Loss of ADAM9 expression impairs β1 integrin endocytosis, focal adhesion formation and cancer cell migration

Spatial proteomics and transcriptomics of the maternal-fetal interface in placenta accreta spectrum

In severe Placenta Accreta Spectrum (PAS), trophoblasts gain deep access in the myometrium (placenta increta). This study investigated alterations at the fetal-maternal interface in PAS cases using a systems biology approach consisting of immunohistochemistry, spatial transcriptomics and proteomics. We identified spatial variation in the distribution of CD4+, CD3+ and CD8+ T-cells at the maternal-interface in placenta increta cases. Spatial transcriptomics identified transcription factors involved in promotion of trophoblast invasion such as AP-1 subunits ATF-3 and JUN, and NFKB were upregulated in regions with deep myometrial invasion. Pathway analysis of differentially expressed genes demonstrated that degradation of extracellular matrix (ECM) and class 1 MHC protein were increased in increta regions, suggesting local tissue injury and immune suppression. Spatial proteomics demonstrated that increta regions were characterised by excessive trophoblastic proliferation in an immunosuppressive environment. Expression of inhibitors of apoptosis such as BCL-2 and fibronectin were increased, while CTLA-4 was decreased and increased expression of PD-L1, PD-L2 and CD14 macrophages. Additionally, CD44, which is a ligand of fibronectin that promotes trophoblast invasion and cell adhesion was also increased in increta regions. We subsequently examined ligand receptor interactions enriched in increta regions, with interactions with ITGβ1, including with fibronectin and ADAMS, emerging as central in increta. These ITGβ1 ligand interactions are involved in activation of epithelial-mesenchymal transition and remodelling of ECM suggesting a more invasive trophoblast phenotype. In PAS, we suggest this is driven by fibronectin via AP-1 signalling, likely as a secondary response to myometrial scarring.

Does rAj-Tspin, a novel peptide from A. japonicus, exert antihepatocellular carcinoma effects via the ITGB1/ZYX/FAK/AKT signaling pathway?

rAj-Tspin, a soluble recombinant peptide from Apostichopus japonicus, can inhibit the integrin β1 (ITGB1)/FAK/AKT signaling pathway in hepatocellular carcinoma (HCC) via cell epithelial-mesenchymal transition (EMT) and apoptosis. Zyxin (ZYX) is a focal adhesion protein that is considered a novel mediator of EMT and apoptosis. However, the inhibitory mechanisms of rAj-Tspin in HCC and whether it is related to ZYX are unclear. We examined the antitumor effect of rAj-Tspin on the Huh7 human HCC cell line and on a nude mouse model generated via subcutaneous injection or orthotopic intrahepatic transplantation of Huh7 cells. Our results revealed that rAj-Tspin strikingly reduced the viability and promoted the apoptosis of Huh7 cells and inhibited HCC tumor growth in nude mice. rAj-Tspin inhibited ITGB1 and ZYX protein expression in vivo and in vitro in a dose-dependent manner. Mechanistically, the FAK/AKT signaling pathway and the proliferation and invasion of HCC cells were suppressed upon ITGB1 and ZYX knockdown. Moreover, the effect of ITGB1 overexpression on the growth of HCC cells was inhibited by rAj-Tspin. In contrast, the promoting effect of ITGB1 overexpression could be inhibited by ZYX knockdown. ZYX knockdown had no effect on ITGB1 expression. These findings suggest that ZYX is required for the indispensable role of ITGB1 in rAj-Tspin-alleviated HCC and provide an important therapeutic target for HCC. In summary, the anti-HCC effect of rAj-Tspin potentially involves the regulation of the ITGB1/ZYX/FAK/AKT pathway, which in turn impacts EMT and apoptosis.

