Paediatric hepatocellular carcinoma due to somatic CTNNB1 and NFE2L2 mutations in the setting of inherited bi-allelic ABCB11 mutations

Exploring bile acid transporters as key players in cancer development and treatment: Evidence from preclinical and clinical studies

Bile acid transporters (BATs) are integral membrane proteins belonging to various families, such as solute carriers, organic anion transporters, and ATP-binding cassette families. These transporters play a crucial role in bile acid transportation within the portal and systemic circulations, with expression observed in tissues, including the liver, kidney, and small intestine. Bile acids serve as signaling molecules facilitating the absorption and reabsorption of fats and lipids. Dysregulation of bile acid concentration has been implicated in tumorigenesis, yet the role of BATs in this process remains underexplored. Emerging evidence suggests that BATs may modulate various stages of cancer progression, including initiation, development, proliferation, metastasis, and tumor microenvironment regulation. Targeting BATs using siRNAs, miRNAs, and small compound inhibitors in preclinical models and their polymorphisms are well-studied for transporters like BSEP, MDR1, MRP2, OATP1A2, etc., and have shed light on their involvement in tumorigenesis, particularly in cancers such as those affecting the liver and gastrointestinal tract. While BATs' role in diseases like Alagille syndrome, biliary atresia, and cirrhosis have been extensively studied, their implications in cancer warrant further investigation. This review highlights the expression and function of BATs in cancer development and emphasizes the potential of targeting these transporters as a novel therapeutic strategy for various malignancies.

The altered lipidome of hepatocellular carcinoma

Alterations in metabolic pathways are a hallmark of cancer. A deeper understanding of the contribution of different metabolites to carcinogenesis is thus vitally important to elucidate mechanisms of tumor initiation and progression to inform therapeutic strategies. Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide and its altered metabolic landscape is beginning to unfold with the advancement of technologies. In particular, characterization of the lipidome of human HCCs has accelerated, and together with biochemical analyses, are revealing recurrent patterns of alterations in glycerophospholipid, sphingolipid, cholesterol and bile acid metabolism. These widespread alterations encompass a myriad of lipid species with numerous roles affecting multiple hallmarks of cancer, including aberrant growth signaling, metastasis, evasion of cell death and immunosuppression. In this review, we summarize the current trends and findings of the altered lipidomic landscape of HCC and discuss their potential biological significance for hepatocarcinogenesis.

How Genetics and Genomics Advances Are Rewriting Pediatric Cancer Research and Clinical Care

In the last two decades, thanks to the data that have been obtained from the Human Genome Project and the development of next-generation sequencing (NGS) technologies, research in oncology has produced extremely important results in understanding the genomic landscape of pediatric cancers, which are the main cause of death during childhood. NGS has provided significant advances in medicine by detecting germline and somatic driver variants that determine the development and progression of many types of cancers, allowing a distinction between hereditary and non-hereditary cancers, characterizing resistance mechanisms that are also related to alterations of the epigenetic apparatus, and quantifying the mutational burden of tumor cells. A combined approach of next-generation technologies allows us to investigate the numerous molecular features of the cancer cell and the effects of the environment on it, discovering and following the path of personalized therapy to defeat an "ancient" disease that has had victories and defeats. In this paper, we provide an overview of the results that have been obtained in the last decade from genomic studies that were carried out on pediatric cancer and their contribution to the more accurate and faster diagnosis in the stratification of patients and the development of new precision therapies.

Rare Inherited Cholestatic Disorders and Molecular Links to Hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the most common primary liver cancer affecting adults and the second most common primary liver cancer affecting children. Recent years have seen a significant increase in our understanding of the molecular changes associated with HCC. However, HCC is a complex disease, and its molecular pathogenesis, which likely varies by aetiology, remains to be fully elucidated. Interestingly, some inherited cholestatic disorders that manifest in childhood are associated with early HCC development. This review will thus explore how three genes that are associated with liver disease in childhood (ABCB11, TJP2 and VPS33B) might play a role in the initiation and progression of HCC. Specifically, chronic bile-induced damage (caused by ABCB11 changes), disruption of intercellular junction formation (caused by TJP2 changes) and loss of normal apical–basal cell polarity (caused by VPS33B changes) will be discussed as possible mechanisms for HCC development.

