Functional divergence of a bacterial enzyme promotes healthy or acneic skin

Acne is a dermatologic disease with a strong pathologic association with human commensal Cutibacterium acnes. Conspicuously, certain C. acnes phylotypes are associated with acne, whereas others are associated with healthy skin. Here we investigate if the evolution of a C. acnes enzyme contributes to health or acne. Two hyaluronidase variants exclusively expressed by C. acnes strains, HylA and HylB, demonstrate remarkable clinical correlation with acne or health. We show that HylA is strongly pro-inflammatory, and HylB is modestly anti-inflammatory in a murine (female) acne model. Structural and phylogenic studies suggest that the enzymes evolved from a common hyaluronidase that acquired distinct enzymatic activity. Health-associated HylB degrades hyaluronic acid (HA) exclusively to HA disaccharides leading to reduced inflammation, whereas HylA generates large-sized HA fragments that drive robust TLR2-dependent pathology. Replacing an amino acid, Serine to Glycine near the HylA catalytic site enhances the enzymatic activity of HylA and produces an HA degradation pattern intermediate to HylA and HylB. Selective targeting of HylA using peptide vaccine or inhibitors alleviates acne pathology. We suggest that the functional divergence of HylA and HylB is a major driving force behind C. acnes health- and acne- phenotype and propose targeting of HylA as an approach for acne therapy.

Sub-1.4 cm3 capsule for detecting labile inflammatory biomarkers in situ

Transient molecules in the gastrointestinal tract such as nitric oxide and hydrogen sulfide are key signals and mediators of inflammation. Owing to their highly reactive nature and extremely short lifetime in the body, these molecules are difficult to detect. Here we develop a miniaturized device that integrates genetically engineered probiotic biosensors with a custom-designed photodetector and readout chip to track these molecules in the gastrointestinal tract. Leveraging the molecular specificity of living sensors1, we genetically encoded bacteria to respond to inflammation-associated molecules by producing luminescence. Low-power electronic readout circuits2 integrated into the device convert the light emitted by the encapsulated bacteria to a wireless signal. We demonstrate in vivo biosensor monitoring in the gastrointestinal tract of small and large animal models and the integration of all components into a sub-1.4 cm3 form factor that is compatible with ingestion and capable of supporting wireless communication. With this device, diseases such as inflammatory bowel disease could be diagnosed earlier than is currently possible, and disease progression could be more accurately tracked. The wireless detection of short-lived, disease-associated molecules with our device could also support timely communication between patients and caregivers, as well as remote personalized care.

Ethnicity-specific myocardial remodelling in hypertensive heart disease by multi-parametric cardiovascular magnetic resonance

Background

Patients with systemic hypertension (HTN) of African ancestry (Afr-a) are at greater risk of incident heart failure (HF), hospitalisation and death than those of European ancestry (Eu-a). This has been related to higher prevalence of HTN-related target organ damage, including high level of circulating cardiac troponins, which is not fully explained by blood pressure level. Thus, one may speculate that Afr-a hypertensives have a higher tendency to develop myocardial damage in response to arterial afterload. However, myocardial composition differences between Afr-a and Eu-a hypertensives remain speculative.

Purpose

To investigate ethnic-specific differences in myocardial tissue composition in Eu-a and Afr-a hypertensives by multi-parametric cardiovascular magnetic resonance (CMR).

Methods

This cross-sectional study included 63 Afr-a and 47 Eu-a hypertensive patients. All patients underwent multi-parametric CMR (1.5-Tesla Aera, Siemens-Healthcare, Erlangen-Germany). Left (LV) and right ventricular (RV) volumes, mass and function, atrial dimensions, and myocardial tissue characterisation (including T1- and T2-mapping) were measured using a standardised imaging protocol, and post-processing recommendations from international scientific societies. Analysis was completed using a commercially available cardiac-software (CVI-42, Calgary-Canada). Central pulse-wave-velocity (PWV) between the ascending and proximal descending thoracic aorta was measured by high-temporal, resolution 2D phase-contrast velocity-encoded parasagittal cine images, using in-house MATLAB software.

Results

Although Afr-a were 5 years older than Eu-a hypertensives, cardiovascular risk factors, anthropometric, body composition and haemodynamic measures were similar between the two groups (Figure 1). Segmental PWV was greater in Afr-a than Eu-a patients (8.16±2.71 vs 6.97±2.82 m/s, P=0.044), underlying higher aortic stiffness in Afr-a hypertensives. Afr-a hypertensives also had greater LV mass and LV-mass/end-diastolic volume ratio than Eu-a (Figure 2), whilst no difference was observed in LV systolic/diastolic function. Native T1 relaxation time and synthetic extracellular volume were also similar between the two ethnicities, though T2 relaxation time was significantly higher in Afr-a hypertensives. Late gadolinium enhancement (LGE), a well-established metric of replacement fibrosis (scarring), was more prevalent in Afr-a than Eu-a hypertensives (14% vs 4%, P=0.001). In patients with LGE, the extent of LGE was higher in Afr-a than Eu-a hypertensives (Figure 2).

Conclusion

Afr-a hypertensives have higher arterial afterload, LV mass and remodelling than Eu-a, despite comparable mean blood pressure, body-mass-index, and body composition. These changes in LV structure and geometry were associated with higher T2 relaxation time, likely reflecting low-grade inflammation, as well as higher prevalence and extent of replacement myocardial fibrosis.

Funding Acknowledgement

Type of funding sources: None.

Racial differences of right ventricular remodelling in systemic hypertension unveiled by multiparametric cardiovascular magnetic resonance

Background

Patients with systemic hypertension (HTN) of African ancestry (Afr-a) are at greater risk of heart failure (HF), hospitalisation and death than those of European ancestry (Eu-a). Compelling evidence suggests that left ventricular (LV) remodelling and hypertrophy are more prevalent in Afr-a than Eu-a hypertensives due to either a high clustering of cardiovascular risk-factors and/or a difference in genetic background. Prior studies in Eu-a subjects have shown that uncomplicated HTN is associated with right ventricular (RV) hypertrophy and remodelling which may contribute to development of HF. However, the impact of ethnicity on RV remodelling in HTN remains speculative.

Purpose

To investigate the influence of ethnicity on RV remodelling/hypertrophy in patients with HTN using cardiovascular magnetic resonance (CMR).

