The tumour suppressor gene encoding p53 has been shown from experimental studies to have a crucial role in how cells respond to DNA damage. p53 has important functions in apoptosis, cell-cycle arrest and DNA repair, largely mediated by its activity on gene transcription. However, despite this wealth of in vitro data, its role in how tumours respond to DNA damage induced by chemotherapeutic drugs remains controversial. In this review, we highlight some of the problems surrounding design and analysis of studies of p53 as a prognostic marker of clinical outcome, using ovarian cancer as an example. We aim to build on the knowledge of the published literature in ovarian cancer to identify criteria for clinical studies that should give a more definitive estimate of the role of p53 in clinical drug resistance. A search of three public databases using keywords combined with Boolean operators identified 64 clinical publications investigating the relationship of p53 to clinical outcome following chemotherapy in ovarian cancer. Although 43% of 215 published analyses from the 64 papers reported a significant correlation between p53 status and a clinical endpoint relevant to chemoresistance, only six analyses fulfil minimum criteria and none of these finds a statistically significant correlation of p53 with chemotherapy-resistance endpoints. The results from published clinical studies suggest a more complex role of p53 mutation in the mechanism of resistance in ovarian cancer than is suggested by in vitro studies.

Retinoids (derivatives of vitamin A) are signalling molecules that play important roles in cell growth, differentiation and death. Retinoids act through two types of receptors – retinoic acid receptors (RARα, RARβ and RARγ) and retinoid X receptors (RXRα, RXRβ and RXRγ) – which themselves act as ligand-dependent transcription factors. Retinoids are of special interest in cancer research owing to their antiproliferative and cancer-preventative properties. They have been used successfully to cure acute promyelocytic leukaemia (APL) and can suppress carcinogenesis in a variety of tissue types (e.g. skin, lung, breast and oral cancers). Extensive research efforts have been dedicated to elucidating the molecular and cellular networks that are induced by retinoids, and this has recently yielded novel insights into how retinoids can both prevent and combat cancer.

Infants born with severe combined immune deficiencies are prone to life-threatening infections and, without treatment, do not survive beyond the first year of life. Haematopoietic stem cell transplantation from a fully matched donor offers the possibility of cure. In the absence of a suitable matched donor, haploidentical transplants from a parental donor may be undertaken, but these are associated with more complications and lower success rates. Recently, an alternative therapeutic option based on retroviral gene delivery has been used to correct X-linked severe combined immune deficiency (SCID-X1) and adenosine deaminase deficiency. Clinical trials have established that in situations where ex vivo gene transfer into haematopoietic progenitor cells confers a strong selective advantage, the procedure is a feasible alternative to haploidentical transplantation, with favourable kinetics of immune reconstitution.

Lyme borreliosis is a systemic infection caused by the spirochaete Borrelia burgdorferi, which is transmitted by tick bites and maintained in a delicately balanced ecological cycle. Recent increases in the population densities of tick hosts, the abundance of ticks and the proximity of man to natural tick habitats have led to an escalating worldwide incidence of Lyme borreliosis, and nonspecific clinical manifestations have yielded significant misunderstanding of the disease. After entry, B. burgdorferi activates local inflammation, yet evades host defences and facilitates dissemination by potentially masquerading with host components such as plasmin and complement. The extent of tissue injury is determined by the aggressiveness of host inflammation and immunological reactions, as well as by genetic attributes of the spirochaete. The clinical presentation can be highly varied, including early manifestations that are limited to erythema migrans and ranging to disseminated infection with arthritis, carditis, cranial nerve palsy, peripheral neuropathy, meningitis, or other manifestations. Diagnostic tests have improved, but are unhelpful during certain stages of infection. Therapy varies depending on the degree of involvement, and recovery is usually rapid and complete. Post-treatment clinical manifestations in the absence of evidence for active infection are still poorly understood. The understanding of how B. burgdorferi survives in the environment and interacts with human and mammalian hosts has improved. However, further advances in prevention and therapy depend on continued investigation of the ecological risks and improved understanding of the pathobiology of this obligate bacterial parasite.

Chronic idiopathic thrombocytopenic purpura (ITP) is an immune-mediated disorder in which platelets are prematurely destroyed in the reticuloendothelial system by platelet autoantibodies. However, it is becoming clear that the pivotal process of the humoral immune response in the pathogenesis of the disorder is a complex interaction between antigen-presenting cells, T cells and B cells. Furthermore, it is increasingly evident that regulatory T cells play an important role and that T-cell-mediated cytotoxicity contributes to the destruction of platelets in ITP. Different new approaches to immunotherapy in chronic ITP have been explored, including use of anti-CD20, anti-CD154 and anti-CD52 antibodies. So far, these therapies have been antigen-nonspecific and the risk of general immunosuppression is a concern. Thus, improving our understanding of the interaction and relative contribution of humoral and cell-mediated mechanisms is essential for developing antigen-specific immunotherapies for the treatment of this disorder. This review aims to elucidate the current status of knowledge of the cellular and humoral immune components of chronic ITP, together with the implications of this knowledge for therapy.

