William K. Kaufmann - US grants

The objectives of the project are to describe and define the operations of a DNA excision repair pathway in carcinogen-damaged human fibroblasts rendered permeable to enzymes, substrates and cofactors. Cells will be treated with 254 nm radiation or with (+-)-7alpha,8beta-dihydroxy-9beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo(a)py rene to damage DNA, then permeabilized and incubated in vitro for assay of each step of excision repair. The conditions for assaying the strand incision step of repair in permeable cells will be optimized with attention directed to maximizing the signal of damage-directed strand incisions while minimizing non-specific DNA breakage. Reparative strand incisions, release of damaged DNA, gap-filling DNA synthesis and strand ligation all will be quantified in permeable cells and the efficiency of operation of each step compared with what is seen in intact cells. The sensitivity to digestion by micrococcal nuclease of repair patches synthesized in permeable cells will also be determined. The DNA repair assays will then be performed using permeable xeroderma pigmentosum cells with moderate or severe reparative deficiencies in order to quantify the reparative deficit in vitro. DNA-free human cell extracts or purified prokaryotic endonucleases will be added to deficient permeable cells to try to restore or stimulate reparative activity. Successful operation of repair in vitro will facilitate the characterization of enzymatic activities that are required of nucleotidyl DNA excision repair in human cells.

This is the continuation of a project to study the operation of the nucleotidyl DNA excision repair pathway (NDERP) in vitro. In the first two years of the project we have characterized UV- dependent and non-specific endodeoxyribonuclease activities in permeable human fibroblasts using alkaline elution methodology to quantify DNA strand breaks. An ATP-dependent and UV- dependent endodeoxyribonuclease activity was observed in normal and xeroderma pigmentosum (XP) variant fibroblasts which represents the rate-limiting, dimer-directed incision step in the NDERP. This activity was undetectable in XP cells from complementation group A. A second UV-endodeoxyribonuclease activity which did not require ATP was identified in all human fibroblast strains which represents the redoxy endodeoxyribonuclease that cuts DNA at ring-saturated pyrimidines. Optimal conditions for assay of the UV- endodeoxyribonucleases were established. Various preparations of cellular extracts were added to permeable XPA to test for in vitro complementation of the defect in dimer-directed incision. UV-dependent incision could not be consistently demonstrated and non-specific endodeoxyribonuclease activities contaminated most cell extracts. Consequently, it appears that restoration of repair in permeable XPA will require fractionation of extracts to remove non-specific endodeoxyribonuclease. This fractionation will be facilitated by establishment of a plasmid-based endodeoxyribonuclease assay that can distinguish non-specific endodeoxyribonucleases from the two specific UV- endodeoxyribonucleases. A plasmid incision assay will be used to identify and isolate the dimer-directed UV-endodeoxyribonuclease from repair-proficient human cells. We will then determine whether incision-defective XPA also express this endodeoxyribonuclease. The isolated enzyme will be added to permeable XPA to test for restoration of dimer-directed incision of nuclear DNA. Peculiarities of reparative incision as demonstrated by other repair-deficient complementation groups of XP also will be examined. These studies will aid in identifying the bases of the various reparative defects seen in XP.

