Meprinα transactivates the epidermal growth factor receptor (EGFR) via ligand shedding, thereby enhancing colorectal cancer cell proliferation and migration

Synthesis and structure-activity relationships of pyrazole-based inhibitors of meprin α and β

Targeting metalloproteinases has been in the focus of drug design for a long time. However, meprin α and β emerged as potential drug targets just recently and are linked to several diseases with different pathological background. Nevertheless, the validation of meprins as suitable drug targets still requires highly potent and selective inhibitors as chemical probes to elucidate their role in pathophysiology. Albeit highly selective inhibitors of meprin β have already been reported, only inhibitors of meprin α with modest activity or selectivity are known. Starting from recently reported heteroaromatic scaffolds, the aim of this study was the optimisation of meprin α and/or meprin β inhibition while keeping the favourable off-target inhibition profile over other metalloproteases. We report potent pan-meprin inhibitors as well as highly active inhibitors of meprin α with superior selectivity over meprin β. The latter are suitable to serve as chemical probes and enable further target validation.

Long non-coding RNA CCL14-AS suppresses invasiveness and lymph node metastasis of colorectal cancer cells by regulating MEP1A

BACKGROUND

Long non-coding RNAs (lncRNAs) play important roles in the biology of colorectal cancer (CRC). There are several lncRNAs associated with invasion and metastasis have been characterized in CRC. However, studies focusing on the precise molecular mechanisms by which lncRNAs function in lymph node (LN) metastasis in CRC are still limited.

METHODS

In this study, by analyzing TCGA dataset, we identified that AC244100.2 (termed CCL14-AS), a novel lncRNA enriched in the cytoplasm, was negatively correlated with LN metastasis and unfavorable prognosis of CRC. In situ hybridization was used to examine CCL14-AS expression in clinical CRC tissues. Various functional experiments including migration assay and wound-healing assay were used to investigate the effects of CCL14-AS on CRC cells migration. The nude mice popliteal lymph node metastasis model assay further confirmed the effects of CCL14-AS in vivo.

RESULTS

CCL14-AS expression was significantly downregulated in CRC tissues compared to adjacent normal tissues. In addition, low CCL14-AS expression was correlated with advanced T classification, LN metastasis, distant metastasis, and shorter disease-free survival of CRC patients. Functionally, CCL14-AS overexpression inhibited the invasiveness of CRC cells in vitro and LN metastasis in nude mice. On the contrary, knockdown of CCL14-AS promoted the invasiveness and LN metastasis abilities of CRC cells. Mechanistically, CCL14-AS downregulated the expression of MEP1A via interacting with MEP1A mRNA and reduced its stability. Overexpression of MEP1A rescued the invasiveness and LN metastasis abilities in CCL14-AS-overexpressing CRC cells. Moreover, the expression levels of CCL14-AS was negatively correlated with that of MEP1A in CRC tissues.

CONCLUSIONS

We identified a novel lncRNA, CCL14-AS, as a potential tumor suppressor in CRC. Our findings supported a model in which the CCL14-AS/MEP1A axis serves as critical regulator in CRC progression, suggesting a novel biomarker and therapeutic target in advanced CRC.

