Oncogenic β-catenin triggers an inflammatory response that determines the aggressiveness of hepatocellular carcinoma in mice

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Its pathogenesis is frequently linked to liver inflammation. Gain-of-function mutations in the gene encoding β-catenin are frequent genetic modifications found in human HCCs. Thus, we investigated whether inflammation was a component of β-catenin-induced tumorigenesis using genetically modified mouse models that recapitulated the stages of initiation and progression of this tumoral process. Oncogenic β-catenin signaling was found to induce an inflammatory program in hepatocytes that involved direct transcriptional control by β-catenin and activation of the NF-κB pathway. This led to a specific inflammatory response, the intensity of which determined the degree of tumor aggressiveness. The chemokine-like chemotactic factor leukocyte cell-derived chemotaxin 2 (LECT2) and invariant NKT (iNKT) cells were identified as key interconnected effectors of liver β-catenin-induced inflammation. In genetic deletion models lacking the gene encoding LECT2 or iNKT cells, hepatic β-catenin signaling triggered the formation of highly malignant HCCs with lung metastasis. Thus, our results identify inflammation as a key player in β-catenin-induced liver tumorigenesis. We provide strong evidence that, by activating pro- and antiinflammatory mediators, β-catenin signaling produces an inflammatory microenvironment that has an impact on tumoral development. Our data are consistent with the fact that most β-catenin-activated HCCs are of better prognosis.

T-cell factor 4 and β-catenin chromatin occupancies pattern zonal liver metabolism in mice

β-catenin signaling can be both a physiological and oncogenic pathway in the liver. It controls compartmentalized gene expression, allowing the liver to ensure its essential metabolic function. It is activated by mutations in 20%-40% of hepatocellular carcinomas (HCCs) with specific metabolic features. We decipher the molecular determinants of β-catenin-dependent zonal transcription using mice with β-catenin-activated or -inactivated hepatocytes, characterizing in vivo their chromatin occupancy by T-cell factor (Tcf)-4 and β-catenin, transcriptome, and metabolome. We find that Tcf-4 DNA bindings depend on β-catenin. Tcf-4/β-catenin binds Wnt-responsive elements preferentially around β-catenin-induced genes. In contrast, genes repressed by β-catenin bind Tcf-4 on hepatocyte nuclear factor 4 (Hnf-4)-responsive elements. β-Catenin, Tcf-4, and Hnf-4α interact, dictating β-catenin transcription, which is antagonistic to that elicited by Hnf-4α. Finally, we find the drug/bile metabolism pathway to be the one most heavily targeted by β-catenin, partly through xenobiotic nuclear receptors.

CONCLUSIONS

β-catenin patterns the zonal liver together with Tcf-4, Hnf-4α, and xenobiotic nuclear receptors. This network represses lipid metabolism and exacerbates glutamine, drug, and bile metabolism, mirroring HCCs with β-catenin mutational activation.

Micro-RNA profiles in osteosarcoma as a predictive tool for ifosfamide response

Micro-RNAs (miRNA) are currently used as cancer biomarkers for hematological cancers and solid tumors. Osteosarcoma is the first primary malignant bone tumor, characterized by a complex genetic and resistance to conventional treatments. For this latter property, the median survival has not been improved since 1990 despite preoperative administration of chemotherapeutic agents. The prediction of tumor response before chemotherapy treatment would constitute a major progress for this pathology. We assessed in this study if miRNA profiling could surpass the current limitations for osteosarcoma diagnosis. We measured the miRNA expression in different osteosarcoma samples: (i) 27 osteosarcoma paraffin-embedded tumors from patients, (ii) human osteosarcoma cell lines, and (iii) tumors from a syngeneic rat osteosarcoma model, recapitulating human osteosarcoma. miRNA profiles were determined using microfluidic cards performing high-throughput TaqMan(®) -based PCR assays, called TaqMan(®) Low Density Arrays. Osteosarcoma of rat and human origins showed a miRNA signature, which could discriminate good from bad responders. In particular, we identified five discriminating miRNAs (miR-92a, miR-99b, miR-132, miR-193a-5p and miR-422a) in patient tumors, which could be easily transferable to diagnosis. These discriminating miRNAs, as well as those identified in rat, targeted the TGFβ, the Wnt and the MAP kinase pathways. These results indicate that our platform constitutes a potent diagnostic tool to predict tumor sensitivity to a drug in attempt to better adapt treatment to tumor biological specificities and also to identify new potential therapeutic strategies.