Methods

In this cross-sectional study we included 16 Afr-a and 32 Eu-a age- and sex-matched healthy-volunteers, and 63 Afr-a and 47 Eu-a hypertensives. All participants underwent a CMR exam (1.5-Tesla, Aera, Siemens-Healthcare, Erlangen-Germany). LV and RV volumes, masses and function were measured according to the current recommendations. Blood pressure was recorded during the CMR.

Results

Age- and sex-matched Afr-a and Eur-a healthy-volunteers (37±10 vs 37±12 years, P=0.975; male 53% vs 44%; P=0.539) exhibited closely comparable LV and RV volumes, masses, and end-diastolic volume/mass ratios. In the HTN group, despite Afr-a hypertensives being roughly 5 years older than Eu-a, baseline characteristics including cardiovascular risk factors, mean blood pressure, body-mass-index, and body composition metrics were similar between the two groups (Figure 1). Afr-a hypertensives also had greater LV and RV masses and mass/end-diastolic volume ratios than Eur-a hypertensives (Figure 2). RV mass correlated with LV mass in both ethnic groups (r=0.593 in Eu-a and r=0.569 in Afr-a; both P<0.001). Multivariable linear regression analysis showed that RV mass was independently associated with African descendance after correction for major confounders including LV mass, biventricular volumes, and body composition.

Conclusion

Our findings support the notion that Afr-a and Eur-a healthy-volunteers have comparable left and right ventricular geometry and masses, arguing against genetic-determinate ventricular geometry and myocardial mass in this population. However, Afr-a individuals exhibit higher sensitivity to myocardial hypertrophy in response to HTN which translates into greater biventricular masses and remodelling, compared to Eu-a hypertensives.

Funding Acknowledgement

Type of funding sources: None.

O025 The epidemiology of gastroenteropancreatic neuroendocrine tumours (GEP-NETS) in the north-east of England and a systematic review of literature

Introduction

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) are rare, indolent malignancies with unknown aetiology and an increasing incidence was observed globally. With limited research on GEP-NET epidemiology, the reasons behind incidence disparities between countries remain unclear. Whether this increase was a true phenomenon or was confounded by factors including diagnostics advancement and classification evolution needs further enquiry. The aims are to evaluate all available literature on GEP-NET incidence rates (IR), and to determine GEP-NET incidence in the North-East and the association between survival and age, gender, grade, stage, and socioeconomic status (SES).

Methods

Systematic review of relevant literature using MEDLINE, Embase, Scopus and Web of Science. Quality of methodology was assessed using the Newcastle-Ottawa Scale. (2) 140 GEP-NET patients from 1996 to 2019 were identified. Crude IR, age-standardised IR and overall survival (OS) were determined. Outcome parameters were identified from Cox-proportional Hazard analysis.

Results

GEP-NET global incidence increased in the last decades, whereas Asia and various European countries reported no significant changes. Ethnic and gender differences were observed. (2) Over 23 years, IR increased by 40.5% per annum (0.08–5.94/1,000,000). 5- and 10-year OS were 71.0% and 28.9% respectively. SES had non-significant associations with the covariates. Age >70 yrs (HR=5.48 [2.20–13.66], p<0.001) and middle SES (HR=2.23 [1.05–3.75], p=0.038) were independent predictors for worse prognosis.

Conclusion

GEP-NETs continue to rise despite differences in reporting methods across the literatures and underlying factors not being captured in this population-based study. A prospective NET registry is necessary to elucidate accurate GEP-NET epidemiology in the UK.

Take-home message

GEP-NET incidence rates are evidently increasing both in the North-East and globally; yet, the reasons behind such increase remain unclear. This highlights the establishment of a prospective neuroendocrine tumour (NET) registry is imperative in the North-East or in the UK so that all GEPNETs can be captured and detect subtle incidence changes over time.

Bone turnover markers as determinants of bone density and fracture in men with distal forearm fractures: the pathogenesis examined in the Mr F study

The pathogenesis for low-trauma wrist fractures in men is not fully understood. This study found that these men had evidence of significantly higher bone turnover compared with control subjects. Bone turnover markers were negative predictors of bone mineral density and were a predictor of fracture.

INTRODUCTION

Men with distal forearm fractures have reduced bone density, an increased risk of osteoporosis and of further fractures. The aim of this study was to investigate whether or not men with distal forearm fractures had evidence of altered bone turnover activity.

METHODS

Fifty eight men with low-trauma distal forearm fracture and 58 age-matched healthy control subjects were recruited. All subjects underwent a DXA scan of the forearm, both hips, and lumbar spine, biochemical investigations, and health questionnaires. Measurements of beta crosslaps (βCTX), procollagen type I N-terminal propeptide (PINP), sclerostin, Dickkopf-1 (Dkk1), and fibroblast growth factor 23 (FGF 23) were made.

RESULTS

Men with fracture had significantly higher PINP than controls at 39.2 ng/ml (SD 19.5) versus 33.4 ng/ml (SD13.1) (p<0.001). They also had significantly higher βCTX at 0.45 ng/ml (SD 0.21) versus 0.37 ng/ml (SD 0.17) (p= 0.037). Fracture subjects had significantly lower aBMD and PINP was a negative predictor of aBMD at the total hip and βCTX a negative predictor of forearm aBMD. Sclerostin was a positive predictor of aBMD at the lumbar spine and hip sites. Sex hormone binding globulin (SHBG) at 37nmol/L (SD 15.0) was lower in fracture cohort compared to 47.9 nmol/L (SD 19.2) (p=0.001) in control. Multiple regression revealed that the best model for prediction of fracture included SHBG, P1NP, and ultra-distal forearm aBMD. The likelihood of distal forearm fracture was decreased by 5.1% for each nmol/L increase in SHBH and by 1.4% for every mg/cm² increase in ultra-distal forearm aBMD, but increased by 6.1 % for every ng/ml increase in P1NP. Men in the highest quartile of PINP had a significantly greater likelihood of distal forearm fracture than those in the lowest quartile.

CONCLUSION

The fracture group had significantly higher PINP and βCTX compared with the control group, and these markers were negative predictors of aBMD at the total hip and forearm sites, respectively. Sclerostin was a positive predictor of the variance of spinal and hip aBMD. Likelihood of forearm fracture was best predicted by a combination of SHBG, PINP, and ultra-distal forearm aBMD. Findings of such cross-sectional data should be treated with caution, as longitudinal studies would be required to confirm or refute them.

