title: Suberoylanilide hydroxamic acid (SAHA) enhances olaparib activity by targeting homologous recombination DNA repair in ovarian cancer.
abstract: OBJECTIVE
  Approximately 50% of serous epithelial ovarian cancers (EOC) contain molecular defects in homologous recombination (HR) DNA repair pathways. Poly(ADP-ribose) polymerase inhibitors (PARPi) have efficacy in HR-deficient, but not in HR-proficient, EOC tumors as a single agent. Our goal was to determine whether the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), can sensitize HR-proficient ovarian cancer cells to the PARPi AZD-2281 (olaparib).
  
  
  METHODS
  Ovarian cancer cell lines (SKOV-3, OVCAR-8, NCI/ADR-Res, UWB1.289 BRCA1null and UWB1.289+BRCA1 wild-type) were treated with saline vehicle, olaparib, SAHA or olaparib/SAHA. Sulforhodamine B (SRB) assessed cytotoxicity and immunofluorescence and Western blot assays assessed markers of apoptosis (cleaved PARP) and DNA damage (pH2AX and RAD51). Drug effects were also tested in SKOV-3 xenografts in Nude mice. Affymetrix microarray experiments were performed in vehicle and SAHA-treated SKOV-3 cells.
  
  
  RESULTS
  In a microarray analysis, SAHA induced coordinated down-regulation of HR pathway genes, including RAD51 and BRCA1. Nuclear co-expression of RAD51 and pH2AX, a marker of efficient HR repair, was reduced approximately 40% by SAHA treatment alone and combined with olaparib. SAHA combined with olaparib induced apoptosis and pH2AX expression to a greater extent than either drug alone. Olaparib reduced cell viability at increasing concentrations and SAHA enhanced these effects in 4 of 5 cell lines, including BRCA1 null and wild-type cells, in vitro and in SKOV-3 xenografts in vivo.
  
  
  CONCLUSIONS
  These results provide preclinical rationale for targeting DNA damage response pathways by combining small molecule PARPi with HDACi as a mechanism for reducing HR efficiency in ovarian cancer.
authors.affiliation: Department of Medical Oncology, Medical Gynecologic Oncology Program, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.
authors.forename: Panagiotis A
authors.initials: PA
authors.lastname: Konstantinopoulos
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wilson
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, USA.
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, USA.
authors.forename: Erica
authors.initials: E
authors.lastname: Wass
authors.affiliation: Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt-Ingram Cancer Center, Nashville, TN, USA. Electronic address: dineo.khabele@vanderbilt.edu.
authors.forename: Dineo
authors.initials: D
authors.lastname: Khabele
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000077216:Carcinoma, Ovarian Epithelial; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects; D004273:DNA, Neoplasm / Q000187:drug effects; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D005260:Female; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D009375:Neoplasms, Glandular and Epithelial / Q000235:genetics*; D010051:Ovarian Neoplasms / Q000235:genetics*; D010793:Phthalazines / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D059767:Recombinational DNA Repair / Q000187:drug effects*; D046888:Tissue Array Analysis; D000077337:Vorinostat; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D010793:Phthalazines; D010879:Piperazines; D000077337:Vorinostat; C531550:olaparib
keywords: Histone deacetylase inhibitors (HDACi); Olaparib (Ola); Ovarian cancer; Phosphorylated gamma histone H2AX (pH2AX); Poly(ADP-ribose) polymerase inhibitors (PARPi); Vorinostat (SAHA)