- Email: [email protected]
International Conference on Biomarkers for Toxicology and Molecular Epidemiology, March 15–17, 2004, Atlanta, GA
Toxicology and Applied Pharmacology 206 (2005) 98 – 101 www.elsevier.com/locate/ytaap
Conference International Conference on Biomarkers for Toxicology and Molecular Epidemiology, March 15–17, 2004, Atlanta, GA
Introduction The National Center for Environmental Health/Agency for Toxic Substances and Disease Registry (NCEH/ ATSDR) hosted the bInternational Conference on Biomarkers for Toxicology and Molecular Epidemiology— New Tools for 21st Century ProblemsQ on March 15–17, 2004, in Atlanta, GA. The conference was co-sponsored by the US Environmental Protection Agency, the National Institute of Occupational Safety and Health, the National Institute of Environmental Health Sciences, the National Cancer Institute, the Armed Forces Institute of Pathology, and the Scientific Committee on the Toxicology of Metals under the International Commission on Occupational Health. Additionally, the conference was also an official activity of the US–India Joint Working Group on Environmental Health of which NCEH/ATSDR is the lead US agency. Recent global events have presented new challenges in the quest to protect the health of the general public and of sensitive sub-populations, in particular, from exposure to chemical agents. The importance of understanding the health consequences of exposures to environmental chemicals has assumed a role of utmost urgency in many countries. A base of scientific knowledge regarding, on one hand, the precise, rapid, and reliable measurements of exposures and, on the other hand, the types and severity of the health consequences is the only solid foundation from which the best responses to new 21st century chemical challenges can emerge. A major purpose of the Biomarkers Conference was to examine the current status of innovative biomarkers that assess low dose exposures in relation to early biological changes at the cellular level. The potential extension of the scientific progress made in the development of biosensors and other new analytical technologies to field applications was a key area of discussion. Conference participants identified gaps in knowledge and research needs that would have to be met in order to effectively use these new tools for rapid exposure assessments of environmental chemicals in the field regardless of the exposure situation. Accidental occupational, environmental, or deliberate chemdoi:10.1016/j.taap.2004.12.014
ical warfare exposures are current examples of these situations. A second purpose of the conference was the establishment of a clear link of understanding between early molecular changes from chemical exposures and specific compromises in human health. Mechanistic understandings of the toxicological consequences of chemical exposures are derived primarily from cellular and animal studies at the molecular level. The translation of laboratory findings to risks for humans is a critical step to application that must be supported by confirmatory human studies. The latest developments in the molecular bomicsQ technologies (genomics, proteomics, and metabolomics) as biomarker classes have been used to evaluate early toxic responses to chemical agents. These relatively new approaches hold great promise since, broadly speaking, early toxicological responses are highly conserved across species and model test systems. Findings from new studies of the health consequences from arsenic in drinking water were examples of how mechanistic understanding of the early cellular responses may be used to understand subsequent clinical manifestations of disease. Finally, these new molecular tools were examined with regard to identifying and assessing different levels and types of risks for sensitive subpopulations, such as children, the elderly, and immunocompromised individuals. Such information can be used to provide improved risk assessments for protecting the health of these highly sensitive sub-populations against environmental chemicals. The invited presenters were established scientists from the international community who were experts in related areas of cutting-edge information and technology. The presentations by these investigators stimulated other conference participants to ask probing questions and provide insightful comments with respect to the future direction of these promising lines of research that will hopefully help to move this promising interdisciplinary field forward in coming years.