Neisseria meningitidis is the leading cause of bacterial meningitis, a potentially fatal condition that particularly affects children. Multiple steps are involved during the pathogenesis of infection, including the colonisation of healthy individuals and invasion of the bacterium into the cerebrospinal fluid. The bacterium is capable of adhering to, and entering into, a range of human cell types, which facilitates its ability to cause disease. This article summarises the molecular basis of host–pathogen interactions at the cellular level during meningococcal carriage and disease.

Parkinson's disease (PD) is a debilitating neurodegenerative disorder arising from loss of dopaminergic neurons in the substantia nigra pars compacta and subsequent depletion of striatal dopamine levels, which results in distressing motor symptoms. The current standard pharmacological treatment for PD is direct replacement of dopamine by treatment with its precursor, levodopa (L-dopa). However, this does not significantly alter disease progression and might contribute to the ongoing pathology. Several features of PD make this disease one of the most promising targets for clinical gene therapy of any neurological disease. The confinement of the major pathology to a compact, localised neuronal population and the anatomy of the basal ganglia circuitry mean that global gene transfer is not required and there are well-defined sites for gene transfer. The multifactorial aetiology of idiopathic PD means that it is unlikely any single gene will cure the disease, and as a result at least three separate gene-transfer strategies are currently being pursued: transfer of genes for enzymes involved in dopamine production; transfer of genes for growth factors involved in dopaminergic cell survival and regeneration; and transfer of genes to reset neuronal circuitry by switching cellular phenotype. The merits of these strategies are discussed here, along with remaining hurdles that might impede transfer of gene therapy technology to the clinic as a treatment for PD.

With the increasing incidence and mortality of cancer worldwide, there is an urgent need for new therapeutic approaches. Gene therapy is one such approach and preliminary data are promising. Viral and nonviral vector systems for gene delivery are available, but most of the current systems suffer from disadvantages such as low transfection efficiencies, in vivo instability, targeting problems, mutagenic potential and immunogenicity. Viruses of the Parvoviridae family, which are characterised by their oncotropism, oncosuppression, long-term gene expression and human apathogenicity, potentially offer advantages as viral vectors. This article evaluates their usefulness in gene therapy strategies for cancer.

Finding the genetic causes for complex diseases is a challenge. Expression studies have shown that the level of expression of many genes is altered in disease compared with normal conditions, but what lies behind these changes? Linkage studies provide hints as to where in the genome the genetic triggers – the mutations – might be located. Fine-mapping and association studies can give yet more information about which genes, and which changes in the genes, are involved in the disease. Recent examples show that single-nucleotide polymorphisms (SNPs), which are variations at the single-nucleotide level within an individual's DNA, in the regulatory regions of some genes constitute susceptibility factors in many complex diseases. This article discusses the nature of regulatory SNPs (rSNPs) and techniques for their functional validation, and looks towards what rSNPs can tell us about complex diseases.

Primary pulmonary hypertension (PPH) is defined clinically by sustained elevation of pulmonary arterial pressure without a demonstrable cause, and is a progressive, often-fatal disease. PPH can be associated with ingestion of appetite suppressants, human immunodeficiency virus infection and certain autoimmune diseases. Familial PPH is known to account for 6% of all cases. Mutations in the gene encoding the bone morphogenetic protein (BMP) type II receptor have been identified in 72% of affected families and 26% of apparently sporadic cases. BMPs are members of the transforming growth factor β superfamily and affect intracellular signalling via Smads and mitogen-activated protein kinases. Evidence supports a ‘two-hit’ hypothesis in which PPH is triggered by accumulation of genetic and environmental insults in a susceptible individual. Elucidation of the precise molecular and cellular mechanisms underlying PPH will provide a powerful basis for the development of novel therapeutic strategies in the treatment of this devastating condition.