In-depth phenotyping by cardiovascular magnetic resonance uncovering differences between ethnic groups in hypertensive heart disease

Background

Black African/African-Caribbean individuals with hypertension (BH) are at greater risk of heart failure than those of white European ethnicity (WH). The mechanisms underlying this dissimilarity remain poorly understood.

Purpose

To investigate the influence of ethnicity on left ventricular (LV) remodelling using multi-parametric cardiovascular magnetic resonance (CMR).

Methods

BH (n=44), WH (n=38) and healthy-volunteers (HV; n=25, 5 of black ethnicity) underwent comprehensive CMR. The exam included: i) Arterial Stiffness/Afterload pulse-wave-velocity (PWV), aortic elastance (Ea) and systemic vascular resistance (SVR) by phase-contrast velocity-encoding imaging; ii) Ventricular remodelling/Function LV and right ventricular (RV) volumes, mass, ejection fraction (EF), LV peak-filling rate by short-axis cine images; myocardial strains were measured by feature tracking; iii) Left atrial (LA) remodelling/Function volumes and functions by long-axis cine images; iv) Tissue characterisation: extracellular volume by pre/post-contrast T1-mapping and late gadolinium enhancement (LGE) for interstitial and replacement myocardial fibrosis, respectively. Multivariate linear regression models were developed to investigate how LV remodelling associates with ethnicity, arterial afterload, including elastance (Ea) and stiffness [PW], and SVR. Models were adjusted for age, gender, body-mass-index, LV volumes or function and LA volumes.

Results

Subject characteristics are summarised in the Table. PWV and Ea and SVR were greater in hypertensives, particularly in BH, than HV; this was paralleled by higher LV mass, interventricular septum thickness (IVS), LA volumes but lower LV-EF. These findings were confirmed after adjusting for age.

On the Model-1, IVS was associated with Ea (β=0.335, P=0.008) and black ethnicity (β=0.226, P=0.019) but not with SVR or PWV. For each increment of Ea there was a similar increase of IVS in BH and WH (P=0.602 for interaction), however BH had greater IVS than WH at each Ea value (Figure, fully-adjusted Model-1). On Model-2, LV end-diastolic volume was associated with Ea (β=−0.268, P=0.001), SVR (β=−0.319, P=0.019) but not with PWV or ethnicity. However, the inverse relation between LV size and Ea was significantly attenuated in BH (P=0.039 for interaction), (Figure, fully-adjusted Model-2). On model-3, LV-EF was associated with Ea (β=0.223, P=0.009) but not with ethnicity, PWV or SVR. LV-EF reduction for each Ea increment was similar for BH and WH (P=0.597 for interaction).

Conclusion

BH and WH show a distinctive LV remodelling phenotype. BH had a greater susceptibility to hypertrophy and an attenuated reduction of chamber size in response to arterial afterload. Further research to disentangle the genetic and environmental factors underlying these ethnic group-specific differences is utterly required.

Funding Acknowledgement

Type of funding sources: None. Figure 1Table 1

Changes in air quality in Mexico City, London and Delhi in response to various stages and levels of lockdowns and easing of restrictions during COVID-19 pandemic

The impacts of COVID-19 lockdown restrictions have provided a valuable global experiment into the extent of improvements in air quality possible with reductions in vehicle movements. Mexico City, London and Delhi all share the problem of air quality failing WHO guideline limits, each with unique situations and influencing factors. We determine, discuss and compare the air quality changes across these cities during the COVID-19, to understand how the findings may support future improvements in their air quality and associated health of citizens. We analysed ground-level PM₁₀, PM_2.5, NO₂, O₃ and CO changes in each city for the period 1st January to August 31, 2020 under different phases of lockdown, with respect to daily average concentrations over the same period for 2017 to 2019. We found major reductions in PM₁₀, PM_2.5, NO₂ and CO across the three cities for the lockdown phases and increases in O₃ in London and Mexico City but not Delhi. The differences were due to the O₃ production criteria across the cities, for Delhi production depends on the VOC-limited photochemical regime. Levels of reductions were commensurate with the degree of lockdown. In Mexico City, the greatest reduction in measured concentration was in CO in the initial lockdown phase (40%), in London the greatest decrease was for NO₂ in the later part of the lockdown (49%), and in Delhi the greatest decrease was in PM₁₀, and PM_2.5 in the initial lockdown phase (61% and 50%, respectively). Reduction in pollutant concentrations agreed with reductions in vehicle movements. In the initial lockdown phase vehicle movements reduced by up to 59% in Mexico City and 63% in London. The cities demonstrated a range of air quality changes in their differing geographical areas and land use types. Local meteorology and pollution events, such as forest fires, also impacted the results.

Introduction of an assessment toolkit associated with increased rate of DLB diagnosis

Background

Dementia with Lewy bodies (DLB) and dementia in Parkinson’s disease (PDD) are recognised to be under-recognised in clinical practice in the UK, with only one third to a half of expected cases diagnosed. We aimed to assess whether clinical diagnostic rates could be increased by the introduction of a structured assessment toolkit for clinicians.

Methods

We established baseline diagnostic rates for DLB and PDD in four memory clinics and three movement disorder/Parkinson’s disease (PD) clinics in two separate geographical regions in the UK. An assessment toolkit specifically developed to assist with the recognition and diagnosis of DLB and PDD was then introduced to the same clinical teams and diagnostic rates for DLB and PDD were reassessed.

For assessing DLB diagnosis, a total of 3820 case notes were reviewed before the introduction of the toolkit, and 2061 case notes reviewed after its introduction. For PDD diagnosis, a total of 1797 case notes were reviewed before the introduction of the toolkit and 3405 case notes after it. Mean values and proportions were analysed using Student’s t test for independent samples and χ² test, respectively.

Results

DLB was diagnosed in 4.6% of dementia cases prior to the introduction of the toolkit, and 6.2% of dementia cases afterwards, an absolute rise of 1.6%, equal to a 35% increase in the number of DLB cases diagnosed when using the toolkit (χ² = 4.2, P = 0.041).

The number of PD patients diagnosed with PDD was not found overall to be significantly different when using the toolkit: 9.6% of PD cases before and 8.2% of cases after its introduction (χ² = 1.8, P = 0.18), though the ages of PD patients assessed after the toolkit’s introduction were lower (73.9 years vs 80.0 years, t = 19.2, p < 0.001).

