SABRSeq: A Randomized Phase Ib Trial of SABR Sequencing with Pembrolizumab in Metastatic Non-Small Cell Lung Cancer (NSCLC)

PURPOSE/OBJECTIVE(S)

The optimal sequencing of stereotactic ablative body radiotherapy (SABR) with anti-PD1 checkpoint blockade is unknown. The purpose of SABRseq was to assess the toxicity of the combination of SABR delivered either before or after the commencement of pembrolizumab. The central hypothesis is that the treatment combination will have a safety profile that is clinically acceptable and demonstrate anti-tumor efficacy. Furthermore, we hypothesize that differences in systemic immune activation will be observed between treatment arms.

MATERIALS/METHODS

This was a single institutional phase Ib randomized clinical trial (Trial ID NCT03307759). Eligible patients had metastatic NSCLC, ECOG performance 0-1, and had not received prior checkpoint immunotherapy, high-dose radiation (>36 Gy) within 6 months, or either systemic or radiation therapy within 4 weeks of randomization. Eligible patients had either TPS≥50% PD-L1 expression in the first-line or TPS≥1% PD-L1 expression with prior chemotherapy exposure. Patients were randomized to SABR before the commencement of pembrolizumab [ARM1] or SABR commencing after pembrolizumab [ARM2]. SABR was delivered in a single fraction of 18-20 Gy to 1-3 lesions. The primary endpoint was treatment-related adverse events (AE's) related to SABR and/or pembrolizumab. Secondary endpoints included best overall response (BOR), overall survival (OS), and progression-free survival (PFS). Translational objectives included the evaluation of longitudinal changes in immunological cellular subsets within peripheral blood to explore changes in systemic immunity and circulating tumor DNA (ctDNA) dynamics.

RESULTS

Between December 2017 and December 2019, 13 patients were randomized. The median follow-up was 37 months. The study was closed early due to poor accrual. Median age was 66 years, with 11 patients (84%) having adenocarcinoma. Nine (69%) were enrolled in the first-line setting. The median [range] number of lesions was 6 [3-11]. The median [range] cycles of pembrolizumab delivered in ARM 1 was 13 [12-32] and ARM 2 was 9 [3-34]. Grade 3 treatment-related AEs were experienced in 0 of 5 patients in ARM1 and in 1 of 8 patients in ARM 2 (hyperglycemia). There were no grade 4 or 5 adverse events reported. The BOR by both RECIST and iRECIST criteria was CR in one patient, PR in seven patients, SD in five patients. Median (95% Cis) PFS was 12.4 months (6.3-21.0), and median (95% Cis) OS was 47.1 months (12.6-not reached; 2-year point estimate 62% [31-82]). Mass cytometry was used on serial peripheral blood samples to examine changes in the frequency of immune cells, changes in T cell activation, differentiation and functional polarization state. Targeted sequencing was performed to assess ctDNA. Translational outcomes will be presented.

CONCLUSION

There was no evidence of a concerning safety signal from either SABR before or after start of pembrolizumab. The combination demonstrated activity with promising PFS and OS and is worthy of evaluation in larger randomized trials.

The 4G/5G Genetic Polymorphism in the Promoter of the Plasminogen Activator Inhibitor-1 (PAI-1) Gene Is Associated with Differences in Plasma PAI-1 Activity but not with Risk of Myocardial Infarction in the ECTIM Study

We have investigated the interrelationships of plasma PAI-1 activity, the PAI-1 4G/5G polymorphism and risk of myocardial infarction (MI) in the ECTIM study, a case-control study of MI based in Belfast, Lille, Strasbourg and Toulouse. Mean PAI-1 levels in cases were similar across all centres but in controls, levels in the French centres were significantly higher. Only in Belfast were PAI-1 levels higher in cases (11.7AU/ml) than controls (10.5AU/ml). The PAI-1 4G allele frequency was similar in cases and controls (0.55 and 0.54). In all groups, 4G homozygotes had the highest mean plasma PAI-1 level (4G4G vs 5G5G; cases overall: 14.2 vs 12.1 AU/ml; controls overall: 15.0 vs 12.6AU/ml), with the heterozygotes generally intermediate. The data from Belfast are consistent with the literature implicating PAI-1 level as an MI risk factor. In ECTIM, the PAI-1 4G/5G polymorphism is not a genetic risk factor for MI but is associated with PAI-1 activity. Thus homozygosity for the 4G allele may predispose to elevated PAI-1 and impaired fibrinolysis, perhaps requiring interaction with other genetic or environmental factors to influence MI risk.