This project will test a hypothesis that carcinogenesis evolves through multiple stages by degradation of growth control pathways. Loss of cell cycle checkpoint controls gives initiated cells a growth advantage and induces genetic instability which accelerates malignant progression. Chemically initiated rat hepatocytes will be isolated based upon their selective ability to grow in vitro under conditions in which normal hepatocytes die. Such extended-lifespan variants correspond to the first stage of growth disregulation in models of multistage carcinogenesis. Extended-lifespan hepatocytes may progress during growth in vitro to immortal lines with indefinite lifespan. Immortal lines may evolve further to hepatocellular carcinoma. Normal rat hepatocytes in primary culture and initiated hepatocytes at these stages of neoplastic evolution will be tested for expression of checkpoints which regulate the transitions between cycle phases. When cellular DNA is damaged by radiation, growth normally is arrested at three checkpoints which control the rates of transition from G1 into S, rates of replicon initiation in S phase cells, and rates of transition from G2 into M. We will establish biological and biochemical features of checkpoint response to DNA damage in normal hepatocytes and determine the patterns of degradation of control at stages of neoplastic evolution. Gene amplification ability also will studied as a quantitative marker of the genetic instability that is associated with loss of checkpoint control. The liver tumor promoter, phenobarbital (PB), is required for expression of the extended lifespan phenotype by initiated hepatocytes in vitro and PB-dependent immortal hepatocyte lines have been isolated. We will determine whether PB promotes the extended and indefinite proliferative lifespans of initiated hepatocytes by inducing an autocrine loop and whether this promoter may suppress checkpoint function in initiated hepatocytes by inhibiting expression of the tumor suppressor gene, p53. We will determine the alterations in p53 structure and expression which may occur as hepatocytes progress to cancer. TGF-alpha is a hepatocyte growth factor which is frequently expressed in hepatocellular neoplasms but rarely expressed in pre-neoplastic foci. We will determine whether acquisition of an autocrine growth pathway can speed malignant conversion by hepatocyte lines. This project will connect a well-described animal model of chemical carcinogenesis to current theories on cell cycle control in cancer and multi-stage carcinogenesis.

Vinyl chloride (VC) is a widespread environmental contaminant, and a known carcinogen in humans. Preliminary data suggest that some workers exposed to VC have persistent elevated mutant frequencies in their peripheral blood lymphocytes, and that others do not . This leads to a hypothesis that there may be genetic differences in susceptibility to VC-induced change. We postulate that either xenobiotic metabolism r DNA repair are responsible for such differential susceptibility. The major goal of this project is to utilize biomarkers of exposure and effect to test these hypotheses. We will collect and store samples, analyze questionnaires and computerize data for a final population of more than 410 individuals that have been occupationally exposed to VC. Blood samples will be processed for analysis of various biomarkers of VC-induced genetic damage. Mutant frequencies at the X-linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus in peripheral T lymphocytes will be determined and the molecular nature of the T-cell receptor gene locus will be analyzed to determine the degree of clonality among observed mutants. These data will allow determination of the actual mutation frequency in each subject. As an independent measure of induced mutation, the frequencies of glycophorin A (GPA) variants in red blood cells will be determined in samples from the same individuals. The molecular nature of the hprt mutants will be analyzed by multiplex PCR and sequencing to determine if there are "signature" mutations induced by vinyl chloride exposures in vivo. Differential susceptibility could be due to variable capacity to metabolize vinyl chloride. Recently, RFLPs have been defined for the cytochrome P-450 CYP2E1 that appear to be associated with different levels of transcriptional activity. Studies will determine whether these RFLPs are associated with high or low mutant frequencies in the exposed workers. Polymorphisms in glutathione-S-transferase mu and the uninvolved P450 species CYP1A1 also will be examined. An alternative to metabolism as a cause for differential susceptibility is DNA repair. Up to ten highly exposed individuals with high mutation frequencies, and ten highly exposed individuals with normal mutation frequencies will be identified. B-lymphoblastoid cell lines, already prepared from these individuals , as well as the original lymphocyte samples, will be examined for DNA repair capacity by (i) measuring the rate of adduct loss after exposure to the VC metabolite CEO (ii) screening for N-methylpurine-DNA glycosylase expression and (iii) determining cell cycle checkpoint response. Representative lines also will be tested for susceptibility to CEO-induced hpri mutation. These studies will determine whether susceptibility to mutation seen in vivo is maintained in the transformed B- cell lines as a consequence of variation in DNA repair or cell cycle checkpoint response. The presence of one particular mutated p21 ras protein - with aspartic acid at codon 13 instead of glycine (Asp13p21 ras) will be monitored in the serum of individuals exposed to VC. The goal of this study is to evaluate whether the presence of this mutated protein is (i) a predictor of individuals with high mutation frequencies, (ii) a predictor of those at high risk for developing a liver angiosarcoma (ASL), and (iii) an early marker of the onset of ASL.

