In Vivo Modeling of Patient Genetic Heterogeneity Identifies New Ways to Target Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy of the bile ducts within the liver characterized by high levels of genetic heterogeneity. In the context of such genetic variability, determining which oncogenic mutations drive ICC growth has been difficult, and developing modes of patient stratification and targeted therapies remains challenging. Here we model the interactions between rare mutations with more common driver genes and combine in silico analysis of patient data with highly multiplexed in vivo CRISPR-spCas9 screens to perform a functional in vivo study into the role genetic heterogeneity plays in driving ICC. Novel tumor suppressors were uncovered, which, when lost, cooperate with the RAS oncoprotein to drive ICC growth. Focusing on a set of driver mutations that interact with KRAS to initiate aggressive, sarcomatoid-type ICC revealed that tumor growth relies on Wnt and PI3K signaling. Pharmacologic coinhibition of Wnt and PI3K in vivo impeded ICC growth regardless of mutational profile. Therefore, Wnt and PI3K activity should be considered as a signature by which patients can be stratified for treatment independent of tumor genotype, and inhibitors of these pathways should be levied to treat ICC.

SIGNIFICANCE

This work shows that, despite significant genetic heterogeneity, intrahepatic cholangiocarcinoma relies on a limited number of signaling pathways to grow, suggesting common therapeutic vulnerabilities across patients.

Notch-IGF1 signaling during liver regeneration drives biliary epithelial cell expansion and inhibits hepatocyte differentiation

In the adult liver, a population of facultative progenitor cells called biliary epithelial cells (BECs) proliferate and differentiate into cholangiocytes and hepatocytes after injury, thereby restoring liver function. In mammalian models of chronic liver injury, Notch signaling is essential for bile duct formation from these cells. However, the continual proliferation of BECs and differentiation of hepatocytes in these models have limited their use for determining whether Notch signaling is required for BECs to replenish hepatocytes after injury in the mammalian liver. Here, we used a temporally restricted model of hepatic repair in which large-scale hepatocyte injury and regeneration are initiated through the acute loss of Mdm2 in hepatocytes, resulting in the rapid, coordinated proliferation of BECs. We found that transient, early activation of Notch1- and Notch3-mediated signaling and entrance into the cell cycle preceded the phenotypic expansion of BECs into hepatocytes. Notch inhibition reduced BEC proliferation, which resulted in failure of BECs to differentiate into hepatocytes, indicating that Notch-dependent expansion of BECs is essential for hepatocyte regeneration. Notch signaling increased the abundance of the insulin-like growth factor 1 receptor (IGF1R) in BECs, and activating IGFR signaling increased BEC numbers but suppressed BEC differentiation into hepatocytes. These results suggest that different signaling mechanisms control BEC expansion and hepatocyte differentiation.

TWEAK/Fn14 signalling promotes cholangiocarcinoma niche formation and progression

BACKGROUND & AIMS

Cholangiocarcinoma (CCA) is a cancer of the hepatic bile ducts that is rarely resectable and is associated with poor prognosis. Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is known to signal via its receptor fibroblast growth factor-inducible 14 (Fn14) and induce cholangiocyte and myofibroblast proliferation in liver injury. We aimed to characterise its role in CCA.

METHODS

The expression of the TWEAK ligand and Fn14 receptor was assessed immunohistochemically and by bulk RNA and single cell transcriptomics of human liver tissue. Spatiotemporal dynamics of pathway regulation were comprehensively analysed in rat and mouse models of thioacetamide (TAA)-mediated CCA. Flow cytometry, qPCR and proteomic analyses of CCA cell lines and conditioned medium experiments with primary macrophages were performed to evaluate the downstream functions of TWEAK/Fn14. In vivo pathway manipulation was assessed via TWEAK overexpression in NICD/AKT-induced CCA or genetic Fn14 knockout during TAA-mediated carcinogenesis.