β-catenin-activated hepatocellular carcinomas are addicted to fatty acids

OBJECTIVES

CTNNB1-mutated hepatocellular carcinomas (HCCs) constitute a major part of human HCC and are largely inaccessible to target therapy. Yet, little is known about the metabolic reprogramming induced by β-catenin oncogenic activation in the liver. We aimed to decipher such reprogramming and assess whether it may represent a new avenue for targeted therapy of CTNNB1-mutated HCC.

DESIGN

We used mice with hepatocyte-specific oncogenic activation of β-catenin to evaluate metabolic reprogramming using metabolic fluxes on tumourous explants and primary hepatocytes. We assess the role of Pparα in knock-out mice and analysed the consequences of fatty acid oxidation (FAO) using etomoxir. We explored the expression of the FAO pathway in an annotated human HCC dataset.

RESULTS

β-catenin-activated HCC were not glycolytic but intensively oxidised fatty acids. We found that Pparα is a β-catenin target involved in FAO metabolic reprograming. Deletion of Pparα was sufficient to block the initiation and progression of β-catenin-dependent HCC development. FAO was also enriched in human CTNNB1-mutated HCC, under the control of the transcription factor PPARα.

CONCLUSIONS

FAO induced by β-catenin oncogenic activation in the liver is the driving force of the β-catenin-induced HCC. Inhibiting FAO by genetic and pharmacological approaches blocks HCC development, showing that inhibition of FAO is a suitable therapeutic approach for CTNNB1-mutated HCC.

Various phosphorylation pathways, depending on agonist and antagonist binding to endogenous estrogen receptor alpha (ERalpha), differentially affect ERalpha extractability, proteasome-mediated stability, and transcriptional activity in human breast cancer cells

Estrogen receptor-alpha (ER) is down-regulated in the presence of its cognate ligand, estradiol (E2), as well as in the presence of antiestrogens, through the ubiquitin proteasome pathway. Here, we show that, at pharmacological concentrations, the degradation rate of pure antagonist/endogenous ER complexes from human breast cancer MCF-7 cells is 10 times faster than that of ER-E2 complexes, while 4-hydroxy-tamoxifen (4-OH-T)-ER complexes are stable. Whereas pure antagonist-ER complexes are firmly bound to a nuclear compartment from which they are not extractable, the 4-OH-T-ER accumulates in a soluble cell compartment. No difference was observed in the fate of ER whether bound to pure antiestrogens ICI 182,780 or RU 58668. Cycloheximide experiments showed that, while the proteasome-mediated destruction of E2-ER (unlike that of RU 58668- and ICI 182,780-ER) complexes could implicate (or not) a protein synthesis-dependent process, both MAPKs (p38 and ERKs p44 and p42) are activated. By using a panel of kinase inhibitors/activators to study the impact of phosphorylation pathways on ER degradation, we found that protein kinase C is an enhancer of proteasome-mediated degradation of both ligand-free and ER bound to either E2, 4-OH-T, and pure antagonists. On the contrary, protein kinase A, MAPKs, and phosphatidyl-inositol-3 kinase all impede proteasome-mediated destruction of ligand free and E2-bound ER while only MAPKs inhibit the degradation of pure antiestrogens/ER species. In addition, no correlation was found between the capacity of kinase inhibitors to affect ER stability and the basal or E2-induced transcription. These results suggest that, in MCF-7 breast cancer cells, ER turnover, localization, and activity are maintained by an equilibrium between various phosphorylation pathways, which are differently modulated by ER ligands and protein kinases.

Antitumour activity of an inhibitor of miR-34a in liver cancer with β-catenin-mutations

OBJECTIVE

Hepatocellular carcinoma (HCC) is the most prevalent primary tumour of the liver. About a third of these tumours presents activating mutations of the β-catenin gene. The molecular pathogenesis of HCC has been elucidated, but mortality remains high, and new therapeutic approaches, including treatments based on microRNAs, are required. We aimed to identify candidate microRNAs, regulated by β-catenin, potentially involved in liver tumorigenesis.

