Christopher A. Wadsworth

A comprehensive analysis of common genetic variation around six candidate loci for intrahepatic cholestasis of pregnancy.

OBJECTIVES:Intrahepatic cholestasis of pregnancy (ICP) has a complex etiology with a significant genetic component. Heterozygous mutations of canalicular transporters occur in a subset of ICP cases and a population susceptibility allele (p.444A) has been identified in ABCB11. We sought to expand our knowledge of the detailed genetic contribution to ICP by investigation of common variation around candidate loci with biological plausibility for a role in ICP (ABCB4, ABCB11, ABCC2, ATP8B1, NR1H4, and FGF19).METHODS:ICP patients (n=563) of white western European origin and controls (n=642) were analyzed in a case–control design. Single-nucleotide polymorphism (SNP) markers (n=83) were selected from the HapMap data set (Tagger, Haploview 4.1 (build 22)). Genotyping was performed by allelic discrimination assay on a robotic platform. Following quality control, SNP data were analyzed by Armitages trend test.RESULTS:Cochran–Armitage trend testing identified six SNPs in ABCB11 together with six SNPs in ABCB4 that showed significant evidence of association. The minimum Bonferroni corrected P value for trend testing ABCB11 was 5.81×10−4 (rs3815676) and for ABCB4 it was 4.6×10−7(rs2109505). Conditional analysis of the two clusters of association signals suggested a single signal in ABCB4 but evidence for two independent signals in ABCB11. To confirm these findings, a second study was performed in a further 227 cases, which confirmed and strengthened the original findings.CONCLUSIONS:Our analysis of a large cohort of ICP cases has identified a key role for common variation around the ABCB4 and ABCB11 loci, identified the core associations, and expanded our knowledge of ICP susceptibility.

Four DNA methylation biomarkers in biliary brush samples accurately identify the presence of cholangiocarcinoma

Early detection of the highly aggressive malignancy cholangiocarcinoma (CCA) remains a challenge but has the potential to render the tumor curable by surgical removal. This study evaluates a biomarker panel for the diagnosis of CCA by DNA methylation analyses of biliary brush samples. The methylation status of 13 candidate genes (CDO1, CNRIP1, DCLK1, FBN1, INA, MAL, SEPT9, SFRP1, SNCA, SPG20, TMEFF2, VIM, and ZSCAN18) was investigated in 93 tissue samples (39 CCAs and 54 nonmalignant controls) using quantitative methylation‐specific polymerase chain reaction. The 13 genes were further analyzed in a test series of biliary brush samples (15 CCAs and 20 nonmalignant primary sclerosing cholangitis controls), and the methylation status of the four best performing markers was validated (34 CCAs and 34 primary sclerosing cholangitis controls). Receiver operating characteristic curve analyses were used to evaluate the performance of individual biomarkers and the combination of biomarkers. The 13 candidate genes displayed a methylation frequency of 26%‐82% in tissue samples. The four best‐performing genes (CDO1, CNRIP1, SEPT9, and VIM) displayed individual methylation frequencies of 45%‐77% in biliary brushes from CCA patients. Across the test and validation biliary brush series, this four‐gene biomarker panel achieved a sensitivity of 85% and a specificity of 98%, with an area under the receiver operating characteristic curve of 0.944. Conclusion: We report a straightforward biomarker assay with high sensitivity and specificity for CCA, outperforming standard brush cytology, and suggest that the biomarker panel, potentially in combination with cytological evaluation, may improve CCA detection, particularly among primary sclerosing cholangitis patients. (Hepatology 2015;61:1651–1659)

Elevated Levels of Neutrophil Gelatinase-Associated Lipocalin in Bile From Patients With Malignant Pancreatobiliary Disease

OBJECTIVES:Accurate differentiation between benign and malignant causes of biliary obstruction remains challenging and reliable biomarkers are urgently needed. Bile is a potential source of such biomarkers. Our aim was to apply a proteomic approach to identify a potential biomarker in bile that differentiates between malignant and benign disease, and to assess its diagnostic accuracy. Neutrophil gelatinase-associated lipocalin (NGAL) is multi-functional protein, released from activated neutrophils, with roles in inflammation, immune function, and carcinogenesis. It has not previously been described in bile.METHODS:Bile, urine, and serum were collected prospectively from 38 patients undergoing endoscopic retrograde cholangiopancreatography (“discovery” cohort); 22 had benign and 16 had malignant pancreatobiliary disease. Initially, label-free proteomics and immunoblotting were performed in samples from a subset of these patients. Enzyme-linked immunosorbent assay was then performed for NGAL as a potential biomarker on all samples in this cohort. The diagnostic performance of biliary NGAL was then validated in a second, independent group (“validation” cohort) of 21 patients with pancreatobiliary disease (benign n=14, malignant n=7).RESULTS:NGAL levels were significantly raised in bile from the malignant disease group, compared with bile from the benign disease group in the discovery cohort (median 1,556 vs. 480 ng/ml, P=0.007). Biliary NGAL levels had a receiver operating characteristic area under curve of 0.76, sensitivity 94%, specificity 55%, positive predictive value 60%, and negative predictive value 92% for distinguishing malignant from benign causes. Biliary NGAL was independent of serum biochemistry and carbohydrate antigen 19-9 (CA 19-9) in differentiating between underlying benign and malignant disease. No significant differences in serum and urine NGAL levels were found between benign and malignant disease. Combining biliary NGAL and serum CA 19-9 improved diagnostic accuracy for malignancy (sensitivity 85%, specificity 82%, positive predictive value 79%, and negative predictive value 87%). The diagnostic accuracy of biliary NGAL was confirmed in the second independent validation cohort.CONCLUSIONS:NGAL in bile is a novel potential biomarker to help distinguish benign from malignant biliary obstruction.

