Identifying metabolic features of colorectal cancer liability using Mendelian randomization

Background

Recognizing the early signs of cancer risk is vital for informing prevention, early detection, and survival.

Methods

To investigate whether changes in circulating metabolites characterize the early stages of colorectal cancer (CRC) development, we examined the associations between a genetic risk score (GRS) associated with CRC liability (72 single-nucleotide polymorphisms) and 231 circulating metabolites measured by nuclear magnetic resonance spectroscopy in the Avon Longitudinal Study of Parents and Children (N = 6221). Linear regression models were applied to examine the associations between genetic liability to CRC and circulating metabolites measured in the same individuals at age 8 y, 16 y, 18 y, and 25 y.

Results

The GRS for CRC was associated with up to 28% of the circulating metabolites at FDR-P < 0.05 across all time points, particularly with higher fatty acids and very-low- and low-density lipoprotein subclass lipids. Two-sample reverse Mendelian randomization (MR) analyses investigating CRC liability (52,775 cases, 45,940 controls) and metabolites measured in a random subset of UK Biobank participants (N = 118,466, median age 58 y) revealed broadly consistent effect estimates with the GRS analysis. In conventional (forward) MR analyses, genetically predicted polyunsaturated fatty acid concentrations were most strongly associated with higher CRC risk.

Conclusions

These analyses suggest that higher genetic liability to CRC can cause early alterations in systemic metabolism and suggest that fatty acids may play an important role in CRC development.

Funding

This work was supported by the Elizabeth Blackwell Institute for Health Research, University of Bristol, the Wellcome Trust, the Medical Research Council, Diabetes UK, the University of Bristol NIHR Biomedical Research Centre, and Cancer Research UK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. This work used the computational facilities of the Advanced Computing Research Centre, University of Bristol - http://www.bristol.ac.uk/acrc/.

In-silico and in-vitro morphometric analysis of intestinal organoids

Organoids offer a powerful model to study cellular self-organisation, the growth of specific tissue morphologies in-vitro, and to assess potential medical therapies. However, the intrinsic mechanisms of these systems are not entirely understood yet, which can result in variability of organoids due to differences in culture conditions and basement membrane extracts used. Improving the standardisation of organoid cultures is essential for their implementation in clinical protocols. Developing tools to assess and predict the behaviour of these systems may produce a more robust and standardised biological model to perform accurate clinical studies. Here, we developed an algorithm to automate crypt-like structure counting on intestinal organoids in both in-vitro and in-silico images. In addition, we modified an existing two-dimensional agent-based mathematical model of intestinal organoids to better describe the system physiology, and evaluated its ability to replicate budding structures compared to new experimental data we generated. The crypt-counting algorithm proved useful in approximating the average number of budding structures found in our in-vitro intestinal organoid culture images on days 3 and 7 after seeding. Our changes to the in-silico model maintain the potential to produce simulations that replicate the number of budding structures found on days 5 and 7 of in-vitro data. The present study aims to aid in quantifying key morphological structures and provide a method to compare both in-vitro and in-silico experiments. Our results could be extended later to 3D in-silico models.

Evaluating the effect of metabolic traits on oral and oropharyngeal cancer risk using Mendelian randomization

A recent World Health Organization report states that at least 40% of all cancer cases may be preventable, with smoking, alcohol consumption, and obesity identified as three of the most important modifiable lifestyle factors. Given the significant decline in smoking rates, particularly within developed countries, other potentially modifiable risk factors for head and neck cancer warrant investigation. Obesity and related metabolic disorders such as type 2 diabetes (T2D) and hypertension have been associated with head and neck cancer risk in multiple observational studies. However, adiposity has also been correlated with smoking, with bias, confounding or reverse causality possibly explaining these findings. To overcome the challenges of observational studies, we conducted two-sample Mendelian randomization (inverse variance weighted [IVW] method) using genetic variants which were robustly associated with adiposity, glycaemic and blood pressure traits in genome-wide association studies (GWAS). Outcome data were taken from the largest available GWAS of 6034 oral and oropharyngeal cases, with 6585 controls. We found limited evidence of a causal effect of genetically proxied body mass index (BMI; OR IVW = 0.89, 95% CI 0.72-1.09, p = 0.26 per 1 standard deviation in BMI [4.81kg/m2]) on oral and oropharyngeal cancer risk. Similarly, there was limited evidence for related traits including T2D and hypertension. Small effects cannot be excluded given the lack of power to detect them in currently available GWAS.