ADAM9 promotes type I interferon-mediated innate immunity during encephalomyocarditis virus infection

Viral myocarditis, an inflammatory disease of the heart, causes significant morbidity and mortality. Type I interferon (IFN)-mediated antiviral responses protect against myocarditis, but the mechanisms are poorly understood. We previously identified A Disintegrin And Metalloproteinase domain 9 (ADAM9) as an important factor in viral pathogenesis. ADAM9 is implicated in a range of human diseases, including inflammatory diseases; however, its role in viral infection is unknown. Here, we demonstrate that mice lacking ADAM9 are more susceptible to encephalomyocarditis virus (EMCV)-induced death and fail to mount a characteristic type I IFN response. This defect in type I IFN induction is specific to positive-sense, single-stranded RNA (+ ssRNA) viruses and involves melanoma differentiation-associated protein 5 (MDA5)-a key receptor for +ssRNA viruses. Mechanistically, ADAM9 binds to MDA5 and promotes its oligomerization and thereby downstream mitochondrial antiviral-signaling protein (MAVS) activation in response to EMCV RNA stimulation. Our findings identify a role for ADAM9 in the innate antiviral response, specifically MDA5-mediated IFN production, which protects against virus-induced cardiac damage, and provide a potential therapeutic target for treatment of viral myocarditis.

A disintegrin and metalloproteinase domain 9 facilitates SARS-CoV-2 entry into cells with low ACE2 expression

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of the Coronavirus disease-19 (COVID-19) pandemic, utilizes angiotensin-converting enzyme 2 (ACE2) as a receptor for virus infection. However, the expression pattern of ACE2 does not coincide with the tissue tropism of SARS-CoV-2, hinting that other host proteins might be involved in facilitating SARS-CoV-2 entry. To explore potential host factors for SARS-CoV-2 entry, we performed an arrayed shRNA screen in H1650 and HEK293T cells. Here, we identified a disintegrin and a metalloproteinase domain 9 (ADAM9) protein as an important host factor for SARS-CoV-2 entry. Our data showed that silencing ADAM9 reduced virus entry, while its overexpression promoted infection. The knockdown of ADAM9 decreased the infectivity of the variants of concern tested-B.1.1.7 (alpha), B.1.617.2 (delta), and B.1.1.529 (omicron). Furthermore, mechanistic studies indicated that ADAM9 is involved in the binding and endocytosis stages of SARS-CoV-2 entry. Through immunoprecipitation experiments, we demonstrated that ADAM9 binds to the S1 subunit of the SARS-CoV-2 Spike. Additionally, ADAM9 can interact with ACE2, and co-expression of both proteins markedly enhances virus infection. Moreover, the enzymatic activity of ADAM9 facilitates virus entry. Our study reveals an insight into the mechanism of SARS-CoV-2 virus entry and elucidates the role of ADAM9 in virus infection. IMPORTANCE COVID-19, an infectious respiratory disease caused by SARS-CoV-2, has greatly impacted global public health and the economy. Extensive vaccination efforts have been launched worldwide over the last couple of years. However, several variants of concern that reduce the efficacy of vaccines have kept emerging. Thereby, further understanding of the mechanism of SARS-CoV-2 entry is indispensable, which will allow the development of an effective antiviral strategy. Here, we identify a disintegrin and metalloproteinase domain 9 (ADAM9) protein as a co-factor of ACE2 important for SARS-CoV-2 entry, even for the variants of concern, and show that ADAM9 interacts with Spike to aid virus entry. This virus-host interaction could be exploited to develop novel therapeutics against COVID-19.

Relevance of A Disintegrin and Metalloproteinase Domain-Containing (ADAM)9 Protein Expression to Bladder Cancer Malignancy

We evaluated the effect of A Disintegrin and Metalloproteinase Domain-Containing (ADAM)9 protein on exacerbation in bladder cancer KK47 and T24. First, we knocked down ADAM9 and investigated cell proliferation, migration, cell cycle, and the epithelial-mesenchymal transition (EMT)-related proteins expression in vitro. We then investigated the expression level of ADAM9 in clinical urine cytology samples and the Cancer Genome Atlas (TCGA) data. Cell proliferation was significantly reduced in both cell lines after ADAM9 knockdown. In the cell-cycle assay, the percentage of G0/G1 cells was significantly increased in ADAM9 knockdown T24. Migration of T24 was more strongly suppressed than KK47. The expression level of EMT-related proteins suggested that EMT was suppressed in ADAM9 knockdown T24. TCGA analysis revealed that ADAM9 mRNA expression was significantly higher in stage IV and high-grade cancer than in other stages and low-grade cancer. Moreover, in the gene expression omnibus (GEO) study, bladder cancer with surrounding carcinoma and invasive carcinoma showed significantly high ADAM9 mRNA expression. We found that ADAM9 knockdown suppressed cell proliferation and migration in bladder cancer and that high-grade bladder cancer is correlated with higher expression of ADAM9.

