Prodrug Nanosensitizer Overcomes the Radiation Resistance of Hypoxic Tumor

Clinical radiation therapy (RT) is often hindered by the low radiation energy absorption coefficient and the hypoxic features of tumor tissues. Among the tremendous efforts devoted to overcoming the barriers to efficient RT, the application of hypoxic radiosensitizers and cell-cycle-specific chemotherapeutics has shown great potential. However, their effectiveness is often compromised by their limited bioavailability, especially in the hypoxic region, which plays a major role in radioresistance. Herein, to simultaneously improve the delivery efficacy of both hypoxic radiosensitizer and cell-cycle-specific drug, a gambogic acid (GA) metronidazole (MN) prodrug (GM) was designed and synthesized based on GA, a naturally occurring chemotherapeutic and multiple pathway inhibitor, and MN, a typical hypoxic radiosensitizer. In combination with MN-containing block copolymers, the prodrug nanosensitizer (NS) of GM was obtained. Owing to the bioreduction of MN, the as-designed prodrug could be efficiently delivered to hypoxic cells and act on mitochondria to cause the accumulation of reactive oxygen species. The strong G₂/M phase arrest caused by the prodrug NS could further sensitize treated cells to external radiation under hypoxic conditions by increasing DNA damage and delaying DNA repair. After coadministration of the NS with a well-established tissue-penetrating peptide, efficient tumor accumulation, deep tumor penetration, and highly potent chemoradiotherapy could be achieved.

Atomic Nanogenerators in Targeted Alpha Therapies: Curie's Legacy in Modern Cancer Management

Atomic in vivo nanogenerators such as actinium-225, thorium-227, and radium-223 are of increasing interest and importance in the treatment of patients with metastatic cancer diseases. This is due to their peculiar physical, chemical, and biological characteristics, leading to astonishing responses in otherwise resistant patients. Nevertheless, there are still a few obstacles and hurdles to be overcome that hamper the broader utilization in the clinical setting. Next to the limited supply and relatively high costs, the in vivo complex stability and the fate of the recoiling daughter radionuclides are substantial problems that need to be solved. In radiobiology, the mechanisms underlying treatment efficiency, possible resistance mechanisms, and late side effect occurrence are still far from being understood and need to be unraveled. In this review, the current knowledge on the scientific and clinical background of targeted alpha therapies is summarized. Furthermore, open issues and novel approaches with a focus on the future perspective are discussed. Once these are unraveled, targeted alpha therapies with atomic in vivo nanogenerators can be tailored to suit the needs of each patient when applying careful risk stratification and combination therapies. They have the potential to become one of the major treatment pillars in modern cancer management.

Integrating mammographic breast density in glandular dose calculation

OBJECTIVE

This work proposes the use of mammographic breast density (MBD) to estimate actual glandular dose (AGD), and assesses how AGD compares to mean glandular dose (MGD) estimated using Dance et al method.

METHODS

A retrospective sample of anonymised mammograms (52,405) was retrieved from a central database. Technical parameters and patient characteristics were exported from the Digital Imaging and Communication in Medicine (DICOM) header using third party software. LIBRA (Laboratory for Individualized Breast Radiodensity Assessment) software package (University of Pennsylvania, Philadelphia, USA) was used to estimate MBDs for each mammogram included in the data set. MGD was estimated using Dance et al method, while AGD was calculated by replacing Dance et al standard glandularities with LIBRA estimated MBDs. A linear regression analysis was used to assess the association between MGD and AGD, and a Bland-Altman analysis was performed to assess their mean difference.

RESULTS

The final data set included 31,097 mammograms from 7728 females. MGD, AGD, and MBD medians were 1.53 , 1.62 mGy and 8% respectively. When stratified per breast thickness ranges, median MBDs were lower than Dance's standard glandularities. There was a strong positive correlation (R2 = 0.987, p < 0.0001) between MGD and AGD although the Bland-Altman analysis revealed a small statistically significant bias of 0.087 mGy between MGD and AGD (p < 0.001).

CONCLUSION

AGD estimated from MBD is highly correlated to MGD from Dance method, albeit the Dance method underestimates dose at smaller CBTs. Advances in knowledge: Our work should provide a stepping-stone towards an individualised dose estimation using automated clinical measures of MBD.