DESIGN

We used a mouse model, in which β-catenin signalling was overactivated exclusively in the liver by the tamoxifen-inducible and Cre-Lox-mediated inactivation of the Apc gene. This model develops tumours with properties similar to human HCC.

RESULTS

We found that miR-34a was regulated by β-catenin, and significantly induced by the overactivation of β-catenin signalling in mouse tumours and in patients with HCC. An inhibitor of miR-34a (locked nucleic acid, LNA-34a) exerted antiproliferative activity in primary cultures of hepatocyte. This inhibition of proliferation was associated with a decrease in cyclin D1 levels, orchestrated principally by HNF-4α, a target of miR-34a considered to act as a tumour suppressor in the liver. In vivo, LNA-34a approximately halved progression rates for tumours displaying β-catenin activation together with an activation of caspases 2 and 3.

CONCLUSIONS

This work demonstrates the key oncogenic role of miR-34a in liver tumours with β-catenin gene mutations. We suggest that patients diagnosed with HCC with β-catenin mutations could be treated with an inhibitor of miR-34a. The potential value of this strategy lies in the modulation of the tumour suppressor HNF-4α, which targets cyclin D1, and the induction of a proapoptotic programme.

Expression of NKG2D ligands is downregulated by β-catenin signalling and associates with HCC aggressiveness

BACKGROUND & AIMS

The NKG2D system is a potent immunosurveillance mechanism in cancer, wherein the activating NK cell receptor (NKG2D) on immune cells recognises its cognate ligands on tumour cells. Herein, we evaluated the expression of NKG2D ligands in hepatocellular carcinoma (HCC), in both humans and mice, taking the genomic features of HCC tumours into account.

METHODS

The expression of NKG2D ligands (MICA, MICB, ULBP1 and ULBP2) was analysed in large human HCC datasets by Fluidigm TaqMan and RNA-seq methods, and in 2 mouse models (mRNA and protein levels) reproducing the features of both major groups of human tumours.

RESULTS

We provide compelling evidence that expression of the MICA and MICB ligands in human HCC is associated with tumour aggressiveness and poor patient outcome. We also found that the expression of ULBP1 and ULBP2 was associated with poor patient outcome, and was downregulated in CTNNB1-mutated HCCs displaying low levels of inflammation and associated with a better prognosis. We also found an inverse correlation between ULBP1/2 expression levels and the expression of β-catenin target genes in patients with HCC, suggesting a role for β-catenin signalling in inhibiting expression. We showed in HCC mouse models that β-catenin signalling downregulated the expression of Rae-1 NKG2D ligands, orthologs of ULBPs, through TCF4 binding.

CONCLUSIONS

We demonstrate that the expression of NKG2D ligands is associated with aggressive liver tumorigenesis and that the downregulation of these ligands by β-catenin signalling may account for the less aggressive phenotype of CTNNB1-mutated HCC tumours.

LAY SUMMARY

The NKG2D system is a potent immunosurveillance mechanism in cancer. However, its role in hepatocellular carcinoma development has not been widely investigated. Herein, we should that the expression of NKG2D ligands by tumour cells is associated with a more aggressive tumour subtype.

Innovative drug delivery nanosystems improve the anti-tumor activity in vitro and in vivo of anti-estrogens in human breast cancer and multiple myeloma