Pathways of integrins in the endo-lysosomal system

In this review, we present recent scientific advances about integrin trafficking in the endo-lysosomal system. In the last few years, plenty of new information has emerged about the endo-lysosomal system, integrins, and the mechanism, how exactly the intracellular trafficking of integrins is regulated. We review the internalization and recycling pathways of integrins, and we provide information about the possible ways of lysosomal degradation through the endosomal and autophagic system. The regulation of integrin internalization and recycling proved to be a complex process worth studying. Trafficking of integrins, together with the regulation of their gene expression, defines cellular adhesion and cellular migration through bidirectional signalization and ligand binding. Thus, any malfunction in this system can potentially (but not necessarily) lead to tumorigenesis or metastasis. Hence, extensive examinations of integrins in the endo-lysosomal system raise the possibility to identify potential new medical targets. Furthermore, this knowledge can also serve as a basis for further determination of integrin signaling- and adhesion-related processes.

Potential Molecular Biomarkers of Vestibular Schwannoma Growth: Progress and Prospects

Vestibular schwannomas (VSs, also known as acoustic neuromas) are relatively rare benign brain tumors stem from the Schwann cells of the eighth cranial nerve. Tumor growth is the paramount factor for neurosurgeons to decide whether to choose aggressive treatment approach or careful follow-up with regular magnetic resonance imaging (MRI), as surgery and radiation can introduce significant trauma and affect neurological function, while tumor enlargement during long-term follow-up will compress the adjacent nerves and tissues, causing progressive hearing loss, tinnitus and vertigo. Recently, with the deepening research of VS biology, some proteins that regulate merlin conformation changes, inflammatory cytokines, miRNAs, tissue proteins and cerebrospinal fluid (CSF) components have been proposed to be closely related to tumor volume increase. In this review, we discuss advances in the study of biomarkers that associated with VS growth, providing a reference for exploring the growth course of VS and determining the optimal treatment strategy for each patient.

Inhibition of Vascular Growth by Modulation of the Anandamide/Fatty Acid Amide Hydrolase Axis

Supplemental Digital Content is available in the text.

Objective:

Pathological angiogenesis is a hallmark of various diseases characterized by local hypoxia and inflammation. These disorders can be treated with inhibitors of angiogenesis, but current compounds display a variety of side effects and lose efficacy over time. This makes the identification of novel signaling pathways and pharmacological targets involved in angiogenesis a top priority.

Approach and Results:

Here, we show that inactivation of FAAH (fatty acid amide hydrolase), the enzyme responsible for degradation of the endocannabinoid anandamide, strongly impairs angiogenesis in vitro and in vivo. Both, the pharmacological FAAH inhibitor URB597 and anandamide induce downregulation of gene sets for cell cycle progression and DNA replication in endothelial cells. This is underscored by cell biological experiments, in which both compounds inhibit proliferation and migration and evoke cell cycle exit of endothelial cells. This prominent antiangiogenic effect is also of pathophysiological relevance in vivo, as laser-induced choroidal neovascularization in the eye of FAAH^−/− mice is strongly reduced.

Conclusions:

Thus, elevation of endogenous anandamide levels by FAAH inhibition represents a novel antiangiogenic mechanism.