This project will study the effects of mutations in genes that regulate the onset of mitosis. Mitosis is begun by activation of a factor known as MPF for mitosis-promoting factor. MPF activity is controlled by phosphate content, subunit structure, location within cells and the status of chromosomes. A surveillance system known as the G2 checkpoint monitors the structure of chromosomes and can inhibit MPF when damage is sensed. After the damage is repaired, the inhibition of MPF is removed and progression of cells to mitosis resumes. Gene mutations that reduce G2 checkpoint function are the focus of this project. Expression of mutant forms of the cyclin-dependent kinase, Cdk1, the catalytic subunit of MPF, or the phosphatase, Cdc25C, that activates MPF, and overexpression of the MPF regulatory subunit, cyclin B1 reduced G2 delay in HeLa cells with damaged DNA, implicating these genes as functional components of the G2 checkpoint in a line of cancer cells. These genes will be induced in diploid human fibroblasts to establish their roles in G2 checkpoint function in normal cells. An enzyme known as DNA topoisomerase II detangles intertwined chromatids after DNA replication. A brief interval of inhibition of topoisomerase II in G2 cells was found to delay the onset of mitosis for several hours, as though a checkpoint had been activated. The hypothesis that chromatid catenation status is monitored by the G2 checkpoint will be tested by determining whether human cell lines with defects in G2 checkpoint genes cannot delay growth in G2 when chromatid detangling is inhibited. Human fibroblasts that bypass the replicative senescence checkpoint due to expression of HPV16E6 oncoprotein display progressive chromosomal destabilization and loss of G2 checkpoint function. Studies will determine whether expression of telomerase to stabilize telomeres preserves G2 checkpoint function in E6-expressing cells. To determine whether the loss of G2 checkpoint function in immortal fibroblasts is a dominant or recessive trait, checkpoint- proficient cells will be fused with checkpoint-defective cells and the function of the checkpoint in cell hybrids will be quantified. This project will define inputs to the G2 checkpoint and identify mechanisms of inactivation in human fibroblasts.

This project concerns the roles of cell cycle checkpoint and DNA repair genes in protecting human cells from mutations and chromosomal aberrations induced by Superfund carcinogens. The "guardian of the genome" and tumor suppressor gene, p53, is now known to coordinate a complex set of checkpoint and DNA repair responses in carcinogen- damaged cells. Sone of the signals to activated p53 function come from the ATM kinase gene product. ATM also signals to p53-independent cell cycle checkpoints. Cells lacking p53 or ATM gene function display genetic instability and increased susceptibility to malignant transformation. Such cells provide a window to the systems of response to DNA damage that protect against human carcinogenesis. One human carcinogen found in many Superfund waste-sites is vinyl chloride (VC). Although not directly reactive with DNA, after absorption and metabolic activation to form chloroethylene oxide (CEO), mutagenic etheno adducts are produced on DNA bases. A subfraction of people exposed to VC in the workplace expressed high frequencies of hprt mutations in blood lymphocytes, while the majority of VC-exposed people did not. We will test whether this elevated mutation frequency is associated with a DNA repair defect by assessing CEO-induced genotoxicity in lymphoblastoid lines derived from sensitive and resistant people. Superfund waste-site carcinogens such as benzene and benzo[a]pyrene can be metabolized within cells to produce reactive electrophiles such as benzene- diolepoxide, respectively, as well as reactive oxygen species (ROS). The electrophiles and ROS both may attack DNA producing mutations and chromosomal aberrations. This project will determine whether p53 and ATM protect against genotoxicity by CEO, ROS, and diolepoxides. Enhanced risk of development of breast cancer has been linked to mutations in genes that participate in DNA repair including p53 and ATM. This project will employ a functional assay for DNA repair capacity in peripheral and lymphocytes that measures rejoining of radiation-induced chromatid breaks. This assay will be used in a case- control study to test the hypothesis that development of breast cancer is associated with a defect in DNA repair. Sensitive cells identified in our case control study will be available as immortalized lines to determine whether hypersensitivity extends to ROS induced by Superfund carcinogens.