Anticancer drug efficiency is governed by its bioavailability. In order to increase this parameter, we synthesized several injectable and biodegradable systems based on incorporation of anti-estrogens (AEs) in nanoparticles (NPs) and liposomes were synthesized. Both nanospheres (NS) and nanocapsules (NCs, polymers with an oily core in which AEs were solubilized) incorporated high amounts of 4-hydroxy-tamoxifen (4-HT) or RU 58668 (RU). Physico-chemical and biological parameters of these delivery systems, and coupling of polyethylene-glycol chains on the NP surface revealed to enhance the anti-tumoral activity of trapped AEs in a breast cancer MCF-7 cell xenograft model and to induce apoptosis. These features correlated with an augmentation of p21(Waf-1/Cip1) and of p27(Kip1) and a concomitant decrease of cyclin D1 and E in tumor extracts. Liposomes containing various ratios of lipids enhanced the apoptotic activity of RU in several multiple myeloma (MM) cell lines tested by flow cytometry. MM cell lines expressed both estrogen receptor alpha and beta subtypes except Karpas 620. Karpas 620 cells which did not respond to AEs became responsive following ER cDNA transfection. A new MM xenograft model was generated after s.c. injection of RPMI 8226 cells in nude mice. RU-loaded liposomes, administered i.v. in this model, at a dose of 12mgRU/kg/week, induced the arrest of tumor growth contrary to free RU or to empty liposomes. Thus, the drug delivery of anti-estrogens enhances their ability to arrest the growth of tumors which express estrogen receptors and are of particular interest for estrogen-dependent breast cancer treatment. In addition it represents a new potent therapeutic approach for multiple myeloma.

Oestrogen receptors pathways to oestrogen responsive elements: the transactivation function-1 acts as the keystone of oestrogen receptor (ER)beta-mediated transcriptional repression of ERalpha

Oestrogen receptors (ER)alpha and beta modify the expression of genes involved in cell growth, proliferation and differentiation through binding to oestrogen response elements (EREs) located in a number of gene promoters. Transient transfection of different luciferase reporter vectors 3xEREs-Vit, 2xEREs-tk and ERE-C3 showed that the transactivation capacity of both ER subtypes was influenced by 1) the nature of the inducer (oestradiol (E2), phyto- and anti-oestrogen (AE)), 2) the structure of the promoter (nucleotidic sequence, number of ERE, length of the promoter sequence) and 3) the cell line (containing endogenous ER (MCF-7) or in which ER was stably expressed (MDA-MB-231-HE-5 (ERalpha+) or MDA-MB-231-HERB (ERbeta+)). ER subtype did not display the same efficacy on the different constructions in the presence of E2 and of AE according to the cell (e.g. in MCF-7 cells: tk>>Vit>>C3 approximately 0 while in MDA-MB-231 cells: Vit>>tk approximately C3). E2 response was higher in MCF-7 cells, probably due to higher ER expression level (maximal at 10(-10)M instead of 10(-8)M for E2 in HE-5 cells). Finally, the same ligand could exert opposite activities on the same promoter according to the ER isoform expressed: in the MDA-MB-231 cells, AE acted as inducers of the C3 promoter via ERbeta whereas ERalpha/AE complexes down-regulated this promoter. Approximately 70% of breast tumours express ER and most tumour cells coexpress both ER isotypes. Thus, different types of ER dimers can be formed in such tumours (ERbeta or ERalpha homodimers or ERalpha/ERbeta heterodimers). We therefore studied the influence of the coexistence of the two ERs on the ligand-induced transcriptional process following transient transfection of ERalpha in ERbeta+ cells, and inversely ERbeta in ERalpha+ cells. ERbeta-transfection inhibited the E2- and genistein-induced ERalpha-dependent transcription on all promoters in all cell lines except C3 in MCF-7; this inhibitory effect was lost following transfection of ERbeta deleted of its AF-1 (ERbeta-AF-2). These results suggest that the dominant negative properties of ERbeta are mainly due to its AF-1 function. Interestingly, transfection of an ERbeta-AF-2 construct into MCF-7 cells potentiated the transcription inhibitory capacity of 4-OH-tamoxifen (OHT) on the Vit and tk promoters. Thus, (1) OHT exerts an agonistic activity through the AF-1 function of ER and (2) expression of ERbeta in breast cancer cells seems to favour the AE treatment. Contrary to ERbeta, ERalpha-transfection had little effect on ERbeta transactivation capacity in HERB cells. Finally, the ratio ERalpha/ERbeta constitutes one decisive parameters to orientate the transcriptional mechanism of a target gene in the presence of agonist as well as of antagonist ligands.