MYH9-dependent polarization of ATG9B promotes colorectal cancer metastasis by accelerating focal adhesion assembly

Tumour metastasis is a major reason accounting for the poor prognosis of colorectal cancer (CRC), and the discovery of targets in the primary tumours that can predict the risk of CRC metastasis is now urgently needed. In this study, we identified autophagy-related protein 9B (ATG9B) as a key potential target gene for CRC metastasis. High expression of ATG9B in tumour significantly increased the risk of metastasis and poor prognosis of CRC. Mechanistically, we further find that ATG9B promoted CRC invasion mainly through autophagy-independent manner. MYH9 is the pivotal interacting protein for ATG9B functioning, which directly binds to cytoplasmic peptide segments aa368-411 of ATG9B by its head domain. Furthermore, the combination of ATG9B and MYH9 enhance the stability of each other by decreasing their binding to E3 ubiquitin ligase STUB1, therefore preventing them from ubiquitin-mediated degradation, which further amplified the effect of ATG9B and MYH9 in CRC cells. During CRC cell invasion, ATG9B is transported to the cell edge with the assistance of MYH9 and accelerates focal adhesion (FA) assembly through mediating the interaction of endocytosed integrin β1 and Talin-1, which facilitated to integrin β1 activation. Clinically, upregulated expression of ATG9B in human CRC tissue is always accompanied with highly elevated expression of MYH9 and associated with advanced CRC stage and poor prognosis. Taken together, this study highlighted the important role of ATG9B in CRC metastasis by promoting focal adhesion assembly, and ATG9B together with MYH9 can provide a pair of potential therapeutic targets for preventing CRC progression.

Ubiquitin-specific peptidase 39 promotes human glioma cells migration and invasion by facilitating ADAM9 mRNA maturation

Glioma cells are characterized by high migration and invasion ability; however, the molecular mechanism behind both processes still remains to be investigated. Several studies have demonstrated that ubiquitin‐specific protease 39 (USP39) plays an oncogenic role in various cancer types. Here, we investigated the expression and function of USP39 in patients with glioma. Oncomine database analysis revealed that high USP39 expression was significantly correlated with poor overall survival in patients with glioma. Knockdown of USP39 in U251 and U87 cell lines significantly inhibited their migration and invasion in vitro. Gene expression profiling of glioma cells transduced with short hairpin RNA (shRNA) against USP39 revealed that disintegrin and metalloproteinase domain‐containing protein 9 (ADAM9), a molecule previously related to tumor cell migration and invasion, was significantly downregulated. Furthermore, USP39 induced ADAM9 messenger RNA (mRNA) maturation and decreased the expression of integrin β1. Additionally, overexpression of ADAM9 inhibited the migration and invasion of glioma cells caused by USP39 depletion in vitro. USP39 promoted the invasion of glioma cells in vivo and reduced the overall survival of the mice. Altogether, our data show that USP39 induces mRNA maturation and elevates the expression of ADAM9 in glioma cells and may thus be considered potential target for treating patients with glioma.

Endocytosis of the non-catalytic ADAM23: Recycling and long half-life properties

A Disintegrin And Metalloprotease 23 (ADAM23) is a member of the ADAMs family of transmembrane proteins, mostly expressed in nervous system, and involved in traffic and stabilization of Kv1-potassium channels, synaptic transmission, neurite outgrowth, neuronal morphology and cell adhesion. Also, ADAM23 has been linked to human pathological conditions, such as epilepsy, cancer metastasis and cardiomyopathy. ADAM23 functionality depends on the molecule presence at the cell surface and along the secretory pathway, as expected for a cell surface receptor. Because endocytosis is an important functional regulatory mechanism of plasma membrane receptors and no information is available about the traffic or turnover of non-catalytic ADAMs, we investigated ADAM23 internalization, recycling and half-life properties. Here, we show that ADAM23 undergoes constitutive internalization from the plasma membrane, a process that depends on lipid raft integrity, and is redistributed to intracellular vesicles, especially early and recycling endosomes. Furthermore, we observed that ADAM23 is recycled from intracellular compartments back to the plasma membrane and thus has longer half-life and higher cell surface stability compared with other ADAMs. Our findings suggest that regulation of ADAM23 endocytosis/stability could be exploited therapeutically in diseases in which ADAM23 is directly involved, such as epilepsy, cancer progression and cardiac hypertrophy.