Conclusion

Introduction of the assessment toolkit was associated with a significant increase in the rate of DLB diagnosis, suggesting that a structured means of assessing symptoms and clinical features associated with DLB can assist clinicians in recognising cases. The assessment toolkit did not alter the overall rate of PDD diagnosis, suggesting that alternate means may be required to improve the rate of diagnosis of dementia in Parkinson’s disease.

Discovery and Structural Characterization of ATP-Site Ligands for the Wild-Type and V617F Mutant JAK2 Pseudokinase Domain

The oncogenic V617F mutation lies in the pseudokinase domain of JAK2, marking it as a potential target for development of compounds that might inhibit the pathogenic activity of the mutant protein. We used differential scanning fluorimetry to identify compounds that bind the JAK2 pseudokinase domain. Crystal structures of five candidate compounds with the wild-type domain reveal their modes of binding. Exploration of analogs of screening hit BI-D1870 led to the identification of compound 2, a 123 nM ligand for the pseudokinase domain. Interestingly, crystal structures of the V617F domain in complex with two unrelated compounds reveal a conformation that is characteristic of the wild-type domain, rather than that previously observed for the V617F mutant. These structures suggest that certain ATP-site ligands can modulate the V617F allosteric site, thereby providing a mechanistic rationale for targeting the pseudokinase domain and a structural foundation for development of more potent and pseudokinase-selective compounds.

Household, Moderate Physical Activity and the Risk of Breast Cancer Among Nigerian Women: An Epidemiological Study

Background: Breast cancer incidence in Nigeria has risen by >120% since 2000. The mortality rate (25.9/100,000/yr) ranks highest in Africa. Inverse associations between household physical activities (PA) as well as moderate PA, and breast cancer risk have been suggested in literature. However, the roles of these activities in breast cancer risk have not been widely studied in Africa. As the socioeconomic status of many Nigerian women improves, their household and daily routines are expected to change. These have implications for their level of physical activity. Aim: The aim of this study was to investigate if there is an association between household, as well as moderate PA and breast cancer risk among Nigerian women. Methods: The study was a multisite hospital based case-control design involving 379 histologically confirmed breast cancer cases and 403 controls. The participants aged ≥ 20 years were interviewed in-person between October 2016 and May 2017 using a pretested questionnaire. Cases were selected from oncology wards and controls from ophthalmology wards. Self-reported household and moderate PA were summarized as both hours per week and metabolic equivalents (MET) hours per week (met-hr/wk). Data were analyzed using multivariable logistic regression, adjusting for known confounders. SPSS version 23 was used for all analyses. Results: The odd of having breast cancer (based on MET-hr/wk) was 40% less among women in the upper tertile of household PA than those in the lowest tertile (95% CI, 0.39-0.94). This was stronger among younger (OR: 0.50, 95% CI, 0.26-0.94), premenopausal (OR: 0.46; 95% CI, 0.24-0.89) and lean women (OR: 39, 95% CI, 0.16-0.87). Moderate PA was also associated with reduced breast cancer risk ( P = 0.04). Conclusion: The study suggested that household and moderate physical activities were protective of breast cancer among Nigerian women. Household chores and other routine moderate activities could provide opportunities for breast cancer prevention in Nigeria. Future studies could consider the use of community controls to authenticate the findings.

Structure of a Thyrotropin Receptor Monoclonal Antibody Variable Region Provides Insight into Potential Mechanisms for its Inverse Agonist Activity

BACKGROUND

The high constitutive, or ligand-independent, activity of the thyrotropin receptor (TSHR) is of clinical importance in some thyroid conditions, particularly well-differentiated thyroid carcinoma remnants following incomplete ablative therapy (surgery and radioiodine). Under these conditions, even total suppression of TSH by thyroid hormone administration does not fully reduce TSHR activity, a driver of thyrocyte growth.

METHODS

CS-17 is a murine monoclonal antibody that has inverse agonist activity in that it suppresses TSHR constitutive activity. This study crystallized the CS-17 Fab and determined its atomic structure at a resolution of 3.4 Å.

RESULTS

In silico docking of this structure to that of the TSHR extracellular domain was accomplished by targeting to TSHR residue tyrosine 195 (Y195) known to contribute to the CS-17 epitope. High affinity interaction between these two molecules, primarily by the CS-17 immunoglobulin heavy chain, was validated by energetic analysis (K_D of 8.7 × 10^-11 M), as well as by previously obtained data on a number of individual TSHR amino acids in three regions whose mutagenesis reduced CS-17 binding as detected by flow cytometry.

CONCLUSIONS

Structural insight at atomic resolution of a TSHR antibody with inverse agonist activity opens the way for the development of a molecule with therapeutic potential, particularly in thyroid carcinoma. For this purpose, CS-17 will require "humanization" by substitution of its constant region (Fc component). In addition, with its epitope defined, the CS-17 affinity can be increased further by mutagenesis of selected amino acids in its heavy- and light-chain complementarity determining regions.

Risk of pre-eclampsia in women taking metformin: a systematic review and meta-analysis

AIMS

To perform meta-analyses of studies evaluating the risk of pre-eclampsia in high-risk insulin-resistant women taking metformin prior to, or during pregnancy.

METHODS

A search was conducted of the Medline, EMBASE, Web of Science and Scopus databases. Both randomized controlled trials and prospective observational cohort studies of metformin treatment vs. placebo/control or insulin either prior to or during pregnancy were selected. The main outcome measure was the incidence of pre-eclampsia in each treatment group.

RESULTS

Overall, in five randomized controlled trials comparing metformin treatment (n = 611) with placebo/control (n = 609), no difference in the risk of pre-eclampsia was found [combined/pooled risk ratio (RR), 0.86 (95% CI 0.33-2.26); P = 0.76; I²  = 66%]. Meta-analysis of four cohort studies again showed no significant effect [RR, 1.21 (95% CI 0.56-2.61); P = 0.62; I²  = 30%]. A meta-analysis of eight randomized controlled trials comparing metformin (n = 838) with insulin (n = 836), however, showed a reduced risk of pre-eclampsia with metformin [RR, 0.68 (95% CI 0.48-0.95); P = 0.02; I²  = 0%]. No heterogeneity was present in the metformin vs. insulin analysis of randomized controlled trials, whereas high levels of heterogeneity were present in studies comparing metformin with placebo/control. Pre-eclampsia was a secondary outcome in most of the studies. The mean weight gain from time of enrolment to delivery was lower in the metformin group (P = 0.05, metformin vs. placebo; P = 0.004, metformin vs. insulin).

