Somatic DNA Damage Research Articles

Genomic characterization of brain metastases (BM) in high-grade serous ovarian cancer (HGSOC).

e13580 Background: BM are a rare occurrence in ovarian cancer (OC) and their molecular characteristics is virtually unknown. DNA damage repair (DDR) deficiency is prevalent in OC, and co-mutated TP53 and any DDR denotes high tumor mutation burden (TMB). We genetically characterized a unique series of high-grade serous ovarian cancer (HGSOC) patients who developed BM to identify alterations of potential clinical relevance. Methods: Whole-exome sequencing (2x150bp, SureSelectXT Library Prep Kit, Illumina’s NovaSeq platform) was performed in matched BM, primary tumors (PT) and normal tissue. DNA was extracted from FFPE samples using QIAamp DNA FFPE Tissue Kit (Qiagen, Germany). All mutations were checked with Catalogue of Somatic Mutations in Cancer (COSMIC) and Integrative Genomics Viewer (IGV). Results: Study group included 10 HGSOC patients (International Federation of Gynecology and Obstetrics classification (FIGO) II-IV, mean age at diagnosis 48 years, range 35-59). Median time from primary HGSOC diagnosis to BM was 38 months (range, 18 to 149). TP53 somatic mutations were found in both primary tumor (PT) and BM in 8 patients. The other 2 cases harbored TP53 mutations not reported in COSMIC catalogue: p.S60L and intronic TP53 mutation preceding p.I322 (IGV). In 9 cases TP53 mutations coexisted with germline or somatic DNA damage repair deficiency. Four cases contained BRCA1 mutations (all germline), and none harbored germline BRCA2 mutation. Other mutated genes included MLH1 (2 somatic, 2 germline), ATR (4 germline, 1 somatic), AMT (1 somatic), RAD50 (1 somatic), ERCC4 (1 somatic), FANCD2 (1 somatic) and RPA1 (1 germline). Three mutation signatures defined in the COSMIC database were indentified in BM: 6, 20 and 30. In 6 cases these mutations were shared in PT, and in another 4 their presence in PT could not be determined due to technical reasons. Median survival from BM was 31 months (range, 5 to 184). Conclusions: Genomic analysis of BM provides an opportunity to identify potentially clinically informative alterations. Mutational profiles in PT are generally reflected in BM. Detected genetic alterations suggest their potential sensitivity to PARP inhibitors and immunotherapy.

Multiple Malignant Meningiomas Presenting As Thrombocytopenia

Backgrounds: Malignant meningiomas are CNS tumors arising from the arachnoids cap cells of the meninges, very rare in infants. Clinically, intracranial hypertension or focal neurological deficits are usually seen for mass effect, rather than leukemoid symptoms. Methods: Retrospectively analyze the detailed clinical development, diagnosis and treatment of a 10-month-old boy initially hospitalized due to leukemoid symptoms. After careful examination, malignant meningioma (WHO grade III) was proved by the biopsy and histopathology. Chemotherapy (three cycle of ifosfamide 100 mg/kg for 3 days, plus doxorubicin 1 mg/ kg for 2 days every 21 days) in combination with imatinib. Results: Dura nodules significantly reduced in size, skin bleeding spots, thrombocytopenia and enlarged superficial lymph almost disappeared. Conclusion: This study was conducted to demonstrate dynamic changes after effective individualized treatment. Meanwhile, we proposed that the invasiveness of meningioma induces somatic DNA damage, leading to abnormal platelet production and megakaryocytic morphology.

