title: Ibrutinib synergizes with poly(ADP-ribose) glycohydrolase inhibitors to induce cell death in AML cells via a BTK-independent mechanism.
abstract: Targeting Bruton's tyrosine kinase (BTK) with the small molecule BTK inhibitor ibrutinib has significantly improved patient outcomes in several B-cell malignancies, with minimal toxicity. Given the reported expression and constitutive activation of BTK in acute myeloid leukemia (AML) cells, there has been recent interest in investigating the anti-AML activity of ibrutinib. We noted that ibrutinib had limited single-agent toxicity in a panel of AML cell lines and primary AML samples, and therefore sought to identify ibrutinib-sensitizing drugs. Using a high-throughput combination chemical screen, we identified that the poly(ADP-ribose) glycohydrolase (PARG) inhibitor ethacridine lactate synergized with ibrutinib in TEX and OCI-AML2 leukemia cell lines. The combination of ibrutinib and ethacridine induced a synergistic increase in reactive oxygen species that was functionally important to explain the observed cell death. Interestingly, synergistic cytotoxicity of ibrutinib and ethacridine was independent of the inhibitory effect of ibrutinib against BTK, as knockdown of BTK did not sensitize TEX and OCI-AML2 cells to ethacridine treatment. Thus, our findings indicate that ibrutinib may have a BTK-independent role in AML and that PARG inhibitors may have utility as part of a combination therapy for this disease.
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.|Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Lianne E
authors.initials: LE
authors.lastname: Rotin
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: Marcela
authors.initials: M
authors.lastname: Gronda
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: Neil
authors.initials: N
authors.lastname: MacLean
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: Rose
authors.initials: R
authors.lastname: Hurren
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: XiaoMing
authors.initials: X
authors.lastname: Wang
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: Feng-Hsu
authors.initials: FH
authors.lastname: Lin
authors.affiliation: Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada.
authors.forename: Jeff
authors.initials: J
authors.lastname: Wrana
authors.affiliation: Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada.|Department of Agricultural, Food, and Environmental Sciences, University of Perugia, Perugia, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Datti
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.
authors.forename: Dwayne L
authors.initials: DL
authors.lastname: Barber
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.|Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Minden
authors.affiliation: Fluorinov Pharma Inc., Toronto, Ontario, Canada.
authors.forename: Malik
authors.initials: M
authors.lastname: Slassi
authors.affiliation: Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.|Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Schimmer
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D004975:Ethacridine / Q000494:pharmacology*; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors*; D006801:Humans; D047348:Hydrolyzable Tannins / Q000494:pharmacology; D019169:Jurkat Cells; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy*; D051379:Mice; D016513:Mice, SCID; D010880:Piperidines; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D011720:Pyrazoles / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D047348:Hydrolyzable Tannins; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011720:Pyrazoles; D011743:Pyrimidines; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C551803:ibrutinib; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000625951:Btk protein, mouse; D006026:Glycoside Hydrolases; C022407:poly ADP-ribose glycohydrolase; D000225:Adenine; D004975:Ethacridine
keywords: AML; BTK; PARG; ethacridine lactate; ibrutinib