RESULTS

Our data reveal TWEAK and Fn14 overexpression in multiple human CCA cohorts, and Fn14 upregulation in early TAA-induced carcinogenesis. TWEAK regulated the secretion of factors from CC-SW-1 and SNU-1079 CCA cells, inducing polarisation of proinflammatory CD206+ macrophages. Pharmacological blocking of the TWEAK downstream target chemokine monocyte chemoattractant protein 1 (MCP-1 or CCL2) significantly reduced CCA xenograft growth, while TWEAK overexpression drove cancer-associated fibroblast proliferation and collagen deposition in the tumour niche. Genetic Fn14 ablation significantly reduced inflammatory, fibrogenic and ductular responses during carcinogenic TAA-mediated injury.

CONCLUSION

These novel data provide evidence for the action of TWEAK/Fn14 on macrophage recruitment and phenotype, and cancer-associated fibroblast proliferation in CCA. Targeting TWEAK/Fn14 and its downstream signals may provide a means to inhibit CCA niche development and tumour growth.

LAY SUMMARY

Cholangiocarcinoma is an aggressive, chemotherapy-resistant liver cancer. Interactions between tumour cells and cells that form a supportive environment for the tumour to grow are a source of this aggressiveness and resistance to chemotherapy. Herein, we describe interactions between tumour cells and their supportive environment via a chemical messenger, TWEAK and its receptor Fn14. TWEAK/Fn14 alters the recruitment and type of immune cells in tumours, increases the growth of cancer-associated fibroblasts in the tumour environment, and is a potential target to reduce tumour formation.

Meta-analysis and Meta-regression of Survival After Liver Transplantation for Unresectable Perihilar Cholangiocarcinoma

OBJECTIVE

To systematically review studies reporting survival data following neoadjuvant chemoradiation and orthotopic liver transplantation (NCR-OLT) for unresectable perihilar cholangiocarcinoma (pCC).

BACKGROUND

Despite survival improvements for other cancers, the prognosis of pCC remains dismal. Since publication of the Mayo protocol in 2000, increasing numbers of series globally are reporting outcomes after NCR-OLT.

METHODS

MEDLINE, EMBASE, Scopus, and Web of Science databases were searched from January 2000 to February 2019. A meta-analysis of proportions was conducted, pooling 1, 3-, and 5-year overall survival and recurrence rates following NCR-OLT across centers. Per protocol and intention to treat data were interrogated. Meta-regression was used to evaluate PSC as a confounder affecting survival.

RESULTS

Twenty studies comprising 428 patients were eligible for analysis. No RCTs were retrieved; the majority of studies were noncomparative cohort studies. The pooled 1, 3-, and 5-year overall survival rates following OLT without neoadjuvant therapy were 71.2% (95% CI 62.2%-79.4%), 48.0% (95% CI 35.0%-60.9%), and 31.6% (95% CI 23.1%-40.7%). These improved to 82.8% (95% CI 73.0%-90.8%), 65.5% (95% CI 48.7%-80.5%), and 65.1% (95% CI 55.1%-74.5%) if neoadjuvant chemoradiation was completed. Pooled recurrence after 3 years was 24.1% (95% CI 17.9%-30.9%) with neoadjuvant chemoradiation, 51.7% (95% CI 33.8%-69.4%) without.

CONCLUSIONS

In unresectable pCC, NCR-OLT confers long-term survival in highly selected patients able to complete neoadjuvant chemoradiation followed by transplantation. PSC patients appear to have the most favorable outcomes. A high recurrence rate is of concern when considering extending national graft selection policy to pCC.

Modulation of Biliary Cancer Chemo-Resistance Through MicroRNA-Mediated Rewiring of the Expansion of CD133+ Cells

BACKGROUND AND AIMS

Changes in single microRNA (miRNA) expression have been associated with chemo-resistance in biliary tract cancers (BTCs). However, a global assessment of the dynamic role of the microRNome has never been performed to identify potential therapeutic targets that are functionally relevant in the BTC cell response to chemotherapy.