Estrogen receptor alpha and beta subtype expression and transactivation capacity are differentially affected by receptor-, hsp90- and immunophilin-ligands in human breast cancer cells

In MCF-7 (estrogen receptor (ER)+) and in MDA-MB-231 (ER-) cells stably transfected with either estrogen receptor alpha (ERalpha) or beta (ERbeta) subtype (MDA-MB-231 stably transfected with the mouse ERalpha cDNA (MERA) and MDA-MB-231 stably transfected with the human ERbeta cDNA (HERB), respectively) N-term heat shock protein of 90kDa (hsp90) ligands (geldanamycin and radicicol) and C-term hsp90 ligands (novobiocin) decrease the basal and estradiol (E(2))-induced transcription activity of ER on an estrogen responsive element (ERE)-LUC reporter construct concomitantly with or 1h after E(2) treatment. All hsp90 ligands induced an E(2)- and MG132-inhibited decrease of both ER cell content. However, the kinetics of these degradations are slower than those induced by the selective estrogen receptor down-regulator RU 58668 (RU). This suggests that inhibition of the hsp90 ATPase activity targets both ERs to the 26S proteasome and that hsp90 interacts with both ER subtypes. Rapamycin (Rapa) and cyclosporin A (CsA), ligands of immunophilins FK506 binding protein (FKBP52) and cyclophilin of 40kDa (CYP40) interacting in separate ER-hsp90 complexes, both induced a proteasomal-mediated degradation of ERs but not of their cognate immunophilin. Moreover, they also decrease the E(2)-induced luciferase transcription but weaker than RU and hsp90 ligands. Fluorescence activated cell sorter (FACS) analysis revealed a blockade of cell progression by RU and 4-hydroxy-tamoxifen at the G(1) phase of the cell cycle and an induction of apoptosis in MCF-7 cells. Rapa and mainly CsA (but not FK506) and hsp90 ligands promote by their own apoptosis in MCF-7, in MERA, and in HERB cells and in MDA-MB-231 ER-null cells. These data suggest that (1) hsp90, as for all steroid receptors, acts as a molecular chaperone for ERbeta; (2) ER-ligands (except tamoxifen), hsp90- and immunophilin-ligands (except FK506) target the two ER subtypes to a proteasome-mediated proteolysis via different signalling pathways; (3) hsp90- and immunophilin-ligands Rapa and CsA, alone or in association with anti-estrogens such as RU, may constitute a potential therapeutic strategy for breast cancer treatment.

Hepatocellular Carcinomas With Mutational Activation of Beta-Catenin Require Choline and Can Be Detected by Positron Emission Tomography

BACKGROUND & AIMS

In one-third of hepatocellular carcinomas (HCCs), cancer cells have mutations that activate β-catenin pathway. These cells have alterations in glutamine, bile, and lipid metabolism. We investigated whether positron emission tomography (PET) imaging allows identification of altered metabolic pathways that might be targeted therapeutically.

METHODS

We studied mice with activation of β-catenin in liver (Apcko-liv mice) and male C57Bl/6 mice given injections of diethylnitrosamine, which each develop HCCs. Mice were fed a conventional or a methionine- and choline-deficient diet or a choline-deficient (CD) diet. Choline uptake and metabolism in HCCs were analyzed by micro-PET imaging of mice; livers were collected and analyzed by histologic, metabolomic, messenger RNA quantification, and RNA-sequencing analyses. Fifty-two patients with HCC underwent PET imaging with 18F-fluorodeoxyglucose, followed by 18F-fluorocholine tracer metabolites. Human HCC specimens were analyzed by immunohistochemistry, quantitative polymerase chain reaction, and DNA sequencing. We used hepatocytes and mouse tumor explants for studies of incorporation of radiolabeled choline into phospholipids and its contribution to DNA methylation. We analyzed HCC progression in mice fed a CD diet.

RESULTS

Livers and tumors from Apcko-liv mice had increased uptake of dietary choline, which contributes to phospholipid formation and DNA methylation in hepatocytes. In patients and in mice, HCCs with activated β-catenin were positive in 18F-fluorocholine PET, but not 18F-fluorodeoxyglucose PET, and they overexpressed the choline transporter organic cation transporter 3. The HCC cells from Apcko-liv mice incorporated radiolabeled methyl groups of choline into phospholipids and DNA. In Apcko-liv mice, the methionine- and choline-deficient diet reduced proliferation and DNA hypermethylation of hepatocytes and HCC cells, and the CD diet reduced long-term progression of tumors.