Ionizing radiation biomarkers in epidemiological studies - An update

Recent epidemiology studies highlighted the detrimental health effects of exposure to low dose and low dose rate ionizing radiation (IR): nuclear industry workers studies have shown increased leukaemia and solid tumour risks following cumulative doses of <100mSv and dose rates of <10mGy per year; paediatric patients studies have reported increased leukaemia and brain tumours risks after doses of 30-60mGy from computed tomography scans. Questions arise, however, about the impact of even lower doses and dose rates where classical epidemiological studies have limited power but where subsets within the large cohorts are expected to have an increased risk. Further progress requires integration of biomarkers or bioassays of individual exposure, effects and susceptibility to IR. The European DoReMi (Low Dose Research towards Multidisciplinary Integration) consortium previously reviewed biomarkers for potential use in IR epidemiological studies. Given the increased mechanistic understanding of responses to low dose radiation the current review provides an update covering technical advances and recent studies. A key issue identified is deciding which biomarkers to progress. A roadmap is provided for biomarker development from discovery to implementation and used to summarise the current status of proposed biomarkers for epidemiological studies. Most potential biomarkers remain at the discovery stage and for some there is sufficient evidence that further development is not warranted. One biomarker identified in the final stages of development and as a priority for further research is radiation specific mRNA transcript profiles.

The contribution of women to radiobiology: Marie Curie and beyond

Marie Sklodowska-Curie, an extraordinary woman, a Polish scientist who lived and worked in France, led to the development of nuclear energy and the treatment of cancer. She was the laureate of two Nobel Prizes, the first woman in Europe who obtained the degree of Doctor of Science and opened the way for women to enter fields which had been previously reserved for men only. As a result of her determination and her love of freedom, she has become an icon for many female scientists active in radiation sciences. They are successors of Maria Curie and without the results of their work, improvement in radiation oncology will not be possible. Many of them shared some elements of Maria Curie's biography, like high ethical and moral standards, passionate dedication to work, strong family values, and scientific collaboration with their husbands. The significance of Tikvah Alper, Alma Howard, Shirley Hornsey, Juliana Denekamp, Helen Evans, Eleanor Blakely, Elizabeth L. Travis, Fiona Stewart, Andree Dutreix, Catharine West, Peggy Olive, Ingela Turesson, Penny Jeggo, Irena Szumiel, Eleonor Blakely, Sara Rockwell and Carmel Mothersill contribution to radiation oncology is presented. All the above mentioned ladies made significant contribution to the development of radiotherapy (RT) and more efficient cancer treatment. Due to their studies, new schedules of RT and new types of ionizing radiation have been applied, lowering the incidence of normal tissue toxicity. Their achievements herald a future of personalized medicine.

Dynamic changes in subcellular localization of cattle XLF during cell cycle, and focus formation of cattle XLF at DNA damage sites immediately after irradiation

Clinically, many chemotherapeutics and ionizing radiation (IR) have been applied for the treatment of various types of human and animal malignancies. These treatments kill tumor cells by causing DNA double-strand breaks (DSBs). Core factors of classical nonhomologous DNA-end joining (C-NHEJ) play a vital role in DSB repair. Thus, it is indispensable to clarify the mechanisms of C-NHEJ in order to develop next-generation chemotherapeutics for cancer. The XRCC4-like factor (XLF; also called Cernunnos or NHEJ1) is the lastly identified core NHEJ factor. The localization of core NHEJ factors might play a critical role in regulating NHEJ activity. The localization and function of XLF have not been elucidated in animal species other than mice and humans. Domestic cattle (Bos taurus) are the most common and vital domestic animals in many countries. Here, we show that the localization of cattle XLF changes dynamically during the cell cycle. Furthermore, EYFP-cattle XLF accumulates quickly at microirradiated sites and colocalizes with the DSB marker γH2AX. Moreover, nuclear localization and accumulation of cattle XLF at DSB sites are dependent on 12 amino acids (288-299) of the C-terminal region of XLF (XLF CTR). Furthermore, basic amino acids on the XLF CTR are highly conserved among domestic animals including cattle, goat and horses, suggesting that the CTR is essential for the function of XLF in domestic animals. These findings might be useful to develop the molecular-targeting therapeutic drug taking XLF as a target molecule for human and domestic animals.

Life-span carcinogenicity studies on Sprague-Dawley rats exposed to γ-radiation: design of the project and report on the tumor occurrence after post-natal radiation exposure (6 weeks of age) delivered in a single acute exposure

BACKGROUND

Experimental long-term carcinogenicity bioassays conducted on rats and mice proved that ionizing radiation can induce a variety of tumor types. However few studies have been conducted on rats.