Summary of specific conference sessions Keynote lecture: the importance of modern biomedical tools to the mission of CDC and the future initiative Dr. Julie L. Gerberding, Director of the Centers for Disease Control (CDC), gave a keynote lecture on how the
Conference
topics addressed at this conference could support the newly defined mission areas of the CDC. The CDC clearly has need for incorporation of the most modern scientific tools in order to meet its expanded role in the areas of disease prevention from exposures to chemical and biological agents. The ability to respond rapidly to accidental- or terrorism-based situations with both accurate analytical information on the exposures in combination with molecular biomarker data is essential. Equally important is the existence of a solid base of scientific data that provide the prognosis of overt disease consequences during early preclinical disease stages. Such information will be critical to meeting many of the public health challenges in the 21st century. Methods for analysis and biosensor technology A major focus of the conference was centered on new and improved methodologies for the speciation of toxic agents of current public health interest. These included inorganic agents, such as arsenic, as well as differentiating common organic chemicals from each other in mixtures, such as trichloroethylene from halomethanes. The review of these methods was followed by a discussion of new biosensor approaches for the rapid measurement of pesticides and cellular viability utilizing evolving biosensor technologies. Prior to being used as tools for making rapid measurements in the field (outside the laboratory), the biosensor technologies must be validated by existing laboratory-based methodologies. The validation process will require both time and effort but ultimately should yield rapid, portable technologies that will have application both in remote areas of the world and in large-scale chemical release situations, including instances of chemical terrorism. The development of new biomonitoring tools for rapid and accurate exposure assessment is hence a key step towards improving risk assessment so that credible information on exposure may be provided in a timely manner to all interested parties. Genomics, proteomics, and metabolomics The second session of the conference was focused on discussion of the bomicsQ technologies which are rapidly growing areas of scientific research. The hierarchical interrelationships between altered gene regulation, manifestations of actual gene expression patterns, as assessed by proteomic analysis, and changes in metabolic systems were discussed from a variety of perspectives. The cellular consequences of altered gene regulation were also linked to the synthesis and degradation of enzymatic proteins in metabolic pathways. As with the analytical methodologies, there is a pressing need for validation of these highly promising technologies. One further exciting prospect is that in the near future, there will be a concerted effort to
99
forge linkages between the bomicQ approaches and new analytical methods for chemical exposure assessment. The linkage between these two modern methodologies would lead to a more precise delineation of the btarget doseQ for a given chemical agent. The ability to identify the presence of particular chemical species in various sub-cellular compartments and chemical species-specific alterations in both gene expression patterns and metabolic pathways would be of enormous value to mechanism-based risk assessment since it would link a chemical dose with a mechanism of effect. Keynote lecture: human subjects protection The second keynote lecture was given by Dr. Bernard Schwetz, Director of the Office of Human Subjects Protection at DHHS. He emphasized the evolving and new types of needs for protecting human volunteers in the current research environment. Federal guidelines have now specifically addressed current issues that have emerged from new types of scientific inquiry. Federal rules have been updated and designed to protect the rights of persons involved in studies utilizing bomicQ approaches to evaluate the effects of toxic chemicals on exposed populations. These types of studies have the need for special vigilance with regard to human protection in the areas of safety and confidentiality. Investigators are now required to be informed and to adhere to these expanded rules in all human studies, such as those evaluating humans at the genomic level of biological organization. In vitro test systems The utility of in vitro test systems as tools for rapidly providing information on the relative potency of chemical agents, either with an exposure to an individual chemical or with an exposure to two or more chemical mixtures, was discussed in detail. The demonstrated value of in vitro systems for understanding mechanisms of both cell injury and cell death in target organ systems, such as the kidney and immune system, and for evaluating neoplastic transformation in cancer cell lines was highlighted by discussants. It is clear that in vitro cellular test systems represent a rapid, highly cost-effective, and proven approach for gathering useful toxicological information in a timely manner. These model systems can hence provide useful scientific information that can supplement both animal and human toxicity data. Further, data from these systems can help to address issues of inter-species differences for risk assessment. Molecular epidemiology studies Findings from epidemiological studies conducted in China, India, and Latin America where human populations
100
Conference
