title: Panobinostat sensitizes cyclin E high, homologous recombination-proficient ovarian cancer to olaparib.
abstract: Homologous recombination (HR) proficient ovarian cancers, including CCNE1 (cyclin E)-amplified tumors, are resistant to poly (ADP-ribose) polymerase inhibitors (PARPi). Histone deacetylase inhibitors (HDACi) are effective in overcoming tumor resistance to DNA damaging drugs. Our goal was to determine whether panobinostat, a newly FDA-approved HDACi, can sensitize cyclin E, HR-proficient ovarian cancer cells to the PARPi olaparib.
  
  
  
  Expression levels of CCNE1 (cyclin E), BRCA1, RAD51 and E2F1 in ovarian tumors and cell lines were extracted from The Cancer Genome Atlas (TCGA) and Broad-Novartis Cancer Cell Line Encyclopedia (CCLE). In HR-proficient ovarian cancer cell line models (OVCAR-3, OVCAR-4, SKOV-3, and UWB1.289+BRCA1 wild-type), cell growth and viability were assessed by sulforhodamine B and xenograft assays. DNA damage and repair (pH2AX and RAD51 co-localization and DRGFP reporter activity) and apoptosis (cleaved PARP and cleaved caspase-3) were assessed by immunofluorescence and Western blot assays.
  
  
  
  TCGA and CCLE data revealed positive correlations (Spearman) between cyclin E E2F1, and E2F1 gene targets related to DNA repair (BRCA1 and RAD51). Panobinostat downregulated cyclin E and HR repair pathway genes, and reduced HR efficiency in cyclin E-amplified OVCAR-3 cells. Further, panobinostat synergized with olaparib in reducing cell growth and viability in HR-proficient cells. Similar co-operative effects were observed in xenografts, and on pharmacodynamic markers of HR repair, DNA damage and apoptosis.
  
  
  
  These results provide preclinical rationale for using HDACi to reduce HR in cyclin E-overexpressing and other types of HR-proficient ovarian cancer as a means of enhancing PARPi activity.
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wilson
authors.affiliation: Meharry Medical College, Nashville, TN, United States.
authors.forename: Kofi
authors.initials: K
authors.lastname: Sarfo-Kantanka
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, United States.
authors.forename: Toby
authors.initials: T
authors.lastname: Barrack
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, United States.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Steck
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, United States.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Saskowski
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, United States; Vanderbilt-Ingram Cancer Center, Nashville, TN, United States.
authors.forename: Marta A
authors.initials: MA
authors.lastname: Crispens
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, United States; Vanderbilt-Ingram Cancer Center, Nashville, TN, United States. Electronic address: dineo.khabele@vanderbilt.edu.
authors.forename: Dineo
authors.initials: D
authors.lastname: Khabele
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D019927:Cyclin E / Q000032:analysis*; D004260:DNA Repair; D004357:Drug Synergism; D005260:Female; D059765:Homologous Recombination; D006801:Humans; D006877:Hydroxamic Acids / Q000627:therapeutic use*; D007211:Indoles / Q000627:therapeutic use*; D015513:Oncogene Proteins / Q000032:analysis*; D010051:Ovarian Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000235:genetics; D000077767:Panobinostat; D010793:Phthalazines / Q000627:therapeutic use*; D010879:Piperazines / Q000627:therapeutic use*
chemical_list: D000970:Antineoplastic Agents; C475820:CCNE1 protein, human; D019927:Cyclin E; D006877:Hydroxamic Acids; D007211:Indoles; D015513:Oncogene Proteins; D010793:Phthalazines; D010879:Piperazines; D000077767:Panobinostat; C531550:olaparib
keywords: High-grade serous ovarian cancer; Homologous recombination; Olaparib (Ola); Panobinostat; Phosphorylated histone H2AX (pH2AX); Poly (ADP-ribose) polymerase inhibitors (PARPi)