APPROACH AND RESULTS

High-throughput screening (HTS) of 997 locked nucleic acid miRNA inhibitors was performed in six cholangiocarcinoma cell lines treated with cisplatin and gemcitabine (CG) seeking changes in cell viability. Validation experiments were performed with mirVana probes. MicroRNA and gene expression was assessed by TaqMan assay, RNA-sequencing, and in situ hybridization in four independent cohorts of human BTCs. Knockout of microRNA was achieved by CRISPR-CAS9 in CCLP cells (MIR1249KO) and tested for effects on chemotherapy sensitivity in vitro and in vivo. HTS revealed that MIR1249 inhibition enhanced chemotherapy sensitivity across all cell lines. MIR1249 expression was increased in 41% of cases in human BTCs. In validation experiments, MIR1249 inhibition did not alter cell viability in untreated or dimethyl sulfoxide-treated cells; however, it did increase the CG effect. MIR1249 expression was increased in CD133+ biliary cancer cells freshly isolated from the stem cell niche of human BTCs as well as in CD133+ chemo-resistant CCLP cells. MIR1249 modulated the chemotherapy-induced enrichment of CD133+ cells by controlling their clonal expansion through the Wnt-regulator FZD8. MIR1249KO cells had impaired expansion of the CD133+ subclone and its enrichment after chemotherapy, reduced expression of cancer stem cell markers, and increased chemosensitivity. MIR1249KO xenograft BTC models showed tumor shrinkage after exposure to weekly CG, whereas wild-type models showed only stable disease over treatment.

CONCLUSIONS

MIR1249 mediates resistance to CG in BTCs and may be tested as a target for therapeutics.

Systematic review of management of incidental gallbladder cancer after cholecystectomy

BACKGROUND

Gallbladder cancer is rare, but cancers detected incidentally after cholecystectomy are increasing. The aim of this study was to review the available data for current best practice for optimal management of incidental gallbladder cancer.

METHODS

A systematic PubMed search of the English literature to May 2018 was conducted.

RESULTS

The search identified 12 systematic reviews and meta-analyses, in addition to several consensus reports, multi-institutional series and national audits. Some 0·25-0·89 per cent of all cholecystectomy specimens had incidental gallbladder cancer on pathological examination. Most patients were staged with pT2 (about half) or pT1 (about one-third) cancers. Patients with cancers confined to the mucosa (T1a or less) had 5-year survival rates of up to 100 per cent after cholecystectomy alone. For cancers invading the muscle layer of the gallbladder wall (T1b or above), reresection is recommended. The type, extent and timing of reresection remain controversial. Observation time may be used for new cross-sectional imaging with CT and MRI. Perforation at initial surgery had a higher risk of disease dissemination. Gallbladder cancers are PET-avid, and PET may detect residual disease and thus prevent unnecessary surgery. Routine laparoscopic staging before reresection is not warranted for all stages. Risk of peritoneal carcinomatosis increases with each T category. The incidence of port-site metastases is about 10 per cent. Routine resection of port sites has no effect on survival. Adjuvant chemotherapy is poorly documented and probably underused.

CONCLUSION

Management of incidental gallbladder cancer continues to evolve, with more refined suggestions for subgroups at risk and a selective approach to reresection.

Notch3 drives development and progression of cholangiocarcinoma

The prognosis of cholangiocarcinoma (CC) is dismal. Notch has been identified as a potential driver; forced exogenous overexpression of Notch1 in hepatocytes results in the formation of biliary tumors. In human disease, however, it is unknown which components of the endogenously signaling pathway are required for tumorigenesis, how these orchestrate cancer, and how they can be targeted for therapy. Here we characterize Notch in human-resected CC, a toxin-driven model in rats, and a transgenic mouse model in which p53 deletion is targeted to biliary epithelia and CC induced using the hepatocarcinogen thioacetamide. We find that across species, the atypical receptor NOTCH3 is differentially overexpressed; it is progressively up-regulated with disease development and promotes tumor cell survival via activation of PI3k-Akt. We use genetic KO studies to show that tumor growth significantly attenuates after Notch3 deletion and demonstrate signaling occurs via a noncanonical pathway independent of the mediator of classical Notch, Recombinant Signal Binding Protein for Immunoglobulin Kappa J Region (RBPJ). These data present an opportunity in this aggressive cancer to selectively target Notch, bypassing toxicities known to be RBPJ dependent.