DESCRIPTION (provided by applicant) The toxicogenomics research program at the University of North Carolina-Chapel Hill (UNC-CH) is focused on genetic determinants of susceptibility to environmental toxicants and chemotherapeutic drugs. Human and murine model systems will be used to determine the patterns of alterations in gene expression when cells and animals are exposed to several classes of toxins. Toxin classes under study include agents that induce oxidative stress, DNA double strand breaks, alkylation of DNA bases, as well as nuclear receptor agonists. cDNA microarrays containing greater than 10,000 expressed genes will be used to determine for human cells and mice, the dose and time kinetics of toxicant-induced changes in gene expression. In two interactive research projects diploid human mammary epithelial cells, fibroblasts and lymphoblasts, will be treated with doses of toxicants ranging about the mean lethal dose (D/o for inactivation of colony formation). Cell lines with heterozygous and homozygous mutations in the tumor suppressor genes p53, ATM and BRCA1, or with genetic inactivation of suppressor function, will be compared to wildtype lines to establish profiles of genetic susceptibility to toxicant stress. Similarly, a third research project will determine patterns of response to the toxicants in liver, mammary gland and colon of ten strains of mice with varying susceptibilities to carcinogenesis. These studies will determine whether murine strain-dependent susceptibility to carcinogenesis resembles human genetic susceptibility due to mutations in tumor suppressors. A Toxicology Resource Core proposes a demonstration project to determine the profiles of altered gene expression in livers of mice exposed to non-genotoxic chemicals which activate the nuclear receptors, AhR, CAR and PPAR-alpha. The three research projects and the Toxicology Resource Core will be served by an Administrative Core, a Microarray Facility Core, and an lnformatics Facility Core. The UNC-CH toxicogenomics research program has the scientific expertise and organizational infrastructure to provide significant and substantial benefits to the Toxicogenomics Research Consortium.

DESCRIPTION (provided by applicant): This project concerns a cellular surveillance pathway known as the S checkpoint that inhibits DNA synthesis when DNA is damaged. Velocity sedimentation analyses indicate that this inhibition is brought about by reduction in the rate of replicon initiation. The process of initiation of replicons in S phase human cells appears to be positively regulated by cyclin-dependent kinase 2 (Cdk2), Dbf4-dependent kinase (Ddk) and Cdc6. Cells from patients with ataxia telangiectasia (AT) are defective in ionizing radiation (lR)-induced S checkpoint function due to inactivating mutations in ATM. Patients with Nijmegen Breakage Syndrome (NBS) have a similar defect in S checkpoint function due to mutations in NBS1 In accord with these observations, it has been shown that ATM kinase phosphorylates NBS1 in response to DNA damage. We postulate that DNA damage by IR induces ATM to phosphorylate NBS1 and other effector substrates to inhibit Cdk2 and Ddk in S phase cells, thereby inhibiting initiation of DNA synthesis at origins of replication. To test this hypothesis we will quantify the lR-induced inhibition of DNA synthesis within defined replicon origins in diploid human fibroblasts immortalized by expression of telomerase. AT, NBS, and AT-like cells will be similarly tested to determine whether radiation-induced inhibition of replicon initiation is dependent upon the ATM, NBS1 and MRE-1 gene products. A cell-free system in which Cdk2 and Cdc6 cooperate to initiate DNA replication in Gi nuclei will be used to assay for S checkpoint function in vitro. We will test whether Cdk2 and Cdc6 are required to initiate DNA replication at bona fide replicon origins in isolated Gi nuclei. This system of in vitro initiation will then be examined to determine whether treatment of nuclei with IR activates ATM-dependent signaling pathways leading to inhibition of Cdk2 and replicon initiation. Studies with intact cells will determine whether Cdk2 and Ddk are inhibited post-irradiation with kinetics equivalent to the inhibition of replicon initiation. Altered Cdc25C and Cdk2 alleles also will be expressed in diploid human fibroblasts to assess the role of active-site phosphorylation of Cdk2 in S checkpoint response. This project will define genetic components of the S checkpoint and elucidate signal transduction mechanisms that underlie S checkpoint response in diploid human fibroblasts.

