title: The BRCA1-Δ11q Alternative Splice Isoform Bypasses Germline Mutations and Promotes Therapeutic Resistance to PARP Inhibition and Cisplatin.
abstract: Breast and ovarian cancer patients harboring BRCA1/2 germline mutations have clinically benefitted from therapy with PARP inhibitor (PARPi) or platinum compounds, but acquired resistance limits clinical impact. In this study, we investigated the impact of mutations on BRCA1 isoform expression and therapeutic response. Cancer cell lines and tumors harboring mutations in exon 11 of BRCA1 express a BRCA1-Δ11q splice variant lacking the majority of exon 11. The introduction of frameshift mutations to exon 11 resulted in nonsense-mediated mRNA decay of full-length, but not the BRCA1-Δ11q isoform. CRISPR/Cas9 gene editing as well as overexpression experiments revealed that the BRCA1-Δ11q protein was capable of promoting partial PARPi and cisplatin resistance relative to full-length BRCA1, both in vitro and in vivo Furthermore, spliceosome inhibitors reduced BRCA1-Δ11q levels and sensitized cells carrying exon 11 mutations to PARPi treatment. Taken together, our results provided evidence that cancer cells employ a strategy to remove deleterious germline BRCA1 mutations through alternative mRNA splicing, giving rise to isoforms that retain residual activity and contribute to therapeutic resistance. Cancer Res; 76(9); 2778-90. ©2016 AACR.
authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
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authors.lastname: Wang
authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Bernhardy
authors.affiliation: High Risk and Cancer Prevention Group, Vall d'Hebron Institute of Oncology, Barcelona, Spain. Experimental Therapeutics Group, Vall d'Hebron Institute of Oncology, Barcelona, Spain.
authors.forename: Cristina
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authors.lastname: Cruz
authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
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authors.initials: JJ
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authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
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authors.lastname: Nacson
authors.affiliation: Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
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authors.lastname: Nicolas
authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Suraj
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authors.affiliation: Division of Pathology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Hanneke
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authors.affiliation: Division of Pathology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Ingrid
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authors.lastname: van der Heijden
authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Shane W
authors.initials: SW
authors.lastname: O'Brien
authors.affiliation: Immune Cell Development and Host Defense Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Yong
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authors.lastname: Zhang
authors.affiliation: Department of Obstetrics and Gynecology and Medicine, University of Washington, Seattle, Washington.
authors.forename: Maribel I
authors.initials: MI
authors.lastname: Harrell
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts.
authors.forename: Shawn F
authors.initials: SF
authors.lastname: Johnson
authors.affiliation: Department of Gynecology and Obstetrics, Ribeirao Preto Medical School, University of Sao Paulo, Sao Paulo, Brazil. Centre for Cancer Genetic Epidemiology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Candido Dos Reis
authors.affiliation: Centre for Cancer Genetic Epidemiology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Paul D P
authors.initials: PD
authors.lastname: Pharoah
authors.affiliation: Women's Cancer Program at the Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California.
authors.forename: Beth
authors.initials: B
authors.lastname: Karlan
authors.affiliation: University of Edinburgh Cancer Research UK Centre, MRC IGMM, Edinburgh, United Kingdom.
authors.forename: Charlie
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authors.affiliation: VIB Vesalius Research Center, University of Leuven, Leuven, Belgium.
authors.forename: Diether
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authors.affiliation: QIMR Berghofer Medical Research Institute, Herston, Australia.
authors.forename: Georgia
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authors.lastname: Chenevix-Trench
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authors.lastname: Benitez
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland.
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authors.affiliation: Royal Marsden NHS Foundation Trust, London, United Kingdom.
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authors.affiliation: University of California San Francisco, Cancer Risk Program, San Francisco, California.
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authors.lastname: Nussbaum
authors.affiliation: Gertner Institute for Epidemiology and Health Policy Research, Sheba Medical Center, Tel Hashomer, Israel.
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authors.lastname: Sadetzki
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California Norris Comprehensive Cancer Center, Los Angeles, California.
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authors.initials: SA
authors.lastname: Gayther
authors.affiliation: Department of Virus, Lifestyle and Genes, Danish Cancer Society Research Center, Copenhagen, Denmark.
authors.forename: Susanne K
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authors.affiliation: Department of Radiation Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts. Department of Pediatrics, Children's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Alan D
authors.initials: AD
authors.lastname: D'Andrea
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts. Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: Shapiro
authors.affiliation: Immune Cell Development and Host Defense Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: David L
authors.initials: DL
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authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Denise C
authors.initials: DC
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authors.affiliation: Risk Assessment Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
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authors.initials: MB
authors.lastname: Daly
authors.affiliation: Department of Obstetrics and Gynecology and Medicine, University of Washington, Seattle, Washington.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Swisher
authors.affiliation: Division of Pathology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Peter
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authors.affiliation: Division of Pathology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Jos
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authors.lastname: Jonkers
authors.affiliation: High Risk and Cancer Prevention Group, Vall d'Hebron Institute of Oncology, Barcelona, Spain.
authors.forename: Judith
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authors.affiliation: Experimental Therapeutics Group, Vall d'Hebron Institute of Oncology, Barcelona, Spain.
authors.forename: Violeta
authors.initials: V
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authors.affiliation: Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania. neil.johnson@fccc.edu.
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mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics*; D002945:Cisplatin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D005455:Fluorescent Antibody Technique; D018095:Germ-Line Mutation; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D010051:Ovarian Neoplasms / Q000235:genetics*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms; D023041:Xenograft Model Antitumor Assays
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D020033:Protein Isoforms; D002945:Cisplatin