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Therapeutic promise of molecular genetics.

The application of molecular genetics to medicine is based on the observation that even common diseases have both genetic and environmental components. Conventional medicines are often effective in managing environmental components of disease but are generally ineffective in managing genetic diseases or manipulating the genetic component of multifactorial diseases. The development of therapies aimed at the genetic component of disease will require non-conventional medicinal applications of molecular genetics. Various approaches have been proposed such as diagnosing the propensity for disease to facilitate early intervention with conventional therapies, selectively eliminating mutant genes from human populations, correcting mutations in human chromosomes, and using genes as medicines to modify the genetic components of disease. Of these, it is the development of gene medicines that has the greatest practical potential. The combination of conventional medicines, focused on the environmental components of disease, and gene medicines, focused on the genetic components, will provide the clinician with broad options for managing health and disease. The challenge to molecular biology is to develop gene medicines that are effective, safe, and socially acceptable, and therapies that map well to established clinical practice and may be employed efficaciously alongside conventional medicines.

Genetic Diseases, Inborn↗

Basal cell carcinoma: from host response and polymorphic variants to tumour suppressor genes.

The molecular factors and events that characterize susceptibility and outcome in cutaneous basal cell carcinoma (BCC) have been the focus of much research interest. As a result, we are beginning to understand the complex relationships between exposure to ultraviolet radiation (UVR), host response and the resulting damage to key genes that characterize these tumours. In this review, we will focus on genetic factors that influence susceptibility and outcome. While the search for susceptibility genes has generally resulted in the identification of low penetrance allelic variants, studies on modifier genes influencing outcome variables such as tumour number, age of onset and tumour subtype have identified factors with higher potential impact. Here we will briefly describe some recent work on the genetic basis of the immune response to UVR, the effect of UVR on the generation of reactive oxygen species and their detoxification, and the role of onco- and tumour suppressor genes. Areas for further research are highlighted, together with a consideration of possible applications in clinical practice.

Basal Cell Carcinoma↗

XRCC1, XRCC3, and XPD polymorphisms as modifiers of the effect of smoking and alcohol on colorectal adenoma risk.

Using a sigmoidoscopy-based case-control study (753 cases, 799 controls) in Los Angeles County, we investigated the potential modifier role in the effect of alcohol and smoking of single-nucleotide polymorphisms (SNP) in three DNA repair genes, XRCC1 (Arg194Trp and Arg399Gln), XRCC3 (Thr241Met), and XPD (Lys751Gln). We have previously reported an inverse association between the XRCC1 codon 399 SNP and adenoma risk among these subjects. We now report that subjects with the XPD Gln/Gln genotype were inversely associated with adenoma risk [odds ratio (OR), 0.7; 95% confidence interval (95% CI), 0.5-1.0] when compared with subjects with the Lys/Lys and Lys/Gln genotypes combined. This association differed between different ethnic groups (gene x race heterogeneity likelihood ratio test, P = 0.009), with a stronger inverse association among Latinos (OR, 0.1; 95% CI, 0.01-0.5) than among non-Latinos (OR, 0.9; 95% CI, 0.-1.3). We found no evidence of an XRCC3 x smoking or alcohol interaction or an XRCC1 x alcohol interaction. Instead, our data supported an XRCC1 x smoking interaction (P = 0.048). Whereas XPD did not modify the effect of smoking, our data suggested an XPD x alcohol interaction. Analyses ignoring XPD showed no association between alcohol intake and adenoma prevalence; however, among carriers of the codon 751 Gln/Gln genotype, we found a significant positive association (OR, 2.5; 95% CI, 1.2-5.2 for ever drinkers; test of interaction P = 0.04). Our data suggest that the effects of smoking and alcohol may vary depending on the genetic background of proteins that participate in the base excision repair and nucleotide excision repair pathways.

Adenoma↗

Prospects for gene therapy in pediatric neurosurgery.