Description (provided by applicant): The Genetic Susceptibility Research Core seeks to elucidate the relative contributions of genetic variants to human risk of environmental disease. There are two broad areas of research into how genes affect the occurrence of environmental disease. One is primarily epidemiologic in approach, using association studies to link the incidence of disease with a particular genetic polymorphism or set of polymorphisms. A second research pathway studies familial cancer genes, which have been identified primarily by genetic linkage analyses. These two approaches thus integrate the efforts of epidemiological scientists with those of molecular biological-based investigators in the evaluation of how changes in cell cycle check points and DNA repair mechanisms can lead to disease phenotypes, particularly those involving various cancers. The Core has five objectives. The first is to support and expand collaborative research in genetic susceptibility utilizing state-of-the-art laboratory methods and rigorously designed epidemiologic approaches. The second is to integrate, on a regular basis, researchers in mechanisms of DNA damage and repair and epidemiologists involved in field studies of gene/environment interactions in carcinogenesis. The third is to promote the integration of molecular genetics into the areas of reproductive, pediatric, pulmonary, and cardiovascular disease research. The fourth is to foster dialogue regarding policy implications of genetic-testing technology and results of genetic research. The final objective is to stimulate new collaborations through pilot projects.

[unreadable] DESCRIPTION (provided by applicant) [unreadable] [unreadable] This program will use a systems biology approach to investigate the mechanism(s) whereby human melanocytes undergo neoplastic transformation, clonal expansion, and malignant progression to cutaneous melanomas. The proposed studies are based on the premise that an environmental carcinogen, solar radiation, contributes to development of melanoma by inducing chromosomal damage in proliferating melanocytes. Malignant melanomas are of significant public health concern because their incidence is rising and no effective medical intervention is available for reducing morbidity and mortality. The guiding hypothesis of this program is that breakdowns in the systems of defense against DNA damage underlie the acquisition by meianocytes of a mutator phenotype, which reduces the effective dose of solar radiation needed to induce each subsequent step in the multi-stage development of cancer. Functional defects in DNA repair and cell cycle checkpoints, individually and in concert, contribute to genome destabilization, and thus increase the probability of accumulation in a single clone of the genetic alterations required for development of melanoma. Three research projects and three service cores will interact extensively to monitor quantitatively and qualitatively the system of response to DNA damage in UV-damaged human and murine melanocytes. Two research projects will determine how nucleotide excision repair, post-replication repair, double-strand break repair, and cell cycle checkpoint responses to UV-induced DNA damage cooperate to suppress chromosomal aberrations and allelic deletions in the melanoma tumor suppressor locus CDKN2A/INK4A. Functional assays will associate chromosomal instability and defective DNA damage responses in melanoma cell lines and melanocytes with alterations in melanomagenic genes. A third research project uses in vivo models of melanoma in mice and humans to monitor chromosomal destabilization during stages of development of melanoma. program investigations will determine how activating mutations in melanoma oncogenes and inactivating mutations in melanoma suppressor genes contribute to chromsomal instability and malignant progression. New findings will lead to the discovery of biomarkers with potential therapeutic and prognostic value for specific types of melanomas and different stages of melanoma progression. Computational models will be created to predict how DNA repair and checkpoint functions suppress UV-induced chromsomal damage. These studies will establish the degree to which melanoma-associated genetic alterations alone and in combinations contribute to a UV-chromosomalmutator phenotype and enhance environmental carcinogenesis. Lessons learned in this program will also impact on methods of risk assessment by showing that the effective dose of a carcinogen falls during the multi-step development of cancer. [unreadable] [unreadable] [unreadable] PROGRAM AS AN INTEGRATED EFFORT [unreadable] [unreadable] [unreadable]