Asthma, allergic rhinitis and atopic dermatitis are allergic immune disorders characterised by a predominance of T helper 2 (Th2) cells, the resulting elevation of allergen-specific IgE, and mast-cell- and basophil-associated inflammation. The cytokine environment at the site of the initial antigen stimulation determines the direction of Th-cell differentiation into Th1 or Th2 cells. The SOCS (suppressor of cytokine signalling) proteins are implicated in the control of the balance between Th1 and Th2 cells in this process. SOCS3 is predominantly expressed in Th2 cells and inhibits Th1 differentiation; conversely, SOCS5 is expressed predominantly in Th1 cells and inhibits Th2 differentiation. Here, we discuss the role of SOCS proteins in Th-cell differentiation and explore the potential of SOCS proteins as targets for therapeutic strategies in allergic disorders.

Src homology 2 (SH2) domains are protein modules (of ~100 amino acids) found in many proteins involved in tyrosine kinase signalling cascades. Their function is to bind tyrosine-phosphorylated sequences in specific protein targets. Binding of an SH2 domain to its cognate tyrosine-phosphorylated target links receptor activation to downstream signalling, both to the nucleus to regulate gene expression and throughout the cytoplasm of the cell. This review recapitulates the roles that SH2 domains play in normal and diseased states, describes the successes of SH2 domain research in deciphering their mechanism of action, and provides an overview of the use of SH2 domains as structural templates for the design of inhibitor drugs.

Epstein-Barr virus (EBV) is a γ-herpesvirus that infects over 90% of the human population worldwide. It is usually transmitted between individuals in saliva, and establishes replicative infection within the oropharynx as well as life-long latent infection of B cells. Primary EBV infection generally occurs during early childhood and is asymptomatic. If delayed until adolescence or later, it can be associated with the clinical syndrome of infectious mononucleosis (also known as glandular fever or ‘mono%rsquo;), an illness characterised by fevers, pharyngitis, lymphadenopathy and malaise. EBV infection is also associated with the development of EBV-associated lymphoid or epithelial cell malignancies in a small proportion of individuals. This review focuses on primary EBV infection in individuals suffering from infectious mononucleosis. It discusses the mechanism by which EBV establishes infection within its human host and the primary immune response that it elicits. It describes the spectrum of clinical disease that can accompany primary infection and summarises studies that are leading to the development of a vaccine designed to prevent infectious mononucleosis.

The primary hyperoxalurias type 1 (PH1) and type 2 (PH2) are autosomal recessive calcium oxalate kidney stone diseases caused by deficiencies of the metabolic enzymes alanine:glyoxylate aminotransferase (AGT) and glyoxylate/hydroxypyruvate reductase (GR/HPR), respectively. Over 50 mutations have been identified in the AGXT gene (encoding AGT) in PH1, associated with a wide variety of effects on AGT, including loss of catalytic activity, aggregation, accelerated degradation, and peroxisome-to-mitochondrion mistargeting. Some of these mutations segregate and interact synergistically with a common polymorphism. Over a dozen mutations have been found in the GRHPR gene (encoding GR/HPR) in PH2, all associated with complete loss of glyoxylate reductase enzyme activity and immunoreactive protein. The crystal structure of human AGT, but not human GR/HPR, has been solved, allowing the effects of many of the mutations in PH1 to be rationalised in structural terms. Detailed analysis of the molecular aetiology of PH1 and PH2 has led to significant improvements in all aspects of their clinical management. Enzyme replacement therapy by liver transplantation can provide a metabolic cure for PH1, but it has yet to be tried for PH2. New treatments that aim to counter the effects of specific mutations on the properties of the enzymes could be feasible in the not-too-distant future.

Angiotensin II, the effector peptide of the renin–angiotensin system (RAS), has potent growth factor properties in a variety of organs. In the retina, a complete RAS exists, with components residing in the vasculature, neurons and glia. There is increasing interest in a pathogenetic role for angiotensin II in ischaemic retinopathies such as diabetic retinopathy and retinopathy of prematurity. In these situations, the retinal RAS becomes activated and stimulates growth factors such as vascular endothelial growth factor, which contribute to vascular leakage, pericyte migration, angiogenesis and fibrosis. Blockade of the RAS, with either angiotensin-converting enzyme (ACE) inhibitors or antagonists selective for angiotensin type 1 (AT1) and angiotensin type 2 (AT2) receptors, attenuates many of the vascular abnormalities that develop in diabetic retinopathy and retinopathy of prematurity. Eagerly awaited are the findings of the Diabetic Retinopathy Candesartan Trial (DIRECT), evaluating the effects of AT1 receptor antagonism in patients with different stages of diabetic retinopathy. This review examines the role of the RAS in diabetic retinopathy and retinopathy of prematurity, and the potential of RAS blockade as a treatment strategy for these vision-threatening diseases.