The epithelial splicing regulator ESRP2 is epigenetically repressed by DNA hypermethylation in Wilms tumour and acts as a tumour suppressor

Wilms tumour (WT), an embryonal kidney cancer, has been extensively characterised for genetic and epigenetic alterations, but a proportion of WTs still lack identifiable abnormalities. To uncover DNA methylation changes critical for WT pathogenesis, we compared the epigenome of foetal kidney with two WT cell lines, filtering our results to remove common cancer-associated epigenetic changes and to enrich for genes involved in early kidney development. This identified four hypermethylated genes, of which ESRP2 (epithelial splicing regulatory protein 2) was the most promising for further study. ESRP2 was commonly repressed by DNA methylation in WT, and this occurred early in WT development (in nephrogenic rests). ESRP2 expression was reactivated by DNA methyltransferase inhibition in WT cell lines. When ESRP2 was overexpressed in WT cell lines, it inhibited cellular proliferation in vitro, and in vivo it suppressed tumour growth of orthotopic xenografts in nude mice. RNA-seq of the ESRP2-expressing WT cell lines identified several novel splicing targets. We propose a model in which epigenetic inactivation of ESRP2 disrupts the mesenchymal to epithelial transition in early kidney development to generate WT.

Using genetic variants to evaluate the causal effect of cholesterol lowering on head and neck cancer risk: A Mendelian randomization study

Head and neck squamous cell carcinoma (HNSCC), which includes cancers of the oral cavity and oropharynx, is a cause of substantial global morbidity and mortality. Strategies to reduce disease burden include discovery of novel therapies and repurposing of existing drugs. Statins are commonly prescribed for lowering circulating cholesterol by inhibiting HMG-CoA reductase (HMGCR). Results from some observational studies suggest that statin use may reduce HNSCC risk. We appraised the relationship of genetically-proxied cholesterol-lowering drug targets and other circulating lipid traits with oral (OC) and oropharyngeal (OPC) cancer risk using two-sample Mendelian randomization (MR). For the primary analysis, germline genetic variants in HMGCR, NPC1L1, CETP, PCSK9 and LDLR were used to proxy the effect of low-density lipoprotein cholesterol (LDL-C) lowering therapies. In secondary analyses, variants were used to proxy circulating levels of other lipid traits in a genome-wide association study (GWAS) meta-analysis of 188,578 individuals. Both primary and secondary analyses aimed to estimate the downstream causal effect of cholesterol lowering therapies on OC and OPC risk. The second sample for MR was taken from a GWAS of 6,034 OC and OPC cases and 6,585 controls (GAME-ON). Analyses were replicated in UK Biobank, using 839 OC and OPC cases and 372,016 controls and the results of the GAME-ON and UK Biobank analyses combined in a fixed-effects meta-analysis. We found limited evidence of a causal effect of genetically-proxied LDL-C lowering using HMGCR, NPC1L1, CETP or other circulating lipid traits on either OC or OPC risk. Genetically-proxied PCSK9 inhibition equivalent to a 1 mmol/L (38.7 mg/dL) reduction in LDL-C was associated with an increased risk of OC and OPC combined (OR 1.8 95%CI 1.2, 2.8, p = 9.31 x10-05), with good concordance between GAME-ON and UK Biobank (I2 = 22%). Effects for PCSK9 appeared stronger in relation to OPC (OR 2.6 95%CI 1.4, 4.9) than OC (OR 1.4 95%CI 0.8, 2.4). LDLR variants, resulting in genetically-proxied reduction in LDL-C equivalent to a 1 mmol/L (38.7 mg/dL), reduced the risk of OC and OPC combined (OR 0.7, 95%CI 0.5, 1.0, p = 0.006). A series of pleiotropy-robust and outlier detection methods showed that pleiotropy did not bias our findings. We found limited evidence for a role of cholesterol-lowering in OC and OPC risk, suggesting previous observational results may have been confounded. There was some evidence that genetically-proxied inhibition of PCSK9 increased risk, while lipid-lowering variants in LDLR, reduced risk of combined OC and OPC. This result suggests that the mechanisms of action of PCSK9 on OC and OPC risk may be independent of its cholesterol lowering effects; however, this was not supported uniformly across all sensitivity analyses and further replication of this finding is required.

