title: HDAC1,2 inhibition impairs EZH2- and BBAP-mediated DNA repair to overcome chemoresistance in EZH2 gain-of-function mutant diffuse large B-cell lymphoma.
abstract: Gain-of-function mutations in the catalytic site of EZH2 (Enhancer of Zeste Homologue 2), is observed in about 22% of diffuse large B-cell lymphoma (DLBCL) cases. Here we show that selective inhibition of histone deacetylase 1,2 (HDAC1,2) activity using a small molecule inhibitor causes cytotoxic or cytostatic effects in EZH2 gain-of-function mutant (EZH2GOF) DLBCL cells. Our results show that blocking the activity of HDAC1,2 increases global H3K27ac without causing a concomitant global decrease in H3K27me3 levels. Our data shows that inhibition of HDAC1,2 is sufficient to decrease H3K27me3 present at DSBs, decrease DSB repair and activate the DNA damage response in these cells. In addition to increased H3K27me3, we found that the EZH2GOF DLBCL cells overexpress another chemotherapy resistance factor - B-lymphoma and BAL-associated protein (BBAP). BBAP monoubiquitinates histone H4K91, a residue that is also subjected to acetylation. Our results show that selective inhibition of HDAC1,2 increases H4K91ac, decreases BBAP-mediated H4K91 monoubiquitination, impairs BBAP-dependent DSB repair and sensitizes the refractory EZH2GOF DLBCL cells to treatment with doxorubicin, a chemotherapy agent. Hence, selective HDAC1,2 inhibition provides a novel DNA repair mechanism-based therapeutic approach as it can overcome both EZH2- and BBAP-mediated DSB repair in the EZH2GOF DLBCL cells.
authors.affiliation: Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Danielle P
authors.initials: DP
authors.lastname: Johnson
authors.affiliation: Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Gabriella S
authors.initials: GS
authors.lastname: Spitz
authors.affiliation: Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Shweta
authors.initials: S
authors.lastname: Tharkar
authors.affiliation: Acetylon Pharmaceuticals, Inc., Boston, MA, USA.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Quayle
authors.affiliation: Acetylon Pharmaceuticals, Inc., Boston, MA, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Shearstone
authors.affiliation: Acetylon Pharmaceuticals, Inc., Boston, MA, USA.
authors.forename: Simon
authors.initials: S
authors.lastname: Jones
authors.affiliation: Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Maria E
authors.initials: ME
authors.lastname: McDowell
authors.affiliation: Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Hannah
authors.initials: H
authors.lastname: Wellman
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Tyler
authors.affiliation: Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Cairns
authors.affiliation: Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Mahesh B
authors.initials: MB
authors.lastname: Chandrasekharan
authors.affiliation: Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.|Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, UT, USA.
authors.forename: Srividya
authors.initials: S
authors.lastname: Bhaskara
mesh_terms: D000328:Adult; D045744:Cell Line, Tumor; D004260:DNA Repair; D000071221:Enhancer of Zeste Homolog 2 Protein; D006367:HeLa Cells; D056284:Histone Deacetylase 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D056464:Histone Deacetylase 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D016403:Lymphoma, Large B-Cell, Diffuse / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D008297:Male; D063151:Polycomb Repressive Complex 2 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D056572:Histone Deacetylase Inhibitors; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2; C475669:DTX3L protein, human; D044767:Ubiquitin-Protein Ligases; C110550:HDAC1 protein, human; C533423:HDAC2 protein, human; D056284:Histone Deacetylase 1; D056464:Histone Deacetylase 2
keywords: DNA repair; EZH2; HDAC1,2; chromatin; epigenetics