METHODS

This report deals with the effects of γ-radiation in groups of 416-1,051 6-weeks old Sprague-Dawley rats exposed to 0, 0.1, 1, or 3 Gy of γ-radiation delivered in a single acute exposure. The experiment lasted for the animals' lifespan and all were necropsied and underwent full histopathological evaluation.

RESULTS

The results confirm the dose-related carcinogenic effects of γ-radiation for several organs and tissues. Moreover they indicate that exposure to 0.1 Gy induces a statistically significant increased incidence in Zymbal gland carcinomas and pancreas islet cell carcinomas in females.

CONCLUSIONS

Our data show that exposure to γ-radiation induces carcinogenic effects at all tested doses.

Etiology and treatment of hematological neoplasms: stochastic mathematical models

Leukemias are driven by stemlike cancer cells (SLCC), whose initiation, growth, response to treatment, and posttreatment behavior are often "stochastic", i.e., differ substantially even among very similar patients for reasons not observable with present techniques. We review the probabilistic mathematical methods used to analyze stochastics and give two specific examples. The first example concerns a treatment protocol, e.g., for acute myeloid leukemia (AML), where intermittent cytotoxic drug dosing (e.g., once each weekday) is used with intent to cure. We argue mathematically that, if independent SLCC are growing stochastically during prolonged treatment, then, other things being equal, front-loading doses are more effective for tumor eradication than back loading. We also argue that the interacting SLCC dynamics during treatment is often best modeled by considering SLCC in microenvironmental niches, with SLCC-SLCC interactions occurring only among SLCC within the same niche, and we present a stochastic dynamics formalism, involving "Poissonization," applicable in such situations. Interactions at a distance due to partial control of total cell numbers are also considered. The second half of this chapter concerns chromosomal aberrations, lesions known to cause some leukemias. A specific example is the induction of a Philadelphia chromosome by ionizing radiation, subsequent development of chronic myeloid leukemia (CML), CML treatment, and treatment outcome. This time evolution involves a coordinated sequence of > 10 steps, each stochastic in its own way, at the subatomic, molecular, macromolecular, cellular, tissue, and population scales, with corresponding time scales ranging from picoseconds to decades. We discuss models of these steps and progress in integrating models across scales.

From 'Image Gently' to image intelligently: a personalized perspective on diagnostic radiation risk

The risk of ionizing radiation from diagnostic imaging has been a popular topic in the radiology literature and lay press. Communicating the magnitude of risk to patients and caregivers is problematic because of the uncertainty in estimates derived principally from epidemiological studies of large populations, and alternative approaches are needed to provide a scientific basis for personalized risk estimates. The underlying patient disease and life expectancy greatly influence risk projections. Research into the biological mechanisms of radiation-induced DNA damage and repair challenges the linear no-threshold dose-response assumption and reveals that individuals vary in sensitivity to radiation. Studies of decision-making psychology show that individuals are highly susceptible to irrational biases when judging risks. Truly informed medical decision-making that respects patient autonomy requires appropriate framing of radiation risks in perspective with other risks and with the benefits of imaging. To follow the principles of personalized medicine and treat patients according to their specific phenotypic and personality profiles, diagnostic imaging should optimally be tailored not only to patient size, body region and clinical indication, but also to underlying disease conditions, radio-sensitivity and risk perception and preferences that vary among individuals.

Assessment of targeted and non-targeted responses in cells deficient in ATM function following exposure to low and high dose X-rays

Radiation sensitivity at low and high dose exposure to X-rays was investigated by means of chromosomal aberration (CA) analysis in heterozygous ATM mutation carrier and A-T patient (biallelic ATM mutation) lymphoblastoid cell lines (LCLs). Targeted and non-targeted responses to acutely delivered irradiation were examined by applying a co-culture system that enables study of both directly irradiated cells and medium-mediated bystander effects in the same experimental setting. No indication of radiation hypersensitivity was observed at doses of 0.01 Gy or 0.1 Gy for the ATM mutation carrier LCL. The A-T patient cells also did not show low-dose response. There was significant increase in unstable CA yields for both ATM mutation carrier and A-T LCLs at 1 and 2 Gy, the A-T cells displaying more distinct dose dependency. Both chromosome and chromatid type aberrations were induced at an increased rate in the irradiated A-T cells, whereas for ATM carrier cells, only unstable chromosomal aberrations were increased above the level observed in the wild type cell line. No bystander effect could be demonstrated in any of the cell lines or doses applied. Characteristics typical for the A-T cell line were detected, i.e., high baseline frequency of CA that increased with dose. In addition, dose-dependent loss of cell viability was observed. In conclusion, CA analysis did not demonstrate low-dose (≤100 mGy) radiosensitivity in ATM mutation carrier cells or A-T patient cells. However, both cell lines showed increased radiosensitivity at high dose exposure.