are exposed to arsenic-containing ground water were presented and discussed in detail. These studies incorporated leading-edge scientific methodology in the measurements of molecular biomarkers in humans to examine early biological effects. The prospects of utilizing molecular tools for assessing the development of cancer and target organ toxicity at early stages were discussed in relation to providing linkages with ongoing analytical studies of arsenic species in drinking water. The epidemiological studies of arsenic-exposed populations demonstrated, for example, how the inclusion of molecular biomarkers improved interpretation of risk assessments. The investigations provided some excellent examples of how the scientific validity of epidemiological findings could be strengthened by the inclusion of molecular biomarkers. Biomarkers for organ system toxicities Investigators discussed the application of non-invasive biomarkers of exposure and of effect for assessing chemical toxicity to target organ systems, such as the kidney, liver, and central nervous system. These included the biological effects of exposure to organic air pollutants, of simultaneous exposure to cadmium and arsenic, and the impacts of chemical exposures in the presence of other susceptibility factors. The utilization of these approaches for evaluating persons exposed to pesticides, PCBs, or methyl mercury provided further evidence of the value of molecular biomarker approaches for improving risk assessments among human populations. Molecular biomarkers can also play an important role in identifying sub-groups with characteristics, such as age, nutritional status, or the presence of specific genes, that are highly sensitive to organ system toxicity from chemical agents. The identification of such subgroups greatly enhances the ability to make more refined risk assessments. Predictive biomarkers for chemical toxicity in children Children are generally regarded as a population at special risk for chemical toxicity. Growing and developing organ systems may be more sensitive to chemicalinduced disturbances than those of adults. There is hence a need for validation of molecular biomarkers to assess chemical-induced toxicity to developing organ systems of children. Specifically, participants at the conference focused on developmental molecular biomarkers for the immune, hematopoietic, and neurological systems. The impact of major chemical classes, such as pesticides and organic solvents, on these systems was assessed in relation to newer classes of biomarkers. The essential roles of sample collection techniques and the use of national biomarker databases for assessing and tracking changes in biomarker system responses to chemical
exposures were discussed in relation to the fidelity of biomarker assays for children and the evaluation of how generated data may be interpreted in relation to national trends. The degree to which molecular biomarkers developed for adult populations may require further validation in order to be applicable and interpreted for children was clearly identified as a needed area of future research.
Future directions The presentations from the conference demonstrate a continuum of interrelated activities that range from new analytical methodologies, biosensors, and molecular biomarker development, to the direct application of these new methodologies to molecular epidemiology and public health practice. Efforts must now be focused on bringing these modern tools from the research arena into central public health usage through the thoughtful application of translational research (e.g., technology transfer of basic scientific knowledge to practical applications). The implementation process must, of necessity, involve scientific validation of these new tools and approaches by existing methodologies that are considered the current bgold standardsQ. The reasons for this approach are manifold. First, scientific resources are limited and hence the further development of these tools must be focused on clearly defined achievable goals and application of sound scientific principles of validation. This approach will insure that these new methodologies will be useful tools and not simply technical achievements. The biosensor technologies must be validated against existing and accepted analytical methodologies, such as mass spectroscopy, in order to understand their limits. Molecular biomarkers must be understood in relation to other accepted parameters, such as histopathological, ultrastructural changes, or current clinical tests, that are now used to define organ system damage or cancer. Finally, once the promise of these new tools is understood and accepted, they must be tested in molecular epidemiology studies to determine the extent to which they permit early detection of clinical disease among exposed human populations. The public health challenges of the 21st century are clearly significant. If we are to deliver a healthy and safe planet to future generations, we must consolidate the knowledge and skills available to us now. The generation of new knowledge that can more specifically address more pressing public health needs will then follow. Further, development of biological monitoring through new chemical speciation methods, biosensors, and linkage of these exposure assessment tools to molecular biomarkers can make possible the detection of both the cellular btarget doseQ of chemical agents and the early manifestations of toxicity. It is also important to
Conference
recognize that these new approaches generate large quantities of data, and the conversion of this information into understandable information requires sophisticated data processing. Incorporation of new computer-based technologies for rapid analysis and data reduction into meaningful patterns will be essential for accurate evaluation of interdisciplinary results from these complementary analytical and biotechnology-based methodologies. The future holds both great risks and opportunities, but there is good reason for optimism if scientists in the public health community work collaboratively, share information, and craft a new generation of interdisciplinary tools to meet both current and as yet unknown public health challenges.