Germline and Somatic DNA Damage Repair Gene Mutations and Overall Survival in Metastatic Pancreatic Adenocarcinoma Patients Treated with FOLFIRINOX.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with lack of predictive biomarkers. We conducted a study to assess DNA damage repair (DDR) gene mutations as a predictive biomarker in PDAC patients treated with FOLFIRINOX. Indiana University Simon Cancer Center pancreatic cancer database was used to identify patients with metastatic PDAC, treated with FOLFIRINOX and had tissue available for DNA sequencing. Baseline demographic, clinical, and pathologic information was gathered. DNA isolation and targeted sequencing was performed using the Ion AmpliSeq protocol. Overall survival (OS) analysis was conducted using Kaplan-Meier, logistic regression and Cox proportional hazard methods. Multivariate models were adjusted for age, gender, margin status, CA 19-9, adjuvant chemotherapy, tumor and nodal stage. Overall, 36 patients were sequenced. DDR gene mutations were found in 12 patients. Mutations were seen in BRCA1 (N = 7), BRCA2 (N = 5), PALB2 (N = 3), MSH2 (N = 1), and FANCF (N = 1) of all the DDR genes sequenced. Median age was 65.5 years, 58% were male, 97.2% were Caucasian and 51.4% had any family history of cancer. The median OS was near significantly superior in those with DDR gene mutations present vs. absent [14 vs. 5 months; HR, 0.58; 95% confidence interval (CI), 0.29-1.14; log-rank P = 0.08]. Multivariate logistic (OR, 1.47; 95% CI, 1.04-2.06; P = 0.04) and Cox regression (HR, 0.37; 95% CI, 0.15-0.94; P = 0.04) showed presence of DDR gene mutations was associated with improved OS. In a single institution, retrospective study, we found that the presence of DDR gene mutations are associated with improved OS in PDAC patients treated with FOLFIRINOX.

717P - Germline and somatic DNA damage repair gene mutations and overall survival in metastatic pancreatic ductal adenocarcinoma patients treated with FOLFIRINOX

717P - Germline and somatic DNA damage repair gene mutations and overall survival in metastatic pancreatic ductal adenocarcinoma patients treated with FOLFIRINOX

Neuronal complex I deficiency occurs throughout the Parkinson\u2019s disease brain, but is not associated with neurodegeneration or mitochondrial DNA damage

Mitochondrial complex I deficiency occurs in the substantia nigra of individuals with Parkinson’s disease. It is generally believed that this phenomenon is caused by accumulating mitochondrial DNA damage in neurons and that it contributes to the process of neurodegeneration. We hypothesized that if these theories are correct, complex I deficiency should extend beyond the substantia nigra to other affected brain regions in Parkinson’s disease and correlate tightly with neuronal mitochondrial DNA damage. To test our hypothesis, we employed a combination of semiquantitative immunohistochemical analyses, Western blot and activity measurements, to assess complex I quantity and function in multiple brain regions from an extensively characterized population-based cohort of idiopathic Parkinson’s disease (n = 18) and gender and age matched healthy controls (n = 11). Mitochondrial DNA was assessed in single neurons from the same areas by real-time PCR. Immunohistochemistry showed that neuronal complex I deficiency occurs throughout the Parkinson’s disease brain, including areas spared by the neurodegenerative process such as the cerebellum. Activity measurements in brain homogenate confirmed a moderate decrease of complex I function, whereas Western blot was less sensitive, detecting only a mild reduction, which did not reach statistical significance at the group level. With the exception of the substantia nigra, neuronal complex I loss showed no correlation with the load of somatic mitochondrial DNA damage. Interestingly, α-synuclein aggregation was less common in complex I deficient neurons in the substantia nigra. We show that neuronal complex I deficiency is a widespread phenomenon in the Parkinson’s disease brain which, contrary to mainstream theory, does not follow the anatomical distribution of neurodegeneration and is not associated with the neuronal load of mitochondrial DNA mutation. Our findings suggest that complex I deficiency in Parkinson’s disease can occur independently of mitochondrial DNA damage and may not have a pathogenic role in the neurodegenerative process.

Phase 2 Trial of Gemcitabine, Cisplatin, plus Ipilimumab in Patients with Metastatic Urothelial Cancer and Impact of DNA Damage Response Gene Mutations on Outcomes

