Metalloproteinase inhibitors for the disintegrin-like metalloproteinases ADAM10 and ADAM17 that differentially block constitutive and phorbol ester-inducible shedding of cell surface molecules

ADAMs in cancer cell proliferation and progression

A disintegrin and metalloproteinases (ADAMs) are a new gene family of proteins with sequence similarity to the reprolysin family of snake venomases that share the metalloproteinase domain with matrix metalloproteinases (MMPs). They are structurally classified into two groups: the membrane-anchored ADAM and ADAM with thrombospondin motifs (ADAMTS). These molecules are involved in various biological events such as cell adhesion, cell fusion, cell migration, membrane protein shedding and proteolysis. Studies on the biochemical characteristics and biological functions of ADAMs are in progress, and accumulated lines of evidence have shown that some ADAMs are expressed in malignant tumors and participate in the pathology of cancers. The activities of ADAMs are regulated by gene expression, intracytoplasmic and pericellular regulation, activation of the zymogens and inhibition of activities by inhibitors. Many ADAM species, including ADAM8, ADAM9, ADAM10, ADAM12, ADAM15, ADAM17, ADAM19, ADAM28, ADAMTS1, ADAMTS4 and ADAMTS5, are expressed in human malignant tumors. Many of them are involved in the regulation of growth factor activities and integrin functions, leading to promotion of cell growth and invasion, although the precise mechanisms of these are not clear at the present time. In this article, we review recent information about ADAM family members and their implications for cancer cell proliferation and progression.

Induction of chemokine production by latent Kaposi's sarcoma-associated herpesvirus infection of endothelial cells

Infection with Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is linked strongly to development of KS, an endothelial neoplasm also characterized by striking neoangiogenesis and infiltration with inflammatory cells. To elucidate the links between endothelial infection and inflammation, primary human umbilical vein endothelial cells (HUVECs) were examined for the production of chemokines following latent KSHV infection. Several chemokines that are produced in the ground state, including MCP-1, NAP 2 and RANTES, are upregulated significantly by KSHV infection. Moreover, the chemokine CXCL16, which is nearly absent in uninfected cells, is induced significantly following infection. This induction is attributable primarily to expression of vFLIP, a known inducer of NF-kappaB. CXCL16 induces the chemotaxis of activated T cells, whose products have been proposed to positively regulate KS tumour-cell survival and growth. Whilst CXCL16 has also been proposed as a direct endothelial chemoattractant and mitogen, neither proliferation nor chemotaxis of HUVECs was observed following CXCL16 exposure. These results suggest that CXCL16 induction by KSHV contributes to the inflammatory phenotype of KS, but plays little role in the recruitment of endothelial spindle cells.

ADAM10 inhibition of human CD30 shedding increases specificity of targeted immunotherapy in vitro

CD30 is a transmembrane protein selectively overexpressed on many human lymphoma cells and therefore an interesting target for antibody-based immunotherapy. However, binding of therapeutic antibodies stimulates a juxtamembrane cleavage of CD30 leading to a loss of target antigen and an enhanced release of the soluble ectodomain of CD30 (sCD30). Here, we show that sCD30 binds to CD30 ligand (CD153)-expressing non-target cells. Because antibodies bind to sCD30, this results in unwanted antibody binding to these cells via sCD30 bridging. To overcome shedding-dependent damage of normal cells in CD30-specific immunotherapy, we analyzed the mechanism involved in the release. Shedding of CD30 can be enhanced by protein kinase C (PKC) activation, implicating the disintegrin metalloproteinase ADAM17 but not free cytoplasmic calcium. However, antibody-induced CD30 shedding is calcium dependent and PKC independent. This shedding involved the related metalloproteinase ADAM10 as shown by the use of the preferential ADAM10 inhibitor GI254023X and by an ADAM10-deficient cell line generated from embryonically lethal ADAM10(-/-) mouse. In coculture experiments, the antibody-induced transfer of sCD30 from the human Hodgkin's lymphoma cell line L540 to the CD30-negative but CD153-expressing human mast cell line HMC-1 was inhibited by GI254023X. These findings suggest that selective metalloproteinase inhibitors blocking antibody-induced shedding of target antigens could be of therapeutic value to increase the specificity and reduce side effects of immunotherapy with monoclonal antibodies.

Antagonistic roles of full-length N-cadherin and its soluble BMP cleavage product in neural crest delamination

During neural crest ontogeny, an epithelial to mesenchymal transition is necessary for cell emigration from the dorsal neural tube. This process is likely to involve a network of gene activities, which remain largely unexplored. We demonstrate that N-cadherin inhibits the onset of crest delamination both by a cell adhesion-dependent mechanism and by repressing canonical Wnt signaling previously found to be necessary for crest delamination by acting downstream of BMP4. Furthermore, N-cadherin protein, but not mRNA, is normally downregulated along the dorsal tube in association with the onset of crest delamination, and we find that this process is triggered by BMP4. BMP4 stimulates cleavage of N-cadherin into a soluble cytoplasmic fragment via an ADAM10-dependent mechanism. Intriguingly, when overexpressed, the cytoplasmic N-cadherin fragment translocates into the nucleus, stimulates cyclin D1 transcription and crest delamination, while enhancing transcription of beta-catenin. CTF2 also rescues the mesenchymal phenotype of crest cells in ADAM10-inhibited neural primordia. Hence, by promoting its cleavage, BMP4 converts N-cadherin inhibition into an activity that is likely to participate, along with canonical Wnt signaling, in the stimulation of neural crest emigration.