Circulating immunoreactive substance P in man

Immunoreactive substance P (iSP) has been measured in plasma in 77 normal subjects and in 125 hospital patients. Factors affectingin-vitro degradation of iSP were studied.In vivo, iSP is degraded in the liver and its level in the circulation is independent of kidney excretory function.During insulin-induced hypoglycaemic stress and also during glucose-tolerance test, iSP in plasma decreased transiently. No circadian rhythm of iSP was observed, but in a study in sleeping volunteers episodic secretory bursts were seen, separated by one- to two-hour intervals, the first peak appearing about 90 minutes after the subjects fell asleep.In a patient with carcinoid metastases in the liver, an elevated level of iSP was found in the general circulation with a marked gradient at the hepatic venous effluent.

The community development in health project

This paper describes the purpose and process of a 15 month project established to develop resources to assist people who are seeking to use a community development approach in addressing health issues.

Carotid Artery Angioplasty for Restenosis Following Endarterectomy

INTRODUCTION

The higher complication rate associated with the surgical treatment of restenosis following carotid endarterectomy (CEA) has led several authors to advocate angioplasty as the treatment of choice in the management of restenosis. We describe our experience with internal carotid artery angioplasty for post-endarterectomy restenosis over 7 years.

PATIENTS AND METHODS

From January 1994 to April 2001, all patients with a >90% restenosis following CEA were considered for angioplasty. Thirty angioplasties were carried out in 25 patients, 80% (24/30), for asymptomatic recurrent stenosis. There was no difference between those who had intervention for recurrent stenosis (n=31) and those who did not (n=545) in age, sex, smoking status or incidence of diabetes or hypertension. A significantly greater number of patients who underwent angioplasty were hypercholesterolaemic (p<0.05, Chi-squared test).

RESULTS

Mean time from surgery to angioplasty was 13 months (range 1-23). Angioplasty was technically successful in 29 cases (97%). Three patients (10%) experienced transient neurological symptoms during the procedure. There were no strokes. Ninety-six percent (28/29) of patients were followed up with duplex scanning. Mean follow-up was 20 months (range 2-48). Three patients developed a greater than 90% restenosis.

CONCLUSION

Angioplasty is an acceptable alternative to surgery in the management of internal carotid artery restenosis following endarterectomy.

Quality assurance: what is the consumers' role?

We commenced with the question: what is the "proper" role for consumers in quality assurance? Quality assurance has been discussed as encompassing three phases: clinical review, linkage and drive. We have discussed a range of mechanisms which can contribute to expressing a consumer perspective or the consumers' interest in each of these phases of quality assurance. It is clear that the consumers' experience is a useful and legitimate input to clinical review. It is clear that mechanisms for listening more carefully to the consumers' perspective could be introduced more widely. It is clear that greater consumer understanding of an involvement in the whole quality assurance cycle is practicable and, from the point of view of many consumers, highly desirable. Whilst more detailed answers have not been brought forward, a useful framework for considering how to proceed from here has been presented.

Therapeutic arterial embolisation in children

Arterial embolisation was performed in five paediatric patients. Indications were hypersplenism in two, gastrointestinal bleeding in two and treatment of an aneurysmal bone cyst in one. Embolisation provided definitive treatment in each case with no complications.

Computed tomographic arteriography in the pre-surgical evaluation of hepatic tumours

Five patients with hepatic neoplasms considered suitable for surgical resection were examined by computed tomography (CT), hepatic angiography and then a combination of angiography and CT (CTA). In each patient the tumour was more clearly defined and its extent more accurately determined than by routine CT. Three patients were spared surgery when further hepatic tumour was shown by CTA. The left lobe was shown to be free of tumour in the other two patients and surgical resection was carried out. Examination by CTA is recommended in all patients with hepatic tumours considered suitable for hepatic resection.