Decline in Antigenicity of Tumor Markers by Storage Time Using Pathology Sections Cut From Tissue Microarrays

Sectioning a whole tissue microarrray (TMA block) and storing the sections maximizes the number of sections obtained, but may impair the antigenicity of the stored sections. We have investigated the impact of TMA section storage on antigenicity. First, we reexamined existing TMA data to determine whether antigenicity in stored sections changes over time. Component scores for each marker, based on cellular compartment of staining and score-type, were evaluated separately. Residual components scores adjusted for grade, tumor size, and node positivity, were regressed on the number of days storage to evaluate the effect of storage time. Storage time ranged from 2 to 1897 days, and the mean change in antigenicity per year ranged from -0.88 (95% confidence interval, -1.11 to -0.65) to 0.035 (95% confidence interval, 0.016-0.054). Further analysis showed no significant improvement in the fit of survival models if storage time adjusted scores were included in the models rather than unadjusted scores. We then compared 3 ways of processing TMA sections after cutting-immediate staining, staining after 1 year, and staining after 1 year coated in wax-on the immunohistochemistry results for: progesterone receptor, a routinely used, robust antibody, and MKI67, which is generally considered less robust. The progesterone receptor scores for stored sections were similar to those for unstored sections, whereas the MKI67 scores for stored sections were substantially different to those for unstored sections. Wax coating made little difference to the results. Biomarker antigenicity shows a small decline over time that is unlikely to have an important effect on studies of prognostic biomarkers.

Triple negative breast cancers: clinical and prognostic implications

Triple negative breast cancers are defined by the absence of oestrogen, progesterone and HER2 expression. Most triple negative cancers display distinct clinical and pathological characteristics with a high proportion of these tumours occurring at a younger age of onset and in African-American women. Triple negative tumours typically demonstrate high histological grade and are the most common breast cancer subtype in BRCA1 carriers. In addition, many of the features of triple negative cancers are similar to those identified in the basal-like molecular subtype which has recently been characterised by gene expression profiling. Although the two groups overlap, they are not synonymous. Triple negative breast cancers are of pivotal clinical importance given the lack of therapeutic options. The prognostic significance of triple negative tumours remains unclear since the group is heterogeneous and worst prognosis seems to be mostly confined to those that express basal cytokeratins or epidermal growth factor receptor (EGFR). This review focuses on outlining the pathological, molecular, and clinical features of triple negative breast cancers, discusses its prognostic value and summarises current therapeutic approaches and future directions of research.

Severe hypoglycaemia after long-acting octreotide in a patient with an unrecognized malignant insulinoma

Insulinomas are the most common hormone-producing pancreatic neuroendocrine tumours (NETs), and patients usually present with symptoms secondary to hypoglycaemia. Octreotide has been widely used in the symptomatic treatment of patients with pancreatic NETs, including insulinomas. We describe a case of a patient with a metastatic NET, subsequently identified as a malignant insulinoma, who developed severe hypoglycaemia after treatment with long-acting octreotide.

A phase I/II trial of celecoxib with chemotherapy and radiotherapy in the treatment of patients with locally advanced oesophageal cancer

BACKGROUND

The study's aim was to determine the maximum tolerated dose (MTD) of celecoxib combined with chemoradiotherapy (CRT) for locally advanced oesophageal cancer (OC).

METHODS

CRT comprised of 5FU (1000 mg/m(2)/day, days 1-4, weeks 1 & 5), cisplatin (75 mg/m(2), days 1 & 29) and radiotherapy (50 Gy in 25 fractions or 50.4 Gy in 28 fractions). Celecoxib was given daily during CRT at one of five doses (200 mg bd to 600 mg bd). Three to six patients were assigned per dose.

RESULTS

Thirteen patients were recruited before trial closure due to external safety concerns regarding celecoxib. Median follow up was 17 months (95% CI 9 - >39). The highest administered dose was 400 mg bd (n=4) with one dose-limiting toxicity at this level: grade 3 rash. Five (38%) and 8(62%) patients had grade 3 non-haematological and haematological toxicities respectively. No grade 4 toxicities occurred. Radiological response rate was 54% (n=7: all CR). Six patients had resection with one pathological CR. Median progression-free and overall survival were 8.8 (95% CI 5.1 - >24.8) and 19.6 months (95% CI 7.3 - >39) respectively.

CONCLUSIONS

A MTD was not reached. The regimen was tolerable, indicating that celecoxib can be safely administered with CRT for locally advanced OC.

Listeria outbreak associated with sandwich consumption from a hospital retail shop, United Kingdom

An outbreak of listeriosis occurred in the Swindon area of the UK in autumn 2003. Five cases were detected in pregnant women. Four of these women were thought to have eaten prepacked sandwiches from a retail outlet in one particular hospital. Sampling at the supplier detected Listeria monocytogenes, which was indistinguishable on molecular testing from the patients’ isolates. Recent changes in UK food legislation should help diminish the risk of further outbreaks/cases such as ours occurring.

Listeria outbreak associated with sandwich consumption from a hospital retail shop, United Kingdom

An outbreak of listeriosis occurred in the Swindon area of the UK in autumn 2003. Five cases were detected in pregnant women. Four of these women were thought to have eaten prepacked sandwiches from a retail outlet in one particular hospital. Sampling at the supplier detected Listeria monocytogenes, which was indistinguishable on molecular testing from the patients isolates. Recent changes in UK food legislation should help diminish the risk of further outbreaks/cases such as ours occurring.

Survey, characterization and susceptibility to fusidic acid of Staphylococcus aureus in the Carmarthen area

OBJECTIVE

This retrospective study was designed to investigate the possible reasons for an apparent increase in fusidic acid resistance among Staphylococcus aureus.

