Lydie Lefrancois

Common dysregulation of Wnt/Frizzled receptor elements in human hepatocellular carcinoma.

Dysregulation of growth factors and their receptors is central to human hepatocellular carcinoma (HCC). We previously demonstrated that the Frizzled-7 membrane receptor mediating the Wnt signalling can activate the β-catenin pathway and promotes malignancy in human hepatitis B virus-related HCCs. Expression patterns of all the 10 Frizzled receptors, and their extracellular soluble autoparacrine regulators (19 Wnt activators and 4 sFRP inhibitors) were assessed by real-time RT–PCR in 62 human HCC of different etiologies and their matched peritumorous areas. Immunostaining was performed to localise Frizzled on cell types in liver tissues. Regulation of three known Frizzled-dependent pathways (β-catenin, protein kinase C, and C-Jun NH2-terminal kinase) was measured in tissues by western blot. We found that eight Frizzled-potentially activating events were pleiotropically dysregulated in 95% HCC and 68% peritumours as compared to normal livers (upregulations of Frizzled-3/6/7 and Wnt3/4/5a, or downregulation of sFRP1/5), accumulating gradually with severity of fibrosis in peritumours and loss of differentiation status in tumours. The hepatocytes supported the Wnt/Frizzled signalling since specifically overexpressing Frizzled receptors in liver tissues. Dysregulation of the eight Frizzled-potentially activating events was associated with differential activation of the three known Frizzled-dependent pathways. This study provides an extensive analysis of the Wnt/Frizzled receptor elements and reveals that the dysregulation may be one of the most common and earliest events described thus far during hepatocarcinogenesis.

Pharmacological inhibition of Frizzled-7 displays anti-tumor properties in hepatocellular carcinoma

BACKGROUND & AIMS We previously reported the frequent overexpression of the FZD7 membrane receptor in hepatocellular carcinoma (HCC) and its role for controlling cancer phenotype. Herein, this study aimed at assessing the anticancer properties of compounds inhibiting FZD7 activity by disrupting its binding with the cytosolic Dishevelled (DVL) adaptator. METHODS We have designed small interfering peptides (RHPDs) that are able to enter within cells and to competitively antagonize the binding of FZD7 to the PDZ domain of DVL. Their anti-neoplastic properties were assessed in vitro on a panel of human HCC cell lines and in vivo on the SV40-TAg transgenic mouse model of HCC. RESULTS We have shown that RHPDs decrease cell viability via apoptosis depending on their affinity for PDZ, with a therapeutic index between cancerous and non-cancerous cells. RHPD properties were linked to β-catenin degradation and PKCδ activation. In transgenic mice, intra-tumor injection of RHPDs inhibited HCC progression. CONCLUSIONS We have completed a proof-of-concept showing that in vitro and in vivo the pharmacological inhibition of FZD7 displays anti-cancerous properties against HCC. The mechanisms can involve β-catenin and PKCδ modulations. Further studies are warranted to design protocols showing the compatibility with systemic in vivo applications.

Long-term high-dose interferon-α therapy delays Hepadnavirus-related hepatocarcinogenesis in X/myc transgenic mice

The role of interferon-α (IFN-α) remains unclear in prevention of virus-induced hepatocellular carcinoma in humans. We have investigated it herewith in the X/myc transgenic mouse model of Hepadnavirus-related hepatocarcinogenesis because of upregulation of c-myc oncogene in the liver. We have demonstrated that IFN-α can downregulate dose-dependently hepatocyte proliferation and c-myc overexpression at early premalignant stages, while it does not affect either hepatocyte apoptosis or telomerase activity at these steps. However, continuous and long-term administration of IFN-α dose-dependently delays tumor onset in dysplastic livers and increases overall survival of animals, more efficiently whether started before the onset of dysplasia. The present study therefore highlights that early preventive administration of IFN-α can slow down evolution towards hepatocellular carcinoma via repression of c-myc and hepatocyte proliferation at premalignant steps in experimental c-myc-induced hepatocarcinogenesis. However, the transient effect observed in this study emphasizes a need to clarify the possible mechanisms of acquired resistance and subsequent therapeutic escape. Our experimental model may be a pertinent tool to explore antioncogenic properties of IFN-α in human cirrhotic livers showing c-myc upregulation.

Down-regulation of the Wnt/β-catenin signaling pathway by Cacnb4

The cytoplasmic β4-subunit of the voltage-gated calcium channels has been shown be involved in the regulation of gene transcription. This subunit interacts with the transcription factor TCF4 and inhibits the Wnt/β-catenin signaling pathway. These results may also explain the inhibitory effect of the β4-subunit on cell proliferation.