Gene therapy represents a powerful tool for both the study and potential treatment of pediatric neurological diseases. The majority of strategies for brain gene therapy have focused upon the use of modified viruses as vehicles for efficient delivery of genes into cells of the central nervous system. Retroviruses were originally the most popular vehicles for gene transfer outside the brain; however, these only function in actively dividing cells and have thus been limited to developmental neurobiology and treatment of brain tumors. Viruses with DNA-based genomes can transfer genes to both dividing and nondividing cells such as neurons, and these include adenovirus, adeno-associated virus and herpes simplex virus. Each system has special features, and the choice of vehicle may be based upon a variety of factors including toxicity or immunogenicity of the vector in vivo, size of the gene which can be inserted, titer of virus which can be obtained and technical difficulty in generating reagent grade viruses. Pediatric patients present unique opportunities for gene therapy, and inherited genetic defects and brain tumors are among the pediatric disorders which would most benefit from this new field. Preclinical studies using each of these systems in a variety of models of pediatric CNS disease have proven promising. Several ongoing studies have been initiated for treatment of pediatric brain tumors, and a protocol for treatment of an inherited neurological defect has recently achieved approval for initial clinical trials. Continued advances in gene therapy technology and delivery systems combined with the explosion of available genetic information should make gene therapy an increasingly important tool for the future of pediatric neurosurgery.

Adenoviridae↗

Introduction of vascular smooth muscle cells expressing recombinant genes in vivo.

Vascular smooth muscle cells contribute to the formation of atherosclerotic plaques by proliferating in response to vascular injury and releasing growth-promoting factors. Because their autocrine and paracrine effects are not fully understood, expression of such growth factor genes in specific cell types in vivo would help to determine their mechanism of action. We describe a method to transfer vascular smooth muscle cells expressing recombinant gene products to localized segments of the arterial wall. Vascular smooth muscle cells from the inbred Yucatan minipig were infected in vitro with an amphotropic, replication-defective retrovirus transducing the gene for Escherichia coli beta-galactosidase. Vascular smooth muscle cells expressing this recombinant gene were implanted, using a catheter, into denuded iliofemoral artery segments of pigs in vivo. These arteries subsequently demonstrated beta-galactosidase activity in cells of the intima and media. This method, which provides for the introduction of genetically modified smooth muscle cells, can be used to define the biological effects of recombinant genes in the vessel wall and potentially to provide alternative treatments of vascular diseases.

Animals↗

Anti-tumor effect of murine renal cell carcinoma cells genetically modified to express B7-1 combined with cytokine secreting fibroblasts.

Recently, many experiments have shown that the expression of the costimulatory molecule B7-1 on tumor cells can induce tumor-specific immunity. These results suggest that tumor cells modified to express costimulatory molecules can be used as a potential tumor vaccine. For this purpose, we transduced B7-1 gene into renal adenocarcinoma cells of spontaneous origin (Renca) in BALB/c mouse using the retroviral vector system. Our results indicated that approximately 60% of cells expressed B7-1 gene product using the retroviral vector system, and that B7-1 transduction did not affect the expression of MHC molecules on tumor cells nor the in vitro growth rate of tumor cells, but only in vivo tumorigenicity. As for the antitumor effect on the remote site, there were no significant differences among parental Renca, Renca lac Z and Renca B7-1 sublines, although tumors grew a little more slowly in the mice injected with Renca B7-1 cells as a vaccine. Even if the growth of tumors was significantly delayed in the mice treated by Renca B7-1 as a vaccine combined with the injection of BALB/c3T3 IL-12 near to the tumor on the same or following day, no significant antitumor effects were observed when the Renca B7-1 cells were injected as a vaccine compared with cytokines near the vaccine site. These results indicated that B7-1 gene transduction can decrease the tumorigenicity of murine renal cell carcinoma cells, but fails to induce sufficient antitumor response when it is used as a tumor vaccine. It is necessary to develop immunogenicity, by such means as irradiation or a combination of appropriate cytokines, to stimulate effective tumor immunity in a therapeutic setting.

3T3 Cells↗

Bioresorbable microporous stents deliver recombinant adenovirus gene transfer vectors to the arterial wall.