MATERIALS AND METHODS

The Datastore records of the Communicable Disease Surveillance Centre, Wales, UK were reviewed in conjunction with information concerning the prescribing of fusidic acid.

RESULTS

During the 5 year study period (1997-2001), a rise in the incidence of fusidic acid resistance was noted, particularly among paediatric patients presenting with infected eczema and impetigo, which may be related to the observed increase in prescriptions of topical fusidic acid. Extended phenotypic and genotypic characterization of a limited number (n=31) of isolates from 2002 showed that fusidic acid-resistant strains of S. aureus were typically from patients with impetigo and isolates fell into a single clonal group. Conversely, isolates from other skin disease (eczema, dermatitis and abscesses) were usually susceptible to fusidic acid and proved a diverse group.

CONCLUSION

This study provides valuable data on the prevalence of fusidic acid-resistant S. aureus, the genetic background of the strains, and their association with clinical disease in both the healthcare environment and community setting in the catchment area served by the Laboratory.

The role of the infection control link nurse

Link nurses act as a link between their own clinical area and the infection control team. Their role is to increase awareness of infection control issues in their ward and motivate staff to improve practice. It is essential that they receive training from the infection control team to ensure their competence. They have been shown to be of value to Trusts by improving clinical ward audit scores, helping infection control nurses implement policies and collecting data on hospital-acquired infections. In some hospitals, however, there are operational difficulties for link nurse schemes including high turnover of staff and insufficient time for training and monitoring their effectiveness.

Variable fate of virus-specific CD4(+) T cells during primary HIV-1 infection

Impairment of CD4(+) T lymphocyte responses to human immunodeficiency virus (HIV)-derived antigens is the classic immunological defect observed during the chronic phase of HIV-1 infection. Early intervention with potent antiretroviral therapy (ART) can preserve HIV-specific CD4(+) T lymphocyte reactivity, providing indirect evidence that such responses are mounted during primary infection and subsequently lost in the majority of infected individuals. Here, we demonstrate early and dramatic expansions of functional HIV-specific CD4(+) T lymphocyte frequencies directly ex vivo. These responses are initially of broad specificity, and can disappear rapidly during the natural course of primary infection. This process of loss is variable, such that the rapidity and extent of functional compromise differs between individuals. Institution of ART during these early phases of HIV-1 infection preserves patterns of functional reactivity within the HIV-specific CD4(+) T lymphocyte population. However, there was no evidence for the restoration of deleted responses. These findings indicate that, in some individuals at least, ART must be administered within a narrow window of opportunity during primary HIV-1 infection to effect substantial immune preservation.

The human CD8 coreceptor effects cytotoxic T cell activation and antigen sensitivity primarily by mediating complete phosphorylation of the T cell receptor zeta chain

Recognition of antigen by cytotoxic T lymphocytes (CTL) is determined by interaction of both the T cell receptor and its CD8 coreceptor with peptide-major histocompatibility complex (pMHC) class I molecules. We examine the relative roles of these receptors in the activation of human CTL using mutations in MHC class I designed to diminish or abrogate the CD8/pMHC interaction. We use surface plasmon resonance to determine that point mutation of the alpha3 loop of HLA A2 abrogates the CD8/pMHC interaction without affecting the affinity of the T cell receptor/pMHC interaction. Antigen-presenting cells expressing HLA A2 which does not bind to CD8 fail to activate CTL at any peptide concentration. Comparison of CTL activation by targets expressing HLA A2 with normal, abrogated, or diminished CD8/pMHC interaction show that the CD8/pMHC interaction enhances sensitivity to antigen. We determine that the biochemical basis for coreceptor dependence is the activation of the 23-kDa phosphoform of the CD3zeta chain. In addition, we produce mutant MHC class I multimers that specifically stain but do not activate CTL. These reagents may prove useful in circumventing undesirable activation-related perturbation of intracellular processes when pMHC multimers are used to phenotype antigen-specific CD8+ lymphocytes.

Case control study of epidural catheter infections in a district general hospital

Ten infections associated with the use of epidural catheters for post-operative pain relief were identified in patients of a district general hospital in 1997 and 1998. A case control study showed that the infections were commoner in the summer months and associated with analgesia infused by syringes rather than pumps. Infection rates and risk factors can be analysed regularly if pain teams maintain a database of epidural catheters inserted, which includes information about infections.

Meningococcal disease in siblings caused by rifampicin sensitive and rifampicin resistant strains

Two brothers presented with meningococcal infection in a five day period, the first with a rifampicin sensitive strain and the second, who had received rifampicin chemoprophylaxis, with a resistant strain. Secondary cases of meningococcal disease can occur despite chemoprophylaxis, and may be rifampicin resistant. Close contacts should be informed of the early symptoms of meningococcal disease and of the need to seek medical advice urgently if they occur.

