Objectives 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 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.

Vitamin C (ascorbic acid, AA) depletion during pre-natal and post-natal development can lead to oxidative stress in the developing brains and other organs. Such damage may lead to irreversible effects on later brain function. We studied the relationship between AA deficiency and oxidative stress during development in gulonolactone oxidase (gulo) knockout mice that are unable to synthesize their own ascorbic acid. Heterozygous gulo(+/−) mice can synthesize AA and typically have similar tissue levels to wild-type mice. Gulo(+/−) dams were mated with gulo(+/−) males to provide offspring of each possible genotype. Overall, embryonic day 20 (E20) and post-natal day 1 (P1) pups were protected against oxidative stress by sufficient AA transfer during pregnancy. On post-natal day 10 (P10) AA levels were dramatically lower in liver and cerebellum in gulo (−/−) mice and malondialdehyde (MDA) levels were significantly increased. In post-natal day 18 pups (P18) AA levels decreased further in gulo(−/−) mice and oxidative stress was observed in the accompanying elevations in MDA in liver, and F2-isoprostanes in cortex. Further, total glutathione levels were higher in gulo(−/−) mice in cortex, cerebellum and liver, indicating that a compensatory antioxidant system was activated. These data show a direct relationship between AA level and oxidative stress in the gulo(−/−) mice. They reinforce the critical role of ascorbic acid in preventing oxidative stress in the developing brain in animals that, like humans, cannot synthesize their own AA.

BackgroundNuclear factor-kappa B (NF-kappaB) signaling is an important link between inflammation and peritoneal carcinomatosis in human ovarian cancer. Our objective was to track NF-kappaB signaling during ovarian cancer progression in a syngeneic mouse model using tumor cells stably expressing an NF-kappaB reporter.MethodsID8 mouse ovarian cancer cells stably expressing an NF-kappaB-dependent GFP/luciferase (NGL) fusion reporter transgene (ID8-NGL) were generated, and injected intra-peritoneally into C57BL/6 mice. NGL reporter activity in tumors was non-invasively monitored by bioluminescence imaging and measured in luciferase assays in harvested tumors. Ascites fluid or peritoneal lavages were analyzed for inflammatory cell and macrophage content, and for mRNA expression of M1 and M2 macrophage markers by quantitative real-time RT-PCR. 2-tailed Mann-Whitney tests were used for measuring differences between groups in in vivo experiments.ResultsIn ID8-NGL cells, responsiveness of the reporter to NF-kappaB activators and inhibitors was confirmed in vitro and in vivo. ID8-NGL tumors in C57BL/6 mice bore histopathological resemblance to human high-grade serous ovarian cancer and exhibited similar peritoneal disease spread. Tumor NF-kappaB activity, measured by the NGL reporter and by western blot of nuclear p65 expression, was markedly elevated at late stages of ovarian cancer progression. In ascites fluid, macrophages were the predominant inflammatory cell population. There were elevated levels of the M2-like pro-tumor macrophage marker, mannose-receptor, during tumor progression, and reduced levels following NF-kappaB inhibition with thymoquinone.ConclusionsOur ID8-NGL reporter syngeneic model is suitable for investigating changes in tumor NF-kappaB activity during ovarian cancer progression, how NF-kappaB activity influences immune cells in the tumor microenvironment, and effects of NF-kappaB-targeted treatments in future studies.

Objective Romidepsin (FK228) was recently approved by the FDA for the treatment of cutaneous and peripheral T cell lymphoma. We have shown in vitro efficacy of FK228 in ovarian cancer. Here, our goal was to evaluate FK228 combined with cisplatin in ovarian cancer in vitro and in vivo. Methods Ovarian cancer cell lines were treated with cisplatin, FK228 or the combination of drugs. Colorimetric assays were used to determine cytotoxicity in vitro. Mice engrafted with 7 × 106 SKOV-3 ovarian cancer cells were treated with cisplatin, FK228 or the combination, and tumor weights and volumes were measured. We assessed molecular markers of proliferation (mib-1), apoptosis (cleaved PARP and cleaved caspase 3) and DNA damage (pH2AX, RAD51 and 53BP1). Results FK228 enhanced the cytotoxic effects of cisplatin in ovarian cells compared to vehicle-treated controls or each drug alone. The combination of FK228 and cisplatin- induced apoptosis and activated aberrant DNA damage responses demonstrated by increased expression of pH2AX, RAD51 and 53BP1. Mice treated with FK228, cisplatin and both drugs reduced tumor weights and volumes. Drug-treated tumors showed decreased mib-1 and increased cleaved-caspase 3 expression levels. The number and intensity of pH2AX stained cells was greatest in tumors exposed to the combination of FK228 and cisplatin. Conclusion FK228 causes DNA damage-induced apoptosis and enhances the anti-tumor effects of cisplatin. The DNA damage mark pH2AX is activated by FK228 and may be a useful pharmacodynamic mark of these effects.

Objective 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. Methods 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. Results 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. Conclusions 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.