The overall function of the Cell and Molecular Biology (CMB) Core will be to provide the program with carefully controlled and characterized human cell cultures that are needed in each project. Services provided by the core wjll include the isolation, culture, storage and distribution of primary melanocytes, keratinocytes and fibroblasts. In addition, the CMB Core will also culture and distribute all of the melanoma cell lines that will also be characterized for DNA mutations in B-RAF, N-RAS and PTEN. The CMB Core will ensure that all cells used in the program are free of contamination with mycoplasma or other contaminants by providing regular testing and decontamination when necessary.The CMB core will generate virus for transduction of primary melanocytes with melanomagenic genes or shRNA's to knockdown DNAdamage response genes. Transduced cells will be characterized for expression and function of these genes and knockdown vectors using informative assays such as western blot analysis. The CMB Core will generate in vitro human skin reconstructs (also referred to as orgariotypic skin cultures or skin equivalents) in which artificial human skin is created in vitro in a three-dimensional system with a mixture of primary melanocytes, keratinocytes and fibroblasts. These skin reconstructs will be supplied to Project 1 for in vitro analysis of DNA damage response and Project 3 for engraftment on the backs of SCID mice for in vivo analysis of DNA damage response. The PI of the CMB Core (Dr. Shields) recently completed an NCI-sponsored two-week training program at the Wistar Institute with Dr. Meenhard Herlyn (an internationally recognized leader in melanoma research and Program externaladvisor) to gain hands-on training in preparation of human skin reconstructs. The Cell and Molecular Biology core serves the Program Project by providing important biological reagents to program investigators.

Project 2, Cell Cycle Checkpoints, will focus on checkpoint responses to UV-induced DMAdamage. Because cell cycle checkpoints enhance the repair of DNA damage, defects in checkpoint function enhance UV-induced chromosomal aberrations arid produce a"mutator" phenotype. UV induces and activates p53, which induces G1 arrest or apoptosis, it activates ATR to induce an intra-S checkpoint response to slow the ate of replicon initiation, and it triggers a p38 kinase-dependent G2 delay. Quantitative metrics will establish the functional capacities of normal human melanocytes for thesis checkpoint functions and whether melanoma lines display functional defects. Studies in Aim 1will express a dominant-negative p53 allele in normal human melanocytes to determine whether p53 signaling is required to arrest growth or induce apoptosis in response to UV damage. Studies in Aim 2 will determine whether melanocytes use the Rad17/ATR/Chk1 signaling pathway to inhibit replicon initiation in response to UV damage and whether knockdown of expression of a replication fork-protection complex composed of Timeless and Timeless- interacting protein inactivates the intra-S checkpoint response to UV. Studies in Aim 3 will determine whether expression of mutant B-Raf and N-Ras oncogenes in normal human melanocytes produces an attenuation of G2 checkpoint function. Melanocyte lines with selective inactivation of p16 and ARF will also be monitored to determine how inherited and somatic mutations in the CDKN2A/INK4A locus affect checkpoint responses to DNA damage. Microarray technology will be used to define signatures of basal gene expression that predict G1 and G2 checkpoint functions in melanoma lines and whether the signatures distinguish melanoma lines from lymph node and visceralmetastases. In Aim 4 a mathematical model of G2 checkpoint function will be developed to test how variation in levels of protein expression affect response outcomes. A computational model of UV-clastogenesis will be developed in Aim 4 to test how DNA repair and cell cycle checkpoint functions collaborate to protect against UV-induced chromosomal aberrations. Project 2 will enumerate cell cycle checkpoint function in normal human melanocytes, melanoma lines, and melanocytes with melanomagenic genetic alterations to determine whether defects in checkpoint function produce a chromosomal mutator phenotype to enhance UV-induced malignant progression.