Activation of the iNOS gene promoter by Brn-3 POU family transcription factors is dependent upon the octamer motif in the promoter

The promoter of the gene encoding the inducible nitric oxide synthase (iNOS) contains an octamer motif which is of importance for its activation by specific stimuli. We show that in contrast to the promoter of the neuronal nitric oxide synthase gene (nNOS) which is strongly activated by the Oct-2 octamer-binding POU family transcription factor, the iNOS gene is only weakly activated by Oct-2 via its octamer motif. Unlike the nNOS promoter, however, the iNOS promoter is strongly activated by the POU family transcription factors Brn-3a and Brn-3b. This activation is dependent upon the octamer motif in the iNOS promoter and requires the activation domain located within the POU domain of Brn-3a or Brn-3b but not the N-terminal activation domain of Brn-3a. Thus different but related POU proteins play important roles in the regulation of the genes encoding different forms of nitric oxide synthase.

The N-terminal domain unique to the long form of the Brn-3a transcription factor is essential to protect neuronal cells from apoptosis and for the activation of Bbcl-2 gene expression

The ability of the POU family transcription factor Brn-3a to stimulate neurite outgrowth and the expression of the genes encoding neuronal proteins such as the neurofilaments and SNAP-25 has previously been shown to be dependent upon the C-terminal POU domain which can mediate both DNA binding and transcriptional activation. We show here, however, that the ability of Brn-3a to activate Bcl-2 expression and protect neuronal cells from apoptosis (programmed cell death) requires a distinct N-terminal activation domain. Bcl-2 gene activation and protection from apoptosis are thus produced only by the long form of Brn-3a which contains this domain and not by a naturally occurring short form lacking this domain or by the isolated POU domain, although all these forms of Brn-3a can stimulate neurite outgrowth. Hence Brn-3a is a multi-functional transcription factor with different regions of the factor mediating its different effects and two distinct forms with different properties being generated by alternative splicing.

Functional role of position 22 in the homeodomain of Brn-3 transcription factors

The Brn-3a POU family transcription factor activates a number of neuronal promoters which are repressed by the closely related Brn-3b factor. Although transcriptional activation by mutant forms of Brn-3a/Brn-3b can occur with a number of different amino acids at position 22 of the POU homeodomain, an isoleucine at this position is of critical importance for transcriptional repression. In addition, this isoleucine residue can mediate an interaction with the herpes simplex virus Vmw65 regulatory protein whereas the valine found in Brn-3a cannot do so. Thus, position 22 in the homeodomain plays a critical role in the function of neuronally expressed POU factors by controlling their interaction with viral and cellular co-activator/co-repressor proteins.

Adjacent proline residues in the inhibitory domain of the Oct-2 transcription factor play distinct functional roles

A 40 amino acid region of Oct-2 from amino acids 142 to 181 functions as an active repressor domain capable of inhibiting both basal activity and activation of promoters containing a TATA box, but not of those that contain an initiator element. Based on our observation that the equivalent region of the closely related Oct-1 factor does not act as an inhibitory domain, we have mutated specific residues in the Oct-2 domain in an attempt to probe their importance in repressor domain function. Although mutations of several residues have no or minimal effect, mutation of proline 175 to arginine abolishes the ability to inhibit both basal and activated transcription. In contrast, mutation of proline 174 to arginine confers upon the domain the ability to repress activation of an initiator-containing promoter by acidic activation domains, and also suppresses the effect of the proline 175 mutation. Hence, adjacent proline residues play key roles in the functioning of the inhibitory domain and in limiting its specificity to TATA-box-containing promoters.

Differential regulation of genes encoding synaptic proteins by the Oct-2 transcription factor

In order to investigate the effect of the Oct-2 POU family transcription factor on the regulation of genes encoding synaptic proteins, we have used cell lines in which the level of Oct-2 has been greatly reduced using an antisense approach. The reduced Oct-2 level results in enhanced expression of SNAP-25 and synapsin I, indicating that the genes encoding these proteins are normally repressed by Oct-2 in neuronal cells. In contrast, no alteration was observed in the levels of the synaptic proteins, synaptophysin and synaptotagmin. Although the neuronal forms of Oct-2 can repress the synapsin I promoter in co-transfection experiments, indicating that they have a direct effect on the expression of this gene, they have no effect on the activity of the SNAP-25 promoter, indicating that the effect of Oct-2 on this gene is likely to be indirect. These effects are discussed in terms of the differential effect of Oct-2 and the related POU family transcription factor Brn-3a, on the promoters of genes encoding different synaptic proteins.

The different inhibitory domains of the Oct-2 transcription factor have distinct functional activities

The Oct-2 POU family transcription factor contains three distinct regions whose deletion reduces its ability to inhibit transcription via its octamer binding site. Here we show that only one of these inhibitory domains is capable of also inhibiting the activity of activating molecules bound at adjacent sites upstream of a TATA box-containing promoter whereas the other two regions are inactive in this assay. None of the three regions is able to achieve this effect when located upstream of the same promoter containing an initiator motif. The mechanisms of action of these domains and their role in the functioning of the Oct-2 factor are discussed.