Endoscopic radiofrequency ablation for cholangiocarcinoma.

Purpose of review To describe the use of endobiliary radiofrequency ablation (RFA) in the treatment of malignant disease of the bile duct and offer a comprehensive review of the emerging evidence on the safety and effectiveness of this new technique. Recent findings Ex-vivo and in-vivo porcine studies have been reported, confirming the feasibility of the technique, gathering preliminary safety data and defining appropriate power settings for human studies. Moderate-sized case series have now reported the use of RFA in mixed cohorts of human individuals with pancreatic cancer, cholangiocarcinoma and other malignant diseases of the bile duct. Endoscopic and percutaneous approaches have both been investigated. Small case series of blocked self-expanding metal stent clearance using RFA have been published. Summary Intraductal RFA, via both endoscopic and percutaneous approaches, is feasible. Complication rates appear to be comparable with the current standard endoscopic and percutaneous approaches to palliation of malignant strictures of the bile duct. The current body of literature is germinal, but warrants the further investigation of planned clinical trials.

Genetic Factors in the Pathogenesis of Cholangiocarcinoma

Background: Cholangiocarcinoma (CC) is increasing in incidence, but its pathogenesis remains poorly understood. Chronic inflammation of the bile duct and cholestasis are major risk factors, but most cases in the West are sporadic. Genetic polymorphisms in biliary transporter proteins have been implicated in benign biliary disease and, in the case of progressive familial cholestasis, have been associated with childhood onset of CC. In the current study, five biologically plausible candidate genes were investigated: ABCB11 (BSEP), ABCB4 (MDR3), ABCC2 (MRP2), ATP8B1 (FIC1) and NR1H4 (FXR). Methods: DNA was collected from 172 Caucasian individuals with confirmed CC. A control cohort of healthy Caucasians was formed. Seventy-three SNPs were selected using the HapMap database to capture genetic variation around the five candidate loci. Genotyping was undertaken with a competitive PCR-based system. Confirmation of Hardy-Weinberg equilibrium and Cochran-Armitage trend testing were performed using PLINK. Haplotype frequencies were compared using haplo.stats. Results: All 73 SNPs were in Hardy-Weinberg equilibrium. Four SNPs in ABCB11 were associated with altered susceptibility to CC, including the V444A polymorphism, but these associations did not retain statistical significance after Bonferroni correction for multiple testing. Haplotype analysis of the genotyped SNPs in ATP8B1 identified significant differences in frequencies between cases and controls (global p value of 0.005). Conclusion: Haplotypes in ATP8B1 demonstrated a significant difference between CC and control groups. There was a trend towards significant association of V444A with CC. Given the biological plausibility of polymorphisms in ABCB11 and ATP8B1 as risk modifiers for CC, further study in a validation cohort is required.

The McKittrick-Wheelock syndrome: A case of acute renal failure due to neoplastic cholera

The McKittrick Wheelock syndrome is characterized by severe electrolyte and fluid depletion as a result of rectal tumor hypersecretion. Typically, a metabolic acidosis ensues. We report the case of a 58-year-old man who presented with a mixed metabolic acidosis and alkalosis. He was hyponatremic, hypokalemic, and hypochloremic, with acute renal failure on blood testing. Following fluid resuscitation, a predominant alkalemia was observed. The patient was found to be passing 1.5 L of mucous per rectum per day, containing high concentrations of sodium and potassium, similar to that observed in cholera stool. A large rectal villous adenoma was discovered on sigmoidoscopy, and definitive management was achieved by removal of the tumor. This case provides a demonstration of the ranging metabolic disturbance associated with secretory diarrhea. Other endogenous and infective causes are discussed, and mechanisms compared with the case described.