The Environmental Mutagenesis and Genomics Society (EMGS) was founded in 1969 to provide a forum for the establishment and support of scientists in the field of environmental mutagenesis. The mission of the Society is (1) to foster scientific research and education on the causes and mechanistic bases of DNA damage and repair, mutagenesis, heritable effects, epigenetic alterations in genome function, and their relevance to disease, and (2) to promote the application and communication of this knowledge to genetic toxicology testing, risk assessment, and regulatory policy-making to protect human health and the environment. For the past 49 years, EMGS members have made many of the most important discoveries pertaining to the mechanisms of the induction of mutations, the roles of DNA repair defects and resulting mutations in toxicology and disease susceptibility, and the challenges of assessing risks from environmental exposures to mutagens. Recognizing the importance of its diverse mix of professionals to exchange ideas and the latest experimental findings, the EMGS held its first meeting in Washington, DC on March 22-25, 1970, and has continued this tradition by providing a venue for these professionals to meet annually. Each year, the EMGS Annual Meeting Program Committee strives to represent the full spectrum of strengths of the Society, encompassing most of the areas of current research that converge on the issues of environmental exposure and how cells and organisms respond to such challenges. In this proposal, we are requesting funds to defray part of the expenses for 2019? 2023 EMGS Annual Meetings. The 2019 Program Committee has arranged for an outstanding and expansive scientific program that consists of a workshop, symposia, and platform and poster sessions. To commemorate the 50th anniversary of our Society, we have assembled speakers to talk briefly about the past, present, and future of some of the main fields of interest represented by the EMGS membership. In addition to the scientific program, the Annual Meeting will convene meetings of the nine Special Interest Groups (SIGs) that represent the diversity of the Society.

The Environmental Mutagenesis and Genomics Society (EMGS) is the primary scientific society fostering research on basic mechanisms of DNA repair, mutagenesis, and environmental epigenetics and application of this knowledge to understanding human health effects from environmental exposures. Studies of DNA repair, mutagenesis, and epigenetics by EMGS scientists are integrated with research on inherited and acquired genetic alterations that predispose individuals to cancer, premature aging, neurodegenerations and birth defects. Fundamental understanding of the mechanisms and consequences of cellular, tissue, whole organism, and human population responses to genotoxic agents is crucial to informed regulatory decision- making with respect to environmental health hazards. The integration of multi-disciplinary basic and applied research is essential to this process. Such integration remains the central focus of the EMGS, and the annual meetings are key to the dissemination of information and fostering the necessary interactions. In addition, meetings provide an important forum for students and new/early stage investigators to present their research and to interact with leading scientists in their field in a setting that encourages open exchange of ideas. The 50th Annual Meeting of the EMGS will be held in Washington D.C. from September 19-23, 2019. The theme is ?Environmental Mutagenesis and Genomics: The Next Fifty Years?, encompassing areas of current research that converge on the issues of environmental exposure, how cells and organisms respond to such challenges, and how this information can be applied to promote human health in the era of high-throughput data. The themes for the 51st and 52nd Annual Meetings will be selected approximately a year before each meeting. Comprised of symposia, workshops, plenary lectures, platform and poster sessions, the Annual Meeting will encompass the full range of scientific interests within the Society, bringing together academic, industrial, and governmental scientists interested in how environmental factors lead to genotoxic and epigenetic outcomes. The objectives of this application are to request funds for Travel Awards for students and new/early stage investigators to attend the Annual Meeting and partial support for travel expenses of invited speakers. Travel Awards assist in offsetting the financial burden that might otherwise prevent students and new/early stage investigators from attending. Support to defray travel costs for invited speakers enables the Society to provide the greatest value at lower costs to attendees. Speakers from both within and outside the society provides the cross-fertilization of research and ideas necessary for a world-class meeting.