Coordinate induction of the three neurofilament genes by the Brn-3a transcription factor

The POU domain transcription factor Brn-3a is able to stimulate neurite outgrowth when overexpressed in the neuronal ND7 cell line, whereas the closely related Brn-3b factor does not have this effect. We show that Brn-3a overexpression also enhances the expression of the three neurofilament genes at both the mRNA and protein levels, whereas Brn-3b overexpression has no effect. In addition Brn-3a activates the three neurofilament gene promoters in co-transfection assays in both neuronal and non-neuronal cells. As observed for enhanced neurite outgrowth, the stimulation of neurofilament gene expression and activation of the neurofilament gene promoters is observed with the isolated POU domain of Brn-3a. A single amino acid change in the POU homeodomain of Brn-3a to the equivalent amino acid in Brn-3b abolishes its ability to activate the neurofilament promoters, whereas the reciprocal change converts Brn-3b to an activator of these promoters.

A single residue within the homeodomain of the Brn-3 POU family transcription factors determines whether they activate or repress the SNAP-25 promoter

The closely related POU family transcription factors Brn-3a and Brn-3b differ in their effect on a number of different neuronally expressed promoters such as that of the gene encoding the synaptic vesicle component SNAP-25. Thus Brn-3a activates these promoters whilst Brn-3b represses both their basal activity and their activation by Brn-3a. We show here that alterations of a single amino acid at position 22 in the POU-homeodomain from the isoleucine found in Brn-3b to the valine found at the equivalent position in Brn-3a converts Brn-3b from a repressor to an activator of the SNAP-25 gene promoter. The converse mutation in Brn-3a abolishes its ability to activate the SNAP-25 gene promoter and allows it to repress the basal activity of the promoter and its activation by wild type Brn-3a. This is the first time that a single amino acid change has been shown to convert an activator of a naturally occurring promoter to a repressor and vice versa. These results are discussed in terms of the critical role of position 22 in the POU homeodomain in the protein-protein interactions of POU proteins.

Therapeutic monitoring, the concentration-effect relationship and impact on the clinical efficacy of antibiotic agents

Therapeutic monitoring is now technically feasible for a wide variety of antibiotic agents and data are accumulating on the relationship of blood levels and clinical efficacy. For each antibiotic a therapeutic range and dosage regimen can be based theoretically on its known pharmacokinetics, pharmacodynamics in vitro, and also use in animal and human treatment studies. Antibiotics can be characterised into types by their mechanism of kill, as either concentration-dependent (for which achieving a large post-dose concentration to MIC ratio appears important) or concentration-independent/time-dependent (where efficacy is related to maintain the overall concentration above the MIC). Hopefully, concentration-controlled trials will be performed when new antibiotics are introduced, to determine a therapeutic range which correlates with clinical efficacy, and so enable monitoring to lead to a more rational approach to antibiotic administration.

Inhibition of neuronal process outgrowth and neuronal specific gene activation by the Brn-3b transcription factor

The differentiation of the ND7 neuronal cell line to a nondividing phenotype bearing numerous neurite processes is accompanied by a dramatic increase in the levels of the activating POU family transcription factor Brn-3a and a corresponding fall in the levels of the closely related inhibitory factor Brn-3b. We have previously shown that the artificial overexpression of Brn-3a in these cells can induce neurite outgrowth and the activation of genes encoding synaptic vesicle proteins in the absence of a differentiation-inducing stimulus. Here we show that overexpression of Brn-3b can reduce process outgrowth and synaptic vesicle gene expression following exposure to a stimulus which would normally induce differentiation. These inhibitory effects are abolished by altering a single amino acid in the POU homeodomain of Brn-3b to its equivalent in Brn-3a. The converse mutation in Brn-3a allows it to inhibit process outgrowth in response to a differentiation-inducing stimulus. Hence a single amino acid difference results in these closely related factors having opposite effects and allows the balance between them to regulate differentiation.

The Brn-3a transcription factor induces neuronal process outgrowth and the coordinate expression of genes encoding synaptic proteins

The Brn-3a POU family transcription factor is expressed only in posmitotic neurons in the central nervous system and identifies the first differentiated neurons to appear in the midbrain, hindbrain, and spinal cord during development. This factor is also induced when undifferentiated proliferating ND7 cells cease dividing and differentiate to a mature neuronal-like phenotype bearing numerous neurite processes. We show that overexpression of Brn-3a in undifferentiated ND7 cells induces a mature neuronal phenotype characterized by process outgrowth and the induction of genes encoding synaptic proteins, although the cells continue to proliferate. In contrast, the closely related factors Brn-3b and Brn-3c do not have this effect. Although the N-terminal activation domain of Brn-3a is required for maximum induction of neurite outgrowth and gene expression, these effects are primarily dependent on the DNA binding POU domain, which also acts as an activation domain. Overexpression of the isolated POU domain of Brn-3a is sufficient to induce neurite outgrowth, while the ability of full-length Brn-3a to do so is abolished by mutating a single amino acid in the Brn-3a POU homeodomain to its equivalent in Brn-3b. Thus, Brn-3a appears to play a critical role in the specification of the mature neuronal phenotype, acting by stimulating the expression of genes whose products are required for process outgrowth and synapse formation.