101
Bruce A. Fowler * Marie Socha Division of Toxicology, Agency for Toxic Substances and Disease Registry, Centers for Disease Control, Atlanta, GA 30333, USA E-mail address: bxf [email protected]. Babasaheb Sonawane National Center for Environmental Assessment, Office of Research and Development, 1200 Pennsylvania, Avenue NW, U.S. Environmental Protection Agency, Washington, DC 20460, USA TCorresponding author. 12 October 2004
Conference International Conference on Biomarkers for Toxicology and Molecular Epidemiology, March 15–17, 2004, Atlanta, GA
Introduction The National Center for Environmental Health/Agency for Toxic Substances and Disease Registry (NCEH/ ATSDR) hosted the bInternational Conference on Biomarkers for Toxicology and Molecular Epidemiology— New Tools for 21st Century ProblemsQ on March 15–17, 2004, in Atlanta, GA. The conference was co-sponsored by the US Environmental Protection Agency, the National Institute of Occupational Safety and Health, the National Institute of Environmental Health Sciences, the National Cancer Institute, the Armed Forces Institute of Pathology, and the Scientific Committee on the Toxicology of Metals under the International Commission on Occupational Health. Additionally, the conference was also an official activity of the US–India Joint Working Group on Environmental Health of which NCEH/ATSDR is the lead US agency. Recent global events have presented new challenges in the quest to protect the health of the general public and of sensitive sub-populations, in particular, from exposure to chemical agents. The importance of understanding the health consequences of exposures to environmental chemicals has assumed a role of utmost urgency in many countries. A base of scientific knowledge regarding, on one hand, the precise, rapid, and reliable measurements of exposures and, on the other hand, the types and severity of the health consequences is the only solid foundation from which the best responses to new 21st century chemical challenges can emerge. A major purpose of the Biomarkers Conference was to examine the current status of innovative biomarkers that assess low dose exposures in relation to early biological changes at the cellular level. The potential extension of the scientific progress made in the development of biosensors and other new analytical technologies to field applications was a key area of discussion. Conference participants identified gaps in knowledge and research needs that would have to be met in order to effectively use these new tools for rapid exposure assessments of environmental chemicals in the field regardless of the exposure situation. Accidental occupational, environmental, or deliberate chemdoi:10.1016/j.taap.2004.12.014
ical warfare exposures are current examples of these situations. A second purpose of the conference was the establishment of a clear link of understanding between early molecular changes from chemical exposures and specific compromises in human health. Mechanistic understandings of the toxicological consequences of chemical exposures are derived primarily from cellular and animal studies at the molecular level. The translation of laboratory findings to risks for humans is a critical step to application that must be supported by confirmatory human studies. The latest developments in the molecular bomicsQ technologies (genomics, proteomics, and metabolomics) as biomarker classes have been used to evaluate early toxic responses to chemical agents. These relatively new approaches hold great promise since, broadly speaking, early toxicological responses are highly conserved across species and model test systems. Findings from new studies of the health consequences from arsenic in drinking water were examples of how mechanistic understanding of the early cellular responses may be used to understand subsequent clinical manifestations of disease. Finally, these new molecular tools were examined with regard to identifying and assessing different levels and types of risks for sensitive subpopulations, such as children, the elderly, and immunocompromised individuals. Such information can be used to provide improved risk assessments for protecting the health of these highly sensitive sub-populations against environmental chemicals. The invited presenters were established scientists from the international community who were experts in related areas of cutting-edge information and technology. The presentations by these investigators stimulated other conference participants to ask probing questions and provide insightful comments with respect to the future direction of these promising lines of research that will hopefully help to move this promising interdisciplinary field forward in coming years.