CONCLUSIONS

In studies randomizing pregnant women to glucose-lowering therapy, metformin was associated with lower gestational weight gain and a lower risk of pre-eclampsia compared with insulin.

Leveraging Gas-Phase Fragmentation Pathways for Improved Identification and Selective Detection of Targets Modified by Covalent Probes

The recent approval of covalent inhibitors for multiple clinical indications has reignited enthusiasm for this class of drugs. As interest in covalent drugs has increased, so too has the need for analytical platforms that can leverage their mechanism-of-action to characterize modified protein targets. Here we describe novel gas phase dissociation pathways which yield predictable fragment ions during MS/MS of inhibitor-modified peptides. We find that these dissociation pathways are common to numerous cysteine-directed probes as well as the covalent drugs, Ibrutinib and Neratinib. We leverage the predictable nature of these fragment ions to improve the confidence of peptide sequence assignment in proteomic analyses and explore their potential use in selective mass spectrometry-based assays.

Regulation of gene expression and nitric oxide production in murine macrophages by the serine/threonine phosphatase inhibitor okadaic acid

LPS-stimulated macrophages produce cytokines which, at appropriate levels, direct successful immune responses against harmful pathogens. However, excessive cytokine production, as seen in endotoxemia, results in pathophysiological damage to the host. Therefore, understanding mechanisms of cytokine regulation may aid the development of strategies designed to control cytokine production during an ongoing immune response. We have examined the role of okadaic acid-sensitive phosphatases in the production of cytokines and nitric oxide by macrophages. Okadaic acid induces TNFα, IL-1β, IL-6, IFN-β, and IP-10, but not IL-10 or IL-12 (p40) mRNA. Okadaic acid differentially regulates the expression of LPS-inducible IL-10 and IL-12 (p40) mRNA. These findings suggest that okadaic acid-sensitive phosphatases are key regulators of cytokine production in unstimulated and immune-activated macrophages. Finally, okadaic acid inhibits iNOS mRNA and nitric oxide production by macrophages activated by LPS and IFN-γ.

LPS-inducible responses in severe combined immunodeficiency (SCID) mice

Lipopolysaccharide (LPS) is a potent bacterial product that has been shown to act on many different cell types both in vivo and in vitro. Injection of immunologically competent mice with LPS results in increased serum cytokine levels, followed by an array of pathophysiologic alterations that can ultimately lead to death. In this study, we examined the response of severe combined immunodeficient (SCID) mice to LPS. These mice lack mature T and B cells and have been shown to be an important model for analyzing the contribution of innate immune responses to infectious agents. Injection of SCID mice with LPS resulted in increases in CSF, TNF, and IFN levels in serum that were similar to the responses of immunocompetent controls. In response to LPS, both SCID and control mice exhibited similar levels of hypoglycemia. LPS-induced toxicity was assessed in D(+)-galactosamine-sensitized animals. SCID mice were comparably sensitive to the lethal effects of LPS as control BALB/c mice. To assess the role of natural killer (NK) cells in LPS-induced cytokine responses, BALB/c and SCID mice were injected with anti-asialo-GM1 antibody prior to injection of LPS. No significant effect on LPS-induced CSF or blood glucose levels were seen, although NK-depleted SCID mice produced somewhat more IFN in response to LPS than normal mice. Thus, NK cells are not a major source of these early LPS-induced cytokines. These data suggest that mature T and B cells and NK cells do not contribute to the initial wave of cytokines produced in response to LPS, but may contribute as secondary producers of cytokines involved in the cytokine cascade elicited by LPS injection.

Crystal Structure of the FERM-SH2 Module of Human Jak2

Jak-family tyrosine kinases mediate signaling from diverse cytokine receptors. Binding of Jaks to their cognate receptors is mediated by their N-terminal region, which contains FERM and SH2 domains. Here we describe the crystal structure of the FERM-SH2 region of Jak2 at 3.0Å resolution. The structure reveals that these domains and their flanking linker segments interact intimately to form an integrated structural module. The Jak2 FERM-SH2 structure closely resembles that recently described for Tyk2, another member of the Jak family. While the overall architecture and interdomain orientations are preserved between Jak2 and Tyk2, we identify residues in the putative receptor-binding groove that differ between the two and may contribute to the specificity of receptor recognition. Analysis of Jak mutations that are reported to disrupt receptor binding reveals that they lie in the hydrophobic core of the FERM domain, and are thus expected to compromise the structural integrity of the FERM-SH2 unit. Similarly, analysis of mutations in Jak3 that are associated with severe combined immunodeficiency suggests that they compromise Jak3 function by destabilizing the FERM-SH2 structure.

Development of Selective Covalent Janus Kinase 3 Inhibitors

The Janus kinases (JAKs) and their downstream effectors, signal transducer and activator of transcription proteins (STATs), form a critical immune cell signaling circuit, which is of fundamental importance in innate immunity, inflammation, and hematopoiesis, and dysregulation is frequently observed in immune disease and cancer. The high degree of structural conservation of the JAK ATP binding pockets has posed a considerable challenge to medicinal chemists seeking to develop highly selective inhibitors as pharmacological probes and as clinical drugs. Here we report the discovery and optimization of 2,4-substituted pyrimidines as covalent JAK3 inhibitors that exploit a unique cysteine (Cys909) residue in JAK3. Investigation of structure-activity relationship (SAR) utilizing biochemical and transformed Ba/F3 cellular assays resulted in identification of potent and selective inhibitors such as compounds 9 and 45. A 2.9 Å cocrystal structure of JAK3 in complex with 9 confirms the covalent interaction. Compound 9 exhibited decent pharmacokinetic properties and is suitable for use in vivo. These inhibitors provide a set of useful tools to pharmacologically interrogate JAK3-dependent biology.

Analysis of the role of PCNA-DNA contacts during clamp loading

BACKGROUND

Sliding clamps, such as Proliferating Cell Nuclear Antigen (PCNA) in eukaryotes, are ring-shaped protein complexes that encircle DNA and enable highly processive DNA replication by serving as docking sites for DNA polymerases. In an ATP-dependent reaction, clamp loader complexes, such as the Replication Factor-C (RFC) complex in eukaryotes, open the clamp and load it around primer-template DNA.

