Utilization of biomarker data for clinical and environmental intervention

On the use of biomarkers for environmental health research

This article discusses the growing interest in the use of biomarker data in environmental health research and considers some of the challenging statistical issues that arise. We specify a modeling framework that links environmental exposure, biomarkers and outcome, and discuss in conceptual terms how such a formulation could be used to inform dose response modeling for the purpose of quantitative risk assessment. We then analyse some biomarker data from a case-control study designed to elucidate the mechanisms of smoking induced lung cancer. Because of sample size limitations, we use a likelihood-based analysis which subsumes both cohort and case-control designs as special cases. Our analysis allows us to 1) investigate the extent to which the markers explain the pathway from exposure to outcome; 2) quantify the degree to which biomarker data can improve on predicting outcome over and above exposure; and 3) estimate the association among multiple markers.

Sequencing and its consequences: path dependence and the relationships between genetics and medicalization

Both advocacy for and critiques of the Human Genome Project assume a self-sustaining relationship between genetics and medicalization. However, this assumption ignores the ways in which the meanings of genetic research are conditional on its position in sequences of events. Based on analyses of three conditions for which at least one putative gene or genetic marker has been identified, this article argues that critical junctures in the institutional stabilization of phenotypes and the mechanisms that sustain such classifications over time configure the practices and meanings of genetic research. Path dependence is critical to understanding the lack of consistent fit between genetics and medicalization.

The use of biomarkers in surveillance, medical screening, and intervention

Building on mechanistic information, much of molecular epidemiologic research has focused on validating biomarkers, that is, assessing their ability to accurately indicate exposure, effect, disease, or susceptibility. To be of use in surveillance, medical screening, or interventions, biomarkers must already be validated so that they can be used as outcomes or indicators that can serve a particular function. In surveillance, biomarkers can be used as indicators of hazard, exposure, disease, and population risk. However, to obtain rates for these measures, the population at risk will need to be assessed. In medical screening, biomarkers can serve as early indicators of disease in asymptomatic people. This allows for the identification of those who should receive diagnostic confirmation and early treatment. In intervention (which includes risk assessment and communication, risk management, and various prevention efforts), biomarkers can be used to assess the effectiveness of a prevention or control strategy as well as help determine whether the appropriate individuals are assigned to the correct intervention category. Biomarkers can be used to provide group and individual risk assessments that can be the basis for marshalling resources. Critical for using biomarkers in surveillance, medical screening, and intervention is the justification that the biomarkers can provide information not otherwise accessible by a less expensive and easier-to-obtain source of information, such as medical records, surveys, or vital statistics. The ability to use validated biomarkers in surveillance, medical screening, and intervention will depend on the extent to which a strategy for evidence-based procedures for biomarker knowledge transfer can be developed and implemented. This will require the interaction of researchers and decision-makers to collaborate on public health and medical issues.

Locating gene-environment interaction: at the intersections of genetics and public health

Over the past two decades, the applications of genetic and genomic technologies have begun to transform research questions and practices within epidemiology and toxicology, the "core sciences" of public health (Annu. Rev. Public Health 21 (2000) 1). These technologies provide new models and techniques for studying genetic traits, environmental exposures, and gene-environment interaction in the production of human health and illness. This paper explores the consequences of emergent genetic and genomic approaches, their ongoing redefinitions of both genetic and environmental "risks", and their potential implications for public health practice. The central argument of the paper is that the increasing focus on gene-environment interaction directs scientific, biomedical, and public health attention both inward, to the gene/genome, and outward, to particular places. In so doing, studies of gene-environment interaction create a challenging and productive tension-at the same time that bodies are being geneticized (Am. J. Law Med. 17 (1992) 15), they also are emphatically emplaced, located where social and cultural practices come to matter. This tension, this simultaneous movement outward and inward, towards the gene and towards the environment, into the body and into place, opens up a vista into the processes through which culture and biology form a locally and historically situated dialectic (Encounters With Aging: Mythologies of Menopause in Japan and North America, University of California Press, Berkeley, CA, 1993) and raises important questions about the production of health and illness.

Mitochondrial membrane potential: a novel biomarker of oxidative environmental stress

Epidemiologic analyses, traditionally based on long-term cohort or case-control studies, provide retrospective causal associations between exposure to a particular environmental stressor and an exposure-related disease end point. Recent research initiatives have propelled a shift toward exploring molecular epidemiology and molecular biological markers (biomarkers) as a means of providing more immediate, quantitative risk assessment of potentially deleterious environmental exposures. We compared, in normal human monocytes isolated from the blood of healthy donors, variations in Hsp70 expression and mitochondrial membrane potential (delta psi m) in response to exposure to either tobacco smoke or gamma-irradiation, two models for environmentally mediated oxidant exposure. On the basis of its mechanistic specificity for oxidants and little baseline variation in cells from distinct individuals, we propose that delta psi m represents a selective in vitro and in vivo biomarker for oxidant exposure. delta psi m may be used to gauge risks associated with oxidant-mediated air pollution and radiation.

Applying genomic technologies in environmental health research: challenges and opportunities

Recent discoveries in molecular biology and genetics have made it possible for environmental health researchers to examine how genetic characteristics affect response to environmental exposures. Understanding such gene-environment interactions offers exciting possibilities for the prevention and control of environmentally induced diseases. Despite these potential benefits, the collection and analysis of genetic information in environmental health research presents many of the same ethical, legal, and social (ELSI) challenges found in other types of genetic research. In this article, we describe a number of ELSI challenges in environmental genomic research and the opportunities and responsibilities that accompany this research.

Smoking and the molecular epidemiology of lung cancer

Lung carcinogenesis in humans requires exposure to environmental agents, including the inhalation of tobacco smoke, radioactive compounds, asbestos, heavy metals, and petrochemicals. Tobacco smoking is the risk factor with the highest attributable lung cancer risk worldwide. This article discusses occupational carcinogen exposure and exposure from tobacco use, and the lung-cancer risk associated with these types of exposure.

Purification and recovery of bulky hydrophobic DNA adducts

For many years (32)P postlabeling has detected DNA adducts at very low levels and yet has not been able to identify unknown adducts. Mass spectrometry offers substantially improved identification powers, albeit at some loss in detection limits. With this ultimate utilization of mass spectrometry in mind, the current research presents a new method to quantitatively purify bulky hydrophobic DNA adducts at levels that are pertinent to ongoing DNA adduct research in human health and environmental fields. This method was demonstrated with benzo[a]pyrene adducts. Purification was accomplished with the use of small columns (7.5-mm frits) with an 11 mg bed of polystyrene-divinlybenzene beads which retained the adducts while permitting the nonadducted nucleotides to be washed out with water. Subsequently, the adducts were eluted with 50% MeOH and the sample was reduced in volume in an evacuated centrifuge. Purification was demonstrated at adduct levels ranging from 4 adducts in 10(6) nonadducted nucleotides to 4 in 10(8). For these levels, analyses by capillary electrophoresis with sample stacking and UV detection determined that recoveries ranged from 91 to 54%, respectively. The adduct quantities isolated should be sufficient to allow the use of current MS capabilities that are linked on-line to separation methodologies such as capillary electrophoresis, capillary electrochromatography, and high-pressure liquid chromatography.