Summary of specific conference sessions Keynote lecture: the importance of modern biomedical tools to the mission of CDC and the future initiative Dr. Julie L. Gerberding, Director of the Centers for Disease Control (CDC), gave a keynote lecture on how the
Conference
topics addressed at this conference could support the newly defined mission areas of the CDC. The CDC clearly has need for incorporation of the most modern scientific tools in order to meet its expanded role in the areas of disease prevention from exposures to chemical and biological agents. The ability to respond rapidly to accidental- or terrorism-based situations with both accurate analytical information on the exposures in combination with molecular biomarker data is essential. Equally important is the existence of a solid base of scientific data that provide the prognosis of overt disease consequences during early preclinical disease stages. Such information will be critical to meeting many of the public health challenges in the 21st century. Methods for analysis and biosensor technology A major focus of the conference was centered on new and improved methodologies for the speciation of toxic agents of current public health interest. These included inorganic agents, such as arsenic, as well as differentiating common organic chemicals from each other in mixtures, such as trichloroethylene from halomethanes. The review of these methods was followed by a discussion of new biosensor approaches for the rapid measurement of pesticides and cellular viability utilizing evolving biosensor technologies. Prior to being used as tools for making rapid measurements in the field (outside the laboratory), the biosensor technologies must be validated by existing laboratory-based methodologies. The validation process will require both time and effort but ultimately should yield rapid, portable technologies that will have application both in remote areas of the world and in large-scale chemical release situations, including instances of chemical terrorism. The development of new biomonitoring tools for rapid and accurate exposure assessment is hence a key step towards improving risk assessment so that credible information on exposure may be provided in a timely manner to all interested parties. Genomics, proteomics, and metabolomics The second session of the conference was focused on discussion of the bomicsQ technologies which are rapidly growing areas of scientific research. The hierarchical interrelationships between altered gene regulation, manifestations of actual gene expression patterns, as assessed by proteomic analysis, and changes in metabolic systems were discussed from a variety of perspectives. The cellular consequences of altered gene regulation were also linked to the synthesis and degradation of enzymatic proteins in metabolic pathways. As with the analytical methodologies, there is a pressing need for validation of these highly promising technologies. One further exciting prospect is that in the near future, there will be a concerted effort to
99
forge linkages between the bomicQ approaches and new analytical methods for chemical exposure assessment. The linkage between these two modern methodologies would lead to a more precise delineation of the btarget doseQ for a given chemical agent. The ability to identify the presence of particular chemical species in various sub-cellular compartments and chemical species-specific alterations in both gene expression patterns and metabolic pathways would be of enormous value to mechanism-based risk assessment since it would link a chemical dose with a mechanism of effect. Keynote lecture: human subjects protection The second keynote lecture was given by Dr. Bernard Schwetz, Director of the Office of Human Subjects Protection at DHHS. He emphasized the evolving and new types of needs for protecting human volunteers in the current research environment. Federal guidelines have now specifically addressed current issues that have emerged from new types of scientific inquiry. Federal rules have been updated and designed to protect the rights of persons involved in studies utilizing bomicQ approaches to evaluate the effects of toxic chemicals on exposed populations. These types of studies have the need for special vigilance with regard to human protection in the areas of safety and confidentiality. Investigators are now required to be informed and to adhere to these expanded rules in all human studies, such as those evaluating humans at the genomic level of biological organization. In vitro test systems The utility of in vitro test systems as tools for rapidly providing information on the relative potency of chemical agents, either with an exposure to an individual chemical or with an exposure to two or more chemical mixtures, was discussed in detail. The demonstrated value of in vitro systems for understanding mechanisms of both cell injury and cell death in target organ systems, such as the kidney and immune system, and for evaluating neoplastic transformation in cancer cell lines was highlighted by discussants. It is clear that in vitro cellular test systems represent a rapid, highly cost-effective, and proven approach for gathering useful toxicological information in a timely manner. These model systems can hence provide useful scientific information that can supplement both animal and human toxicity data. Further, data from these systems can help to address issues of inter-species differences for risk assessment. Molecular epidemiology studies Findings from epidemiological studies conducted in China, India, and Latin America where human populations
100
Conference