RESULTS

We built a model of RFC bound to PCNA and DNA based on existing crystal structures of clamp loaders. This model suggests that DNA would enter the clamp at an angle during clamp loading, thereby interacting with positively charged residues in the center of PCNA. We show that simultaneous mutation of Lys 20, Lys 77, Arg 80, and Arg 149, which interact with DNA in the RFC-PCNA-DNA model, compromises the ability of yeast PCNA to stimulate the DNA-dependent ATPase activity of RFC when the DNA is long enough to extend through the clamp. Fluorescence anisotropy binding experiments show that the inability of the mutant clamp proteins to stimulate RFC ATPase activity is likely caused by reduction in the affinity of the RFC-PCNA complex for DNA. We obtained several crystal forms of yeast PCNA-DNA complexes, measuring X-ray diffraction data to 3.0 A resolution for one such complex. The resulting electron density maps show that DNA is bound in a tilted orientation relative to PCNA, but makes different contacts than those implicated in clamp loading. Because of apparent partial disorder in the DNA, we restricted refinement of the DNA to a rigid body model. This result contrasts with previous analysis of a bacterial clamp bound to DNA, where the DNA was well resolved.

CONCLUSION

Mutational analysis of PCNA suggests that positively charged residues in the center of the clamp create a binding surface that makes contact with DNA. Disruption of this positive surface, which had not previously been implicated in clamp loading function, reduces RFC ATPase activity in the presence of DNA, most likely by reducing the affinity of RFC and PCNA for DNA. The interaction of DNA is not, however, restricted to one orientation, as indicated by analysis of the PCNA-DNA co-crystals.

The mechanism of ATP-dependent primer-template recognition by a clamp loader complex

Clamp loaders load sliding clamps onto primer-template DNA. The structure of the E. coli clamp loader bound to DNA reveals the formation of an ATP-dependent spiral of ATPase domains that tracks only the template strand, allowing recognition of both RNA and DNA primers. Unlike hexameric helicases, in which DNA translocation requires distinct conformations of the ATPase domains, the clamp loader spiral is symmetric and is set up to trigger release upon DNA recognition. Specificity for primed DNA arises from blockage of the end of the primer and accommodation of the emerging template along a surface groove. A related structure reveals how the psi protein, essential for coupling the clamp loader to single-stranded DNA-binding protein (SSB), binds to the clamp loader. By stabilizing a conformation of the clamp loader that is consistent with the ATPase spiral observed upon DNA binding, psi binding promotes the clamp-loading activity of the complex.

Results of a phase II trial of single-agent amrubicin (AMR) in patients with extensive disease small cell lung cancer (ED-SCLC) refractory to first-line platinum-based chemotherapy: An update

8103

Background: Amrubicin (AMR), a third-generation synthetic anthracycline and potent topoisomerase II inhibitor, is approved in Japan for the treatment of lung cancer. Patients (pts) with SCLC, who are refractory to first-line chemotherapy or progress within 3 months (mos) of treatment completion, are less likely to respond to additional chemotherapy and have an expected median survival of 3–5 mos. Here, we investigate the efficacy and safety of single-agent AMR in the treatment of Western pts with refractory ED-SCLC. Methods: In this phase II trial, pts with ED-SCLC refractory to prior 1st-line platinum-based chemotherapy (defined as progression (PD) while on therapy or relapse within 90 days of treatment completion) and ECOG performance status (PS) ≤2 were eligible. Patients were treated with intravenous AMR 40 mg/m2/day x 3 days every 21 days until PD or intolerable toxicity. The primary endpoint was response rate (ORR, by RECIST), with a goal to demonstrate an ORR ≥18% (point estimate). Secondary endpoints included progression-free survival (PFS) and overall survival (OS). Results: In all, 75 pts were enrolled with a median age of 63 years (range 43–88), 52% female, 17% PS 2. Response to 1st-line therapy was 5% complete remission (CR), 36% partial remission (PR) and 28% PD. Median time from completion of 1st-line therapy to PD was 1.3 mos. Sixty-nine pts received AMR for a median of 4 cycles (range 1–12). Six pts died or discontinued before receiving treatment. The primary endpoint was met with an ORR of 21% (16/75, 95% confidence interval [CI] 13.6% - 31.9%), including CR in 1 pt (1%) and PR in 15 pts (20%). Stable disease was achieved in 40% of pts. Two pts with PD as best response to 1st line chemotherapy achieved a PR. Median OS was 6.0 mos (95% CI 4.8–7.1 mos). Median PFS was 3.2 mos (95% CI 2.4–4.0 mos). The most common grade 3 or 4 adverse events were neutropenia (65%), thrombocytopenia (39%), and leukopenia (35%). Seven (10%) patients experienced febrile neutropenia. Dose reductions were required in 26 patients (38%). Conclusions: AMR shows promising activity, with an ORR of 21%, and an acceptable safety profile in patients with refractory ED-SCLC, and warrants further study in these pts.

[Table: see text]

Amrubicin (AMR) and cardiotoxicity in second-line treatment of small cell lung cancer (SCLC): A pooled analysis of left ventricular ejection fraction (LVEF) in two phase II trials

e19019

Background: Amrubicin (AMR) is a third-generation synthetic anthracycline and a potent topoisomerase II inhibitor approved in Japan for the treatment of lung cancer. In Japanese pre and postmarking studies, AMR treatment was not associated with cardiotoxicity. The purpose of this analysis was to determine if AMR treatment of Western patients (pts) is associated with anthracycline-induced cardiomyopathy. Methods: To evaluate risk of cardiomyopathy, LVEF was measured by echocardiogram or by multiple gated acquisition (MUGA) scan and pooled from pts enrolled in 2 trials of IV AMR, 40 mg/m2/day x 3 days q 21 days for second-line treatment of sensitive or refractory SCLC. Pts with measurable disease, ECOG PS 0–2, LVEF ≥50%, and prior platinum-based treatment were assessed at baseline (BL), cycles 3, 6, then every 2 cycles, and end of treatment. Pts were to be assessed by the same method (ECHO or MUGA) throughout the study. Pts with a persistent ≥20% decrease in LVEF during treatment were to be removed from the study. Results: 112 patients were treated (sensitive n=43, median 6 cycles; refractory, n=69, median 5 cycles) and had at least 1 LVEF assessment. Median age was 63 years and median BL LVEF was 60%. Changes in LVEF from baseline were minimal ( Table ) and similar across cumulative dosing groups including 15 pts who received a cumulative dose of >1,000 mg/m2 AMR. Two refractory pts (1.8%) experienced drops in LVEF >20%. One had BL LVEF of 85%, then 60% at cycle 3, and 70% subsequently with ongoing therapy. The second, with a history of cardiomegaly, had LVEF of 55% at BL, cycle 3, and 5 by ECHO, and 29% at the time of progression after cycle 9 (cumulative AMR dose 840 mg/m2) by MUGA. The patient died due to progressive disease with no evidence of CHF. Conclusions: In this pooled analysis of SCLC pts, LVEF remained stable even in pts with cumulative AMR dosing >1,000 mg/m2. AMR for second-line treatment of SCLC does not appear to cause anthracycline-related cardiomyopathy.

