Age- and Lifespan-Dependent Differences in GO Caused DNA Damage in Acheta domesticus.

The rising applicability of graphene oxide (GO) should be preceded by detailed tests confirming its safety and lack of toxicity. Sensitivity to GO of immature, or with different survival strategy, individuals has not been studied so far. Therefore, in the present research, we focused on the GO genotoxic effects, examining selected parameters of DNA damage (total DNA damage, double-strand breaks-DSB, 8-hydroxy-2'-deoxyguanosine-8-OHdG, abasic site-AP sites), DNA damage response parameters, and global methylation in the model organism Acheta domesticus. Special attention was paid to various life stages and lifespans, using wild (H), and selected for longevity (D) strains. DNA damage was significantly affected by stage and/or strain and GO exposure. Larvae and young imago were generally more sensitive than adults, revealing more severe DNA damage. Especially in the earlier life stages, the D strain reacted more intensely/inversely than the H strain. In contrast, DNA damage response parameters were not significantly related to stage and/or strain and GO exposure. Stage-dependent DNA damage, especially DSB and 8-OHdG, with the simultaneous lack or subtle activation of DNA damage response parameters, may result from the general life strategy of insects. Predominantly fast-living and fast-breeding organisms can minimize energy-demanding repair mechanisms.

[Dynamic changes of pH2AX expression in the reversibility of mouse testicular reproductive function impaired by single heat stress].

OBJECTIVE: To investigate the role of pH2AX in the reversibility of mouse testicular reproductive function impaired by single heat stress. METHODS: Twenty-four C57 male mice were randomly divided into heat stress and control groups and immersed in water at 43℃ and 25℃, respectively, for 15 minutes. At 1, 7, and 14 days of heat exposure, all the mice were sacrificed and their testis tissues collected for determining the apoptosis of the germ cells by TUNEL and measuring the expression level of the pH2AX protein by immunohistochemistry and Western blot. RESULTS: The highest percentage of apoptotic cells were found in the seminiferous tubules of the mice in the heat stress group on the 1st day of the exposure and almost no apoptosis was observed at 7 and 14 days. The pH2AX protein was expressed in the nuclei of the basement membrane of adjacent seminiferous tubules. Compared with the control group, the expression of pH2AX was significantly increased on the 1st day of exposure (0.47 ± 0.02 vs 1.61 ± 0.04, P <0.01), then decreased at 7 days (0.85 ± 0.03) in comparison with that on the 1st day (P <0.01), and again elevated at 14 days (1.72 ± 0.02) as compared with either those at 1 and 7 days (P <0.01) or that of the control (P <0.01). CONCLUSIONS: Heat stress causes dynamic changes of the pH2AX expression in the testis of the mouse, which are associated with heat stress-induced proliferation and division of the testicular spermatogenic cells.

Panobinostat sensitizes cyclin E high, homologous recombination-proficient ovarian cancer to olaparib.

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.

Suberoylanilide hydroxamic acid (SAHA) enhances olaparib activity by targeting homologous recombination DNA repair in ovarian cancer.

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 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.