P53-participated cellular and molecular responses to irradiation are cell differentiation-determined in murine intestinal epithelium

AIM

Cells respond differently to DNA damaging agents, which may related to cell context and differentiation status. The aim of present study was to observe the cellular and molecular responses of cells in different differentiation status to ionizing irradiation (IR).

METHODS

Crypt-villus unit of murine small intestine was adopted as a cell differentiation model. DNA damage responses (DDRs) of crypt and villus were observed 1-24 h after 12 Gy IR using gene expression microarray analysis, immunohistochemical staining, Western blotting and Electrophoretic Mobility Shift Assay.

RESULTS

Microarray analysis revealed that most differentially expressed genes were related to p53 signaling pathway in crypt 4h after IR and in both crypt and villus 24h after IR. In crypt stem cells/progenitor cells, H2AX was phosphorylated and dephosphorylated quickly, Ki67 attenuated, cell apoptosis enhanced, phosphorylated P53 increased and translocated into nuclear with the ability to bind p53-specific sequence. In upper crypt (transit amplifying cells) and crypt-villus junction, cells kept survive and proliferate as indicated by retained Ki67 expression, suppressed p53 activation, and rare apoptosis.

CONCLUSIONS

DDRs varied with cell differentiation status and cell function in small intestinal epithelium. P53 signaling pathway could be an important regulatory mechanism of DDRs.

Non invasive assessment of lung disease in ataxia telangiectasia by high-field magnetic resonance imaging

PURPOSE

A sensitive imaging technique that assesses ataxia telangiectasia (AT) lung disease without ionizing radiation is highly desirable. We designed a study to evaluate lung changes using magnetic resonance imaging (MRI), and to investigate the relationships among severity and extent of pulmonary abnormalities and clinical, microbiological and functional data in children and young adults with AT.

METHODS

Fifteen AT patients (age, 11.3 years; range, 6-31) underwent 3.0-T MRI, spirometry, and deep throat or sputum culture. Images were scored using a modified Helbich score.

RESULTS

Although only 8 patients (53 %) had recurrent/chronic respiratory symptoms, MRI identified lung abnormalities in all. Bronchiectasis, peribronchial thickening, mucous plugging, and collapse/consolidation were present in 60 %, 87 %, 67 %, and 13 % of cases, respectively, with no difference between subjects with or without respiratory symptoms. No difference in changes of specific scores was found between the two groups, but the total MRI score was higher in patients with respiratory symptoms (6.5 versus 5, respectively; p = 0.02). Total or specific MRI scores were not associated with patients' age. Of all scores, only mucous plugging subscore appeared significantly related to FEV1 (r = 0.7, p = 0.04) and FEF25-75% (r = 0.9, p = 0.001). MRI scores from patients with positive (n = 5) or negative (n = 10) sputum culture were not significantly different.

CONCLUSIONS

MRI is valuable in the assessment of extent and severity of pulmonary changes in children and adults with AT. It represents an helpful tool for the longitudinal evaluation of patients and may be also used as an outcome surrogate to track the effects of medications.

Chemoprevention by N-acetylcysteine of low-dose CT-induced murine lung tumorigenesis