An Overview of ADAM9: Structure, Activation, and Regulation in Human Diseases

ADAM9 (A disintegrin and a metalloprotease 9) is a membrane-anchored protein that participates in a variety of physiological functions, primarily through the disintegrin domain for adhesion and the metalloprotease domain for ectodomain shedding of a wide variety of cell surface proteins. ADAM9 influences the developmental process, inflammation, and degenerative diseases. Recently, increasing evidence has shown that ADAM9 plays an important role in tumor biology. Overexpression of ADAM9 has been found in several cancer types and is correlated with tumor aggressiveness and poor prognosis. In addition, through either proteolytic or non-proteolytic pathways, ADAM9 promotes tumor progression, therapeutic resistance, and metastasis of cancers. Therefore, comprehensively understanding the mechanism of ADAM9 is crucial for the development of therapeutic anti-cancer strategies. In this review, we summarize the current understanding of ADAM9 in biological function, pathophysiological diseases, and various cancers. Recent advances in therapeutic strategies using ADAM9-related pathways are presented as well.

miR-126a-3p induces proliferation, migration and invasion of trophoblast cells in pre-eclampsia-like rats by inhibiting A Disintegrin and Metalloprotease 9

The present study aimed to investigate the underlying mechanism of miR-126a-3p in the proliferation, migration and invasion of trophoblast cells in pre-eclampsia-like rats by targeting A Disintegrin and Metalloprotease 9 (ADAM9). First, the interaction between miR-126a-3p and ADAM9 was confirmed via biochemical assays. Placental tissues and trophoblast cells were then obtained. RNA in situ hybridization was performed in order to detect miR-126a-3p expression in the placenta. Subsequently, a series of biological assays, including reverse transcription-quantitative PCR (RT-qPCR), Western blotting, MTT assay, apoptosis assay, cell cycle assay, wound healing assay and transwell assay were adopted in order to determine the cell proliferation, cell cycle distribution, apoptotic rate, and migration and invasion of trophoblast cells in each group. The results revealed that miR-126a-3p was down-regulated in the placenta of pre-eclampsia-like rats. In vivo experiments’ results indicated that miR-126a-3p could inhibit ADAM9 expression, and induce cyclin D1, Matrix metalloproteinase (MMP) 2 (MMP-2), MMP-9 expression. MTT, apoptosis and cell cycle assay results revealed that trophoblast cells transfected with miR-126a-3p mimic or si-ADAM9 exhibited higher proliferative activity and a lower apoptotic rate compared with the blank group (all P<0.05). The wound healing assay and transwell assay results confirmed that, compared with the blank group, the migration and invasion ability of trophoblast cells in the miR-126a-3p mimic group and small interfering RNA (siRNA)-ADAM9 group were significantly increased (all P<0.05). Conversely, miR-126a-3p inhibitor treatment revealed the opposite effect (all P<0.05). In conclusion, the present study demonstrated that miR-126a-3p could enhance proliferation, migration and invasion, but decrease the apoptosis rate of trophoblast cells in pre-eclampsia-like rats through targeting ADAM9.

Reverse of microtubule-directed chemotherapeutic drugs resistance induced by cancer-associated fibroblasts in breast cancer

PURPOSE

This study was designed to expound the underlying mechanism of microtubule-directed chemotherapeutic drugs resistance induced by cancer-associated fibroblasts (CAFs) in breast cancer.

MATERIALS AND METHODS

We collected 10 microtubule-directed chemotherapeutic drugs resistant breast tumor samples and 10 normal breast tumor samples to analyze the CAFs distribution by immunohistochemistry and flow cytometry. We also detected the collagen expression in CAFs by real-time PCR. We detected the activation of PI3K/AKT signaling pathway in tumor cells by Western blotting and immunofluorescence. The subcutaneous 4T1/MCF-7 bearing mice were used to investigate the anticancer effects of integrin β1 inhibitor combined with microtubule-directed chemotherapeutic drugs.

