Wnt signaling and hepatocarcinogenesis: Molecular targets for the development of innovative anticancer drugs

SummaryHepatocellular carcinoma (HCC) is one of the most common causes of cancer death worldwide. HCC can be cured by radical therapies if early diagnosis is done while the tumor has remained of small size. Unfortunately, diagnosis is commonly late when the tumor has grown and spread. Thus, palliative approaches are usually applied such as transarterial intrahepatic chemoembolization and sorafenib, an anti-angiogenic agent and MAP kinase inhibitor. This latter is the only targeted therapy that has shown significant, although moderate, efficiency in some individuals with advanced HCC. This highlights the need to develop other targeted therapies, and to this goal, to identify more and more pathways as potential targets. The Wnt pathway is a key component of a physiological process involved in embryonic development and tissue homeostasis. Activation of this pathway occurs when a Wnt ligand binds to a Frizzled (FZD) receptor at the cell membrane. Two different Wnt signaling cascades have been identified, called non-canonical and canonical pathways, the latter involving the β-catenin protein. Deregulation of the Wnt pathway is an early event in hepatocarcinogenesis and has been associated with an aggressive HCC phenotype, since it is implicated both in cell survival, proliferation, migration and invasion. Thus, component proteins identified in this pathway are potential candidates of pharmacological intervention. This review focuses on the characteristics and functions of the molecular targets of the Wnt signaling cascade and how they may be manipulated to achieve anti-tumor effects

Role of lysyl oxidase in hypoxic response and tumor progression of Human colorectal carcinoma

Au sein d’une tumeur des régions hypoxiques se forment ce qui conduit à l’activation du facteur de transcription HIF1. HIF1, composé des deux protéines HIF1a et HIF1b, permet l’adaptation des cellules à des faibles concentrations d’oxygène en activant la transcription de gène cible. Un de ces gènes est celui codant pour la lysyl oxydase (LOX). Cette enzyme structure la matrice extracellulaire et est impliquée dans la tumorigénèse. Pour comprendre les liens entre LOX et HIF1a, nous avons modulé leurs expressions dans des lignées humaines de carcinome du côlon. En condition hypoxique, HIF1a contrôle l’expression de LOX et réciproquement, LOX régule la synthèse protéique d’HIF1a via l’activation de la voie de signalisation PI3K/AKT. Nous avons donc mis en évidence l’existence d’une boucle de régulation positive entre LOX et HIF1 en conditions hypoxique. Sachant que ces deux protéines sont des acteurs majeurs de la progression tumorale, nous avons cherché à comprendre le rôle de cette régulation mutuelle dans ce processus. Nos résultats démontrent que l’activité enzymatique de LOX promeut la croissance tumorale in vitro et in vivo et que son action est potentialisée par la présence de son partenaire HIF1a. De plus, LOX et HIF1a agissent en synergie afin d’augmenter la potentiel métastatiques des cellules tumorale de côlon in vitro. Ainsi, ce travail de thèse a permis de mettre en évidence l’existence d’une boucle de régulation entre HIF1a et LOX qui est critique dans la progression tumorale et semble également être impliquée dans le processus métastatiquesThe microenvironment of solid tumors is exposed to hypoxic conditions which lead to the activation of Hypoxia‐Inducible Factor 1 (HIF1). HIF1, composed by a heterodimer of HIF1a and HIF1b protein, is a key transcription factor involved in cellular adaptation to changes in oxygen level, inducing the expression of several transcriptional targets such as Lysyl Oxidase (LOX). LOX is an amine oxidase that catalyzes crosslinking of fibrillar collagens and elastin in the extracellular matrix. Furthermore, LOX is implied in tumor progression. To clarify, the link between LOX and HIF1a, their expression were modulated in human colorectal carcinoma cell lines. We pointed out that besides HIF1‐dependant regulation of LOX, LOX can also act on the HIF1 pathway under hypoxic conditions. Indeed, LOX enzymatic activity upregulates HIF1a protein synthesis, and this action is mediated by the PI3K/AKT pathway. Thus, these results emphasize the existence of a regulation loop between HIF‐1a and LOX, which represent two main actors of tumoral progression. Thus, we wanted to determine the implication of this amplification loop in tumor progression. Our results show that LOX enzymatic activity increase tumor growth in vitro and in vivo, and this role is partially dependant of its partner HIF1a. Furthermore, we established that that LOX and HIF1a act in synergy to foster metastatic potential in colorectal carcinoma cell lines. Taken together, our results demonstrate a regulation loop between LOX and HIF1a with is critical for tumor progression and metastasis formatio

Lysyl Oxidase silencing impairs keratinocyte differentiation in a reconstructed-epidermis model

International audienceLysyl Oxidase (LOX) is an extracellular enzyme involved in the maturation of connective tissues. It also acts in many cell types as a regulator of cell behaviour and phenotype through intracellular signalling pathways. Recently, LOX was shown to be present in human epidermis where its precise functions remain unclear. We showed here that in confluent monolayer cultures of normal human keratinocytes (KCs) and N/TERT-1-immortalized KCs, LOX expression was induced during the first differentiation steps. Moreover, the silencing of LOX by stable RNA interference disrupted the expression of early differentiation markers. In a reconstructed-epidermis model, LOX silencing did not impair the stratification process nor the formation of the first differentiated layers. However, terminal differentiation was strongly impaired, as shown by a decreased expression of late differentiation proteins and by the absence of stratum corneum. Nonetheless, inhibition of LOX enzymatic activity by β-aminopropionitrile did not affect the differentiation process. Therefore, LOX protein acts during the first steps of KC differentiation and is important for subsequent commitment into terminal differentiation. Taken together, these results suggest that a finely regulated expression of LOX is necessary for normal KC differentiation and thus for maintenance of epidermal homeostasis