Data from the National Lung Screening Trial suggested that annual computed tomography (CT) screening of at-risk patients decreases lung cancer mortality by 20%. We assessed the effects of low-dose CT radiation in mice exposed to 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK) to mimic the effects of annual CT screening in heavy smokers and ex-smokers. A/J mice were treated at 8 weeks with NNK followed 1 week later by 4 weekly doses of 0, 10, 30 or 50 mGy of whole-body CT and euthanized 8 months later. Irradiated mice exhibited significant 1.8- to 2-fold increases in tumor multiplicity in males (16.1 ± 0.8 versus 9.1 ± 1.5 tumors per mouse; P < 0.0001) and females (21.6 ± 0.8 versus 10.5 ± 1.4 tumors per mouse; P < 0.0001), respectively, compared with unirradiated mice with no dose effect observed; female mice exhibited higher sensitivity to radiation exposure than did males (P < 0.0001). Similar results were obtained when tumor area was determined. To assess if the deleterious effects of radiation could be prevented by antioxidants, female mice were fed a diet containing 0.7% N-acetylcysteine (NAC) starting 3 days prior to the first CT exposure and continuing for a total of 5 weeks. NAC prevented CT induced increases in tumor multiplicity (10.5 ± 1.2 versus 20.7 ± 1.5 tumors per mouse; P < 0.0001) back to levels seen in NNK/unirradiated mice (10.5 ± 1.2). Our data suggest that exposure of sensitive populations to CT radiation increases the risk of tumorigenesis, and that antioxidants may prevent the long-term carcinogenic effects of low-dose radiation exposure. This would allow annual screening with CT while preventing the potential long-term toxicity of radiation exposure.

Heterochromatinization associated with cell differentiation as a model to study DNA double strand break induction and repair in the context of higher-order chromatin structure

Cell differentiation is associated with extensive gene silencing, heterochromatinization and potentially decreasing need for repairing DNA double-strand breaks (DSBs). Differentiation stages of blood cells thus represent an excellent model to study DSB induction, repair and misrepair in the context of changing higher-order chromatin structure. We show that immature granulocytes form γH2AX and 53BP1 foci, contrary to the mature cells; however, these foci colocalize only rarely and DSB repair is inefficient. Moreover, specific chromatin structure of granulocytes probably influences DSB induction.

Possible role of the WDR3 gene on genome stability in thyroid cancer patients

The role of the WDR3 gene on genomic instability has been evaluated in a group of 115 differentiated thyroid cancer (DTC) patients. Genomic instability has been measured according to the response of peripheral blood lymphocytes to ionizing radiation (0.5 Gy). The response has been measured with the micronucleus (MN) test evaluating the frequency of binucleated cells with MN (BNMN), both before and after the irradiation. No differences between genotypes, for the BNMN frequencies previous the irradiation, were observed. Nevertheless significant decreases in DNA damage after irradiation were observed in individuals carrying the variant alleles for each of the three genotyped SNPs: rs3754127 [−8.85 (−15.01 to −2.70), P<0.01]; rs3765501 [−8.98 (−15.61 to −2.36), P<0.01]; rs4658973 [−8.70 (−14.94 to −2.46), P<0.01]. These values correspond to those obtained assuming a dominant model. This study shows for the first time that WDR3 can modulate genome stability.

Irradiation induced foci (IRIF) as a biomarker for radiosensitivity

It has long been known that the level of radiosensitivity between individuals covers a considerable range. This range is reflected in analysis of patient cell lines with some cell lines showing significantly reduced sensitivity to in vitro radiation exposure. Our increased exposure to radiation from diagnostic medical procedures and other life style changes has raised concerns that there may be individuals who are at an elevated risk from the harmful impact of acute or chronic low dose radiation exposure. Additionally, a subset of patients show an enhanced normal tissue response following radiotherapy, which can cause significant discomfort and, at the extreme, be life threatening. It has long been realised that the ability to identify sensitive individuals and to understand the mechanistic basis underlying the range of sensitivity within the population is important. A reduced ability to efficiently repair DNA double strand breaks (DSB) and/or activate the DSB damage response underlies some, although not necessarily all, of this sensitivity. In this article, we consider the utility of the recently developed γH2AX foci analysis to provide insight into radiation sensitivity within the population. We consider the nature of sensitivity including the impact of radiation on cell survival, tissue responses and carcinogenesis and the range of responses within the population. We overview the current utility of the γH2AX assay for assessing the efficacy of the DNA damage response to low and high dose radiation and its potential future exploitation.

Combined haploinsufficiency and genetic control of the G2/M checkpoint in irradiated cells

When cells are exposed to a dose of radiation large enough to cause chromosome aberrations, they become arrested at the G(2)/M checkpoint, facilitating DNA repair. Defects in checkpoint control genes can impart radiosensitivity. Arrest kinetics were monitored in mouse embryo fibroblasts at doses ranging from 10 mGy to 5.0 Gy of γ radiation over a time course of 0 to 12 h. We observe no significant checkpoint engagement at doses below 100 mGy. The checkpoint is only fully activated at doses where most of the cells are either bound for mitotic catastrophe or are reproductively dead. Atm null cells with ablated checkpoint function exhibited no robust arrest. Surprisingly, haploinsufficiency for ATM alone or in combination with other radioresistance genes did not alter checkpoint activation. We have shown previously that haploinsufficiency for several radioresistance genes imparts intermediate phenotypes for several end points including apoptosis, transformation and survival. These findings suggest that checkpoint control does not contribute toward these intermediate phenotypes and that different biological processes can be activated at high doses compared to low doses.