[Table: see text]

[Table: see text]

Results of a randomized phase II trial of amrubicin (AMR) versus topotecan (Topo) in patients with extensive-disease small cell lung cancer (ED-SCLC) sensitive to first-line platinum-based chemotherapy

8028

Background: SCLC presents as ED-SCLC in 60%-70% of patients (pts). AMR, a synthetic anthracycline, is approved for these pts in Japan. We compare the efficacy and safety of single-agent AMR vs topotecan in non-Japanese pts with 2nd-line ED-SCLC sensitive to 1st-line platinum-based chemotherapy. Methods: This phase II, open-label, multicenter study enrolled pts with ED-SCLC sensitive to 1st-line platinum-based chemotherapy (recurrence or progression ≥90 days from 1st-line treatment). Pts aged ≥18 years with ECOG performance status (PS) ≤2 and only 1 prior therapy were eligible. Pts were randomized (2:1) to receive IV AMR 40 mg/m2/d (d, 1–3) or IV topotecan 1.5 mg/m2/d (d 1–5) and treated every 21 days until progression, unacceptable toxicity, or withdrawal. The primary endpoint, overall response rate (ORR, complete + partial response), used RECIST criteria. Secondary endpoints were progression-free survival (PFS), overall survival (OS), and safety. Results: In all, 76 pts were randomized to AMR (n=50) or topotecan (n=26) with AMR given for a median of 6 cycles (range 1–16) and topotecan 3 cycles (1–16). AMR significantly improved ORR rates vs topotecan (p<0.012; Table ). Median PFS/OS was 4.3 months (95% CI 2.0, 6.1)/9.3 months (95% CI 5.7, 12.0) with AMR vs 3.5 months (95% CI 2.1, 6.3)/8.9 months (95% CI 4.8, 13.8) with topotecan. There was a higher proportion of ECOG PS 2 pts in the AMR group (n=6) vs the topotecan group (n=2). A trend towards improved OS was observed in the ECOG 0–1 subgroup of 68 pts: median OS was 10.5 months with AMR vs 9.7 months with topotecan. The most common grade ≥3 adverse events with AMR vs topotecan were neutropenia (53% vs 74%), thrombocytopenia (31% vs 52%) and leukopenia (27% vs 30%). Three AMR pts (6%) and 1 topotecan pt (4%) died of neutropenic infection. Conclusions: AMR significantly improves ORR and has acceptable tolerability as 2nd-line treatment in pts with sensitive ED-SCLC.

[Table: see text]

[Table: see text]

Parental smoking and childhood cancer: results from the United Kingdom Childhood Cancer Study

There are strong a priori reasons for considering parental smoking behaviour as a risk factor for childhood cancer but case - control studies have found relative risks of mostly only just above one. To investigate this further, self-reported smoking habits in parents of 3838 children with cancer and 7629 control children included in the United Kingdom Childhood Cancer Study (UKCCS) were analysed. Separate analyses were performed for four major groups (leukaemia, lymphoma, central nervous system tumours and other solid tumours) and more detailed diagnostic subgroups by logistic regression. In the four major groups, after adjustment for parental age and deprivation there were nonsignificant trends of increasing risk with number of cigarettes smoked for paternal preconception smoking and nonsignificant trends of decreasing risk for maternal preconception smoking (all P-values for trend >0.05). Among the diagnostic subgroups, a statistically significant increased risk of developing hepatoblastoma was found in children whose mothers smoked preconceptionally (OR=2.68, P=0.02) and strongest (relative to neither parent smoking) for both parents smoking (OR=4.74, P=0.003). This could be a chance result arising from multiple subgroup analysis. Statistically significant negative trends were found for maternal smoking during pregnancy for all diagnoses together (P<0.001) and for most individual groups, but there was evidence of under-reporting of smoking by case mothers. In conclusion, the UKCCS does not provide significant evidence that parental smoking is a risk factor for any of the major groups of childhood cancers.

Preliminary quantitative investigation of postmortem adipocere formation

The accurate determination of postmortem interval (PMI) using the formation of adipocere presents a significant challenge to forensic scientists interested in determining the time of death. Several attempts have been made to determine the time since the occurrence of death. However, up to date, this has been difficult because previous approaches have been mainly qualitative, focusing on the later stages of degradation processes. This work presents preliminary results of an experimental model of postmortem adipocere formation using liquid chromatography. Three pig cadavers were submerged in distilled water, chlorinated water, and saline water. Fresh specimens resulting from the degradation in the subcutaneous fat were obtained from the pigs at two-week intervals for a period of ten weeks, and were subjected to chromatographic analysis. By correlating the ratio of the disappearance of hydrolyzed fatty acids with the formation of hydroxystearic and oxostearic acids after death, a simple, quantitative analytical method was developed for the determination of PMI. Experimental observation of the chemistry of adipocere formation indicated that adipocere can be formed only a few hours after an incidence of death and this continues until the saturation of oleic acid degradation after several weeks. Different time courses were obtained for cadavers immersed in distilled, chlorinated, and saline water, respectively. This work has not in any way solved the time since death problem. But it may be an approach to the problem that has not been adequately explored.

Adult psychosocial outcomes in long-term survivors of acute lymphoblastic leukaemia and Wilms' tumour: a controlled study

BACKGROUND

Variability in methods and deficits in design have contributed to conflicting findings about adult psychosocial functioning after childhood cancer. We did a controlled study of psychosocial outcomes in adult survivors of childhood acute lymphoblastic leukaemia (ALL) and Wilms' tumour to address previous methods limitations.