Genetics in Familial Intrahepatic Cholestasis: Clinical Patterns and Development of Liver and Biliary Cancers: A Review of the Literature

The family of inherited intrahepatic cholestasis includes autosomal recessive cholestatic rare diseases of childhood involved in bile acids secretion or bile transport defects. Specific genetic pathways potentially cause many otherwise unexplained cholestasis or hepatobiliary tumours in a healthy liver. Lately, next-generation sequencing and whole-exome sequencing have improved the diagnostic procedures of familial intrahepatic cholestasis (FIC), as well as the discovery of several genes responsible for FIC. Moreover, mutations in these genes, even in the heterozygous status, may be responsible for cryptogenic cholestasis in both young and adults. Mutations in FIC genes can influence serum and hepatic levels of bile acids. Experimental studies on the NR1H4 gene have shown that high bile acids concentrations cause excessive production of inflammatory cytokines, resistance to apoptosis, and increased cell regeneration, all risk conditions for developing hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). NR1H4 gene encodes farnesoid X-activated receptor having a pivotal role in bile salts synthesis. Moreover, HCC and CCA can emerge in patients with several FIC genes such as ABCB11, ABCB4 and TJP2. Herein, we reviewed the available data on FIC-related hepatobiliary cancers, reporting on genetics to the pathophysiology, the risk factors and the clinical presentation.

Serial circulating tumor DNA to predict early recurrence in patients with hepatocellular carcinoma: a prospective study

We studied the value of circulating tumor DNA (ctDNA) in predicting early postoperative tumor recurrence and monitoring tumor burden in patients with hepatocellular carcinoma (HCC). Plasma-free DNA, germline DNA, and tissue DNA were isolated from 41 patients with HCC. Serial ctDNAs were analyzed by next-generation sequencing before and after operation. Whole-exome sequencing was used to detect the DNA of HCC and adjacent tissues. In total, 47 gene mutations were identified in the ctDNA of the 41 patients analyzed before surgery. ctDNA was detected in 63.4% and 46% of the patient plasma pre- and postoperation, respectively. The preoperative ctDNA positivity rate was significantly lower in the nonrecurrence group than in the recurrence group. With a median follow-up of 17.7 months, nine patients (22%) experienced tumor recurrence. ctDNA positivity at two time-points was associated with significantly shorter recurrence-free survival (RFS). Tumors with NRAS, NEF2L2, and MET mutations had significantly shorter times to recurrence than those without mutations and showed high recurrence prediction performance by machine learning. Multivariate analyses showed that the median variant allele frequency (VAF) of mutations in preoperative ctDNA was a strong independent predictor of RFS. ctDNA is a real-time monitoring indicator that can accurately reflect tumor burden. The median VAF of baseline ctDNA is a strong independent predictor of RFS in individuals with HCC.

Disordered farnesoid X receptor signaling is associated with liver carcinogenesis in Abcb11-deficient mice

ABCB11 encodes the bile salt export pump (BSEP), a key regulator in maintaining bile acid (BA) homeostasis. Although inherited ABCB11 mutations have previously been linked to primary liver cancer, whether ABCB11 deficiency leads to liver cancer remains unknown. Here, we analyzed ABCB11 mRNA expression levels in liver tumor specimens [29 with hepatocellular carcinoma (HCC), one with intrahepatic cholangiocarcinoma (ICC), and one with mixed HCC/ICC] with adjacent normal specimens and published human datasets. Liver tissues obtained from Abcb11-deficient (Abcb11^-/- ) mice and wild-type mice at different ages were compared by histologic, RNA-sequencing, and BA analyses. ABCB11 was significantly downregulated in human liver tumors compared with normal controls. Abcb11^-/- mice demonstrated progressive intrahepatic cholestasis and liver fibrosis, and spontaneously developed HCC and ICC over 12 months of age. Abcb11 deficiency increased BAs in the liver and serum in mice, most of which are farnesoid X receptor (FXR) antagonists/non-agonists. Accordingly, the hepatic expression and transcriptional activity of FXR were downregulated in Abcb11^-/- mouse livers. Administration of the FXR agonist obeticholic acid reduced liver injury and tumor incidence in Abcb11^-/- mice. In conclusion, ABCB11 is aberrantly downregulated and plays a vital role in liver carcinogenesis. The cholestatic liver injury and liver tumors developed in Abcb11^-/- mice are associated with increased FXR antagonist BAs and thereby decreased activation of FXR. FXR activation might be a therapeutic strategy in ABCB11 deficiency diseases. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Nuclear factor erythroid 2-related factor 2 and β-Catenin Coactivation in Hepatocellular Cancer: Biological and Therapeutic Implications