BackgroundChemotherapy may exert immunomodulatory effects, thereby combining favorably with the immune checkpoint blockade. The pharmacodynamic effects of such combinations, and potential predictive biomarkers, remain unexplored. ObjectiveTo determine the safety, efficacy, and immunomodulatory effects of gemcitabine and cisplatin (GC) plus ipilimumab and explore the impact of somatic DNA damage response gene alterations on antitumor activity. Design, setting, and participantsMulticenter single arm phase 2 study enrolling 36 chemotherapy-naïve patients with metastatic urothelial cancer. Peripheral blood flow cytometry was performed serially on all patients and whole exome sequencing of archival tumor tissue was performed on 28/36 patients. InterventionTwo cycles of GC followed by four cycles of GC plus ipilimumab. Outcome measurements and statistical analysisThe primary endpoint was 1-yr overall survival (OS). Secondary endpoints included safety, objective response rate, and progression-free survival. Results and limitationsGrade ≥3 adverse events occurred in 81% of patients, the majority of which were hematologic. The objective response rate was 69% and 1-yr OS was 61% (lower bound 90% confidence interval: 51%). On exploratory analysis, there were no significant changes in the composition and frequency of circulating immune cells after GC alone. However, there was a significant expansion of circulating CD4 cells with the addition of ipilimumab which correlated with improved survival. The response rate was significantly higher in patients with deleterious somatic DNA damage response mutations (sensitivity=47.6%, specificity=100%, positive predictive value=100%, and negative predictive value=38.9%). Limitations are related to the sample size and single-arm design. ConclusionsGC+ipilimumab did not achieve the primary endpoint of a lower bound of the 90% confidence interval for 1-yr OS of >60%. However, within the context of a small single-arm trial, the results may inform current approaches combining chemotherapy plus immunotherapy from the standpoint of feasibility, appropriate cytotoxic backbones, and potential predictive biomarkers. Trial registration: ClinicalTrials.gov NCT01524991. Patient summaryCombining chemotherapy and immune checkpoint blockade in patients with metastatic urothelial cancer is feasible. Further studies are needed to refine optimal combinations and evaluate tests that might identify patients most likely to benefit.

Differences in somatic DNA damage repair (DDR) gene alterations between primary and secondary muscle invasive bladder cancer (MIBC).

4519Background: Alterations in DDR genes, including the nucleotide excision repair gene ERCC2, have been shown to be associated with response to systemic chemotherapy in MIBC (Van Allen, 2014). We ...

Abstract 602: Deleterious alterations in DNA damage response genes are associated with improved outcome in muscle-invasive bladder cancer patients treated with radiation-based bladder preservation

Abstract Purpose: Radiotherapy (RT)-based bladder preservation is an alternative to perioperative chemotherapy and radical cystectomy (RC) for selected patients with muscle-invasive bladder cancer (MIBC). Recent data suggest that somatic DNA damage response (DDR) alterations are associated with improved outcome in MIBC patients receiving RC +/- perioperative chemotherapy. Improved understanding of the influence of DDR genetics on response to RT-based bladder preservation may aid patient selection. Methods: We performed deep, targeted capture sequencing of primary bladder tumors and paired/pooled normal specimens from 48 RT treated MIBC patients with a DDR gene-enriched panel. To test whether correlations of DDR alterations with outcomes were specific to a RT cohort, we also assessed a subset of these DDR genes that were sequenced in a previously published series of 89 patients who received RC +/- neoadjuvant platinum-based chemotherapy. Specimens were re-reviewed to confirm urothelial histology. Deleterious alterations were defined as somatic nonsense, frameshift, or splice site mutations, or missense mutations at or near functionally significant residues validated in the literature. Results: In the RT cohort, median RT dose was 66 Gy, and chemotherapy use was neoadjuvant and concurrent (46%), concurrent only (48%), or none (6%). Visibly complete TURBT was achieved in 71% of patients. Median surviving follow up was 28 months. There were 30 progression events (crude rate 63%), comprised of 22 metastases (crude 46%) and 24 local in-bladder recurrences (crude 50%). While 30 (63%) patients had alterations in DDR genes, only 13 (27%) patients had deleterious DDR alterations, specifically in ATM (2), BRCA1 (1), BRIP1 (1), ERCC2 (6), FANCD2 (1), and PALB2 (1). On multivariable Cox proportional hazards analysis, the presence of a deleterious DDR alteration was associated significantly with lower relapse risk (HR 0.28, 95% CI 0.08-0.95; p = 0.041), as well as with a trend towards lower risk for metastasis (HR 0.32, 95% CI 0.10-1.11; p = 0.07) and any disease progression (HR 0.35, 95% CI 0.12-1.03; p = 0.06). In the RC cohort, neoadjuvant chemotherapy was given in 39% of patients, and deleterious DDR gene alterations were noted only in 8% of the patients. On 2-sided log-rank testing, such alterations conferred a non-significant trend for improved recurrence-free survival (p = 0.20) and disease-specific survival (p = 0.10). Conclusion: Deleterious somatic alterations in DDR genes were associated with significantly improved outcomes in bladder cancer patients undergoing RT-based therapy and with a trend for improved outcomes in those treated with RC +/- platinum chemotherapy. Further research is warranted to validate these findings on an independent RT-treated dataset and to clarify the relationship in a larger chemotherapy-treated RC cohort. Citation Format: Neil B. Desai, Gopa Iyer, Eugene K. Cha, Sasinya N. Scott, Joseph Hreiki, John P. Sfakianos, Philip Kim, Aditya Bagroida, Bernard H. Bochner, Jonathan E. Rosenberg, Dean F. Bajorin, Michael F. Berger, Marisa A. Kollmeier, Hikmat Al-Ahmadie, David B. Solit. Deleterious alterations in DNA damage response genes are associated with improved outcome in muscle-invasive bladder cancer patients treated with radiation-based bladder preservation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 602. doi:10.1158/1538-7445.AM2015-602