The use of intravascular stents as an adjunct for percutaneous transluminal revascularization is limited by two principal factors, acute thrombosis and neointimal proliferation, resulting in restenosis. To overcome these limitations, we have investigated the potential of microporous bioresorbable polymer stents formed from poly(L-lactic acid) (PLLA)/poly(epsilon-caprolactone) (PCL) blends to function both to provide mechanical support and as reservoirs for local delivery of therapeutic molecules and particles to the vessel wall. Tubular PLLA/PCL stents were fabricated by the flotation-precipitation method, and helical stents were produced by a casting/winding technique. Hybrid structures in which a tubular sheath is deposited on a helical skeleton were also generated. Using a two-stage solvent swelling technique, polyethylene oxide has been incorporated into these stents to improve hydrophilicity and water uptake, and to facilitate the ability of these devices to function as drug carriers. Stents modified in this manner retain axial and radial mechanical strength sufficient to stabilize the vessel wall against elastic recoil caused by vasoconstrictive and mechanical forces. Because of the potential of direct gene transfer into the vessel wall to ameliorate thrombosis and neointimal proliferation, we have investigated the capacity of these polymer stents to function in the delivery of recombinant adenovirus vectors to the vessel wall. In vitro, virus stock was observed to readily absorb into, and elute from these devices in an infectious form, with suitable kinetics. Successful gene transfer and expression has been demonstrated following implantation of polymer stents impregnated with a recombinant adenovirus carrying a nuclear-localizing betaGal reporter gene into rabbit carotid arteries. These studies suggest that surface-modified polymer stents may ultimately be useful adjunctive devices for both mechanical support and gene transfer during percutaneous transluminal revascularization.

Adenoviridae↗

Targeted expression of the neuropeptide calcitonin gene-related peptide to beta cells prevents diabetes in NOD mice.

To investigate whether the immunosuppressive neuropeptide calcitonin gene-related peptide (CGRP) was a potential candidate for tissue-specific gene therapy, we engineered nonobese diabetic (NOD) mice to produce CGRP in beta cells by placing the modified calcitonin gene under the control of the rat insulin promoter. CGRP inhibits CD4 T cell production of the cytokines that have been implicated in the pathogeny of type I diabetes. Three transgene-positive mouse lines were obtained, two of which expressed immunoreactive CGRP in beta cells (NOD-CGRP mice). Isolated islets from one of these two transgene-positive founders produced active CGRP, whereas islets from transgene-negative littermates did not. The production of CGRP by beta cells prevented insulin-dependent diabetes mellitus in male and reduced its incidence by 63% in female mice. This prevention was due to a local immunosuppressive effect of CGRP as no difference was detected between NOD-CGRP and NOD littermate lymph node, spleen, and thymus cells by either FACS analysis or proliferative response to stimulation by Ag, alloantigen or anti-CD3. These data suggest that CGRP is a potential therapeutic molecule to prevent or treat diabetes and possibly other diseases and conditions in which immune cells are involved. These data also suggest that endogenous CGRP concentrated in sensory nerve endings may regulate locally the immune response, further strengthening the importance of the functional neuroimmune link.

Animals↗

RNA interference and chemically modified small interfering RNAs.

RNA interference (RNAi) is a powerful biological process for specific silencing of gene expression in diversified eukaryotic cells and has tremendous potential for functional genomics, drug discovery through in vivo target validation, and development of novel gene-specific medicine. The future success of this technology relies on identifying appropriate chemical modifications to improve stability, potency and in vivo cellular delivery. The present review summarizes the role of the chemist's toolbox in this emerging technology.

Animals↗

Phenotype variability of two FAP families with an identical APC germline mutation at codon 1465: a potential modifier effect?

We report the cases of two familial adenomatous polyposis (FAP) families who presented with the same 2 base pair deletion (AG) at codon 1465 of the adenomatous polyposis coli (APC) gene, but showed phenotypic variability. The mutation was revealed by a simple nonradioactive method using a heteroduplex analysis and identified by a sequence analysis. This observation suggests the responsibility of modifier genes in FAP patients' phenotype.

Adenomatous Polyposis Coli↗

Incorporating basic nutrition science into health interventions for cancer prevention.