BACKGROUND AND AIMS

HCC remains a major unmet clinical need. Although activating catenin beta-1 (CTNNB1) mutations are observed in prominent subsets of HCC cases, these by themselves are insufficient for hepatocarcinogenesis. Coexpression of mutant CTNNB1 with clinically relevant co-occurrence has yielded HCCs. Here, we identify cooperation between β-catenin and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling in HCC.

APPROACH AND RESULTS

Public HCC data sets were assessed for concomitant presence of CTNNB1 mutations and either mutations in nuclear factor erythroid-2-related factor-2 (NFE2L2) or Kelch like-ECH-associated protein 1 (KEAP1), or Nrf2 activation by gene signature. HCC development in mice and similarity to human HCC subsets was assessed following coexpression of T41A-CTNNB1 with either wild-type (WT)-, G31A-, or T80K-NFE2L2. Based on mammalian target of rapamycin complex 1 activation in CTNNB1-mutated HCCs, response of preclinical HCC to mammalian target of rapamycin (mTOR) inhibitor was investigated. Overall, 9% of HCC cases showed concomitant CTNNB1 mutations and Nrf2 activation, subsets of which were attributable to mutations in NFE2L2/KEAP1. Coexpression of mutated CTNNB1 with mutant NFE2L2, but not WT-NFE2L2, led to HCC development and mortality by 12-14 weeks. These HCCs were positive for β-catenin targets, like glutamine synthetase and cyclin-D1, and Nrf2 targets, like NAD(P)H quinone dehydrogenase 1 and peroxiredoxin 1. RNA-sequencing and pathway analysis showed high concordance of preclinical HCC to human HCC subset showing activation of unique (iron homeostasis and glioblastoma multiforme signaling) and expected (glutamine metabolism) pathways. NFE2L2-CTNNB1 HCC mice were treated with mTOR inhibitor everolimus (5-mg/kg diet ad libitum), which led to >50% decrease in tumor burden.

CONCLUSIONS

Coactivation of β-catenin and Nrf2 is evident in 9% of all human HCCs. Coexpression of mutant NFE2L2 and mutant CTNNB1 led to clinically relevant HCC development in mice, which responded to mTOR inhibitors. Thus, this model has both biological and therapeutic implications.

Inference of gene regulatory networks using pseudo-time series data

MOTIVATION

Inferring gene regulatory networks (GRNs) from high-throughput data is an important and challenging problem in systems biology. Although numerous GRN methods have been developed, most have focused on the verification of the specific data set. However, it is difficult to establish directed topological networks that are both suitable for time-series and non-time-series datasets due to the complexity and diversity of biological networks.

RESULTS

Here, we proposed a novel method, GNIPLR (Gene networks inference based on projection and lagged regression) to infer GRNs from time-series or non-time-series gene expression data. GNIPLR projected gene data twice using the LASSO projection (LSP) algorithm and the linear projection (LP) approximation to produce a linear and monotonous pseudo-time series, and then determined the direction of regulation in combination with lagged regression analyses. The proposed algorithm was validated using simulated and real biological data. Moreover, we also applied the GNIPLR algorithm to the liver hepatocellular carcinoma (LIHC) and bladder urothelial carcinoma (BLCA) cancer expression datasets. These analyses revealed significantly higher accuracy and AUC values than other popular methods.

AVAILABILITY

The GNIPLR tool is freely available at https://github.com/zyllluck/GNIPLR.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Structure and Function of Hepatobiliary ATP Binding Cassette Transporters

The liver is beyond any doubt the most important metabolic organ of the human body. This function requires an intensive crosstalk within liver cellular structures, but also with other organs. Membrane transport proteins are therefore of upmost importance as they represent the sensors and mediators that shuttle signals from outside to the inside of liver cells and/or vice versa. In this review, we summarize the known literature of liver transport proteins with a clear emphasis on functional and structural information on ATP binding cassette (ABC) transporters, which are expressed in the human liver. These primary active membrane transporters form one of the largest families of membrane proteins. In the liver, they play an essential role in for example bile formation or xenobiotic export. Our review provides a state of the art and comprehensive summary of the current knowledge of hepatobiliary ABC transporters. Clearly, our knowledge has improved with a breath-taking speed over the last few years and will expand further. Thus, this review will provide the status quo and will lay the foundation for new and exciting avenues in liver membrane transporter research.