FANCB is essential in the male germline and regulates H3K9 methylation on the sex chromosomes during meiosis.

Fanconi anemia (FA) is a recessive X-linked and autosomal genetic disease associated with bone marrow failure and increased cancer, as well as severe germline defects such as hypogonadism and germ cell depletion. Although deficiencies in FA factors are commonly associated with germ cell defects, it remains unknown whether the FA pathway is involved in unique epigenetic events in germ cells. In this study, we generated Fancb mutant mice, the first mouse model of X-linked FA, and identified a novel function of the FA pathway in epigenetic regulation during mammalian gametogenesis. Fancb mutant mice were infertile and exhibited primordial germ cell (PGC) defects during embryogenesis. Further, Fancb mutation resulted in the reduction of undifferentiated spermatogonia in spermatogenesis, suggesting that FANCB regulates the maintenance of undifferentiated spermatogonia. Additionally, based on functional studies, we dissected the pathway in which FANCB functions during meiosis. The localization of FANCB on sex chromosomes is dependent on MDC1, a binding partner of H2AX phosphorylated at serine 139 (γH2AX), which initiates chromosome-wide silencing. Also, FANCB is required for FANCD2 localization during meiosis, suggesting that the role of FANCB in the activation of the FA pathway is common to both meiosis and somatic DNA damage responses. H3K9me2, a silent epigenetic mark, was decreased on sex chromosomes, whereas H3K9me3 was increased on sex chromosomes in Fancb mutant spermatocytes. Taken together, these results indicate that FANCB functions at critical stages of germ cell development and reveal a novel function of the FA pathway in the regulation of H3K9 methylation in the germline.

The genotoxicity and systemic toxicity of a pharmaceutical effluent in Wistar rats may involve oxidative stress induction.

There is scarcity of information on the possible mechanisms of pharmaceutical effluent induced genotoxicity and systemic toxicity. This study investigated the genotoxicity and systemic toxicity of a pharmaceutical effluent in Wistar rats. Rats were orally treated with 5–50% concentrations of the effluent for 28 days. At post-exposure, blood, liver, kidney and bone marrow cells were examined for alterations in serum biochemical parameters and hematological indices, histopathological lesions and micronucleated polychromatic erythrocytes formation (MNPCE). The effluent caused concentration independent significant (p < 0.05) alterations in aspartate (AST) and alanine (ALT) aminotransferases, superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), total and direct bilirubin and creatinine. There was reduction in red blood count (RBC), hemoglobin concentration (HGB), platelets, percentage hematocrit (HCT), white blood count (WBC) and mean corpuscle hemoglobin (MCH) except mean corpuscle hemoglobin concentration (MCHC), which increased in the treated rats. Histopathological lesions observed in the liver and kidney of the effluent treated rats were thinning of the hepatic cord, kuffer cell hyperplasia, vacuolation of the hepatocytes and renal cells, multifocal inflammatory changes, necrosis and congestion of the renal blood vessels and central vein. MNPCE significantly increase in the bone marrow of the treated rats compared to the negative control. The concentration of some toxic metals and anions in the effluent were above standard permissible limits. These findings showed that the pharmaceutical effluent caused somatic DNA damage and systemic toxicity in rats may involve induction of oxidative stress, suggesting environmental contamination and health risks in wildlife and humans.