CONCLUSIONS

In mice and humans, HCCs with mutations that activate β-catenin are characterized by increased uptake of a fluorocholine tracer, but not 18F-fluorodeoxyglucose, revealed by PET. The increased uptake of choline by HCCs promotes phospholipid formation, DNA hypermethylation, and hepatocyte proliferation. In mice, the CD diet reverses these effects and promotes regression of HCCs that overexpress β-catenin.

Deleting the β-catenin degradation domain in mouse hepatocytes drives hepatocellular carcinoma or hepatoblastoma-like tumor growth

BACKGROUND & AIMS

One-third of hepatocellular carcinomas (HCCs) harbor mutations activating the β-catenin pathway, predominantly via mutations in the CTNNB1 gene itself. Mouse models of Apc loss-of-function are widely used to mimic β-catenin-dependent tumorigenesis. Given the low prevalence of APC mutations in human HCCs, we aimed to generate liver tumors through CTNNB1 exon 3 deletion (βcatΔex3). We then compared βcatΔex3 liver tumors with liver tumors generated via frameshift in exon 15 of Apc (Apcfs-ex15).

METHODS

We used hepatocyte-specific and inducible mouse models generated through either a Cre-Lox or a CRISPR/Cas9 approach using adeno-associated virus vectors. Tumors generated by the Cre-Lox models were phenotypically analyzed using immunohistochemistry and were selected for transcriptomic analysis by RNA-sequencing (RNAseq). Mouse RNAseq data were compared to human RNAseq data (8 normal tissues, 48 HCCs, 9 hepatoblastomas) in an integrative analysis. Tumors generated via CRISPR were analyzed using DNA sequencing and immuno-histochemistry.

RESULTS

Mice with CTNNB1 exon 3 deletion in hepatocytes developed liver tumors indistinguishable from Apcfs-ex15 liver tumors. Both Apcfs-ex15 and βcatΔex3 mouse models induced growth of phenotypically distinct tumors (differentiated or undifferentiated). Integrative analysis of human and mouse tumors showed that differentiated mouse tumors cluster with well-differentiated human CTNNB1-mutated tumors. Conversely, undifferentiated mouse tumors cluster with human mesenchymal hepatoblastomas and harbor activated YAP signaling.

CONCLUSION

Apcfs-ex15 and βcatΔex3 mouse models both induce growth of tumors that are transcriptionally similar to either well-differentiated and β-catenin-activated human HCCs or mesenchymal hepatoblastomas.

LAY SUMMARY

New and easy-to-use transgenic mouse models of primary liver cancers have been generated, with mutations in the gene encoding beta-catenin, which are frequent in both adult and pediatric primary liver cancers. The mice develop both types of cancer, constituting a strong preclinical model.

Lymphoma and myeloma cell resistance to cytotoxic agents and ionizing radiations is not affected by exposure to anti-IL-6 antibody

BACKGROUND

Production of high levels of IL-6 is often correlated with resistance to cytotoxics or ionizing radiations, in cancer cell lines as in various cancer patients. We investigated whether monoclonal antibodies directed against IL-6 may enable to reverse resistance of cancer cell lines.

METHODOLOGY/PRINCIPAL FINDINGS

We exposed ten haematological cancer cells from lymphoma, myeloma, or leukemia origins to cytotoxics or ionizing radiations and assessed the effects of anti-IL-6 antibody addition on cell proliferation, apoptosis, or IL-6 signaling. A strong correlation between IL-6 secretion, measured by ELISA, and resistance to doxorubicin as ionizing radiations was observed in the multiple myeloma U266 and the Burkitt's lymphoma Daudi and Namalwa cells. Although an anti-IL-6 antibody combined to both treatments efficiently blocked IL-6 signaling in U266 cells, expressing the IL-6 receptor gp80, it did not increase treatment-induced anti-proliferative and pro-apoptotic effects on these cells, as well as on Daudi and Namalwa cells. This lack of effect could be related to diverse factors: 1) a higher release of the soluble form of IL-6 receptor gp80 in response to doxorubicin and irradiation from all cell lines, 2) an impaired level of the IL-6 pathway inhibitor SOCS3 in Daudi cells, and 3) an increased release of IL-10 and TNFalpha, two cytokines involved in cell radio- and chemoresistance.