Nrf1 Is Endowed with a Dominant Tumor-Repressing Effect onto the Wnt/β-Catenin-Dependent and Wnt/β-Catenin-Independent Signaling Networks in the Human Liver Cancer

Our previous work revealed that Nrf1α exerts a tumor-repressing effect because its genomic loss (to yield Nrf1α^-/- ) results in oncogenic activation of Nrf2 and target genes. Interestingly, β-catenin is concurrently activated by loss of Nrf1α in a way similar to β-catenin-driven liver tumor. However, a presumable relationship between Nrf1 and β-catenin is not yet established. Here, we demonstrate that Nrf1 enhanced ubiquitination of β-catenin for targeting proteasomal degradation. Conversely, knockdown of Nrf1 by its short hairpin RNA (shNrf1) caused accumulation of β-catenin so as to translocate the nucleus, allowing activation of a subset of Wnt/β-catenin signaling responsive genes, which leads to the epithelial-mesenchymal transition (EMT) and related cellular processes. Such silencing of Nrf1 resulted in malgrowth of human hepatocellular carcinoma, along with malignant invasion and metastasis to the lung and liver in xenograft model mice. Further transcriptomic sequencing unraveled significant differences in the expression of both Wnt/β-catenin-dependent and Wnt/β-catenin-independent responsive genes implicated in the cell process, shape, and behavior of the shNrf1-expressing tumor. Notably, we identified that β-catenin is not a target gene of Nrf1, but this CNC-bZIP factor contributes to differential or opposing expression of other critical genes, such as CDH1, Wnt5A, Wnt11A, FZD10, LEF1, TCF4, SMAD4, MMP9, PTEN, PI3K, JUN, and p53, each of which depends on the positioning of distinct cis-regulatory sequences (e.g., ARE and/or AP-1 binding sites) in the gene promoter contexts. In addition, altered expression profiles of some Wnt/β-catenin signaling proteins were context dependent, as accompanied by decreased abundances of Nrf1 in the clinic human hepatomas with distinct differentiation. Together, these results corroborate the rationale that Nrf1 acts as a bona fide dominant tumor repressor, by its intrinsic inhibition of Wnt/β-catenin signaling and relevant independent networks in cancer development and malignant progression.

Exome Sequencing in Clinical Hepatology

The clinical relevance of the Human Genome Project and next-generation sequencing technology was demonstrated for the first time in 2009, when whole-exome sequencing (WES) provided the definitive diagnosis of congenital chloride diarrhea in an infant with presumed renal salt-wasting disease. Over the past decade, numerous studies have shown the utility of WES for clinical diagnosis as well as for discovery of novel genetic disorders through analysis of a single or a handful of informative pedigrees. Hence, advances in improving the speed, accuracy, and computational analysis combined with exponential decrease in the cost of sequencing the human genome is transforming the practice of medicine. The impact of WES has been most noticeable in pediatric disorders and oncology, but its utility in the liver clinic is recently emerging. Here, we assess the current status of WES for clinical diagnosis and acceleration of translation research to enhance care of patients with liver disease.

Association between Itch and Cancer in 3836 Pediatric Pruritus Patients at a Tertiary Care Center

Background: Pruritus is a well-recognized paraneoplastic phenomenon. Previous studies have examined the association of itch with a variety of malignancies in adults. However, no large study has examined this association in a pediatric population. Methods: A retrospective study was conducted of patients age 18 or less seen at Johns Hopkins Health System between 2012 and 2019. Results: A pediatric hospital population of 1,042,976 patients was reviewed. Pruritus was observed in 3836 pediatric patients of whom 130 also had cancer. Pediatric patients with pruritus were significantly more likely to have concomitant malignancy compared to pediatric patients without pruritus (OR 12.84; 95% CI 10.73–15.35, p < 0.001). Malignancies most strongly associated with pruritus included neoplasms of the blood (OR 14.38; 95% CI 11.30–18.29, p < 0.001), bone (OR 29.02, 95% CI 18.28–46.06, p < 0.001) and skin (OR 22.76, 95% CI 9.14–56.72, p < 0.001. Conclusions: Pruritus is significantly associated with malignancy in the pediatric hospital population. Clinicians should also be aware of the high burden of itch in pediatric malignancies and the variation in pruritus across malignancies.