Hepatic progenitor cells of biliary origin with liver repopulation capacity

Hepatocytes and cholangiocytes self-renew following liver injury. Following severe injury hepatocytes are increasingly senescent, but whether hepatic progenitor cells (HPCs) then contribute to liver regeneration is unclear. Here, we describe a mouse model where the E3 ubiquitin ligase Mdm2 is inducibly deleted in more than 98% of hepatocytes, causing apoptosis, necrosis and senescence with nearly all hepatocytes expressing p21. This results in florid HPC activation, which is necessary for survival, followed by complete, functional liver reconstitution. HPCs isolated from genetically normal mice, using cell surface markers, were highly expandable and phenotypically stable in vitro. These HPCs were transplanted into adult mouse livers where hepatocyte Mdm2 was repeatedly deleted, creating a non-competitive repopulation assay. Transplanted HPCs contributed significantly to restoration of liver parenchyma, regenerating hepatocytes and biliary epithelia, highlighting their in vivo lineage potency. HPCs are therefore a potential future alternative to hepatocyte or liver transplantation for liver disease.

Recurrent gallstone ileus due to a residual gallstone: A case report and literature review

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Recurrence should be considered in all patients with gallstone ileus.

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A review of pre-operative imaging and meticulous inspection of the bowel and gallbladder should always be undertaken.

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Faceted gallstones should alert the surgeon to the potential presence of a second stone.

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Cholecystolithotomy should be considered as a safer alternative to cholecystectomy with fistula repair in high risk patients.

Introduction

Mechanical small bowel obstruction is an uncommon but important complication of cholelithiasis. Recurrent gallstone ileus has historically been considered a rare occurrence; however, the incidence is likely to be underreported and the condition carries a high mortality rate.

Presentation of case

We present a case in which a 67 year old man suffered a recurrence of gallstone ileus 10 days after his initial enterolithotomy, requiring further laparotomy.

Discussion

We review the literature to highlight potential clinical predictors as well as the benefits and pitfalls of management options in preventing repeated episodes of gallstone ileus in the same patient.

Conclusion

The presence of multifaceted gallstones and multiple stones of size ≥ 2cm on pre-operative imaging should alert the clinician to potential for recurrence.

WNT signaling drives cholangiocarcinoma growth and can be pharmacologically inhibited

Cholangiocarcinoma (CC) is typically diagnosed at an advanced stage and is refractory to surgical intervention and chemotherapy. Despite a global increase in the incidence of CC, little progress has been made toward the development of treatments for this cancer. Here we utilized human tissue; CC cell xenografts; a p53-deficient transgenic mouse model; and a non-transgenic, chemically induced rat model of CC that accurately reflects both the inflammatory and regenerative background associated with human CC pathology. Using these systems, we determined that the WNT pathway is highly activated in CCs and that inflammatory macrophages are required to establish this WNT-high state in vivo. Moreover, depletion of macrophages or inhibition of WNT signaling with one of two small molecule WNT inhibitors in mouse and rat CC models markedly reduced CC proliferation and increased apoptosis, resulting in tumor regression. Together, these results demonstrate that enhanced WNT signaling is a characteristic of CC and suggest that targeting WNT signaling pathways has potential as a therapeutic strategy for CC.