DAF-16/FOXO and EGL-27/GATA promote developmental growth in response to persistent somatic DNA damage.

Genome maintenance defects cause complex disease phenotypes characterized by developmental failure, cancer susceptibility, and premature aging. It remains poorly understood how DNA damage responses function during organismal development and maintain tissue functionality when DNA damage accumulates with aging. Here we show that the FoxO transcription factor DAF-16 is activated in response to DNA damage during development while the DNA damage responsiveness of DAF-16 declines with aging. We find that in contrast to its established role in mediating starvation arrest, DAF-16 alleviates DNA damage-induced developmental arrest and even in the absence of DNA repair promotes developmental growth and enhances somatic tissue functionality. We demonstrate that the GATA transcription factor EGL-27 co-regulates DAF-16 target genes in response to DNA damage and together with DAF-16 promotes developmental growth. We propose that EGL-27/GATA activity specifies DAF-16 mediated DNA damage responses to enable developmental progression and to prolong tissue functioning when DNA damage persists.

Induction of Fish Biomarkers by Synthetic-Based Drilling Muds

The study investigated the effects of chronic exposure of pink snapper (Pagrus auratus Forster), to synthetic based drilling muds (SBMs). Fish were exposed to three mud systems comprised of three different types of synthetic based fluids (SBFs): an ester (E), an isomerized olefin (IO) and linear alpha olefin (LAO). Condition factor (CF), liver somatic index (LSI), hepatic detoxification (EROD activity), biliary metabolites, DNA damage and stress proteins (HSP-70) were determined. Exposure to E caused biologically significant effects by increasing CF and LSI, and triggered biliary metabolite accumulation. While ester-based SBFs have a rapid biodegradation rate in the environment, they caused the most pronounced effects on fish health. IO induced EROD activity and biliary metabolites and LAO induced EROD activity and stress protein levels. The results demonstrate that while acute toxicity of SBMs is generally low, chronic exposure to weathering cutting piles has the potential to affect fish health. The study illustrates the advantages of the Western Australian government case-by-case approach to drilling fluid management, and highlights the importance of considering the receiving environment in the selection of SBMs.

Good, Bad, Mobile Elements: Genome’s Most Successful “Parasites” as Emerging Players in Cell and Organismal Aging

The biological bases of cellular and organismal aging are thought to involve, among others, basic stress response mechanisms. In this field an increasing amount of evidence, in recent years, point towards an important role of endogenous retroelements. During evolution these mobile genetic elements interpreted the dual role of selfish genomic parasites and useful "boosters" of genomic evolution. Similarly, in living cell these elements have an important role in stress response and in generating neuronal plasticity, but studies on in vitro cell cultures and animal models show that their excessive activation or misregulation may lead to DNA damage and cell senescence, and can trigger both innate immunity and a pro-inflammatory response. Being cell senescence, somatic DNA damage and inflammation three supposed key processes in human aging, and observing that several intracellular mechanisms normally controlling the activation of retroelements show a tendency to fade at late ages, a possible role of endogenous retroelements in organismal senescence is taken in consideration. A better knowledge of the basic mechanisms linking stress response, activation of endogenous retroelements and age-related cell/tissue alterations could not only help us gain a better understanding of the basic mechanisms of aging, but will also allow the experimentation of new therapeutic targets for different age-related diseases.

Increased Oxidative Stress and Genomic Instability in Peripheral Blood and Bone Marrow of Individuals with Fanconi Anemia,