CONCLUSIONS/SIGNIFICANCE

These data support the fact that IL-6 is not the preponderant actor of cell resistance to cytotoxics and ionizing radiations, which seems to be regulated by a complex network of proteins.

miRNA Profiling: How to Bypass the Current Difficulties in the Diagnosis and Treatment of Sarcomas

Sarcomas are divided into a group with specific alterations and a second presenting a complex karyotype, sometimes difficult to diagnose or with few therapeutic options available. We assessed if miRNA profiling by TaqMan low density arrays could predict the response of undifferentiated rhabdomyosarcoma (RMS) and osteosarcoma to treatment. We showed that miRNA signatures in response to a therapeutic agent (chemotherapy or the mTOR inhibitor RAD-001) were cell and drug specific on cell lines and a rat osteosarcoma model. This miRNA signature was related to cell or tumour sensitivity to this treatment and might be not due to chromosomal aberrations, as revealed by a CGH array analysis of rat tumours. Strikingly, miRNA profiling gave promising results for patient rhabdomyosarcoma, discriminating all types of RMS: (Pax+) or undifferentiated alveolar RMS as well as embryonal RMS. As highlighted by these results, miRNA profiling emerges as a potent molecular diagnostic tool for complex karyotype sarcomas.

[microRNA: new diagnostic and therapeutic tools in liver disease?]

microRNA are small non coding RNA, which negatively regulate the expression of their targets. Due to their various targets, miRNAs play a key role in number of physiological processes and in oncogenesis. The identification of specific miRNA signatures in various types of tumours, including hepatocellular carcinoma (HCC), highlights the dual role of miRNA, both oncogenes and tumour suppressors. Here, we review the current knowledge concerning the deregulation of miRNA expression in liver disease. All studies focusing on miRNAs argue for their possible use as diagnostic, prognostic and therapeutic markers. Here, we preferentially discuss the promising therapeutic strategies based on miRNAs that have been tested in HCC.

MicroRNA-feedback loop as a key modulator of liver tumorigenesis and inflammation

A recent work of Iliopoulos et al published in Cell highlighted a circuit orchestrated by microRNAs (miRNAs) that results in liver tumorigenesis and inflammation. This feedback loop, governed by miR-24 and miR-629, promotes a hepatocyte nuclear factor-4α transient inhibition resulting in miR-124 induction and signal transducer and activator of transcription 3 activation. These promising data support the use of miRNA mimics or inhibitors as potent therapeutic approaches in liver cancer.

Exosomal microRNAs as a potential therapeutic strategy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the second cause of cancer-related death worldwide. The incidence of HCC is constantly increasing in correlation with the rise in diabetes and obesity, arguing for an urgent need for new developments in the treatment of this lethal cancer. Exosomes are small double-membrane vesicles loaded with distinct cargos, particularly small non-coding RNAs called microRNAs, representative of each donor cell and secreted to affect the features of neighboring cells or recipient cells located further away, like in the case of metastasis. A better understanding of the role of exosomes with a microRNA signature in cancer pathogenesis gave rise to the concept of their use as a non-invasive diagnostic biomarker and in the treatment of cancer, including HCC. In this communication, we review recent works that demonstrate that hepatic stellate cells establish an epigenetic communication with liver cancer cells, which affects their pro-malignant features. If naturally secreted patient-derived exosomes show major limitations concerning their clinical use, bio-engineered exosome mimetics that incorporate controlled components and exhibit no protumoral properties could be promising carriers for the treatment of liver cancers, which is the organ preferentially targeted by systemic injection of exosomes.