Polysialic acid/neural cell adhesion molecule modulates the formation of ductular reactions in liver injury

In severe liver injury, ductular reactions (DRs) containing bipotential hepatic progenitor cells (HPCs) branch from the portal tract. Neural cell adhesion molecule (NCAM) marks bile ducts and DRs, but not mature hepatocytes. NCAM mediates interactions between cells and surrounding matrix; however, its role in liver development and regeneration is undefined. Polysialic acid (polySia), a unique posttranslational modifier of NCAM, is produced by the enzymes, ST8SiaII and ST8SiaIV, and weakens NCAM interactions. The role of polySia with NCAM synthesizing enzymes ST8SiaII and ST8SiaIV were examined in HPCs in vivo using the choline-deficient ethionine-supplemented and 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet models of liver injury and regeneration, in vitro using models of proliferation, differentiation, and migration, and by use of mouse models with gene defects in the polysialyltransferases (St8sia 2+/-4+/-, and St8sia2-/-4-/-). We show that, during liver development, polySia is required for the correct formation of bile ducts because gene defects in both the polysialyltransferases (St8sia2+/-4+/- and St8sia2-/-4-/- mice) caused abnormal bile duct development. In normal liver, there is minimal polySia production and few ductular NCAM+ cells. Subsequent to injury, NCAM+ cells expand and polySia is produced by DRs/HPCs through ST8SiaIV. PolySia weakens cell-cell and cell-matrix interactions, facilitating HGF-induced migration. Differentiation of HPCs to hepatocytes in vitro results in both transcriptional down-regulation of polySia and cleavage of polySia-NCAM. Cleavage of polySia by endosialidase (endoN) during liver regeneration reduces migration of DRs into parenchyma.

CONCLUSION

PolySia modification of NCAM+ ductules weakens cell-cell and cell-matrix interactions, allowing DRs/HPCs to migrate for normal development and regeneration. Modulation of polySia levels may provide a therapeutic option in liver regeneration.

Cell lineage tracing reveals a biliary origin of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma is a treatment refractory malignancy with a high mortality and an increasing incidence worldwide. Recent studies have observed that activation of Notch and AKT signaling within mature hepatocytes is able to induce the formation of tumors displaying biliary lineage markers, thereby raising the suggestion that it is hepatocytes, rather than cholangiocytes or hepatic progenitor cells that represent the cell of origin of this tumor. Here, we use a cholangiocyte-lineage tracing system to target p53 loss to biliary epithelia and observe the appearance of labeled biliary lineage tumors in response to chronic injury. Consequent to this, upregulation of native functional Notch signaling is observed to occur spontaneously within cholangiocytes and hepatocytes in this model as well as in human intrahepatic cholangiocarcinoma. These data prove that in the context of chronic inflammation and p53 loss, frequent occurrences in human disease, biliary epithelia are a target of transformation and an origin of intrahepatic cholangiocarcinoma.

Carotid Endarterectomy: Are We Meeting the Two Week Target?

Objective

It has been recommended that carotid endarterectomy should be carried out within fourteen days of the index event if maximum stroke prevention benefit is to be achieved. The aim of this study was to see whether this target was being met in our region and where in the pathway delays occurred.

Methods

This was a retrospective review of all patients (n=75) undergoing carotid endarterectomy in 2006 in a regional vascular unit. Eleven patients were excluded as the timing of onset of symptoms was unclear, leaving 64 patients for further analysis.

Results

The median time-interval from onset of symptoms to surgery was 47 days (interquartile range 32-65 days). Five of 64 patients (4.5%) had a carotid endarterectomy within 14 days. Median time from onset of symptoms to presentation to health services was one day (IQR 0-7 days), from presentation to health services to neurovascular clinic was 16 days (IQR 10-23 days), from neurovascular clinic to vascular surgery clinic was 13 days (IQR 9-24 days), and from vascular surgery clinic to operation was 13 days (IQR 8-22 days). Fifteen of the 51 patients (29%) attending a neurovascular clinic and five of the 57 patients (9%) attending a vascular surgery clinic were seen within 14 days.

Conclusion

The fourteen-day target is difficult to achieve due to the number of steps in the referral pathway. This delay may be jeopardising outcome. Reduction in the delay to surgery would require a multi-disciplinary approach and should involve education of the general public.