Abstract 3425Impaired anti-oxidant defenses and overproduction of reactive oxygen species (ROS) in individuals with Fanconi anemia (FA) are associated with a pro-oxidant state in this population. Cells derived from individuals with FA demonstrate increased sensitivity to DNA damage by ambient oxygen and increased frequency of chromosomal aberrations. Studies in animals and human subjects indicate that higher levels of and increased sensitivity to both ROS and tumor necrosis factor-alpha in individuals with FA play key roles in the pathogenesis of bone marrow failure (BMF) and neoplastic transformation. Accumulation of somatic DNA damage can be assessed using the Glycophorin A assay (GPA), which is designed to detect potentially inactivating mutations caused by chromosome loss, large deletions, or recombination events at the erythrocyte GPA locus. Previous cross-sectional studies in individuals with FA have shown a markedly increased frequency of GPA variant cells, demonstrating increased DNA damage. Knowledge regarding the timecourse of the accumulation of this somatic DNA damage is lacking. The goal of the current study is to evaluate serum ROS levels and accumulation of somatic DNA damage in individuals with FA to better understand the contribution of oxidative stress to disease phenotype and progression to marrow failure or malignant transformation. ROS levels were assessed ex vivo from peripheral blood and bone marrow of individuals with FA and healthy controls. We used a flow cytometric method to quantify ROS level by incubation of samples with CM-H2DCFDA, a cell-permeable fluorescence dye that reacts to a broad spectrum of ROS. Peripheral blood was also serologically typed on first submission using anti-M and anti-N sera. As only heterozygous (MN) individuals are informative, only these individuals were studied further. We used the GPA assay to quantify the accumulation of somatic cell damage in peripheral blood samples as measured by GPA variant cell frequencies. Peripheral blood and/or bone marrow samples from 19 individuals with FA and normal controls were evaluated for ROS on 23 occasions. ROS levels were variable, with 13 of the FA patients demonstrating high levels of ROS as measured by MFI signal strength. Overall ROS levels in individuals with FA were higher than those of normal control individuals (132% of control ROS levels, p<0.09, see Table). When stratified by age, older individuals with FA (age ≥10 years) had significantly higher ROS than normal controls (159% of control levels, p<0.05). Evaluation of 32 children at our center with FA by MN genotyping has identified 13 who are MN heterozygotes eligible for GPA testing. The frequency of NO and NN variant cell frequencies were markedly increased in children with FA (range of 1.2 to 187.5 fold and 0.46 to 201.8 fold over controls respectively). Additionally, longitudinal samples over a 5 year period revealed stable elevation of NO variant frequency with increasing NN variant cell frequency. NN variant frequency was closer to normal in younger individuals with FA and progressively increased with age and development of bone marrow failure.Mean age (years)ROS (% normal control)p-valueAll FA10.21320.09FA age ≥ 10 years12.81590.05FA age < 10 years7.7910.31We demonstrate that individuals with FA have increased levels of ROS, and that ROS seems to increase with age. This correlates with accumulation of somatic DNA damage over time in this patient population. We hypothesize that ROS levels are low in younger FA individuals and progressively increase with age, resulting in accumulation of DNA damage. Additional longitudinal studies evaluating timecourse, intra-individual variability, and effects of complementation as well as environmental triggers are underway. We expect these studies to identify biomarkers that allow for earlier diagnosis leading to more timely therapy and to elucidate additional targets for novel therapeutic interventions to prevent BMF and myelodysplastic/leukemic transformation. Disclosures:No relevant conflicts of interest to declare.

PCNA ubiquitination-independent activation of polymerase η during somatic hypermutation and DNA damage tolerance

The generation of high affinity antibodies in B cells critically depends on translesion synthesis (TLS) polymerases that introduce mutations into immunoglobulin genes during somatic hypermutation (SHM). The majority of mutations at A/T base pairs during SHM require ubiquitination of PCNA at lysine 164 (PCNA-Ub), which activates TLS polymerases. By comparing the mutation spectra in B cells of WT, TLS polymerase η (Polη)-deficient, PCNA K164R-mutant, and PCNA K164R;Polη double-mutant mice, we now find that most PCNA-Ub-independent A/T mutagenesis during SHM is mediated by Polη. In addition, upon exposure to various DNA damaging agents, PCNA K164R mutant cells display strongly impaired recruitment of TLS polymerases, reduced daughter strand maturation and hypersensitivity. Interestingly, compared to the single mutants, PCNA K164R;Polη double-mutant cells are dramatically delayed in S phase progression and far more prone to cell death following UV exposure. Taken together, these data support the existence of PCNA ubiquitination-dependent and -independent activation pathways of Polη during SHM and DNA damage tolerance.