Magnetic Resonance Imaging Duodenoscope

A side-viewing duodenoscope capable of both optical and magnetic resonance imaging (MRI) is described. The instrument is constructed from MR-compatible materials and combines a coherent fiber bundle for optical imaging, an irrigation channel and a side-opening biopsy channel for the passage of catheter tools with a tip saddle coil for radio-frequency signal reception. The receiver coil is magnetically coupled to an internal pickup coil to provide intrinsic safety. Impedance matching is achieved using a mechanically variable mutual inductance, and active decoupling by PIN-diode switching. 1H MRI of phantoms and ex vivo porcine liver specimens was carried out at 1.5 T. An MRI field-of-view appropriate for use during endoscopic retrograde cholangiopancreatography (ERCP) was obtained, with limited artefacts, and a signal-to-noise ratio advantage over a surface array coil was demonstrated.

The risk factors and diagnosis of cholangiocarcinoma.

Cholangiocarcinoma (CC) is a generally fatal malignancy of the biliary tree. Its incidence is increasing worldwide. Unfortunately, the diagnosis of CC frequently occurs late in the course of the disease, which contributes to the high mortality rate. Securing the diagnosis can prove difficult and may require a combination of imaging modalities, serum markers, and tissue sampling. Even with current best practice accurate diagnosis and staging is often elusive. We review current trends in the epidemiology of CC, current best practice in its diagnosis, and some of the emerging technologies and systems that may lead to improved diagnosis, staging, and, perhaps, outcome.

PTU-068 Biliary matrix metalloproteinase 9 levels are independent of neutrophil gelatinase-associated lipocalin in patients with malignant biliary obstruction

Introduction Better biomarkers are urgently needed to assist accurate diagnosis and appropriate treatment of malignant biliary obstruction, as, although malignancy is a common cause of obstructive jaundice, current diagnostic techniques often fail to differentiate benign from malignant disease. Molecular analysis of bile has recently produced promising candidate biomarkers. Previous work from our group found that biliary neutrophil gelatinase-associated lipocalin (NGAL), a small extracellular 25-kDa protein with several biological functions, differentiates obstructive jaundice from malignancy from that in benign disease. The mechanism of NGAL in hepatopancreatobiliary (HPB) malignancy is unknown, although in other systems it promotes neoplastic diffusion by complexing and stabilising matrix metalloproteinase-9 (MMP9), enabling local invasion. Aims (1) To investigate possible biliary complexing of MMP9 and NGAL as a mechanism of tumorigenesis. (2) To validate our previous findings of biliary NGAL as a novel biomarker of malignancy in biliary obstruction. Methods Bile samples were collected from 77 patients undergoing ERCP (n=77, 22 with malignant disease and 55 with benign disease) at Imperial College London. ELISA was used to quantify levels of MMP9/NGAL complexes and of NGAL and MMP9 occurring independently in bile. Pearsons correlation analysis was used to determine the relationship between NGAL, MMP9 and NGAL/MMP9 complex levels, and statistical significance assessed by the Mann–Whitney U test. Results Biliary NGAL levels were significantly higher in malignant biliary obstruction compared to benign disease (median 1555 ng/ml vs 402 ng/ml, p=0.003), giving a ROC AUC of 0.74. Biliary MMP9 and NGAL/MMP9 complex levels were not different between these groups (p=0.527, p=0.760). Unbound biliary NGAL and MMP9 levels correlated poorly (r2=0.03, p>0.05). Unbound NGAL correlated poorly with complex (r2=0.07, p>0.05) whereas unbound MMP9 correlated with NGAL/MMP9 complex level (r2=0.73, p<0.05). Conclusion This study is novel in confirming the presence of MMP9 in bile, alone and in complex with NGAL. However, although NGAL was increased in malignancy, MMP9 and MMP9/NGAL complex were not, suggesting that NGAL acts independently of MMP9 in endobiliary HPB malignancy. Mechanisms remain to be elucidated. This study also supports previous reports of NGAL as a novel and independent bile biomarker of malignant biliary obstruction. Competing interests None declared.

Magneto-Inductive Magnetic Resonance Imaging Duodenoscope

A magnetic resonance imaging (MRI) duodenoscope is demonstrated, by combining nonmagnetic endoscope components with a thin-film receiver based on a magneto-inductive waveguide. The waveguide elements consist of figure-of-eight shaped inductors formed on either side of a flexible substrate and parallel plate capacitors that use the substrate as a dielectric. Operation is simulated using equivalent circuit models and by computation of twoand three-dimensional sensitivity patterns. Circuits are fabricated for operation at 127.7 MHz by double-sided patterning of copper-clad Kapton and assembled onto non-magnetic flexible endoscope insertion tubes. Operation is verified by bench testing and by 1H MRI at 3T using phantoms. The receiver can form a segmented coaxial image along the length of the endoscope, even when bent, and shows a signal-to-noise-ratio advantage over a surface array coil up to three times the tube diameter at the tip. Initial immersion imaging experiments have been carried out and confirm an encouraging lack of sensitivity to RF heating.