Lysyl oxidase is a strong determinant of tumor cell colonization in bone. Short Title: LOX triggers tumor cell colonization in bone

International audienceLysyl oxidase (LOX) is a secreted copper-dependent amine oxidase whose primary function is to drive collagen crosslinking and extracellular matrix stiffness. LOX in colorectal cancer (CRC) synergizes with hypoxia-inducible factor-1 (HIF-1 to promote tumor progression. Here we investigated whether LOX/HIF1 endows CRC cells with full competence for aggressive colonization in bone. We show that a high LOX expression in primary tumors from CRC patients was associated with poor clinical outcome, irrespective of HIF-1. Additionally, LOX was expressed by tumor cells in the bone marrow from CRC patients with bone metastases. In vivo experimental studies show that LOX overexpression in CRC cells or systemic delivery of the conditioned medium from LOX-overexpressing CRC cells promoted tumor cell dissemination in the bone marrow and enhanced osteolytic lesion formation, irrespective of HIF-1. Conversely, silencing or pharmacological inhibition of LOX activity blocked dissemination of CRC cells in the bone marrow and tumor-driven osteolytic lesion formation. In vitro, tumor-secreted LOX supported the attachment and survival of CRC cells to and in the bone matrix, and inhibited osteoblast differentiation. LOX overexpression in CRC cells also induced a robust production of IL-6. In turn, both LOX and IL-6 were acting in concert to promote RANKL-dependent osteoclast differentiation, thereby creating an imbalance between bone resorption and bone formation. Collectively, our findings show that LOX supports CRC cell dissemination in the bone marrow and they reveal a novel mechanism through which LOX-driven IL-6 production by CRC cells impairs bone homeostasis

Efficacy of live attenuated porcine reproductive and respiratory syndrome virus 2 strains to protect pigs from challenge with a heterologous Vietnamese PRRSV 2 field strain

Abstract Background Effective vaccines against porcine reproductive and respiratory syndrome virus (PRRSV), especially against highly pathogenic (HP) PRRSV are still missing. The objective of this study was to evaluate the protective efficacy of an experimental live attenuated PRRSV 2 vaccine, composed of two strains, against heterologous challenge with a Vietnamese HP PRRSV 2 field strain. For this reason, 20 PRRSV negative piglets were divided into two groups. The pigs of group 1 were vaccinated with the experimental vaccine, group 2 remained unvaccinated. All study piglets received an intranasal challenge of the HP PRRSV 2 on day 0 of the study (42 days after vaccination). Blood samples were taken on days 7 and 21 after vaccination and on several days after challenge. On day 28 after challenge, all piglets were euthanized and pathologically examined. Results On days 7 and 21 after vaccination, a PRRSV 2 viraemia was seen in all piglets of group 1 which remained detectable in seven piglets up to 42 days after vaccination. On day 3 after challenge, all piglets from both groups were positive in PRRSV 2 RT-qPCR. From day 7 onwards, viral load and number of PRRSV 2 positive pigs were lower in group 1 than in group 2. All pigs of group 1 seroconverted after PRRSV 2 vaccination. PRRSV antibodies were detected in serum of all study pigs from both groups from day 14 after challenge onwards. In group 2, moderate respiratory symptoms with occasional coughing were seen following the challenge with HP PRRSV 2. Pigs of group 1 remained clinically unaffected. Interstitial pneumonia was found in four piglets of group 1 and in all ten piglets of group 2. Histopathological findings were more severe in group 2. Conclusions It was thus concluded that the used PRRSV 2 live experimental vaccine provided protection from clinical disease and marked reduction of histopathological findings and viral load in pigs challenged with a Vietnamese HP PRRSV 2 field strain

Lysyl oxidase is a strong determinant of tumor cell colonization in bone. Short Title: LOX triggers tumor cell colonization in bone

International audienceLysyl oxidase (LOX) is a secreted copper-dependent amine oxidase whose primary function is to drive collagen crosslinking and extracellular matrix stiffness. LOX in colorectal cancer (CRC) synergizes with hypoxia-inducible factor-1 (HIF-1 to promote tumor progression. Here we investigated whether LOX/HIF1 endows CRC cells with full competence for aggressive colonization in bone. We show that a high LOX expression in primary tumors from CRC patients was associated with poor clinical outcome, irrespective of HIF-1. Additionally, LOX was expressed by tumor cells in the bone marrow from CRC patients with bone metastases. In vivo experimental studies show that LOX overexpression in CRC cells or systemic delivery of the conditioned medium from LOX-overexpressing CRC cells promoted tumor cell dissemination in the bone marrow and enhanced osteolytic lesion formation, irrespective of HIF-1. Conversely, silencing or pharmacological inhibition of LOX activity blocked dissemination of CRC cells in the bone marrow and tumor-driven osteolytic lesion formation. In vitro, tumor-secreted LOX supported the attachment and survival of CRC cells to and in the bone matrix, and inhibited osteoblast differentiation. LOX overexpression in CRC cells also induced a robust production of IL-6. In turn, both LOX and IL-6 were acting in concert to promote RANKL-dependent osteoclast differentiation, thereby creating an imbalance between bone resorption and bone formation. Collectively, our findings show that LOX supports CRC cell dissemination in the bone marrow and they reveal a novel mechanism through which LOX-driven IL-6 production by CRC cells impairs bone homeostasis

Toll-like receptor 3 downregulation is an escape mechanism from apoptosis during hepatocarcinogenesis

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Corrigendum to “Toll-like receptor 3 downregulation is an escape mechanism from apoptosis during hepatocarcinogenesis” [J Hepatol 71 (2019) 763–772]

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