Differential regulation of genes encoding synaptic proteins by members of the Brn-3 subfamily of POU transcription factors

The three members of the Brn-3 subfamily of POU transcription factors have distinct effects on target gene expression. We show that the promoter of the gene encoding the presynaptic nerve terminal protein SNAP-25 resembles previously characterised target genes in being activated by Brn-3a and Brn-3c, but being repressed by Brn-3b. Unlike other target genes, however, the SNAP-25 promoter can be activated by either the N- or C-terminal activation domains of Brn-3a. In contrast to the SNAP-25 gene, the gene encoding the synaptic vesicle protein synapsin 1 is activated by all the Brn-3 factors, the first gene for which this activation pattern has been reported Interestingly, however, similar activation by all three Brn-3 factors can be observed if the SNAP-25 promoter is truncated by removal of sequences from -2200 to -288 relative to the transcriptional start site. Moreover, a region of the SNAP-25 promoter from -283 to -126 can render a heterologous promoter responsive to activation by all three Brn-3 factors. Differences in promoter structure may thus result in differences in the response to different Brn-3 factors, thus allowing these factors to produce diverse activation patterns of neuronally expressed genes, such as those encoding different synaptic proteins.

Differential regulation of the two neuronal nitric-oxide synthase gene promoters by the Oct-2 transcription factor

The Oct-2 transcription factor has been shown previously to repress both the cellular tyrosine hydroxylase and the herpes simplex virus immediate-early genes in neuronal cells. Here we identify the gene encoding the neuronal nitric-oxide synthase (nNOS) as the first example of a gene activated in neuronal cells by Oct-2. The levels of the nNOS mRNA and protein are greatly reduced in neuronal cell lines in which Oct-2 levels have been reduced by an antisense method, although these cells have enhanced levels of tyrosine hydroxylase. Moreover, the nNOS gene regulatory region is activated by Oct-2 expression vectors upon cotransfection into both neuronal and non-neuronal cells, and this response is dependent upon a 20-amino acid region within the COOH-terminal activation domain of Oct-2. Of the two closely linked promoters that drive nNOS gene expression, only the downstream 5.1 promoter is activated by Oct-2, whereas the 5.2 promoter is unaffected. These effects are discussed in terms of the potential role of Oct-2 in regulating nNOS expression in the nervous system.

The ability of the inhibitory domain of the POU family transcription factor Oct-2 to interfere with promoter activation by different classes of activation domains is dependent upon the nature of the basal promoter elements

The Oct-2 transcription factor contains an inhibitory domain which is able to repress transcription following DNA binding. Here we show that within the neuronally expressed Oct-2.5 form, the inhibitory domain can strongly inhibit activation by transcription factor activation domains which are either composed predominantly of acidic residues or contain the HOB motif, whereas it has a weaker effect or no effect on proline-rich activation domains and on a glutamine-rich domain. In contrast, the isolated inhibitory domain of Oct-2 can efficiently repress all types of activation domains. This effect is observed however, only on TATA box-containing promoters and not on promoters containing an initiator motif. This widespread inhibition of different activation domains and its dependence on the nature of the basal promoter elements indicate that the inhibitory domain is likely to act by contacting a common downstream target of activation domains within the basal transcriptional complex bound at the TATA box rather than quenching specific activation domains by direct interaction. These effects are discussed in terms of the functional role of the inhibitory domain within Oct-2.5 and the mechanism by which it acts.

A single amino acid change converts an inhibitory transcription factor into an activator

The closely related POU family transcription factors Brn-3a and Brn-3b differ in their functional activity with Brn-3a activating several target promoters, which are repressed by Brn-3b. Brn-3b also prevents promoter activation by Brn-3a. Here we have altered a single isoleucine residue in the POU homeodomain of Brn-3b to the valine residue found at the equivalent position in Brn-3a. This change not only abolishes the ability of Brn-3b to repress basal and Brn-3a-stimulated promoter activity but also converts it to an activator of similar potency to Brn-3a. Hence a single amino acid difference determines the difference between an activator and a repressor in the Brn-3 family.

The different activities of the two activation domains of the Brn-3a transcription factor are dependent on the context of the binding site

The POU (Pit-Oct-Unc) family transcription factor Brn-3a contains two distinct activation domains, one at the N terminus of the molecule and one at the C terminus coincident with the DNA binding domain. These different activation domains have been shown previously to differ in their ability to activate an artificial test promoter containing a Brn-3a binding site and the naturally occurring alpha-internexin gene promoter. Here we identify the target site for Brn-3a in the alpha-internexin gene promoter and show that it can confer responsiveness to Brn-3a on a heterologous promoter. One of the single-stranded DNA sequences derived from either this novel Brn-3a binding site or from the previously characterized site in the test promoter are shown to bind Brn-3a preferentially compared with the complementary single strand or the corresponding double-stranded sequence. The pattern of responsiveness of these two sequences when cloned upstream of the same test promoter and co-transfected with constructs encoding various portions of Brn-3a indicates that the activity of the two Brn-3a activation domains is dependent upon differences in the context of the target sequence in each promoter rather than on differences in the target sequence itself.