RESULTS

In our studies, accumulation of CAFs was observed in tumor samples from microtubule-directed chemotherapeutic drugs resistant patients. Those isolated CAFs could efficiently induce the acquisition of microtubule-directed chemotherapeutic drugs resistance in breast cancer cells. More importantly, we found that CAFs could regulate the microtubule-directed chemotherapeutic drugs resistance through the secretion of collagen to activate the integrin β1/PI3K/AKT signaling pathway. Combination of integrin α2β1 inhibitor and paclitaxel/vincristine sulfate could efficiently overcome the microtubule-directed chemotherapeutic drugs resistance induced by CAFs and enhanced the anticancer effects of chemotherapy in subcutaneous 4T1/MCF-7 bearing mice.

CONCLUSION

Our results demonstrated that CAFs constitute a supporting niche for cancer drug resistance acquisition. Thus, traditional microtubule-directed chemotherapeutic drugs combined with integrin β1 inhibitor may present an innovative therapeutic strategy for breast cancer therapy.

Encephalomyocarditis Virus Entry Unveiled

Picornaviruses are a widespread group of pathogens that can cause diverse pathologies. Pathogenesis is thought to be driven by the tissue-specific tropisms displayed by these viruses.

Picornaviruses are a widespread group of pathogens that can cause diverse pathologies. Pathogenesis is thought to be driven by the tissue-specific tropisms displayed by these viruses. For example, many picornaviruses can infect the heart and cause viral myocarditis. Encephalomyocarditis virus (EMCV) is a rodent pathogen that causes myocarditis in rodent models and has been used to model this biology. However, the receptor and entry requirements for this virus are poorly understood. L. E. Bazzone, M. King, C. R. MacKay, P. P. Kyawe, et al. (mBio 10:e02734-18, 2019, https://doi.org/10.1128/mBio.02734-18) tackled this problem using CRISPR knockout screening in human cells that are susceptible to EMCV and identified ADAM9 as an essential entry factor for EMCV in mouse and human cells. Since the extracellular domain but not the enzymatic activity or intracellular domain is required for infection, the data suggest that ADAM9 acts as an entry receptor or at an early step in the process, shedding light on the biology of EMCV infection and pathogenesis.

A Disintegrin and Metalloproteinase 9 Domain (ADAM9) Is a Major Susceptibility Factor in the Early Stages of Encephalomyocarditis Virus Infection

Encephalomyocarditis virus (EMCV) is a picornavirus that produces lytic infections in murine and human cells. Employing a genome-wide CRISPR-Cas9 knockout screen to find host factors required for EMCV infection, we identified a role for ADAM9 in EMCV infection. CRISPR-mediated deletion of ADAM9 in multiple human cell lines rendered the cells highly resistant to EMCV infection and cell death. Primary fibroblasts from ADAM9 KO mice were also strongly resistant to EMCV infection and cell death. In contrast, ADAM9 KO and WT cells were equally susceptible to infection with other viruses, including the picornavirus Coxsackie virus B. ADAM9 KO cells failed to produce viral progeny when incubated with EMCV. However, bypassing EMCV entry into cells through delivery of viral RNA directly to the cytosol yielded infectious EMCV virions from ADAM9 KO cells, suggesting that ADAM9 is not required for EMCV replication post-entry. These findings establish that ADAM9 is required for the early stage of EMCV infection, likely for virus entry or viral genome delivery to the cytosol.IMPORTANCE Viral myocarditis is a leading cause of death in the United States, contributing to numerous unexplained deaths in people ≤35 years old. Enteroviruses contribute to many cases of human myocarditis. Encephalomyocarditis virus (EMCV) infection causes viral myocarditis in rodent models, but its receptor requirements have not been fully identified. CRISPR-Cas9 screens can identify host dependency factors essential for EMCV infection and enhance our understanding of key events that follow viral infection, potentially leading to new strategies for preventing viral myocarditis. Using a CRISPR-Cas9 screen, we identified a disintegrin and metalloproteinase 9 domain (ADAM9) as a major factor required for the early stages of EMCV infection in both human and murine infection.

