Role of glypican-1 in regulating multiple cellular signaling pathways.
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ABSTRACT:
SUBMITTER: Pan J
PROVIDER: S-EPMC8616591 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BACKGROUND AIMS: Our previous results showed that the knockdown of woodchuck hepatitis virus (WHV) by RNA interference (RNAi) led to upregulation of interferon stimulated genes (ISGs) in primary hepatocytes. In the present study, we tested the hypothesis that the cellular signaling pathways recognizing RNA molecules may be involved the ISG stimulation by RNAi. METHODS: Primary murine hepatocytes (PMHs) from wild type mice and WHV transgenic (Tg) mice were prepared and treated with defined siRNAs. The mRNA levels of target genes and ISGs were detected by real-time RT-PCR. The involvement of the signaling pathways including RIG-I/MDA5, PKR, and TLR3/7/8/9 was examined by specific inhibition and the analysis of their activation by Western blotting. RESULTS: In PMHs from WHV Tg mice, specific siRNAs targeting WHV, mouse ?-actin, and GAPDH reduced the levels of targeted mRNAs and increased the mRNA expression of IFN-?, MxA, and IP-10. The enhanced ISG expression by siRNA transfection were abolished by siRNA-specific 2'-O-methyl antisense RNA and the inhibitors 2-AP and chloroquine blocking PKR and other TLR-mediated signaling pathways. Furthermore, Western blotting revealed that RNAi results in an increase in PKR phosphorylation and nuclear translocation of IRF3 and NF-êB, indicating the possible role of IRF3 in the RNAi-directed induction of ISGs. In contrast, silencing of RIG-I and MDA5 failed to block RNAi-mediated MxA induction. CONCLUSIONS: RNAi is capable of enhancing innate immune responses through the PKR- and TLR-dependent signaling pathways in primary hepatocytes. The immune stimulation by RNAi may contribute to the antiviral activity of siRNAs in vivo.
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Project description:Glypican-3 (GPC3) is highly expressed in human hepatocellular carcinoma (HCC) and a growing body of evidence supports the role of GPC3 in HCC pathogenesis. In this review, we discuss recent developments regarding the regulation of GPC3 in HCC and provide insight about GPC3 as a potential therapeutic target in liver cancer. One of the most well studied pathways related to the biological functions of GPC3 is the Wnt signaling pathway. GPC3 may form a complex with Wnt and stimulates HCC growth. GPC3 does this by facilitating and/or stabilizing the interaction between Wnt and Frizzled, leading to the activation of downstream signaling pathways. This signaling complex is also affected by Sulfatase 2 (SULF2), a heparin-degrading endosulfatase. Removing the sulfate groups from GPC3 enhances Wnt signaling and HCC proliferation suggesting that GPC3, Wnts and SULF2 may be part of "a glypican-Wnt/growth factor complex", which may determine cell growth, differentiation and migration. Given the high expression of GPC3 in HCC, GPC3 has been suggested as a potential target for antibody-based therapy for liver cancer. A monoclonal antibody (GC33) is being evaluated in clinical studies as a single agent or in combination with Sorafenib to treat patients with advanced or metastatic HCC. Ongoing clinical trials will help define the utility of GPC3 as a novel target for liver cancer therapy.
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