are exposed to arsenic-containing ground water were presented and discussed in detail. These studies incorporated leading-edge scientific methodology in the measurements of molecular biomarkers in humans to examine early biological effects. The prospects of utilizing molecular tools for assessing the development of cancer and target organ toxicity at early stages were discussed in relation to providing linkages with ongoing analytical studies of arsenic species in drinking water. The epidemiological studies of arsenic-exposed populations demonstrated, for example, how the inclusion of molecular biomarkers improved interpretation of risk assessments. The investigations provided some excellent examples of how the scientific validity of epidemiological findings could be strengthened by the inclusion of molecular biomarkers. Biomarkers for organ system toxicities Investigators discussed the application of non-invasive biomarkers of exposure and of effect for assessing chemical toxicity to target organ systems, such as the kidney, liver, and central nervous system. These included the biological effects of exposure to organic air pollutants, of simultaneous exposure to cadmium and arsenic, and the impacts of chemical exposures in the presence of other susceptibility factors. The utilization of these approaches for evaluating persons exposed to pesticides, PCBs, or methyl mercury provided further evidence of the value of molecular biomarker approaches for improving risk assessments among human populations. Molecular biomarkers can also play an important role in identifying sub-groups with characteristics, such as age, nutritional status, or the presence of specific genes, that are highly sensitive to organ system toxicity from chemical agents. The identification of such subgroups greatly enhances the ability to make more refined risk assessments. Predictive biomarkers for chemical toxicity in children Children are generally regarded as a population at special risk for chemical toxicity. Growing and developing organ systems may be more sensitive to chemicalinduced disturbances than those of adults. There is hence a need for validation of molecular biomarkers to assess chemical-induced toxicity to developing organ systems of children. Specifically, participants at the conference focused on developmental molecular biomarkers for the immune, hematopoietic, and neurological systems. The impact of major chemical classes, such as pesticides and organic solvents, on these systems was assessed in relation to newer classes of biomarkers. The essential roles of sample collection techniques and the use of national biomarker databases for assessing and tracking changes in biomarker system responses to chemical
exposures were discussed in relation to the fidelity of biomarker assays for children and the evaluation of how generated data may be interpreted in relation to national trends. The degree to which molecular biomarkers developed for adult populations may require further validation in order to be applicable and interpreted for children was clearly identified as a needed area of future research.
Future directions The presentations from the conference demonstrate a continuum of interrelated activities that range from new analytical methodologies, biosensors, and molecular biomarker development, to the direct application of these new methodologies to molecular epidemiology and public health practice. Efforts must now be focused on bringing these modern tools from the research arena into central public health usage through the thoughtful application of translational research (e.g., technology transfer of basic scientific knowledge to practical applications). The implementation process must, of necessity, involve scientific validation of these new tools and approaches by existing methodologies that are considered the current bgold standardsQ. The reasons for this approach are manifold. First, scientific resources are limited and hence the further development of these tools must be focused on clearly defined achievable goals and application of sound scientific principles of validation. This approach will insure that these new methodologies will be useful tools and not simply technical achievements. The biosensor technologies must be validated against existing and accepted analytical methodologies, such as mass spectroscopy, in order to understand their limits. Molecular biomarkers must be understood in relation to other accepted parameters, such as histopathological, ultrastructural changes, or current clinical tests, that are now used to define organ system damage or cancer. Finally, once the promise of these new tools is understood and accepted, they must be tested in molecular epidemiology studies to determine the extent to which they permit early detection of clinical disease among exposed human populations. The public health challenges of the 21st century are clearly significant. If we are to deliver a healthy and safe planet to future generations, we must consolidate the knowledge and skills available to us now. The generation of new knowledge that can more specifically address more pressing public health needs will then follow. Further, development of biological monitoring through new chemical speciation methods, biosensors, and linkage of these exposure assessment tools to molecular biomarkers can make possible the detection of both the cellular btarget doseQ of chemical agents and the early manifestations of toxicity. It is also important to
Conference
recognize that these new approaches generate large quantities of data, and the conversion of this information into understandable information requires sophisticated data processing. Incorporation of new computer-based technologies for rapid analysis and data reduction into meaningful patterns will be essential for accurate evaluation of interdisciplinary results from these complementary analytical and biotechnology-based methodologies. The future holds both great risks and opportunities, but there is good reason for optimism if scientists in the public health community work collaboratively, share information, and craft a new generation of interdisciplinary tools to meet both current and as yet unknown public health challenges.
101
Bruce A. Fowler * Marie Socha Division of Toxicology, Agency for Toxic Substances and Disease Registry, Centers for Disease Control, Atlanta, GA 30333, USA E-mail address: bxf [email protected]. Babasaheb Sonawane National Center for Environmental Assessment, Office of Research and Development, 1200 Pennsylvania, Avenue NW, U.S. Environmental Protection Agency, Washington, DC 20460, USA TCorresponding author. 12 October 2004