Interleukin-33 (IL-33), the most recently identified member of the IL-1 family, induces synthesis of T Helper 2 (Th2)-type cytokines via its heterodimeric ST2/IL-1RAcP receptor. Th2-type cytokines play an important role in fibrosis; thus, we investigated the role of IL-33 in liver fibrosis. IL-33, ST2 and IL-1RAcP gene expression was analysed in mouse and human normal (n= 6) and fibrotic livers (n= 28), and in human hepatocellular carcinoma (HCC; n= 22), using real-time PCR. IL-33 protein was detected in normal and fibrotic liver sections and in isolated liver cells using Western blotting and immunolocalization approaches. Our results showed that IL-33 and ST2 mRNA was overproduced in mouse and human fibrotic livers, but not in human HCC. IL-33 expression correlated with ST2 expression and also with collagen expression in fibrotic livers. The major sources of IL-33 in normal liver from both mice and human beings are the liver sinusoidal endothelial cells and, in fibrotic liver, the activated hepatic stellate cells (HSC). Moreover, IL-33 expression was increased in cultured HSC when stimulated by pro-inflammatory cytokines. In conclusion, IL-33 is strongly associated with fibrosis in chronic liver injury and activated HSC are a source of IL-33.

. We have investigated ADAM expression in human liver cancers and their regulation by several cytokines involved in liver injury. Using degenerative RT-PCR, cDNA encoding sequences for ADAM9 and ADAM12 were identified in human activated hepatic stellate cells (HSCs). Northern blot analyses showed that HSCs, but not hepatocytes, expressed transcripts for ADAM9 messenger RNA (mRNA) and both the long and short forms of ADAM12. This expression was associated with the transition from quiescent to activated state of rat HSCs and markedly increased in human livers with cirrhosis. ADAM12 but not ADAM9 expression was up-regulated by transforming growth factor ␤ (TGF-␤) in human activated HSCs. The PI3K inhibitor LY294002 and the mitogen-activated protein kinase kinase (MEK) inhibitor UO126 prevented ADAM12 induction by TGF-␤, suggesting the involvement of PI3K and MEK activities. In vivo, the steady-state of both ADAM9 and ADAM12 mRNA levels was nearly undetectable in both normal livers and benign tumors and increased in hepatocellular carcinomas (up to 3-and 6-fold, respectively) and liver metastases from colonic carcinomas (up to 40-and 60-fold, respectively). The up-regulation of both ADAM9 and ADAM12 was correlated with an increase in matrix metalloproteinase 2 expression and activity. In conclusion, in liver cancers ADAM9 and ADAM12 expression is associated with tumor aggressiveness and progression. I ncreased expression and activities of matrix metalloproteinase (MMP) has been shown widely in malignant phenotypes facilitating the breakdown of extracellular matrix component and cell evasion, but also unmasking bioactive cryptic fragments and releasing active growth factors which, in turn, favor tumor growth. 1 The ADAMs (a disintegrin and metalloproteinase-containing proteins) are a family of multidomain glycoproteins highly homologous to the class III snake venom metalloprotease-disintegrins. 2 The common extracellular part of the proteins includes a regulatory prodomain and metalloprotease, disintegrin-like and cystein-rich domains. Further, ADAMs are characterized by an epidermal growth factor (EGF)-like domain, a transmembrane domain, and a cytoplasmic tail. More than 30 members have been identified in the ADAM family with a broad tissue distribution and have been involved in specific cellular processes including sperm-egg interaction, 3 myocyte fusion, 4 neurogenesis, 5 and adipogenesis. 6 Recently, ADAM12 gene therapy was shown to rescue the pathology of mdx-gene deficient dystrophic mice.

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Matrix metalloproteinase-2 (MMP2) is a key enzyme in the process of extracellular matrix remodeling involved in tumor invasion and metastasis. The activation of MMP2 involves interplay with the membrane type-matrix metalloproteinase-1 (MT1-MMP) and the tissue inhibitor of metalloproteinase-2 (TIMP2). In vitro, activated hepatic stellate cells are a main source of MMP2 and collagen I induces MMP2 activation. The steady-state mRNA levels of MMP2, MT1-MMP, TIMP2, collagen I, collagen IV, and laminin ␥1 were compared with MMP2 activity in 55 hepatocellular carcinomas, 47 matching nontumor biopsies and 19 histologically normal livers. In hepatocellular carcinomas, increased collagen I mRNA levels were strongly associated with those of MMP2 (Spearman R ‫؍‬ .74, P < .001), MT1-MMP (R ‫؍‬ .65, P < .001) and TIMP2 (R ‫؍‬ 0.61, P < .001). MMP2 activity was correlated with the mRNA expression of collagen I (R ‫؍‬ .45 P < .01), collagen IV (R ‫؍‬ .40, P < .01) and laminin ␥1 (R ‫؍‬ .33, P < .05). Unlike collagen IV and laminin ␥1 mRNAs, MMP2, MT1-MMP, TIMP2, collagen I mRNA levels were increased in nonencapsulated compared with encapsulated tumors (P < .05). In addition, MMP2 activity was fourfold higher (P < .01) in tumors arising in cirrhotic livers than in those arising in noncirrhotic livers. Moreover, tumor recurrence was associated with 4.6-and 2.8-fold (P < .05) higher collagen I and MMP2 mRNA levels, respectively, in hepatocellular carcinomas arising in cirrhotic livers. Thus, a high extracellular matrix remodeling favors tumor progression in hepatocellular carcinomas. (HEPATOLOGY 2001;34:82-88.)Tumor progression depends on the interplay between transformed cells and their micro-environment, particularly the surrounding extracellular matrix (ECM). 1 The balance between synthesis and degradation of ECM components is indeed a key modulator of tumor growth and metastasis. Among the proteases involved in the turnover of ECM, matrix metalloproteinase 2 (MMP2), the type IV collagenase/gelatinase, was shown to specifically act in the process of basementmembrane remodeling related to tumor progression. 2 MMP2 is secreted as a proenzyme and the critical step of MMP2 activation occurs at the cell surface through the formation of a molecular complex involving MMP2, the membrane-type matrix metalloproteinase MT1-MMP 3 and the tissue inhibitor of MMP2, TIMP2, which promotes the binding of MT1-MMP to MMP2. 4 Thus, TIMP2 plays a dual role by acting at a high concentration as a specific inhibitor of MMP2 activation and at a low concentration as a trigger of MMP2 and MT1-MMP clustering. 5 In human livers, fibrogenesis underlies the development of HCC in at least 90% of cases and HCC is an ominous complication of cirrhosis in 30% of the patients. 6,7 However, direct relationships between fibrosis and the progression of HCC were not shown, so far. Increased expression of MMP2, tissue inhibitors of metalloproteinase (TIMP1 and TIMP2), and MT1-MMP by nonparenchymal cells were reported in fibrosis 8-9 and in HCC. [10][11][12] Indeed, hep...