Abstract Although patients benefit from immune checkpoint inhibition (ICI) therapy in a broad variety of tumors, resistance may arise from immune suppressive tumor microenvironments (TME), which is ...particularly true of hepatocellular carcinoma (HCC). Since oncolytic viruses (OV) can generate a highly immune-infiltrated, inflammatory TME, OVs could potentially restore ICI responsiveness via recruitment, priming, and activation of anti-tumor T cells. Here we find that on the contrary, an oncolytic vesicular stomatitis virus, expressing interferon-ß (VSV-IFNß), antagonizes the effect of anti-PD-L1 therapy in a partially anti-PD-L1-responsive model of HCC. Cytometry by Time of Flight shows that VSV-IFNß expands dominant anti-viral effector CD8 T cells with concomitant relative disappearance of anti-tumor T cell populations, which are the target of anti-PD-L1. However, by expressing a range of HCC tumor antigens within VSV, combination OV and anti-PD-L1 therapeutic benefit could be restored. Our data provide a cautionary message for the use of highly immunogenic viruses as tumor-specific immune-therapeutics by showing that dominant anti-viral T cell responses can inhibit sub-dominant anti-tumor T cell responses. However, through encoding tumor antigens within the virus, oncolytic virotherapy can generate anti-tumor T cell populations upon which immune checkpoint blockade can effectively work.
Cholestatic liver diseases result from impaired bile flow and are characterized by inflammation, atypical ductular proliferation, and fibrosis. The Wnt/β‐catenin pathway plays a role in bile duct ...development, yet its role in cholestatic injury remains indeterminate. Liver‐specific β‐catenin knockout mice and wild‐type littermates were subjected to cholestatic injury through bile duct ligation or short‐term exposure to 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine diet. Intriguingly, knockout mice exhibit a dramatic protection from liver injury, fibrosis, and atypical ductular proliferation, which coincides with significantly decreased total hepatic bile acids (BAs). This led to the discovery of a role for β‐catenin in regulating BA synthesis and transport through regulation of farnesoid X receptor (FXR) activation. We show that β‐catenin functions as both an inhibitor of nuclear translocation and a nuclear corepressor through formation of a physical complex with FXR. Loss of β‐catenin expedited FXR nuclear localization and FXR/retinoic X receptor alpha association, culminating in small heterodimer protein promoter occupancy and activation in response to BA or FXR agonist. Conversely, accumulation of β‐catenin sequesters FXR, thus inhibiting its activation. Finally, exogenous suppression of β‐catenin expression during cholestatic injury reduces β‐catenin/FXR complex activation of FXR to decrease total BA and alleviate hepatic injury. Conclusion: We have identified an FXR/β‐catenin interaction whose modulation through β‐catenin suppression promotes FXR activation and decreases hepatic BAs, which may provide unique therapeutic opportunities in cholestatic liver diseases. (Hepatology 2018;67:955–971)
Liver‐specific β‐catenin knockout (β‐Catenin‐LKO) mice have revealed an essential role of β‐catenin in metabolic zonation where it regulates pericentral gene expression and in initiating liver ...regeneration (LR) after partial hepatectomy (PH), by regulating expression of Cyclin‐D1. However, what regulates β‐catenin activity in these events remains an enigma. Here we investigate to what extent β‐catenin activation is Wnt‐signaling‐dependent and the potential cell source of Wnts. We studied liver‐specific Lrp5/6 KO (Lrp‐LKO) mice where Wnt‐signaling was abolished in hepatocytes while the β‐catenin gene remained intact. Intriguingly, like β‐catenin‐LKO mice, Lrp‐LKO exhibited a defect in metabolic zonation observed as a lack of glutamine synthetase (GS), Cyp1a2, and Cyp2e1. Lrp‐LKO also displayed a significant delay in initiation of LR due to the absence of β‐catenin‐TCF4 association and lack of Cyclin‐D1. To address the source of Wnt proteins in liver, we investigated conditional Wntless (Wls) KO mice, which lacked the ability to secrete Wnts from either liver epithelial cells (Wls‐LKO), or macrophages including Kupffer cells (Wls‐MKO), or endothelial cells (Wls‐EKO). While Wls‐EKO was embryonic lethal precluding further analysis in adult hepatic homeostasis and growth, Wls‐LKO and Wls‐MKO were viable but did not show any defect in hepatic zonation. Wls‐LKO showed normal initiation of LR; however, Wls‐MKO showed a significant but temporal deficit in LR that was associated with decreased β‐catenin‐TCF4 association and diminished Cyclin‐D1 expression. Conclusion: Wnt‐signaling is the major upstream effector of β‐catenin activity in pericentral hepatocytes and during LR. Hepatocytes, cholangiocytes, or macrophages are not the source of Wnts in regulating hepatic zonation. However, Kupffer cells are a major contributing source of Wnt secretion necessary for β‐catenin activation during LR. (Hepatology 2014;60:964–976)