METHODS

We assessed 102 survivors of childhood ALL and Wilms' tumour, who had been free from relapse for 5 years and were aged 19-30 years, and 102 unrelated healthy controls. We used standard measures of adult psychiatric disorder, interpersonal and social-role performance, and intellectual ability to assess past and current functioning.

FINDINGS

Cancer survivors had no increased rates of psychiatric disorder. Mean scores of cancer survivors were significantly higher (indicating poorer functioning) than those of controls for love/sex relationships (mean difference 0.87 [95% CI 0.53-1.22]), friendships (0.37 [0.07-0.67]), non-specific social contacts (0.40 [0.20-0.60]), and day-to-day coping (0.35 [0.14-0.57]). Cancer survivors were more likely than controls to have a combination of deficits in love/sex relationships and friendships (ALL survivors odds ratio 10.83 [95% CI 3.87-30.82], Wilms' tumour survivors 4.85 [1.43-16.47]), which was associated with more recent treatment (p=0.005). Poor coping was associated with lower intellectual ability scores (p=0.018).

INTERPRETATION

Childhood ALL and Wilms' tumour have long-term effects on interpersonal functioning and coping, probably mediated by different mechanisms. Prospective studies with each of these tumour groups are needed with similar adolescent and adult outcome measures.

IL-12 is dysregulated in macrophages from IRF-1 and IRF-2 knockout mice

Macrophages derived from IFN-regulatory factor-1 (IRF-1) and IRF-2 knockout (-/-) and wild-type (+/+) mice were utilized to examine the role of these transcription factors in the regulation of IL-12 mRNA and protein expression. Induction of IL-12 p40 mRNA by LPS was markedly diminished in both IRF-1(-/-) and IRF-2(-/-) macrophages. In contrast, IRF-1(-/-), but not IRF-2(-/-), macrophages exhibited impaired LPS-induced IL-12 p35 mRNA expression. The ability of IFN-gamma to augment LPS-induced IL-12 p40 mRNA further when both stimuli were present simultaneously was significantly diminished in both IRF-1(-/-) and IRF-2(-/-) macrophages, with the most profound impairment observed for IRF-1(-/-) macrophages. Reductions in IL-12 mRNA expression after stimulation with LPS or LPS plus IFN-gamma were accompanied by substantial reductions in IL-12 p40 and IL-12 p70 protein in both IRF-1(-/-) and IRF-2(-/-) macrophages. Priming IRF-1(-/-) and IRF-2(-/-) macrophages with IFN-gamma for 24 h before LPS treatment partially restored impaired IL-12 mRNA and protein production in both IRF-1(-/-) and IRF-2(-/-) macrophages. Depressed IL-12 levels were paralleled by significant reductions in IFN-gamma mRNA expression in IRF-1(-/-) and IRF-2(-/-) macrophages. These results indicate that both IRF-1 and IRF-2 are critical transcription factors in the regulation of macrophage IL-12 and consequently IFN-gamma production.

The rise in incidence of lymphomas in Europe 1985-1992

A collaborative study was carried out of the descriptive epidemiology of the lymphomas from seven countries across Europe in the period 1985-1992. Careful attention was paid to sources of information and the data quality in close collaboration with expert histopathologists. The data were classified as non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). An attempt was made to put the data into a modified version of the Revised European American Lymphoma (REAL) classification. We observed an overall rise in total NHL throughout the time period in all European countries but no such trend in HD. The increase in NHL overall being 4.2% per annum, representing an increase of 4.8% in males and 3.4% in females per annum, was only marked in middle and old age. Such increases were observed in all participating areas except in Burgundy. Different countries, however, have different base rates, the rates being highest in Scandinavia and the Netherlands. The analysis by subcategory classification suggested that the increase in NHL was confined to the follicle centre cell type, extranodal B-cell, nodal T-cell and nodal lymphomas not otherwise specified, categories. These new observations present a picture of real increase in case incidence with no obvious explanation. The increases in NHL do not appear to be due solely to better diagnoses. Pending other explanations or refutation, these present a compelling picture of an inexorable rise in incidence of this disease.

Incidence and time trends in Hodgkin's disease: from parts of the United Kingdom (1984-1993)

Over 3,000 cases of Hodgkin's Disease diagnosed between 1984-93 were used to examine incidence and time trends. These data are part of the Leukaemia Research Fund's specialist Data Collection Study, which is the only large, population-based data set of its type in Europe. The age specific incidence curves showed different patterns for nodular sclerosis contrasted with all other subtypes combined (non-nodular sclerosis). For nodular sclerosis, there was a female excess for young adults, while for non-nodular sclerosis a gradual rise in incidence with age in both sexes was observed. Incidence varied over time, showing a complex pattern with a decreasing trend in males in all Rye-subtypes and no significant change among females diagnosed with nodular sclerosis. These complex patterns of change are different from those seen in other countries. It is concluded that the results provide clear evidence of the heterogeneity of Hodgkin's disease between the sexes and between subtypes, which should be taken into account in future studies.

The changing incidence of lymphoproliferative disorders in Yorkshire

Secular trends in the incidence of lymphoproliferative disorders on North and West Yorkshire and Humberside from 1985 to 94 were studied and changes in incidence by tumour subtype were analysed. Population-based data on the incidence of lymphoproliferative disorders were obtained from a specialist registry with a high level of ascertainment. Cases of chronic lymphocytic leukaemia and plasma cell myeloma were excluded and the remaining cases classified as Hodgkin's disease and non-Hodgkin's lymphoma (NHL). NHL were subdivided by site of origin and immunophenotype. Nodal B-cell lymphomas were further classified as diffuse large B-cell lymphoma, follicle centre lymphoma, mantle cell lymphoma and miscellaneous. During the study period there was a significant increase in total lymphoproliferative disorders with an average change of 2.5% per annum equivalent to 0.84/10,0000. Most of this increase was due to an increasing incidence of extranodal B-cell lymphomas and peripheral T-cell lymphomas. A numerically small but significant increase in diffuse large B-cell lymphomas was seen. There was no significant increase in other subtypes. The increased incidence of lymphomas in the area studied is mainly due to changes in two specific subgroups. There are several reasons why changes in extranodal B-cell lymphoma and peripheral T-cell lymphoma may have been particularly affected by changing diagnostic practices. Epidemiological studies of particular subtypes of lymphoproliferative disorder facilitate the identification of environmental factors involved in the pathogenesis of these tumours.