The incidence and epidemiology of beta-lactam resistance in Haemophilus influenzae

Consecutive isolates of Haemophilus influenzae were collected by the Public Health Laboratory, Bath between 1 June 1992 and 31 May 1993. Of 379 apparently distinct isolates, 216 originated from the respiratory tract, 102 from eyes and 61 from other sites. The minimum inhibitory concentrations of amoxycillin, amoxycillin/clavulanate, cefaclor, cefuroxime, cefotaxime and cefpodoxime were determined for each isolate. Forty strains (10.6%) were beta-lactamase producers. MIC50 and MIC90 values and the range of MICs were determined for all isolates. The overall resistance rates were: amoxycillin (MIC > 1.0 mg/L), 22.7%; amoxycillin/clavulanate (MIC > 1.0 mg/L), 14.8%; cefuroxime (MIC > 1.0 mg/L), 18.5%, (MIC > 4.0 mg/L), 5.5%; cefaclor (MIC > 8 mg/L), 15.6%; cefpodoxime (MIC > 1.0 mg/L), 0.3%; cefotaxime (MIC > 1.0 mg/L), 0%. Twenty non-beta-lactamase producing but beta-lactam resistant strains (cefuroxime MIC > 4.0 mg/L) were matched with 20 susceptible strains on the basis of patient age, sex, and specimen type. The strains were characterised by outer-membrane protein (OMP), random amplified polymorphic DNA (RAPD) and ribotyping patterns. Eleven of the 20 resistant strains were indistinguishable by the methods used, suggesting spread of a single beta-lactam resistant, non-beta-lactamase producing clone. The distribution of resistant strains within the local community was plotted geographically.

Alternative splicing of the Brn-3a and Brn-3b transcription factor RNAs is regulated in neuronal cells

The closely related and functionally antagonistic POU family transcription factors Brn-3a and Brn-3b are encoded by two distinct genes that are expressed primarily in neuronal cells. In addition, however, the primary transcript of each of these genes is alternatively spliced to produce two distinct mRNAs encoding long and short isoforms that differ at the N-terminus of the protein. We show that this process is regulated so that different proportions of the mRNAs encoding the long and short forms of either Brn-3a or Brn-3b are produced in different rat tissues. Similarly, the ratio of each of these forms can be modulated by specific stimuli in both a neuronal cell line and primary neurons. The significance of these effects is discussed in relation to the functional differences between the two forms of each factor.

The ability of POU family transcription factors to activate or repress gene expression is dependent on the spacing and context of their specific response elements

The different forms of the Oct-2 and Brn-3 POU family transcription factors can have distinct effects on their target promoters involving both the activation and repression of gene expression. To investigate the requirements for these effects we have altered both the context and spacing of the two TAATGARAT binding sites for these factors within the herpes simplex virus immediate-early 3 gene promoter. We show that the activation of this promoter by Brn-3a and its repression by Brn-3b is dependent on the correct spacing of these binding sites. In contrast, repression of the promoter by Oct-2.4 and Oct-2.5 is dependent on both the spacing and context of these sites with the requirements for repression by Oct-2.4 or Oct-2.5 being different. These effects are discussed in the context of the mechanisms by which POU factors activate or repress their target genes.

Direct evidence that the POU family transcription factor Oct-2 represses the cellular tyrosine hydroxylase gene in neuronal cells

The POU family transcription factor Oct-2 was originally identified in B lymphocytes but has been shown to be expressed in neuronal cells, although it is absent in most other cell types. Cotransfection of Oct-2 expression vectors into nonneuronal cells with a tyrosine hydroxylase promoter/reporter plasmid suggests that Oct-2 can repress this promoter in this artificial situation. Here we report that reduction of endogenous Oct-2 levels in a neuronal cell line by an antisense approach results in an increase in endogenous tyrosine hydroxylase levels. In contrast, the level of the neuronal marker protein PGP9.5 remains unchanged in the antisense lines whereas that of the neuronal nitric oxide synthase decreases. Hence, the tyrosine hydroxylase gene is a natural target for repression by Oct-2 in neuronal cells. The significance of this effect is discussed in terms of the processes that regulate tyrosine hydroxylase gene expression and the role of Oct-2 in neuronal cells.

The 4G/5G genetic polymorphism in the promoter of the plasminogen activator inhibitor-1 (PAI-1) gene is associated with differences in plasma PAI-1 activity but not with risk of myocardial infarction in the ECTIM study. Etude CasTemoins de I'nfarctus du Mycocarde

We have investigated the interrelationships of plasma PAI-1 activity, the PAI-1 4G/5G polymorphism and risk of myocardial infarction (MI) in the ECTIM study, a case-control study of MI based in Belfast, Lille, Strasbourg and Toulouse. Mean PAI-1 levels in cases were similar across all centres but in controls, levels in the French centres were significantly higher. Only in Belfast were PAIl1 levels higher in cases (11.7 AU/ml) than controls (10.5 AU/ml). The PAI-1 4G allele frequency was similar in cases and controls (0.55 and 0.54). In all groups, 4G homozygotes had the highest mean plasma PAI-1 level (4G4G vs 5G5G; cases overall: 14.2 vs 12.1AU/ml; controls overall: 15.0 vs 12.6AU/ml), with the heterozygotes generally intermediate. The data from Belfast are consistent with the literature implicating PAI-1 level as an MI risk factor. In ECTIM, the PAI-1 4G/5G polymorphism is not a genetic risk factor for MI but is associated with PAI-1 activity. Thus homozygosity for the 4G allele may predispose to elevated PAI-1 and impaired fibrinolysis, perhaps requiring interaction with other genetic or environmental factors to influence MI risk.

