone or in combination with ATRA.


METHODS
Efficacy of EZN-2208 in APL was measured in vitro by assessing expression of HIF-1α target genes, cell migration, clonogenicity, and differentiation, vis a vis the cytotoxic and cytostatic effects of this compound. In vivo, EZN-2208 was used in mouse models of APL driven by PML-RARα or PLZF-RARα, either alone or in combination with ATRA.


RESULTS
Treatment of APL cell lines with noncytotoxic doses of EZN-2208 causes dose-dependent downregulation of HIF-1α bona fide target genes and affects cell migration and clonogenicity in methylcellulose. In vivo, EZN-2208 impairs leukemia progression and prolongs mice survival in APL mouse models. More importantly, when used in combination with ATRA, EZN-2208 synergizes in debulking leukemia and eradicating leukemia-initiating cells.


CONCLUSIONS
Our preclinical data suggest that the combination ATRA-EZN-2208 may be tested to treat patients with APL who develop resistance to ATO or patients carrying the PLZF-RARα fusion protein.
Laboratory of Pre-clinical Models of Cancer, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. Leukemia Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy. bernardi.rosa@hsr.it coltella.nadia@hsr.it.
Nadia
N
Coltella
Laboratory of Pre-clinical Models of Cancer, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy.
Roberta
R
Valsecchi
Laboratory of Pre-clinical Models of Cancer, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. Vita-Salute San Raffaele University, Milan, Italy.
Manfredi
M
Ponente
Leukemia Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy. Vita-Salute San Raffaele University, Milan, Italy. Pathology Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy.
Maurilio
M
Ponzoni
Laboratory of Pre-clinical Models of Cancer, Division of Experimental Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. Leukemia Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy. bernardi.rosa@hsr.it coltella.nadia@hsr.it.
Rosa
R
Bernardi
D000818:Animals; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives; D002454:Cell Differentiation / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D004195:Disease Models, Animal; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D015473:Leukemia, Promyelocytic, Acute / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D051379:Mice; D009154:Mutation; D009363:Neoplasm Proteins / Q000096:biosynthesis; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D010087:Oxides / Q000008:administration & dosage; D011092:Polyethylene Glycols / Q000008:administration & dosage; D014212:Tretinoin / Q000008:administration & dosage*
D001152:Arsenicals; C528970:EZN-2208; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009363:Neoplasm Proteins; D015514:Oncogene Proteins, Fusion; D010087:Oxides; C118318:PLZF-RARalpha fusion protein, human; C093476:promyelocytic leukemia-retinoic acid receptor alpha fusion oncoprotein; D011092:Polyethylene Glycols; D014212:Tretinoin; D000077237:Arsenic Trioxide; D002166:Camptothecin