Epigenetic mechanisms of liver tumor resistance to immunotherapy

Hepatocellular carcinoma (HCC) is the most common primary liver tumor, which stands fourth in rank of cancer-related deaths worldwide. The incidence of HCC is constantly increasing in correlation with the epidemic in diabetes and obesity, arguing for an urgent need for new treatments for this lethal cancer refractory to conventional treatments. HCC is the paradigm of inflammation-associated cancer, since more than 80% of HCC emerge consecutively to cirrhosis associated with a vast remodeling of liver microenvironment. In the recent decade, immunomodulatory drugs have been developed and have given impressive results in melanoma and later in several other cancers. In the present review, we will discuss the recent advancements concerning the use of immunotherapies in HCC, in particular those targeting immune checkpoints, used alone or in combination with other anti-cancers agents. We will address why these drugs demonstrate unsatisfactory results in a high proportion of liver cancers and the mechanisms of resistance developed by HCC to evade immune response with a focus on the epigenetic-related mechanisms.

Non-coding RNAs open a new chapter in liver cancer treatment

Despite the intensive efforts to identify the molecular events responsible for the emergence of liver cancer, hepatocellular carcinoma (HCC) remains a major health problem in the world. Thus, the identification of new therapeutic opportunities is a short-term necessity. These last few decades, non-coding RNAs appeared as interesting therapeutic strategies with their pleiotropic inhibitory action in the cell itself but also in recipient cells via their secretion into extracellular vesicles. This short review recapitulates recent advancements concerning non-coding RNAs and their deregulations in liver cancer.

The concomitant loss of APC and HNF4α in adult hepatocytes does not contribute to hepatocarcinogenesis driven by β-catenin activation

BACKGROUND & AIMS

Loss of hepatocyte nuclear factor-4α (HNF4α), a critical factor driving liver development and differentiation, is frequently associated with hepatocellular carcinoma (HCC). Our recent data revealed that HNF4α level was decreased in mouse and human HCCs with activated β-catenin signalling. In addition, increasing HNF4α level by miR-34a inhibition slowed tumour progression of β-catenin-activated HCC in mice.

METHODS

We generated a Hnf4aflox/flox/ Apcflox/flox /TTR-CreERT2 (Hnf4a/Apc∆Hep ) mouse line and evaluated the impact of Hnf4a disruption on HCC development and liver homoeostasis.

RESULTS

There was no significant impact of Hnf4a disruption on tumour onset and progression in Apc∆Hep model. However, we observed an unexpected phenotype in 28% of Hnf4a∆Hep mice maintained in a conventional animal facility, which presented disorganized portal triads, characterized by stenosis of the portal vein and increased number and size of hepatic arteries and bile ducts. These abnormal portal structures resemble the human idiopathic non-cirrhotic portal hypertension syndrome. We correlated the presence of portal remodelling with a higher expression of protein and mRNA levels of TGFβ and BMP7, a key regulator of the TGFβ-dependent endothelial-to-mesenchymal transition.

CONCLUSION

These data demonstrate that HNF4α does not play a major role during β-catenin-driven HCC, thus revealing that the tumour suppressor role of HNF4α is far more complex and dependent probably on its temporal expression and tumour context. However, HNF4α loss in adult hepatocytes could induce abnormal portal structures resembling the human idiopathic non-cirrhotic portal hypertension syndrome, which may result from endothelial- and epithelial-to-mesenchymal transitions.

ARID1A loss in adult hepatocytes activates β-catenin-mediated erythropoietin transcription

Erythropoietin (EPO) is a key regulator of erythropoiesis. The embryonic liver is the main site of erythropoietin synthesis, after which the kidney takes over. The adult liver retains the ability to express EPO, and we discovered here new players of this transcription, distinct from the classical hypoxia-inducible factor pathway. In mice, genetically invalidated in hepatocytes for the chromatin remodeler Arid1a, and for Apc, the major silencer of Wnt pathway, chromatin was more accessible and histone marks turned into active ones at the Epo downstream enhancer. Activating β-catenin signaling increased binding of Tcf4/β-catenin complex and upregulated its enhancer function. The loss of Arid1a together with β-catenin signaling, resulted in cell-autonomous EPO transcription in mouse and human hepatocytes. In mice with Apc-Arid1a gene invalidations in single hepatocytes, Epo de novo synthesis led to its secretion, to splenic erythropoiesis and to dramatic erythrocytosis. Thus, we identified new hepatic EPO regulation mechanism stimulating erythropoiesis.