Integrin trafficking in cells and tissues

Cell adhesion to the extracellular matrix is fundamental to metazoan multicellularity and is accomplished primarily through the integrin family of cell-surface receptors. Integrins are internalized and enter the endocytic-exocytic pathway before being recycled back to the plasma membrane. The trafficking of this extensive protein family is regulated in multiple context-dependent ways to modulate integrin function in the cell. Here, we discuss recent advances in understanding the mechanisms and cellular roles of integrin endocytic trafficking.

ADAM9 contributes to vascular invasion in pancreatic ductal adenocarcinoma

A disintegrin and a metalloprotease (ADAM)‐9 is a metzincin cell‐surface protease with strongly elevated expression in solid tumors, including pancreatic ductal adenocarcinoma (PDAC). In this study, we performed immunohistochemistry (IHC) of a tissue microarray (TMA) to examine the expression of ADAM9 in a cohort of >100 clinically annotated PDAC cases. We report that ADAM9 is prominently expressed by PDAC tumor cells, and increased ADAM9 expression levels correlate with poor tumor grading (P = 0.027) and the presence of vasculature invasion (P = 0.017). We employed gene expression silencing to generate a loss‐of‐function system for ADAM9 in two established PDAC cell lines. In vitro analysis showed that loss of ADAM9 does not impede cellular proliferation and invasiveness in basement membrane. However, ADAM9 plays a crucial role in mediating cell migration and adhesion to extracellular matrix substrates such as fibronectin, tenascin, and vitronectin. This effect appears to depend on its catalytic activity. In addition, ADAM9 facilitates anchorage‐independent growth. In AsPC1 cells, but not in MiaPaCa‐2 cells, we noted a pronounced yet heterogeneous impact of ADAM9 on the abundance of various integrins, a process that we characterized as post‐translational regulation. Sprout formation of human umbilical vein endothelial cells (HUVECs) is promoted by ADAM9, as examined by transfer of cancer cell conditioned medium; this finding further supports a pro‐angiogenic role of ADAM9 expressed by PDAC cancer cells. Immunoblotting analysis of cancer cell conditioned medium highlighted that ADAM9 regulates the levels of angiogenic factors, including shed heparin‐binding EGF‐like growth factor (HB‐EGF). Finally, we carried out orthotopic seeding of either wild‐type AsPC‐1 cells or AsPC‐1 cells with silenced ADAM9 expression into murine pancreas. In this in vivo setting, ADAM9 was also found to foster angiogenesis without an impact on tumor cell proliferation. In summary, our results characterize ADAM9 as an important regulator in PDAC tumor biology with a strong pro‐angiogenic impact.

The pleiotropic roles of ADAM9 in the biology of solid tumors

A disintegrin and a metalloprotease (ADAM) 9 is a metzincin cell-surface protease involved in several biological processes such as myogenesis, fertilization, cell migration, inflammatory response, proliferation, and cell-cell interactions. ADAM9 has been found over-expressed in several solid tumors entities such as glioma, melanoma, prostate cancer, pancreatic ductal adenocarcinoma, gastric, breast, lung, and liver cancers. Immunohistochemical analyses highlight ADAM9 expression by actual cancer cells and associate its abundant presence with clinicopathological features such as shortened overall survival, poor tumor grade, de-differentiation, therapy resistance, and metastasis formation. In each of these tumors, ADAM9 may contribute to tumor biology via proteolytic or non-proteolytic mechanisms. For example, in liver cancer, ADAM9 has been found to shed MHC class I polypeptide-related sequence A, contributing towards the evasion of tumor immunity. ADAM9 may also contribute to tumor biology in non-proteolytic ways probably through interaction with different integrins. For example, in melanoma, the interaction between ADAM9 and β1 integrins facilitates tumor stroma cross talks, which then promotes invasion and metastasis via the activation of MMP1 and MMP2. In breast cancer, the interaction between β1 integrins on endothelial cells and ADAM9 on tumor cells facilitate tumor cell extravasation and invasion to distant sites. This review summarizes the present knowledge on ADAM9 in solid cancers, and the different mechanisms which it employ to drive tumor progression.