Clinical utility of genomic analysis in adults with idiopathic liver disease

BACKGROUND & AIMS

Adult patients suffering from liver disease of unknown cause represent an understudied and underserved population. The use of whole-exome sequencing (WES) for the assessment of a broader spectrum of non-oncological diseases, among adults, remains poorly studied. We assessed the utility of WES in the diagnosis and management of adults with unexplained liver disease despite comprehensive evaluation by a hepatologist and with no history of alcohol overuse.

METHODS

We performed WES and deep phenotyping of 19 unrelated adult patients with idiopathic liver disease recruited at a tertiary academic health care center in the US.

RESULTS

Analysis of the exome in 19 cases identified 4 monogenic disorders in 5 unrelated adults. Patient 1 suffered for 18 years from devastating complications of undiagnosed type 3 familial partial lipodystrophy due to a deleterious heterozygous variant in PPARG. Molecular diagnosis enabled initiation of leptin replacement therapy with subsequent normalization of liver aminotransferases, amelioration of dyslipidemia, and decreases in daily insulin requirements. Patients 2 and 3 were diagnosed with MDR3 deficiency due to recessive mutations in ABCB4. Patient 4 with a prior diagnosis of non-alcoholic steatohepatitis was found to harbor a mitochondrial disorder due to a homozygous pathogenic variant in NDUFB3; this finding enabled initiation of disease preventive measures including supplementation with antioxidants. Patient 5 is a lean patient with hepatic steatosis of unknown etiology who was found to have a damaging heterozygous variant in APOB.

CONCLUSIONS

Genomic analysis yielded an actionable diagnosis in a substantial number (∼25%) of selected adult patients with chronic liver disease of unknown etiology. This study supports the use of WES in the evaluation and management of adults with idiopathic liver disease in clinical practice.

LAY SUMMARY

We performed whole-exome sequencing in 19 adult patients with unexplained liver disease after an unrevealing conventional work-up performed by a hepatologist. In 5 cases, genomic analysis led to a diagnosis and informed treatment and management of the disease. Therefore, we suggest using whole-exome sequencing in the evaluation and management of adults with unexplained liver disease.

Is hepatocellular carcinoma the same disease in children and adults? Comparison of histology, molecular background, and treatment in pediatric and adult patients

Pediatric hepatocellular carcinoma (HCC) is rare, resulting in scattered knowledge of tumor biology and molecular background. Thus far, the variant in children has been treated as a different entity from adult HCC. We weigh the hypothesis that HCC in the pediatric and adult groups may be the same entity and may benefit from the same treatment. Although certain differences between adult and pediatric HCC are obvious and certain types of HCC may ask for a customized approach, in conventional HCC, similarities predominate, warranting treatment aiming at common molecular targets in adult and pediatric HCC patients.

Vacuolar Protein Sorting 33B Is a Tumor Suppressor in Hepatocarcinogenesis

Polarity defects are frequently involved in liver diseases, such as chronic hepatitis and hepatocellular carcinoma (HCC). It was reported that vacuolar protein sorting 33B (Vps33b) plays critical roles in the maintenance of hepatocyte polarity; however, the functional roles and mechanisms of Vps33b in HCC occurrence and progression remain unknown. First of all, we showed that Vps33b is down-regulated in human and mouse liver cancer samples, and the low expression levels of Vps33b correlate with the poor prognosis of many HCC patients. Liver-specific Vps33b deficiency induces liver damage, progressive hepatitis, fibrosis, and HCC in male mice, indicating that Vps33b is a crucial contributory factor to hepatocarcinogenesis. Vps33b deficiency-caused liver damage was primarily due to the disorders of structural and functional hepatocyte polarity, which were reflected by the decreased protein levels of E-cadherin because of inaccurate location to lysosomes and polarity defects at both apical and lateral plasma membrane proteins. The results of a mechanism study revealed that Vps33b interacts with VPS33B-interacting protein, which is involved in polarity and apical protein restriction; vesicle-trafficking protein Sec22b; and Flotillin-1 in hepatocytes and is in charge of the normal distribution of polarity-determined proteins. Expression levels of Vps33b negatively correlated with the degree of inflammatory cell infiltration in livers from diethylnitrosamine-induced or transgenic HCC mouse models, and the inflammatory stimuli suppressed the expression of Vps33b in vitro. Conclusion: Down-regulation of Vps33b expression is a critical step for inflammation-driven HCC, and Vps33b serves as an important tumor suppressor in hepatocarcinogenesis.