The incidence of hepatocellular cancer (HCC) is gradually rising. HCC occurs as a sequela to various chronic liver diseases and ensuing cirrhosis. There have been many therapies approved for ...unresectable HCC in the last 5 years, including immune checkpoint inhibitors, and the overall
response rates have improved. However, there are many cases that do not respond, and personalized medicine is lacking, making HCC an unmet clinical need. Generation of appropriate animal models have been key to our understanding of HCC. Based on the overall concept of hepatocarcinogenesis,
two major categories of animal models are discussed herein that can be useful to address specific questions. One category is described as the outside-in model of HCC and is based on the premise that it takes decades of hepatocyte injury, death, wound healing, and regeneration to eventually
lead to DNA damage and mutations in a hepatocyte, which initiates tumorigenesis. Several animal models have been generated, which attempt to recapitulate this complex tissue damage and cellular interplay through genetics, diets, and toxins. The second category is the inside-out model of HCC,
where clinically relevant genes can be coexpressed in a small subset of hepatocytes to yield a tumor, which matches HCC subsets in gene expression. This model has been made possible in part by the widely available molecular characterization of HCC, and in part by modalities like sleeping beauty
transposon/transposase, Crispr/Cas9, and hydrodynamic tail vein injection. These two categories of HCC have distinct pros and cons, which are discussed in this Thinking Out Loud article.
Although the role of Wnt/β-catenin signaling in liver growth and development is well established, its contribution in non-neoplastic hepatic pathologies has not been investigated. Here, we examine ...the role of β-catenin in a murine model of diet-induced liver injury. Mice with hepatocyte-specific β-catenin deletion (KO) and littermate controls were fed the steatogenic methionine and choline-deficient (MCD) diet or the corresponding control diet for 2 weeks and characterized for histological, biochemical, and molecular changes. KO mice developed significantly higher steatohepatitis and fibrosis on the MCD diet compared with wild-type mice. Both wild-type and KO livers accumulated triglyceride on the MCD diet but, unexpectedly, higher hepatic cholesterol levels were observed in KO livers on both control and MCD diets. Gene expression analysis showed that hepatic cholesterol accumulation in KO livers was not attributable to increased synthesis or uptake. KO mice had lower expression of bile acid synthetic enzymes but exhibited higher hepatic bile acid and serum bilirubin levels, suggesting defects in bile export. Therefore, loss of β-catenin in the liver leads to defective cholesterol and bile acid metabolism in the liver and increased susceptibility to developing steatohepatitis in the face of metabolic stress.
Upon liver injury in which hepatocyte proliferation is compromised, liver progenitor cells (LPCs), derived from biliary epithelial cells (BECs), differentiate into hepatocytes. Little is known about ...the mechanisms of LPC differentiation. We used zebrafish and mouse models of liver injury to study the mechanisms.
We used transgenic zebrafish, Tg(fabp10a:CFP-NTR), to study the effects of compounds that alter epigenetic factors on BEC-mediated liver regeneration. We analyzed zebrafish with disruptions of the histone deacetylase 1 gene (hdac1) or exposed to MS-275 (an inhibitor of Hdac1, Hdac2, and Hdac3). We also analyzed zebrafish with mutations in sox9b, fbxw7, kdm1a, and notch3. Zebrafish larvae were collected and analyzed by whole-mount immunostaining and in situ hybridization; their liver tissues were collected for quantitative reverse transcription polymerase chain reaction. We studied mice in which hepatocyte-specific deletion of β-catenin (Ctnnb1flox/flox mice injected with Adeno-associated virus serotype 8 AAV8-TBG-Cre) induces differentiation of LPCs into hepatocytes after a choline-deficient, ethionine-supplemented (CDE) diet. Liver tissues were collected and analyzed by immunohistochemistry and immunoblots. We performed immunohistochemical analyses of liver tissues from patients with compensated or decompensated cirrhosis or acute on chronic liver failure (n = 15).
Loss of Hdac1 activity in zebrafish blocked differentiation of LPCs into hepatocytes by increasing levels of sox9b mRNA and reduced differentiation of LPCs into BECs by increasing levels of cdk8 mRNA, which encodes a negative regulator gene of Notch signaling. We identified Notch3 as the receptor that regulates differentiation of LPCs into BECs. Loss of activity of Kdm1a, a lysine demethylase that forms repressive complexes with Hdac1, produced the same defects in differentiation of LPCs into hepatocytes and BECs as observed in zebrafish with loss of Hdac1 activity. Administration of MS-275 to mice with hepatocyte-specific loss of β-catenin impaired differentiation of LPCs into hepatocytes after the CDE diet. HDAC1 was expressed in reactive ducts and hepatocyte buds of liver tissues from patients with cirrhosis.
