Hunting for electrophiles that harm human DNA: Frits Sobels Award Lecture

This lecture is dedicated to Frits Sobels and his farsighted vision on research directions in genetic toxicology. Some accomplishments by the author's research group in the area of cancer etiology research and pre-clinical drug safety evaluation are presented. Praziquantel, an antischistosomal drug, was found to be devoid of any genetic effects which determined the drug companies to proceed with further safety evaluation and marketing. This highly efficient life-saving drug is now in use world wide. Biomonitoring methods have been developed to quantitate carcinogens, their metabolites or DNA adducts in humans exposed environmentally and endogenously to genotoxic agents. The methods were applied in ecological and case-control studies aimed at establishing causal relationships between exposure and disease. Results from both field studies in Iran and laboratory investigations supported the hypothesis that opium use, in particular ingestion of its pyrolysates, may be a risk factor for esophageal cancer in this region, probably acting together with nutritional deficiencies and thermal injury. By applying the nitrosoproline (NPRO) test in ecological studies on esophageal cancer causation in China some support was obtained for the involvement of N-nitroso compounds. In inhabitants of high risk areas endogenous nitrosamine synthesis could be markedly reduced by ingestion of vitamin C. Ultrasensitive detection methods for etheno-DNA adducts, which are formed by lipid peroxidation products resulting from increased oxidative stress, have been developed. Known cancer risk factors such as metal storage, chronic inflammatory processes and a high omega-6 PUFA fat diet increased the background level of these miscoding DNA adducts many times. They were found to increase progressively in premalignant lesions of cancer-prone tissues of humans and rodents, probably contributing to the genetic instability that drives cells to malignancy. Etheno-DNA adducts are thus promising markers to verify the efficiency of chemopreventive measures in humans.

Advances in the cellular and molecular biology of the beta-amyloid protein in Alzheimer's disease

Alzheimer's disease (AD) is a progressive senile dementia characterized by deposition of a 4 kDa peptide of 39-42 residues known as amyloid beta-peptide (Abeta) in the form of senile plaques and the microtubule associated protein tau as paired helical filaments. Genetic studies have identified mutations in the Abeta precursor protein (APP) as the key triggers for the pathogenesis of AD. Other genes such as presenilins 1 and 2 (PS1/2) and apolipoprotein E (APOE) also play a critical role in increased Abeta deposition. Several biochemical and molecular studies using transfected cells and transgenic animals point to mechanisms by which Abeta is generated and aggregated to trigger the neurodegeneration that may cause AD. Three important enzymes collectively known as "secretases" participate in APP processing. An enzymatic activity, beta-secretase, cleaves APP on the amino side of Abeta producing a large secreted derivative, sAPPbeta, and an Abeta-bearing membrane-associated C-terminal derivative, CTFbeta, which is subsequently cleaved by the second activity, gamma-secretase, to release Abeta. Alternatively, a third activity, alpha-secretase, cleaves APP within Abeta to the secreted derivative sAPPalpha and membrane-associated CTFalpha. The predominant secreted APP derivative is sAPPalpha in most cell-types. Most of the secreted Abeta is 40 residues long (Abeta40) although a small percentage is 42 residues in length (Abeta42). However, the longer Abeta42 aggregates more readily and was therefore considered to be the pathologically important form. Advances in our understanding of APP processing, trafficking, and turnover will pave the way for better drug discovery for the eventual treatment of AD. In addition, APP gene regulation and its interaction with other proteins may provide useful drug targets for AD. The emerging knowledge related to the normal function of APP will help in determining whether or not the AD associated changes in APP metabolism affect its function. The present review summarizes our current understanding of APP metabolism and function and their relationship to other proteins involved in AD.

Impact of the Human Genome Project on the clinical management of sporadic cancers

The publication of the human genome sequence has provided a new basis for cancer research. Molecular analysis of single cancer genes in isolation may lead to an underestimation of the impact of networks of intertwined genes in molecular cancer pathology. However, new technologies such as DNA microarrays or microchips will enable the detection of global gene-expression profiles--already described for lymphomas, acute leukaemias, and various solid tumours--and may help to overcome some of the limitations of gene function analysis. In addition, DNA microchip data banks may uncover new genes that are relevant to the molecular pathology of specific cancers and trigger detailed analysis of their function. Clinically, microchips will enable us to identify new molecular cancer markers or marker profiles of prognostic and predictive value, since global gene-expression patterns can highlight molecular tumour characteristics that relate to clinically distinct entities within heterogeneous cancers, such as non-Hodgkin lymphomas or breast cancer. However, before its promise can be realised, all molecular information stemming from the Human Genome Project will need to be tested for its clinical relevance in appropriate cancer trials; this presents a formidable but important challenge.