Exome analysis of the evolutionary path of hepatocellular adenoma-carcinoma transition, vascular invasion and brain dissemination

Hepatocellular adenoma (HCA) is a rare benign liver tumor, predominantly seen in young women. Its major complications are malignant transformation, spontaneous hemorrhage, and rupture. We describe a case of a young female with no underlying liver disease who presented with acute abdominal pain and was found to have a 17cm heterogeneous mass in the left lobe of the liver. She underwent left hepatectomy and pathology revealed a 14cm moderately differentiated hepatocellular carcinoma (HCC) arising in a shell of a HCA. At that time, vascular invasion was already present. She rapidly developed recurrent multifocal hepatic lesions and subsequent spread to the brain, leading to her death 18months after surgery. To investigate the underlying genetic events occurring during hepatocellular adenoma-carcinoma transition and extra-hepatic dissemination, we performed whole exome sequencing of DNA isolated from peripheral blood leucocytes, HCA, HCC, tumor thrombus and brain metastasis. Our data show a step-wise addition of somatic mutations and copy number variations with disease progression, suggesting a linear tumor evolution, which is supported by clonality analysis. Specifically, using a model based clustering of somatic mutations, one single founding clone arising in the HCA, which included catenin beta 1 (CTNNB1) and IL6ST driver mutations, was identified and displayed an increasing clonality rate in HCC, tumor thrombus and brain metastasis. Our data highlight the feasibility of performing whole exome capture, sequencing and analysis using formalin-fixed paraffin-embedded (FFPE) samples, and we describe the first genomic longitudinal study of hepatocellular adenoma-carcinoma transition, vascular invasion and brain metastasis with detailed clinicopathologic annotation.

Vps33b is crucial for structural and functional hepatocyte polarity

BACKGROUND & AIMS

In the normal liver, hepatocytes form a uniquely polarised cell layer that enables movement of solutes from sinusoidal blood to canalicular bile. Whilst several cholestatic liver diseases with defects of hepatocyte polarity have been identified, the molecular mechanisms of pathogenesis are not well defined. One example is arthrogryposis, renal dysfunction and cholestasis syndrome, which in most patients is caused by VPS33B mutations. VPS33B is a protein involved in membrane trafficking that interacts with RAB11A at recycling endosomes. To understand the pathways that regulate hepatocyte polarity better, we investigated VPS33B deficiency using a novel mouse model with a liver-specific Vps33b deletion.

METHODS

To assess functional polarity, plasma and bile samples were collected from Vps33b liver knockout (Vps33bfl/fl-AlfpCre) and control (Vps33bfl/fl) mice; bile components or injected substrates were quantitated by mass spectrometry or fluorometry. For structural analysis, livers underwent light and transmission electron microscopy. Apical membrane and tight junction protein localisation was assessed by immunostaining. Adeno-associated virus vectors were used for in vivo gene rescue experiments.

RESULTS

Like patients, Vps33bfl/fl-AlfpCre mice showed mislocalisation of ATP-binding cassette proteins that are specifically trafficked to the apical membrane via Rab11a-positive recycling endosomes. This was associated with retention of bile components in blood. Loss of functional tight junction integrity and depletion of apical microvilli were seen in knockout animals. Gene transfer partially rescued these defects.

CONCLUSIONS

Vps33b has a key role in establishing structural and functional aspects of hepatocyte polarity and may be a target for gene replacement therapy.

