Since the discovery of the first disintegrin protein from snake venom and the following identification of a mammalian membrane-anchored metalloprotease-disintegrin implicated in fertilization, almost three decades of studies have identified additional members of these families and several biochemical mechanisms regulating their expression and activity in the cell. Most importantly, new in vivo functions have been recognized for these proteins including cell partitioning during development, modulation of inflammatory reactions, and development of cancers. In this review, we will overview the a disintegrin and metalloprotease (ADAM) family of proteases highlighting some of the major research achievements in the analysis of ADAMs’ function that have underscored the importance of these proteins in physiological and pathological processes over the years.

E-type cyclins E1 (CcnE1) and E2 (CcnE2) are regulatory subunits of cyclin-dependent kinase 2 (Cdk2) and thought to control the transition of quiescent cells into the cell cycle. Initial findings indicated that CcnE1 and CcnE2 have largely overlapping functions for cancer development in several tumor entities including hepatocellular carcinoma (HCC). In the present study, we dissected the differential contributions of CcnE1, CcnE2, and Cdk2 for initiation and progression of HCC in mice and patients. To this end, we tested the HCC susceptibility in mice with constitutive deficiency for CcnE1 or CcnE2 as well as in mice lacking Cdk2 in hepatocytes. Genetic inactivation of CcnE1 largely prevented development of liver cancer in mice in two established HCC models, while ablation of CcnE2 had no effect on hepatocarcinogenesis. Importantly, CcnE1-driven HCC initiation was dependent on Cdk2. However, isolated primary hepatoma cells typically acquired independence on CcnE1 and Cdk2 with increasing progression in vitro, which was associated with a gene signature involving secondary induction of CcnE2 and up-regulation of cell cycle and DNA repair pathways. Importantly, a similar expression profile was also found in HCC patients with elevated CcnE2 expression and poor survival. In general, overall survival in HCC patients was synergistically affected by expression of CcnE1 and CcnE2, but not through Cdk2. Our study suggests that HCC initiation specifically depends on CcnE1 and Cdk2, while HCC progression requires expression of any E-cyclin, but no Cdk2.

Proteolytic activities in the extracellular matrix by the matrix metalloproteinase (MMP)-14 have been implicated in the remodeling of collagenous proteins during development. To analyze the function of fibroblast-derived MMP-14 in adult skin homeostasis, we generated mice with inducible deletion of MMP-14 in the dermal fibroblast (MMP-14Sf–/–). These mice are smaller and display a fibrosis-like phenotype in the skin. The skin of these mice showed increased stiffness and tensile strength but no altered collagen cross-links. In vivo, we measured a significantly increased amount of collagen type I accumulated in the skin of MMP-14Sf–/– mice without an increase in collagen fibril diameters. However, bleomycin-induced fibrosis in skin proceeded in a comparable manner in MMP-14Sf+/+ and MMP-14Sf–/– mice, but resolution over time was impaired in MMP-14Sf–/– mice. Increased accumulation of collagen type I was detected in MMP-14Sf–/– fibroblasts in culture without significant enhancement of collagen de novo synthesis. This points to a degradative but not synthetic phenotype. In support of this, MMP-14Sf–/– fibroblasts lost their ability to process fibrillar collagen type I and to activate proMMP-2. Taken together, these data indicate that MMP-14 expression in fibroblasts plays a crucial role in collagen remodeling in adult skin and largely contributes to dermal homeostasis underlying its pathogenic role in fibrotic skin disease.

The nucleotide binding and oligomerization domain-like receptor (NLR) protein NLRP10 is highly expressed in the epidermis and contributes to cell-autonomous responses against invasive bacteria. To investigate the role of NLRP10 in inflammatory responses of the skin we analyzed the effect of full-body and keratinocyte-specific depletion of NLRP10 in croton oil-induced irritant contact dermatitis (ICD) and 1-fluoro-2,4-dinitrobenzene (DNFB)-induced contact hypersensitivity (CHS) in mice. Nlrp10 −/− mice were phenotypically normal and skin repair after wounding was not affected by lack of NLRP10. Similarly, we did not detect a contribution of NLRP10 to the ICD response induced by croton oil. In contrast, Nlrp10 −/− mice showed significantly reduced inflammation in the DNFB-induced CHS response as compared to control animals. Microscopic analysis revealed significantly reduced numbers of CD4 + and CD8 + T cells in the infiltrates of animals lacking NLRP10 expression after CHS challenge. Epidermis-specific deletion of Nlrp10 by keratin-14 promotor driven Cre-recombinase was sufficient to account for this phenotype, although lymphocyte recruitment seemed to be unaltered in animals lacking NLRP10 expression in keratinocytes. Taken together, we provide evidence that NLRP10 contributes to T-cellmediated inflammatory responses in the skin and highlight a physiological role of NLRP10 in epidermal keratinocytes.Keywords: Contact dermatitis r Contact hypersensitivity r NLRP10 r Mouse model Additional supporting information may be found in the online version of this article at the publisher's web-site

ADAM-9 is a metalloproteinase expressed in peritumoral areas by invading melanoma cells and by adjacent peritumoral stromal cells; however, its function in stromal and melanoma cells is not fully understood. To address this question in vivo in a spontaneous melanoma model, we deleted ADAM-9 in mice carrying the hepatocyte growth factor (Hgf) transgene and knock-in mutation Cdk4, demonstrated to spontaneously develop melanoma. Spontaneous melanoma arose less frequently in ADAM-9-deleted mice than in controls. Similarly reduced tumor numbers (although with faster growth kinetics) were detected upon induction of melanoma with 7,12-dimethylbenz[a]anthracene (DMBA). However, more lesions were induced at early time points in the absence of ADAM-9. Increased initial and decreased late tumor numbers were paralleled by altered tumor cell proliferation, but not apoptosis or inflammation. Importantly, significantly reduced lung metastases were detected upon ADAM-9 deletion. Using in vitro assays to address this effect mechanistically, we detected reduced adhesion and transmigration of ADAM-9-silenced melanoma cells to/through the endothelium. This implies that ADAM-9 functionally and cell autonomously mediates extravasation of melanoma cells. In vitro and in vivo we demonstrated that the basement membrane (BM) component laminin β3-chain is a direct substrate of ADAM-9, thus contributing to destabilization and disruption of the BM barrier during invasion. In in vitro invasion assays using human melanoma cells and skin equivalents, depletion of ADAM-9 resulted in decreased invasion of the BM, which remained almost completely intact, as shown by continuous staining for laminin β3-chain. Importantly, supplying soluble ADAM-9 to the system reversed this effect. Taken together, our data show that melanoma derived ADAM-9 autonomously contributes to melanoma progression by modulating cell adhesion to the endothelium and altering BM integrity by proteolytically processing the laminin-β3 chain. This newly described process and ADAM-9 itself may represent potential targets for anti-tumor therapies.