Perspective: cardiovascular disease in the postgenomic era--lessons learned and challenges ahead

Despite remarkable advances in medical therapeutics and technology over the last 40 yr, cardiovascular disease remains the leading cause of mortality in the United States. Elucidation of the human genome and the application of gene mapping techniques to kindreds harboring rare monogenic cardiovascular syndromes have provided fundamental insights into the pathogenesis of common cardiovascular diseases including hypertension, hypercholesterolemia, cardiomyopathy with and without conduction system disease, cardiac arrhythmias, and most recently congenital heart disease. These findings led to the unanticipated conclusion that common cardiovascular pathologies (e.g. cardiomyopathy, congenital heart disease, hypertension, cardiac arrhythmias) are united by association with distinct subsets of genes. In this review, the impact of these data on the molecular pathogenesis and development of future therapies for cardiomyopathy, congenital heart disease, and atherosclerosis are highlighted. In addition, the application and limitations of evolving genetic and genomic technologies to acquired and/or multigenic cardiovascular states including atherosclerosis and high density lipoprotein (HDL) metabolism is discussed.

Muscular dystrophy into the new millennium

Since the identification of the gene for Duchenne muscular dystrophy and its protein product some 15 years ago, the basic defects in all the commoner forms of dystrophy have now been identified. It is thus possible, on the basis of this information, to make a precise diagnosis in an affected individual and to offer accurate genetic counselling and prenatal diagnosis. Now newer technologies are being applied to the investigation of these disorders. These include studies of single nucleotide polymorphisms, microarray analysis and expression profiling, the yeast two-hybrid assay, and proteomics. A great deal of new information is emerging in this way which will hopefully help us to understand the causes of inter-familial and intra-familial variation and particularly pathogenesis, a detailed understanding of which could be the first step in finding effective treatments.

Timeline: the march of structural biology

One hundred years ago, we knew very little about biological macromolecules and had no tools available to study their structure. Structural biology is now a mature science. New structures are being solved at an ever-increasing rate and there are important new initiatives to determine all the protein folds that are used by biological systems (structural genomics). This article traces some of the key developments in the field.

Looking beyond the details: a rise in system-oriented approaches in genetics and molecular biology

With the ever-increasing flow of high-throughput gene expression, protein interaction and genome sequence data, researchers gradually approach a system-level understanding of cells and even multi-cellular organisms. Systems biology is an emerging field that enables us to achieve in-depth understanding at the system level. For this, we need to establish methodologies and techniques that enable us to understand biological systems as systems, which means to understand: (1) the structure of the system, such as gene/metabolic/signal transduction networks and physical structures, (2) the dynamics of such systems, (3) methods to control systems, and (4) methods to design and modify systems to generate desired properties. However, the meaning of "system-level understanding" is still ambiguous. This paper reviews the current status of the field and outlines future research directions and issues that need to be addressed.

Commercial molecular diagnostics in the U.S.: The Human Genome Project to the clinical laboratory

Molecular diagnosis is the detection of pathogenic mutations in DNA and RNA samples to aid in detection, diagnosis, subclassification, prognosis, and monitoring response to therapy. Principles underlying nucleic-based diagnosis originate from localization, identification, and characterization of genes responsible for human disease. Clinical molecular genetics is now part of the mainstream of medical care in the United States. All commercial clinical reference laboratories now have a molecular genetic diagnostic unit, many of which are in contractual agreement with third party payers to provide services. Gene discovery provides valuable insight into the mechanisms of disease processes and gene-based markers will enable clinicians to study disease predisposition, as well as improved methods for diagnoses, prognosis, and monitoring of therapy. The broad range of mutation spectrum and type performed in the clinical laboratory requires the use of multiple technologies rather than a single typing platform. Platform choice depends on such diverse factors as local expertise, test volume, economies of scale, R&D budget, and royalties. Test validation is a major hurdle and positive control samples are often not readily available. Oversight and the regulatory environment for clinical molecular genetics laboratories in the United States are evolving rapidly. Several government agencies and private organizations are currently involved in revision of specific laboratory standards, including the Secretary's Advisory Committee on Genetic Testing (SACGT), Food and Drug Administration (FDA), Center for Disease Control (CDC), College of American Pathologists (CAP), American College of Medical Genetics (ACMG), and the individual states.