Increasing evidence points to numerous dietary components that modify cancer incidence as well as the biological behavior of tumors. These inhibitory or stimulatory effects depend not only on the dietary component examined, but on a number of factors including the cellular DNA profile (nutrigenetic and nutrigenomic effects), protein formation and regulation (proteomic effect), and the effective delivery of the active intermediate at specific target sites (metabolomic effect). Unfortunately, the diet and cancer research domain is strewn with studies that were inadequately designed to monitor biological endpoints, used invalid biomarkers, or monitored irrelevant intakes or exposures. The scientific frontiers in health risk prediction and disease prevention strategies will greatly expand with the building of reliable nutrition and cancer biomarker databases that use modeling techniques to integrate information about intakes, effect biomarkers, and susceptibility biomarkers. Fundamental to this database will be the elucidation of the specific molecular sites of action (targets) for the specific dietary component. Clustering techniques that build on either genes or ratios of genetic expressions or their products will be needed to assess the merit of a particular dietary intervention. Models are already surfacing about how dietary-induced fluctuations in genes and their expression products can modify pathways associated with carcinogen activation and detoxification, alter rates of cellular proliferation, influence apoptosis, and modify angiogenesis. Embracing new genomic technologies offers exciting opportunities for advancing nutrition, especially those related to cancer prevention. We must effectively communicate, within a responsible bioethical framework, the potential value of knowledge about genes and gene products.

DNA Methylation↗

Prediction of allergenicity of gene-modified foods by serum-based testing.

On the basis of applying the IFBC/ILSI decision tree in a number of cases, a refinement of the scheme is suggested. Large differences in allergenic potential may be obtained by altering the route of administration of an allergen. Because an inhalation allergen can induce symptoms at different threshold doses depending on whether it is introduced via the inhalation or oral route, we propose that double-blind, placebo-controlled food challenges be performed in all cases of inhalation allergens being present in foods. Even proteins never previously ingested may cause IgE binding and elicit clinically relevant symptoms.

Allergens↗

Genetic modification of animals in the next century.

Since the initial demonstration in 1982 of profound phenotypic effects stemming from the expression of a single transgene, genetic engineering has revolutionized fundamental biological and biomedical research. The application of transgenic technology to farm animals has held the promise of being able to improve animal agriculture significantly and has resulted in a new industry, i.e., the successful expression of foreign proteins in the mammary gland for the pharmaceutical industry. Work over the last few years in model species (e.g., the mouse) and new technical developments such as cloning have now set the stage for the initial application of transgenic technology for the improvement of farm animals. Major limitations that remain are the lack understanding of which genes we should transfer in order to alter quantitative production traits usefully and the low efficiency of producting transgenic founders. Furthermore, more research is needed concerning the consequences and potential problems arising from the integration of transgenes into populations with varying genetic backgrounds. Recent advances suggest that within the first decade of the 21 st century the first transgenic animals will become available to the livestock industry, with acceptance depending upon their cost versus their potential economic benefit to the producers.

Animal Husbandry↗

Novel methyltransferase for modified uridine residues at the wobble position of tRNA.

We have identified a novel tRNA methyltransferase in Saccharomyces cerevisiae that we designate Trm9. This enzyme, the product of the YML014w gene, catalyzes the esterification of modified uridine nucleotides, resulting in the formation of 5-methylcarbonylmethyluridine in tRNA(Arg3) and 5-methylcarbonylmethyl-2-thiouridine in tRNA(Glu). In intact yeast cells, disruption of the TRM9 gene results in the complete loss of these modified wobble bases and increased sensitivity at 37 degrees C to paromomycin, a translational inhibitor. These results suggest a role for this potentially reversible methyl esterification reaction when cells are under stress.

Amino Acid Sequence↗

Gene therapy in surgical oncology.

BACKGROUND: Surgery remains the only potentially curative treatment modality for the majority of patients with solid tumors. Conventional chemotherapy and radiotherapy only have roles as adjuvant or palliative therapies for most common cancers. Two decades of research have led to the first attempts at producing and introducing clinically useful genetically modified cells into humans. METHODS: Modern molecular methods have been developed that allow the stable transfer of foreign DNA sequences into human and other mammalian somatic cells. At the present time, gene therapy predominantly involves gene insertion either directly into a target cell in situ or into an appropriate cell in vitro that is then introduced to a physiologically relevant site. We present an overview of the potential applications of molecular biology for practicing surgeons, particularly in the field of surgical oncology, to show how genes are harnessed and inserted into target somatic cells. CONCLUSIONS: Although significant clinical therapies have and will continue to emerge from these initial experiments, only the future will provide evidence of whether the present technical skills are sufficient to have an impact on the long-term benefits for patients with cancer and genetic defects.