Comprehensive profiling of radiosensitive human cell lines with DNA damage response assays identifies the neutral comet assay as a potential surrogate for clonogenic survival

In an effort to explore the possible causes of human radiosensitivity and identify more rapid assays for cellular radiosensitivity, we interrogated a set of assays that evaluate cellular functions involved in recognition and repair of DNA double-strand breaks: (1) neutral comet assay, (2) radiation-induced γ-H2AX focus formation, (3) the temporal kinetics of structural maintenance of chromosomes 1 phosphorylation, (4) intra-S-phase checkpoint integrity, and (5) mitochondrial respiration. We characterized a unique panel of 19 "radiosensitive" human lymphoblastoid cell lines from individuals with undiagnosed diseases suggestive of a DNA repair disorder. Radiosensitivity was defined by reduced cellular survival using a clonogenic survival assay. Each assay identified cell lines with defects in DNA damage response functions. The highest concordance rate observed, 89% (17/19), was between an abnormal neutral comet assay and reduced survival by the colony survival assay. Our data also suggested that the neutral comet assay would be a more rapid surrogate for analyzing DNA repair/processing disorders.

Association of BRCA1 functional single nucleotide polymorphisms with risk of differentiated thyroid carcinoma

BACKGROUND

Breast cancer 1, early onset (BRCA1) is a vital DNA repair gene, and the single nucleotide polymorphisms (SNPs) of this gene have been studied in diverse cancer types. In this study, we investigated the association between eight common BRCA1 functional SNPs and the risk of differentiated thyroid carcinoma (DTC).

METHODS

This cancer center-based case-control study included 303 DTC cases and 511 controls. A polymerase chain reaction-based restriction fragment length polymorphism assay was performed for genotyping. Unconditional logistical regression analysis was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) in single-SNP analysis and haplotype analysis.

RESULTS

A decreased risk of DTC was found for the A1988G heterozygous AG genotype (adjusted OR=0.63, 95% CI: 0.45-0.87, Bonferroni-adjusted p-value=0.036). AATAATA and ATAA haplotypes that carry C33420T variant allele were associated with reduced papillary thyroid cancer risk (adjusted OR=0.52, 95% CI: 0.33-0.84; adjusted OR=0.62, 95% CI: 0.40-0.95, respectively). Also, having a combination of ≥3 favorable genotypes was associated with a DTC risk reduction (adjusted OR=0.69, 95% CI: 0.50-0.95). The A31875G AG/GG genotype was associated with a 69% reduced risk of multifocal primary tumor in DTC patients (adjusted OR=0.31, 95% CI: 0.12-0.81).

CONCLUSION

BRCA1 genetic polymorphisms may play a role in DTC risk, while the possible associations warrant confirmation in independent studies.

DNAtraffic--a new database for systems biology of DNA dynamics during the cell life

DNAtraffic (http://dnatraffic.ibb.waw.pl/) is dedicated to be a unique comprehensive and richly annotated database of genome dynamics during the cell life. It contains extensive data on the nomenclature, ontology, structure and function of proteins related to the DNA integrity mechanisms such as chromatin remodeling, histone modifications, DNA repair and damage response from eight organisms: Homo sapiens, Mus musculus, Drosophila melanogaster, Caenorhabditis elegans, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Escherichia coli and Arabidopsis thaliana. DNAtraffic contains comprehensive information on the diseases related to the assembled human proteins. DNAtraffic is richly annotated in the systemic information on the nomenclature, chemistry and structure of DNA damage and their sources, including environmental agents or commonly used drugs targeting nucleic acids and/or proteins involved in the maintenance of genome stability. One of the DNAtraffic database aim is to create the first platform of the combinatorial complexity of DNA network analysis. Database includes illustrations of pathways, damage, proteins and drugs. Since DNAtraffic is designed to cover a broad spectrum of scientific disciplines, it has to be extensively linked to numerous external data sources. Our database represents the result of the manual annotation work aimed at making the DNAtraffic much more useful for a wide range of systems biology applications.