Hdac1 regulates differentiation of LPCs into hepatocytes via Sox9b and differentiation of LPCs into BECs via Cdk8, Fbxw7, and Notch3 in zebrafish with severe hepatocyte loss. HDAC1 activity was also required for differentiation of LPCs into hepatocytes in mice with liver injury after the CDE diet. These pathways might be manipulated to induce LPC differentiation for treatment of patients with advanced liver diseases.
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β‐Catenin, the central component of the canonical Wnt pathway, plays important roles in the processes of liver regeneration, growth, and cancer. Previously, we identified temporal expression of ...β‐catenin during liver development. Here, we characterize the hepatic phenotype, resulting from the successful deletion of β‐catenin in the developing hepatoblasts utilizing Foxa3‐cyclization recombination and floxed‐β‐catenin (exons 2 through 6) transgenic mice. β‐Catenin loss in developing livers resulted in significantly underdeveloped livers after embryonic day 12 (E12) with lethality occurring at around E17 stages. Histology revealed an overall deficient hepatocyte compartment due to (1) increased cell death due to oxidative stress and apoptosis, and (2) diminished expansion secondary to decreased cyclin‐D1 and impaired proliferation. Also, the remnant hepatocytes demonstrated an immature phenotype as indicated by high nuclear to cytoplasmic ratio, poor cell polarity, absent glycogen, and decreased expression of key liver‐enriched transcription factors: CCAAT‐enhancer binding protein‐α and hepatocyte nuclear factor‐4α. A paucity of primitive bile ducts was also observed. While the stem cell assays demonstrated no intrinsic defect in hematopoiesis, distorted hepatic architecture and deficient hepatocyte compartments resulted in defective endothelial cell organization leading to overall fetal pallor. Conclusion: β‐Catenin regulates multiple, critical events during the process of hepatic morphogenesis, including hepatoblast maturation, expansion, and survival, making it indispensable to survival. (HEPATOLOGY 2008.)
PD-1 immune checkpoint inhibitors have produced encouraging results in patients with hepatocellular carcinoma (HCC). However, what determines resistance to anti-PD-1 therapies is unclear. We created ...a novel genetically engineered mouse model of HCC that enables interrogation of how different genetic alterations affect immune surveillance and response to immunotherapies. Expression of exogenous antigens in
HCCs led to T cell-mediated immune surveillance, which was accompanied by decreased tumor formation and increased survival. Some antigen-expressing
HCCs escaped the immune system by upregulating the β-catenin (CTNNB1) pathway. Accordingly, expression of exogenous antigens in
HCCs had no effect, demonstrating that β-catenin promoted immune escape, which involved defective recruitment of dendritic cells and consequently impaired T-cell activity. Expression of chemokine CCL5 in antigen-expressing
HCCs restored immune surveillance. Finally, β-catenin-driven tumors were resistant to anti-PD-1. In summary, β-catenin activation promotes immune escape and resistance to anti-PD-1 and could represent a novel biomarker for HCC patient exclusion. SIGNIFICANCE: Determinants of response to anti-PD-1 immunotherapies in HCC are poorly understood. Using a novel mouse model of HCC, we show that β-catenin activation promotes immune evasion and resistance to anti-PD-1 therapy and could potentially represent a novel biomarker for HCC patient exclusion.
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Hepatic repair is directed chiefly by the proliferation of resident mature epithelial cells. Furthermore, if predominant injury is to cholangiocytes, the hepatocytes can transdifferentiate to ...cholangiocytes to assist in the repair and vice versa, as shown by various fate‐tracing studies. However, the molecular bases of reprogramming remain elusive. Using two models of biliary injury where repair occurs through cholangiocyte proliferation and hepatocyte transdifferentiation to cholangiocytes, we identify an important role of Wnt signaling. First we identify up‐regulation of specific Wnt proteins in the cholangiocytes. Next, using conditional knockouts of Wntless and Wnt coreceptors low‐density lipoprotein‐related protein 5/6, transgenic mice expressing stable β‐catenin, and in vitro studies, we show a role of Wnt signaling through β‐catenin in hepatocyte to biliary transdifferentiation. Last, we show that specific Wnts regulate cholangiocyte proliferation, but in a β‐catenin‐independent manner. Conclusion: Wnt signaling regulates hepatobiliary repair after cholestatic injury in both β‐catenin‐dependent and ‐independent manners. (Hepatology 2016;64:1652‐1666)
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