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The matricellular protein CCN1 suppresses hepatocarcinogenesis by inhibiting compensatory proliferation.

ABSTRACT: Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide, and is on the rise in the United States. Previous studies showed that the matricellular protein CCN1 (CYR61) is induced during hepatic injuries and functions to restrict and resolve liver fibrosis. Here, we show that CCN1 suppresses hepatocarcinogenesis by inhibiting carcinogen-induced compensatory hepatocyte proliferation, thus limiting the expansion of damaged and potentially oncogenic hepatocytes. Consistent with tumor suppression, CCN1 expression is downregulated in human HCC. Ccn1(?Hep) mice with hepatocyte-specific deletion of Ccn1 suffer increased HCC tumor multiplicity induced by the hepatocarcinogen diethylnitrosamine (DEN). Knockin mice (Ccn1(dm/dm)) that express an integrin ?6?1-binding defective CCN1 phenocopied Ccn1(?Hep) mice, indicating that CCN1 acts through its ?6?1 binding sites in this context. CCN1 effectively inhibits epidermal growth factor receptor (EGFR)-dependent hepatocyte proliferation through integrin ?6-mediated accumulation of reactive oxygen species (ROS), thereby triggering p53 activation and cell cycle block. Consequently, Ccn1(dm/dm) mice exhibit diminished p53 activation and elevated compensatory hepatocyte proliferation, resulting in increased HCC. Furthermore, we show that a single dose of the EGFR inhibitor erlotinib delivered prior to DEN-induced injury was sufficient to block compensatory proliferation and annihilate development of HCC nodules observed 8 months later, suggesting potential chemoprevention by targeting CCN1-inhibitable EGFR-dependent hepatocyte proliferation. Together, these results show that CCN1 is an injury response protein that functions not only to restrict fibrosis in the liver, but also to suppress hepatocarcinogenesis by inhibiting EGFR-dependent hepatocyte compensatory proliferation.

SUBMITTER: Chen CC

PROVIDER: S-EPMC4666840 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Project description:Effects of the matricellular protein CCN1 on macrophage inflammatory gene expression was tested in a macrophage cell line I-13.35. CCN1 (CYR61) is a matricellular protein that is highly expressed at sites of inflammation and wound repair. In these contexts, CCN1 can modify the activities of specific cytokines, enabling TNF-alpha to be cytotoxic without blocking NFkB activity and enhancing the apoptotic activity of FasL and TRAIL. Here we show that CCN1 supports the adhesion of macrophages through integrin alphaMbeta2 and syndecan-4, activates NFkB-mediated transcription, and induces a pro-inflammatory genetic program characteristic of classically activated M1 macrophages that participates in Th1 responses. The effects of CCN1 include upregulation of cytokines (TNFa, IL-1a, IL-1b, IL-6, IL-12b), chemokines (MIP-1a, MCP-3, Gro1, Gro2, IP-10), regulators of oxidative stress and complement (iNOS, C3), and downregulation of specific receptors (TLR4, IL-10rb) and anti-inflammatory factors (TGF-b1). CCN1 regulates this genetic program through at least two distinct mechanisms: an immediate-early response resulting from direct activation of NFkB by CCN1, leading to the synthesis of cytokines including TNFa and IP-10; and a delayed response resulting from CCN1-induced TNFa, which acts as an autocrine/paracrine mediator to activate the expression of other cytokines including IL-1b and IL-6. These results identify CCN1 as a novel component of the extracellular matrix that activates pro-inflammatory genes in macrophages, implicating its role in regulating macrophage function during inflammation. Macrophage cell line I-13.35 (from Tlr4-defective C3H/HeJ) was treated with purified recombinant CCN1 protein for 6 hr. Total RNA was isolated, converted to cRNA probes, and hybridized to a oligonucleotide array representing 113 murine inflammation-related genes (from SA Biosciences at www.sabiosciences.com, Cat. Number OMM-011.) The array is a nylon membrane based DNA microarray on which 60-mer oligonucleotides probes were printed. Gene expression profile of resting cells incubated in serum-free medium (containing albumin, BSA) was used as a control for basal levels of gene expression.

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The matricellular protein CCN1 suppresses hepatocarcinogenesis by inhibiting compensatory proliferation.

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