Gene Transfer Techniques↗

[Efficient gene delivery into dendritic cells by fiber-mutant adenovirus vectors].

Dendritic cells (DC) are professional antigen-presenting cells with a key function in the immune system as initiators of T-cell responses against microbial pathogens and tumors. Therefore, the immunization using DC loaded with tumor-associated antigens is potential to represent a powerful method of inducing anti-tumor immunity. Recent studies have demonstrated the usefulness of DC genetically modified by adenovirus vectors (Ad) to immunotherapy, while sufficient gene transduction into DC is required for high doses of Ad. Entry of Ad into target cells occurs by serial two steps: the binding of Ad-fiber knob to Coxsackie-adenovirus receptor (CAR) on the cell surface, and the subsequent interaction between Arg-Gly-Asp (RGD) motif located in Ad-penton base and alpha v-integrins. The reverse transcription-polymerase chain reaction analysis revealed that the relative resistance of DC to Ad-mediated gene transfer was due to the absence of CAR expression, and that DC expressed adequate alpha v-integrins. Therefore, we investigated whether fiber-mutant Ad (FM-Ad) containing the RGD sequence in the fiber knob can efficiently transduce and express high levels of the foreign gene into DC. The gene delivery by FM-Ad was more efficient than that by conventional Ad in both murine DC lines and normal human DC. Furthermore, both antigen presentations via major histocompatibility complex class I molecules and in vivo antigen-specific cytotoxic T lymphocyte induction by DC transduced with antigen gene by FM-Ad were superior to those by DC applied with conventional AD. We propose that alpha v-integrin-targeted FM-Ad is a very powerful tool to implement DC-based vaccination strategies.

Adenoviridae↗

Characterization of the human glycerol kinase promoter: identification of a functional HNF-4alpha binding site and evidence for transcriptional activation.

Glycerol kinase (GK) is an enzyme at the interface of carbohydrate and fat metabolism. Mutations in the GK gene result in a rare inborn error of metabolism, GK deficiency (GKD), and at least one of these mutations (N288D) is associated with insulin resistance and diabetes mellitus. In an attempt to identify potential modifiers of the GKD phenotype, and to elucidate better the relationship between GKD and diabetes mellitus, we investigated the GK promoter. We examined the GK promoter using in silico methods, transient transfections of GK promoter-luciferase constructs in HepG2 hepatocellular carcinoma cells, and gel shift assays using liver nuclear extracts. We determined that the first 100 bp of the GK 5(') upstream region was sufficient for basal levels of transcription and that there was a functional HNF-4alpha binding site in the first 500 bp of the 5(') upstream region that was important for increased levels of GK expression in vitro. The involvement of both GK and HNF-4alpha in the etiology of diabetes mellitus is intriguing, and we speculate that HNF-4alpha represents a potential modifier of the GKD phenotype.

5' Flanking Region↗

Implication of alpha1-antichymotrypsin polymorphism in familial Alzheimer's disease.

A common polymorphism in the alpha1-antichymotrypsin (ACT) gene has been shown to modify the Apolipoprotein E (ApoE) epsilon4-associated Alzheimer's disease (AD) risk identifying the combination of the ACT/AA and ApoE epsilon4/epsilon4 genotypes as a potential susceptibility marker for AD. Using the polymerase chain reaction, we analyzed the segregation of the ACT and ApoE polymorphisms in familial Alzheimer's disease (FAD) patients carrying mutations in Presenilin (PS) and APP genes and in both early onset (EO) and late onset (LO) FAD patients without known mutations. Our data suggest that ACT does not represent an additional risk factor for PS and APP mutated families. However, in LOFAD patients a high frequency of the combined ACT/AA and ApoE epsilon4/epsilon4 genotypes suggest that ACT may interact with ApoE and play a role in LOFAD.

Adult↗