Repression of a herpes simplex virus immediate-early promoter by the Oct-2 transcription factor is dependent on an inhibitory region at the N terminus of the protein

The B-cell form of the Oct-2 transcription factor Oct 2.1 can activate the herpes simplex virus immediate-early gene 3 (IE3) promoter, whereas the neuronally expressed Oct 2.4 and 2.5 forms of the protein, which contain a different C terminus, can repress this promoter. Here we show that partial or full deletion of the C terminus of Oct 2.1 in the presence of an intact N terminus results in a protein which can strongly repress the IE3 promoter. In contrast, deletion of the entire N terminus or a short region within it leaving the C terminus intact results in a very strong activator. Deletion of both N and C termini leaving only the isolated POU domain generates only a very weak repressor. The N-terminal region defined in this way can repress a heterologous promoter when linked to the DNA-binding domain of the GAL4 factor, indicating that it can function as an independent inhibitory domain. These results indicate that a specific region within the N terminus common to Oct 2.1, 2.4, and 2.5 plays a critical role in the ability of neuronally expressed forms of Oct-2 to repress the IE3 promoter but can do so only when the C-terminal region of Oct 2.1 is altered or deleted.

The Oct-2 transcription factor represses tyrosine hydroxylase expression via a heptamer TAATGARAT-like motif in the gene promoter

The tyrosine hydroxylase (TH) gene promoter contains adjacent octamer and heptamer motifs which act as target sites for octamer binding transcription factors. Mutation of the heptamer motif but not the octamer motif enhances TH promoter activity in neuronal cells expressing Oct-2 but not in non-expressing fibroblasts. Similarly addition of the heptamer motif to a minimal TH promoter represses gene expression in neuronal cells but not in fibroblasts. These effects can be reproduced by the artificial expression of neuronal isoforms of Oct-2 in fibroblasts which results in the repression of transfected TH promoters containing an intact heptamer motif but not those in which this motif has been mutated or deleted. The TH promoter thus represents the first example of a cellular promoter which is repressed by Oct-2. The significance of this effect is discussed in terms of the cell type specificity of the TH promoter and its induction by different physiological stimuli.

Chronic active toxoplasmosis in an immunocompetent patient

We report the case of an apparently immunocompetent woman whose symptoms and signs have persisted for 8 years following a serologically and histologically confirmed diagnosis of toxoplasmosis. During this period she had two successful pregnancies despite persistently increased anti-toxoplasma IgM antibodies. Neither child is infected.

Two pathways of iron-catalyzed oxidation of bilirubin: effect of desferrioxamine and trolox, and comparison with microsomal oxidation

The bilirubin-degrading activity of liver microsomes from rats induced with 3-methylcholanthrene has been shown to be markedly stimulated by addition of 3,3',4,4',5,5'-hexabromobiphenyl, a polyhalogenated chemical which resembles in size and shape the most effective inducers of cytochrome P450IA1, but lacks the structural features necessary for it to be metabolised. The degradation of bilirubin by this microsomal system has been compared to oxidation by a chemical model system involving H2O2 and Fe-EDTA (ethylenediaminetetraacetic acid). In both systems bilirubin disappearance was accompanied by bleaching. However, when either desferrioxamine or Trolox were present in the chemical model system, the rate of bilirubin oxidation was greatly enhanced and, at the same time, bilirubin was largely or entirely converted to biliverdin, a pathway of oxidation which proceeds by dehydrogenation. In the presence of desferrioxamine, biliverdin was also further oxidised to an unidentified red pigment.

The two allele sequences of a common polymorphism in the promoter of the plasminogen activator inhibitor-1 (PAI-1) gene respond differently to interleukin-1 in HepG2 cells

We have detected a common (allele frequency 0.53/0.47) single base pair insertion/deletion polymorphism 675 base pairs upstream from the start of transcription of the plasminogen activator inhibitor-1 (PAI-1) gene, using the chemical cleavage mismatch analysis. "Band shift assays" suggest that the allele with the single base pair insertion contains an additional protein binding site which is not present in the del allele. Competition experiments confirmed that the binding was specific to the sequence of the ins allele and suggest that proteins bound to this site may be NF-kB-like proteins. Analysis of chloramphenicol acetyltransferase (CAT) mRNA produced by constructs containing the PAI-1 promoter (-805 to +83) showed that the deletion allele produced six times more mRNA than the insertion allele in response to interleukin-1 (p < 0.001). In a sample of 107 young patients with previous myocardial infarction and 95 healthy population-based subjects, the del allele was associated with increased PAI-1 levels, 21% higher than the sample mean in the del homozygotes (p < 0.05). This study also suggested that individuals homozygous for the del allele may have an altered response to the acute phase stimulus. Taken together these results suggest that the insertion/deletion polymorphism in the PAI-1 promoter is of functional importance in regulating the expression of the PAI-1 gene.