Ectodomain shedding of the EGF-receptor ligand epigen is mediated by ADAM17

All ligands of the epidermal growth factor receptor (EGFR), which has important roles in development and disease, are made as transmembrane precursors. Proteolytic processing by ADAMs (a disintegrin and metalloprotease) regulates the bioavailability of several EGFR-ligands, yet little is known about the enzyme responsible for processing the recently identified EGFR ligand, epigen. Here we show that ectodomain shedding of epigen requires ADAM17, which can be stimulated by phorbol esters, phosphatase inhibitors and calcium influx. These results suggest that ADAM17 might be a good target to block the release of bioactive epigen, a highly mitogenic ligand of the EGFR which has been implicated in wound healing and cancer.

ADAM10 is a principal 'sheddase' of the low-affinity immunoglobulin E receptor CD23

CD23, the low-affinity immunoglobulin E receptor, is an important modulator of the allergic response and of diseases such as rheumatoid arthritis. The proteolytic release of CD23 from cells is considered a key event in the allergic response. Here we used loss-of-function and gain-of-function experiments with cells lacking or overexpressing candidate CD23-releasing enzymes (ADAM8, ADAM9, ADAM10, ADAM12, ADAM15, ADAM17, ADAM19 and ADAM33), ADAM-knockout mice and a selective inhibitor to identify ADAM10 as the main CD23-releasing enzyme in vivo. Our findings provide a likely target for the treatment of allergic reactions and set the stage for further studies of the involvement of ADAM10 in CD23-dependent pathologies.

Regulated ADAM10-dependent ectodomain shedding of gamma-protocadherin C3 modulates cell-cell adhesion

Gamma-protocadherins (Pcdh gamma) are type I transmembrane proteins, which are most notably expressed in the nervous system. They are enriched at synapses and involved in synapse formation, specification, and maintenance. In this study, we show that Pcdh gamma C3 and Pcdh gamma B4 are specifically cleaved within their ectodomains by the disintegrin and metalloprotease ADAM10. Analysis of ADAM10-deficient fibroblasts and embryos, inhibitor studies, as well as RNA interference-mediated down-regulation demonstrated that ADAM10 is not only responsible for the constitutive but also for the regulated shedding of these proteins in fibroblasts and in neuronal cells. In contrast to N-cadherin shedding, which was activated by N-methyl-D-aspartic acid receptor activation in neuronal cells, Pcdh gamma shedding was induced by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrate stimulation, suggesting differential regulation mechanisms of cadherin-mediated functions at synapses. Cell aggregation assays in the presence or absence of metalloprotease inhibitors strongly suggest that the ectodomain shedding events modulate the cell adhesion role of Pcdh gamma. The identification of ADAM10 as the protease responsible for constitutive and regulated Pcdh gamma shedding may therefore provide new insight into the regulation of Pcdh gamma functions.

The neuropeptide PACAP promotes ?‐secretase pathway for processing Alzheimer amyloid precursor protein

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has neurotrophic as well as anti-apoptotic properties and is involved in learning and memory processes. Its specific G protein-coupled receptor PAC1 is expressed in several central nervous system (CNS) regions, including the hippocampal formation. Here we examined the effect of PAC1 receptor activation on alpha-secretase cleavage of the amyloid precursor protein (APP) and the production of secreted APP (APPsalpha). Stimulation of endogenously expressed PAC1 receptors with PACAP in human neuroblastoma cells increased APPsalpha secretion, which was completely inhibited by the PAC1 receptor specific antagonist PACAP-(6-38). In HEK cells stably overexpressing functional PAC1 receptors, PACAP-27 and PACAP-38 strongly stimulated alpha-secretase cleavage of APP. The PACAP-induced APPsalpha production was dose dependent and saturable. This increase of alpha-secretase activity was completely abolished by hydroxamate-based metalloproteinase inhibitors, including a preferential ADAM 10 inhibitor. By using several specific protein kinase inhibitors, we show that the MAP-kinase pathway [including extracellular-regulated kinase (ERK) 1 and ERK2] and phosphatidylinositol 3-kinase mediate the PACAP-induced alpha-secretase activation. Our findings provide evidence for a role of the neuropeptide PACAP in stimulation of the nonamyloidogenic pathway, which might be related to its neuroprotective properties.

Shedding of the amyloid precursor protein-like protein APLP2 by disintegrin-metalloproteinases

Cleavage of the amyloid precursor protein (APP) within the amyloid-beta (Abeta) sequence by the alpha-secretase prevents the formation of toxic Abeta peptides. It has been shown that the disintegrin-metalloproteinases ADAM10 and TACE (ADAM17) act as alpha-secretases and stimulate the generation of a soluble neuroprotective fragment of APP, APPsalpha. Here we demonstrate that the related APP-like protein 2 (APLP2), which has been shown to be essential for development and survival of mice, is also a substrate for both proteinases. Overexpression of either ADAM10 or TACE in HEK293 cells increased the release of neurotrophic soluble APLP2 severalfold. The strongest inhibition of APLP2 shedding in neuroblastoma cells was observed with an ADAM10-preferring inhibitor. Transgenic mice with neuron-specific overexpression of ADAM10 showed significantly increased levels of soluble APLP2 and its C-terminal fragments. To elucidate a possible regulatory mechanism of APLP2 shedding in the neuronal context, we examined retinoic acid-induced differentiation of neuroblastoma cells. Retinoic acid treatment of two neuroblastoma cell lines upregulated the expression of both APLP2 and ADAM10, thus leading to an increased release of soluble APLP2.