LAY SUMMARY

Hepatocytes are liver cells with tops and bottoms; that is, they are polarised. At their bottoms they absorb substances from blood. They then, at their tops, secrete these substances and their metabolites into bile. When polarity is lost, this directional flow of substances from blood to bile is disrupted and liver disease follows. In this study, using a new mouse model with a liver-specific mutation of Vps33b, the mouse version of a gene that is mutated in most patients with arthrogryposis, renal dysfunction and cholestasis (ARC) syndrome, we investigated how the Vps33b gene product contributes to establishing hepatocyte polarity. We identified in these mice abnormalities similar to those in children with ARC syndrome. Gene transfer could partly reverse the mouse abnormalities. Our work contributes to the understanding of VPS33B disease and hepatocyte polarity in general, and may point towards gene transfer mediated treatment of ARC liver disease.

Childhood cancer predisposition syndromes-A concise review and recommendations by the Cancer Predisposition Working Group of the Society for Pediatric Oncology and Hematology

Heritable predisposition is an important cause of cancer in children and adolescents. Although a large number of cancer predisposition genes and their associated syndromes and malignancies have already been described, it appears likely that there are more pediatric cancer patients in whom heritable cancer predisposition syndromes have yet to be recognized. In a consensus meeting in the beginning of 2016, we convened experts in Human Genetics and Pediatric Hematology/Oncology to review the available data, to categorize the large amount of information, and to develop recommendations regarding when a cancer predisposition syndrome should be suspected in a young oncology patient. This review summarizes the current knowledge of cancer predisposition syndromes in pediatric oncology and provides essential information on clinical situations in which a childhood cancer predisposition syndrome should be suspected.

Genetic alterations in hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. Although recent advances in therapeutic approaches for treating HCC have improved the prognoses of patients with HCC, this cancer is still associated with a poor survival rate mainly due to late diagnosis. Therefore, a diagnosis must be made sufficiently early to perform curative and effective treatments. There is a need for a deeper understanding of the molecular mechanisms underlying the initiation and progression of HCC because these mechanisms are critical for making early diagnoses and developing novel therapeutic strategies. Over the past decade, much progress has been made in elucidating the molecular mechanisms underlying hepatocarcinogenesis. In particular, recent advances in next-generation sequencing technologies have revealed numerous genetic alterations, including recurrently mutated genes and dysregulated signaling pathways in HCC. A better understanding of the genetic alterations in HCC could contribute to identifying potential driver mutations and discovering novel therapeutic targets in the future. In this article, we summarize the current advances in research on the genetic alterations, including genomic instability, single-nucleotide polymorphisms, somatic mutations and deregulated signaling pathways, implicated in the initiation and progression of HCC. We also attempt to elucidate some of the genetic mechanisms that contribute to making early diagnoses of and developing molecularly targeted therapies for HCC.

ACOX2 deficiency: A disorder of bile acid synthesis with transaminase elevation, liver fibrosis, ataxia, and cognitive impairment

Acyl CoA Oxidase 2 (ACOX2) encodes branched-chain acyl-CoA oxidase, a peroxisomal enzyme believed to be involved in the metabolism of branched-chain fatty acids and bile acid intermediates. Deficiency of this enzyme has not been described previously. We report an 8-y-old male with intermittently elevated transaminase levels, liver fibrosis, mild ataxia, and cognitive impairment. Exome sequencing revealed a previously unidentified homozygous premature termination mutation (p.Y69*) in ACOX2 Immunohistochemistry confirmed the absence of ACOX2 expression in the patient's liver, and biochemical analysis showed marked elevation of intermediate bile acids upstream of ACOX2. These findings define a potentially treatable inborn error of bile acid biosynthesis caused by ACOX2 deficiency.

Glucose induced activation of canonical Wnt signaling pathway in hepatocellular carcinoma is regulated by DKK4

Elevated glycemic index, an important feature of diabetes is implicated in an increased risk of hepatocellular carcinoma (HCC). However, the underlying molecular mechanisms of this association are relatively less explored. Present study investigates the effect of hyperglycemia over HCC proliferation. We observed that high glucose culture condition (HG) specifically activates canonical Wnt signaling in HCC cells, which is mediated by suppression of DKK4 (a Wnt antagonist) expression and enhanced β-catenin level. Functional assays demonstrated that a normoglycemic culture condition (NG) maintains constitutive expression of DKK4, which controls HCC proliferation rate by suppressing canonical Wnt signaling pathway. HG diminishes DKK4 expression leading to loss of check at G0/G1/S phases of the cell cycle thereby enhancing HCC proliferation, in a β-catenin dependent manner. Interestingly, in NOD/SCID mice supplemented with high glucose, HepG2 xenografted tumors grew rapidly in which elevated levels of β-catenin, c-Myc and decreased levels of DKK4 were detected. Knockdown of DKK4 by shRNA promotes proliferation of HCC cells in NG, which is suppressed by treating cells exogenously with recombinant DKK4 protein. Our in vitro and in vivo results indicate an important functional role of DKK4 in glucose facilitated HCC proliferation.