Cellular adaptive response to chronic radiation exposure in interventional cardiologists

Aims Invasive cardiologists are the most exposed to ionizing radiation among health professionals and show an increased rate of somatic DNA damage. To evaluate the effects of chronic low-dose exposure to ionizing radiation on redox state and apoptotic activation. Methods and results We enrolled 10 healthy exposed professionals (all interventional cardiologists, Group II, exposed: age = 38 ± 5 years) and 10 age- and gender-matched unexposed controls (Group I, non-exposed). Exposed subjects had a median exposure of 4 mSv/year (range 1-8) by film badge dosimetry (below lead apron). We measured reduced glutathione (GSH, a marker of antioxidant response) in erythrocytes and plasma generation of hydrogen peroxide (a marker of oxyradical stress) by ferrous oxidation-xylenol orange assay in plasma. In both groups, lymphocytes were isolated and caspase-3 activity (a marker of apoptotic response) measured at baseline and following 2 Gy in vitro irradiation. Exposed subjects showed a three-fold increase in hydrogen peroxide (Group I = 2.21 ± 1.03 vs. II = 6.51 ± 1.55 μM H(2)O(2) equivalents) and a 1.7-fold increase in GSH (I = 12.37 ± 1.22 vs. II = 20.61 ± 2.16 mM). Exposed subjects also showed higher values of caspase-3 activity, both at baseline and-more strikingly-following high-dose radiation challenge. Conclusion In interventional cardiologists, chronic exposure to low-dose radiation is associated with an altered redox balance mirrored by an increase in hydrogen peroxide and with two possibly adaptive cellular responses: (i) an enhanced antioxidant defence (increase in GSH, counteracting increased oxyradical stress) and (ii) an increased susceptibility to apoptotic induction which might efficiently remove genetically damaged cells.

Lifespan extension by dietary restriction is not linked to protection against somatic DNA damage in Drosophila melanogaster

Dietary restriction (DR) has been shown to robustly extend lifespan in multiple species tested so far. The pro-longevity effect of DR is often ascribed to an increase in cellular defense against somatic damage, most notably damage by reactive oxygen species (ROS), considered a major cause of aging. Especially irreversible damage to DNA, the carrier of genetic information, is considered a critical causal factor in aging. Using a recently developed transgenic Drosophila melanogaster model system harboring a lacZ-plasmid construct that can be recovered in E. coli, spontaneous DNA mutation frequency in flies under DR and ad libitum conditions are measured. Three different DR conditions, imposed by manipulating levels of different types of yeast sources, were tested in females and males of two lacZ reporter gene lines. Feeding with the ROS producer paraquat at 1 mM resulted in a rapid accumulation of somatic mutations, indicating that the frequency of mutations at the lacZ locus is a reliable marker for increased oxidative stress. However, none of the DR conditions altered the accumulation of spontaneous mutations with age. These results suggest that the beneficial effects of DR are unlikely to be linked to protection against oxidative somatic DNA damage.

Differential Requirements for RAD51 inPhyscomitrella patensandArabidopsis thalianaDevelopment and DNA Damage Repair

RAD51, the eukaryotic homolog of the bacterial RecA recombinase, plays a central role in homologous recombination (HR) in yeast and animals. Loss of RAD51 function causes lethality in vertebrates but not in other animals or in the flowering plant Arabidopsis thaliana, suggesting that RAD51 is vital for highly developed organisms but not for others. Here, we found that loss of RAD51 function in the moss Physcomitrella patens, a plant of less complexity, caused a significant vegetative phenotype, indicating an important function for RAD51 in this organism. Moreover, loss of RAD51 caused marked hypersensitivity to the double-strand break-inducing agent bleomycin in P. patens but not in Arabidopsis. Therefore, HR is used for somatic DNA damage repair in P. patens but not in Arabidopsis. These data imply fundamental differences in the use of recombination pathways between plants. Moreover, these data demonstrate that the importance of RAD51 for viability is independent of taxonomic position or complexity of an organism. The involvement of HR in DNA damage repair in the slowly evolving species P. patens but not in fast-evolving Arabidopsis suggests that the choice of the recombination pathway is related to the speed of evolution in plants.