BAG-1 is a multifunctional protein that exists as several differentially localised and functionally distinct isoforms. BAG-1 isoforms interact with a diverse array of molecular targets and regulate a wide range of cellular processes, including proliferation, survival, transcription, apoptosis, metastasis and motility. The BAG domain of BAG-1 interacts with chaperone molecules and this is considered important for many BAG-1 functions. The ability of BAG-1 to regulate such a wide variety of cellular processes suggests it might play an important role in many cancer types. For example, regulation of nuclear hormone receptor function and susceptibility to apoptosis might have a major impact on cancer development, progression and response to therapy. There is also increasing evidence that BAG-1 expression is altered in a variety of human malignancies relative to normal cells, and with further understanding of BAG-1 function it might become a powerful prognostic/predictive marker in human cancer. This review describes the structure and function of BAG-1 isoforms and the potential clinical implications of their expression in tumour cells.

Lithium has emerged as a neuroprotective agent efficacious in preventing apoptosis-dependent cellular death. Lithium neuroprotection is provided through multiple, intersecting mechanisms, although how lithium interacts with these mechanisms is still under investigation. Lithium increases cell survival by inducing brain-derived neurotrophic factor and thereby stimulating activity in anti-apoptotic pathways, including the phosphatidylinositol 3-kinase/Akt and the mitogen-activated protein kinase pathways. In addition, lithium reduces pro-apoptotic function by directly and indirectly inhibiting glycogen synthase kinase-3β activity and indirectly inhibiting N-methyl-D-aspartate (NMDA)-receptor-mediated calcium influx. Lithium-induced regulation of anti- and pro-apoptotic pathways alters a wide variety of downstream effectors, including β-catenin, heat shock factor 1, activator protein 1, cAMP-response-element-binding protein, and the Bcl-2 protein family. Lithium neuroprotection has a wide variety of clinical implications. Beyond its present use in bipolar mood disorder, lithium's neuroprotective abilities imply that it could be used to treat or prevent brain damage following traumatic injury, such as stroke, and neurodegenerative diseases such as Huntington's and Alzheimer's diseases.

Dyskeratosis congenita (DC) is a severe, inherited, bone marrow failure syndrome, with associated cutaneous and noncutaneous abnormalities. DC patients also show signs of premature ageing and have an increased occurrence of cancer. DC can originate through: (1) mutations in DKC1, which result in X-linked recessive DC; (2) mutations in the RNA component of telomerase (TERC), which result in autosomal dominant DC (AD-DC); and (3) mutations in other, currently uncharacterised, genes, which result in autosomal recessive DC (AR-DC). As DKC1 encodes dyskerin, a protein component of small nucleolar ribonucleoprotein (snoRNP) particles, which are important in ribosomal RNA processing, DC was initially described as a disorder of defective ribosomal biogenesis. Subsequently, dyskerin and TERC were shown to closely associate with each other in the telomerase complex, and DC has since come to be regarded as a telomerase deficiency disorder characterised by shorter telomeres. These findings demonstrate the importance of telomerase in humans and highlight how its deficiency (through DKC1 and TERC mutations) results in multiple abnormalities including premature ageing, bone marrow failure and cancer. Identification of the gene(s) involved in AR-DC will help to define the pathophysiology of DC further, as well as expand our insights into telomere function, ageing and cancer.

The haematopoietic system can be manipulated genetically to increase either its resistance to drugs or its sensitivity to certain agents. Gene transfer and expression of specific drug-resistance factors might protect haematopoietic function during antitumour chemotherapy, or allow enrichment of gene-modified cells in vivo. By contrast, gene transfer of a prodrug activator, to confer sensitivity to otherwise nontoxic prodrugs, might allow deletion of engrafted cells in the event of an adverse effect such as graft-versus-host disease or the induction of a neoplasm. In addition, expression of a prodrug activator in tumour-infiltrating haematopoietic cells could provide a means of specifically activating a cytotoxic agent within a tumour mass.

Delivery systems for tumour targeting fall into two basic categories: drug conjugate systems, in which individual drug molecules are chemically modified to target them directly to the tumour; and carrier-based systems, in which the drug or gene is first packaged non-covalently into a synthetic carrier that is then targeted to the tumour. In both cases, the objective is to maximise exposure of the target cells to the drug yet minimise side effects that result from nonspecific toxicity in normal tissues. The creation of such dose differentials is based on phenotypic differences between the tumour and the rest of the body. However, although a wide range of such changes have been linked to the transformation of normal cells to cancer cells, no single common feature exists to allow unambiguous targeting to the tumour. In addition, the tumour microenvironment creates physical barriers that significantly impair transport within the tumour. It is therefore important to match the delivery requirements of the drug to the capabilities of the delivery system. In this review, a brief overview is given of the underlying concepts and principles that help guide the development of such tumour-targeting strategies.