Structural and functional hepatocyte polarity and liver disease

Hepatocytes form a crucially important cell layer that separates sinusoidal blood from the canalicular bile. They have a uniquely organized polarity with a basal membrane facing liver sinusoidal endothelial cells, while one or more apical poles can contribute to several bile canaliculi jointly with the directly opposing hepatocytes. Establishment and maintenance of hepatocyte polarity is essential for many functions of hepatocytes and requires carefully orchestrated cooperation between cell adhesion molecules, cell junctions, cytoskeleton, extracellular matrix and intracellular trafficking machinery. The process of hepatocyte polarization requires energy and, if abnormal, may result in severe liver disease. A number of inherited disorders affecting tight junction and intracellular trafficking proteins have been described and demonstrate clinical and pathophysiological features overlapping those of the genetic cholestatic liver diseases caused by defects in canalicular ABC transporters. Thus both structural and functional components contribute to the final hepatocyte polarity phenotype. Many acquired liver diseases target factors that determine hepatocyte polarity, such as junctional proteins. Hepatocyte depolarization frequently occurs but is rarely recognized because hematoxylin-eosin staining does not identify the bile canaliculus. However, the molecular mechanisms underlying these defects are not well understood. Here we aim to provide an update on the key factors determining hepatocyte polarity and how it is affected in inherited and acquired diseases.

Identification of novel hereditary cancer genes by whole exome sequencing

Whole exome sequencing (WES) provides a powerful tool for medical genetic research. Several dozens of WES studies involving patients with hereditary cancer syndromes have already been reported. WES led to breakthrough in understanding of the genetic basis of some exceptionally rare syndromes; for example, identification of germ-line SMARCA4 mutations in patients with ovarian hypercalcemic small cell carcinomas indeed explains a noticeable share of familial aggregation of this disease. However, studies on common cancer types turned out to be more difficult. In particular, there is almost a dozen of reports describing WES analysis of breast cancer patients, but none of them yet succeeded to reveal a gene responsible for the significant share of missing heritability. Virtually all components of WES studies require substantial improvement, e.g. technical performance of WES, interpretation of WES results, mode of patient selection, etc. Most of contemporary investigations focus on genes with autosomal dominant mechanism of inheritance; however, recessive and oligogenic models of transmission of cancer susceptibility also need to be considered. It is expected that the list of medically relevant tumor-predisposing genes will be rapidly expanding in the next few years.

Hepatocellular carcinoma in children

Liver tumors are relatively rare in childhood, but may be associated with a range of diagnostic, genetic, therapeutic, and surgical challenges sufficient to tax even the most experienced clinician. This article outlines the epidemiology, etiology, pathologic condition, initial workup, and management of hepatocellular carcinoma in children and adolescents.

BSEP expression in liver tissue of hyperlipidemia rats

AIM: To investigate the expression of bile salt export pump (BSEP) in hepatic tissue in a rat model of hyperlipidemia.

METHODS: Sixty wistar rats were randomly divided into two groups (n = 30 for each): a control group that was fed an ordinary diet, and an experimental group fed a high fat diet. Cholesterol and bile acid levels were regularly monitored. Liver tissue samples were taken for detecting the gene expression of BSEP by reverse transcription polymerase chain reaction (RT-PCR) and the protein expression of BSEP by immunohistochemistry.

RESULTS: The levels of cholesterol and bile acid were significantly higher in the experimental group than in the control group. RT-PCR analysis showed that the expression of BSEP mRNA was significantly higher in the experimental group than in the control group. Immunohistochemistry analysis showed that in the experimental group, the positive expression rate of BSEP was 76.7%, significantly higher than that in the control group (12.5%).

CONCLUSION: The expression of Bsep increases significantly in rat hyperlipidemia, which suggests that we can develop drugs acting on BSEP to find new treatment methods and means for hyperlipidemia and related diseases.