Therapeutic arterial embolisation: report of five years' experience

Therapeutic arterial embolisation was performed in 48 patients. Gelfoam, Oxycel, Bucrylate, Gianturco wire coils and lyophilised dura mater were used. Indications included control of acute haemorrhage, pre-operative vascular reduction, palliation of inoperable lesions, or to render such lesions operable, and elective definitive treatment. The technique was not considered to be of significant value as a pre-operative measure but was successful for the control of haemorrhage, the management of inoperable lesions and as an elective definitive treatment for various unusual lesions. One patient died and three had complications. The choice of occlusive material is discussed and depends upon the nature and vascularity of the lesion and whether short- or long-term occlusion is required.

Minimising side effects in lumbar radiculography

An attempt was made to reduce the side effects associated with the use of Metrizamide in lumbar radiculography by the removal of the contrast medium on completion of the examination. Almost complete removal was achieved in 103 patients and of these 73% had no symptoms after examination, while 8% had severe symptoms. Eleven of 14 patients in whom removal was not attempted or was not successful had significant symptoms after examination. It is concluded that aspiration of Metrizamide will reduce the incidence and severity of the side effects associated with the use of this contrast medium.

Glucagon as a hypotonic agent in cholangiography

The effects of Glucagon on 35 cholangiographic studies was examined. Relief of spasm at the choledochoduodenal sphincter resulted in consistently improved demonstration of this area. Diminished spasm-induced pain was also recorded. The use of intravenous Glucagon is recommended for cholangiographic studies where there is total biliary obstruction, or where there is unsatisfactory demonstration of the choledocho-duodenal area.

Percutaneous needle biopsy in the management of solitary lesions of bone

Needle biopsies were performed in 12 patients with solitary bone lesions, employing a simple 18 gauge cutting needle. Material sufficient for reliable diagnosis was obtained from eight of our 12 cases, thereby avoiding exploratory surgery. It is concluded that percutaneous needle biopsy of bone is a safe and simple procedure of value in the management of solitary lesions of bone.

Angiographic evaluation of gastrointestinal haemorrhage complicating pancreatic disease

Seven patients with gastro-oesophageal varices due to splenic or portal vein obstruction from a diseased pancreas have been seen at the Mater Hospital during the past three years. Four of these patients had episodes of acute and massive gastrointestinal bleeding and this paper emphasises the role of angiography in the management of this complication. In three instances the bleeding was the result of the varices, but in one patient with carcinoma of the head of the pancreas the bleeding was shown to result from invasion of the tumour into the duodenum.

The use of prostaglandin F2-alpha in selective pancreatic and left gastric angiography

Prostaglandin F2-Alpha has been used in 10 superselective angiographic studies of the pancreas and 10 left gastric studies. Injection of Prostaglandin into the dorsal pancreatic or gastroduodenal artery increased opacification of small pancreatic vessels and better demonstrated the angiographic changes in three cases of carcinoma of the pancreas. Injection of the drug into the left gastric artery increased opacification of the left gastric vein, allowed identification of the direction of flow of the contrast medium and enhanced demonstration of gastro-oesophageal varices. It is concluded that Prostaglandin improves the quality of pancreatic and left gastric angiographic studies.

The use of prostaglandin F2 alpha in selective hepatic angiography

Comparison has been made between slow infusion hepatic angiographic studies obtained before and after the intra-arterial injection of prostaglandin F2 alpha. The prostaglandin injection resulted in increased caliber of the hepatic arteries, increased opacification of the parenchyma of the liver and improved visualization of the wall of the gallbladder. Poorly vascularized metastatic lesions were better shown on the prostaglandin studies, and carcinoma of the gallbladder was diagnosed in two instances. The demonstration of highly vascularized metastatic tumor was enhanced on the prostaglandin studies, but further improved after the injection of angiotensin.

Cross-modal induction of changes in sensory thresholds

Two experiments are reported in which subliminal stimulation of one modality with emotional material impairs detection performance in a different modality. In the first experiment the visual awareness threshold for neutral material was raised by simultaneous auditory presentation of emotional words. This result supports the hypothesis that threshold changes induced by emotional stimulation are mediated centrally. In the second experiment a similar effect was obtained when the experimental roles of the two modalities were reversed. An analysis of the effect in terms of the parameters of Signal Detectability Theory indicates that it is mediated by a lowering of the sensitivity of the detection mechanism. This may be caused either by attenuation of incoming signals, or by an increase in the level of “noise” against which the signal is received.