Relationships between intertidal clam population and health status of the soft-shell clam Mya arenaria in the St. Lawrence Estuary and Saguenay Fjord (Québec, Canada)

The purpose of this study was to examine the impacts of anthropogenic activity on the health status of intertidal clam populations of the Saguenay Fjord and the St. Lawrence Estuary (Québec, Canada). Clams were collected during low tide at sites subject to direct contamination and at sites far from human activity. Clams were analyzed for tributyltin and dibutyltin total levels and toxic stress (glutathione S-transferase, gonadal lipid peroxidation and DNA strand breaks), immunocompetence (phagocytic activity, hemocyte count and viability), reproduction (gonado-somatic index, gamete maturation, and vitellogenin-like proteins), energy status (temperature-dependent mitochondrial electron transport, and gonad lipids), and individual status (age, condition factor, and growth index). These responses were compared against population characteristics such as live clam density, number of empty shells, and sex ratio. The results show that clam density decreased with distance from the estuary (high salinity level) to upstream of the fjord (low salinity). There was no clear relationship between the number of empty shells and distance or site quality. Clam density values corrected against distance were significantly correlated with hemocyte viability, phagocytic activity, mitochondrial electron transport (MET), DNA damage in gonad, and temperature-dependent mitochondrial electron transport activity. A canonical analysis of the various groups of biomarkers revealed that population metrics were more strongly related with immunocompetence, followed by energy status and temperature-dependent mitochondrial electron transport activity. However, toxic stress biomarkers were strongly associated with energy status and reproduction. This was further confirmed by non-linear modeling using adaptive artificial neural networks (genetic selection and back propagation learning paradigms), where the following parameters were able to predict population parameters with <20% error: gonad maturation and somatic index, MET (at 4 °C), gonad LPO, DNA damage, and phagocytic capacity. Intertidal clam populations were influenced by a distance gradient effect (salinity), where immunocompetence, in addition to energy status, was the strongest physiological parameter related to clam population metrics.

Chronic low-dose radiation exposure from interventional cardiology procedures induces chromosomal abnormalities in originally genetically identical twins

Current radiation protection standards are based on the premise that even low dose of ionizing radiation may result in detrimental health effects, such as long-term development of cancer and hereditary disease [ [1] Committee on the Biological Effects of Ionizing Radiation Health effects from exposure to low levels of ionizing radiation. National Research Council, 2005 Google Scholar ]. Cardiovascular testing accounts for at least one-third of all ionising testing and invasive cardiologists working in a busy catheterization laboratory are the most exposed among professionally exposed physicians. Interventional cardiologists have an exposure per-head per year two to three times higher than that of radiologists [ 2 Cordella J, Faulkner K, Hopewell J, et al. Avoidance of radiation injuries from medical interventional procedures extracted from International Commission on Radiaton Protection.ICRP Publication 85. Ann. ICRP 30:2 (2000). Google Scholar , 3 Hirshfeld Jr., J.W. Balter S. Brinker J.A. et al. American College of Cardiology Foundation; American Heart Association; HRS; SCAI; American College of Physicians Task Force on Clinical Competence and Training. ACCF/AHA/HRS/SCAI clinical competence statement on physician knowledge to optimize patient safety and image quality in fluoroscopically guided invasive cardiovascular procedures: a report of the American College of Cardiology Foundation/American Heart Association/American College. Circulation. 2005; 111: 511-532 Crossref PubMed Scopus (208) Google Scholar ]. Chromosome aberration (CA)-based assays are considered the gold standard of biological dosimeter of radiation exposure and intermediate endpoints of cancer risk [ [4] International Atomic Energy Agency (IAEA) Cytogenetic analysis for radiation dose assessment. Technical Report. vol. 405. 2001 Google Scholar ]. We and others have recently reported that cardiologists working in a high-volume catheterization laboratory chronically exposed to low-dose radiation well within allowed limits show increased chromosomal damage versus non-exposed controls [ 5 Zakeri F. Assaei R.G. Cytogenetic monitoring of personnel working in angiocardiography laboratories in Iran hospitals. Mutat Res. 2004; 562: 1-9 Crossref PubMed Scopus (45) Google Scholar , 6 Andreassi M.G. Cioppa A. Botto N. et al. Somatic DNA damage in interventional cardiologists: a case-control study. FASEB J. 2005; 19: 998-999 Crossref PubMed Scopus (89) Google Scholar ]. However, from a case-control study, it is not completely possible to determine the role of other potentially confounding factors that appear to have great influence on the frequency of CA, such as age, smoking or individual genetic susceptibility.