MT1-MMP and ADAM10/17 exhibit a remarkable overlap of shedding properties

Membrane-type-I matrix metalloproteinase (MT1-MMP) is one of six human membrane-bound MMPs and is responsible for extracellular matrix remodelling by degrading several substrates like fibrillar collagens, including types I-III, or fibronectin. Moreover, MT1-MMP was described as a key player in cancer progression and it is involved in various inflammatory processes, as well as in the pathogenesis of Alzheimer's disease (AD). The membrane-tethered metalloprotease meprin β as well as a disintegrin and metalloproteinase 10 (ADAM10) and ADAM17 are also associated with these diseases. Interestingly, meprin β, ADAM10/17 and MT1-MMP also have a shared substrate pool including the interleukin-6 receptor and the amyloid precursor protein. We investigated the interaction of these proteases, focusing on a possible connection between MT1-MMP and meprin β, to elucidate the potential mutual regulations of both enzymes. Herein, we show that besides ADAM10/17, MT1-MMP is also able to shed meprin β from the plasma membrane, leading to the release of soluble meprin β. Mass spectrometry-based cleavage site analysis revealed that the cleavage of meprin β by all three proteases occurs between Pro₆₀₂ and Ser₆₀₃ , N-terminal of the EGF-like domain. Furthermore, only inactive human pro-meprin β is shed by MT1-MMP, which is again in accordance with the shedding capability observed for ADAM10/17. Vice versa, meprin β also appears to shed MT1-MMP, indicating a complex regulatory network. Further studies will elucidate this well-orchestrated proteolytic web under distinct conditions in health and disease and will possibly show whether the loss of one of the above-mentioned sheddases can be compensated by the other enzymes.

Therapeutic potential of human serum albumin nanoparticles encapsulated actinonin in murine model of lung adenocarcinoma

Non-small cell lung cancer comprises 85% of the global lung cancer cases. Conventional chemotherapeutics possess certain limitations like systemic toxicity and drug resistance that requires the development of new therapeutic agents for successful treatment of lung cancer. Actinonin, a human peptide deformylase inhibitor, has demonstrated anti-cancerous properties in various leukemias and solid cancer types. However, it has limited therapeutic application because of its low bioavailability and systemic toxicity if administered in free form. This limitation can be overcome by using nano-delivery systems that will increase the therapeutic efficacy of actinonin. In the present study, human serum albumin actinonin nanoparticles were prepared using a desolvation technique and folic acid was conjugated to lysine residues of albumin for effective delivery to the lung. The lung adenocarcinoma model was established 24 weeks after intraperitoneal administration of urethane and chemotherapeutic efficacy of free as well as nanoencapsulated actinonin was evaluated. This study demonstrated anti-proliferative potential of folic acid conjugated human serum albumin nanoparticles encapsulating actinonin. The intraperitoneally administered nanoformulation exhibited sustain release profile of actinonin with longer half-life and mean retention time. The reduced dose frequency resulted in therapeutic efficacy comparable to free drug in vivo in terms of 100% survival and reduced tumor burden along with downregulation of epidermal growth factor receptor, folate receptor α and peptide deformylase expression in lung adenocarcinoma mice model. Therefore, actinonin encapsulated albumin nanoparticles-based therapy holds great potential as an alternative strategy to improve its anti-cancerous activity against lung adenocarcinoma.

Helical ultrastructure of the metalloprotease meprin α in complex with a small molecule inhibitor

The zinc-dependent metalloprotease meprin α is predominantly expressed in the brush border membrane of proximal tubules in the kidney and enterocytes in the small intestine and colon. In normal tissue homeostasis meprin α performs key roles in inflammation, immunity, and extracellular matrix remodelling. Dysregulated meprin α is associated with acute kidney injury, sepsis, urinary tract infection, metastatic colorectal carcinoma, and inflammatory bowel disease. Accordingly, meprin α is the target of drug discovery programs. In contrast to meprin β, meprin α is secreted into the extracellular space, whereupon it oligomerises to form giant assemblies and is the largest extracellular protease identified to date (~6 MDa). Here, using cryo-electron microscopy, we determine the high-resolution structure of the zymogen and mature form of meprin α, as well as the structure of the active form in complex with a prototype small molecule inhibitor and human fetuin-B. Our data reveal that meprin α forms a giant, flexible, left-handed helical assembly of roughly 22 nm in diameter. We find that oligomerisation improves proteolytic and thermal stability but does not impact substrate specificity or enzymatic activity. Furthermore, structural comparison with meprin β reveal unique features of the active site of meprin α, and helical assembly more broadly.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

Heteroaromatic Inhibitors of the Astacin Proteinases Meprin α, Meprin β and Ovastacin Discovered by a Scaffold-Hopping Approach

Astacin metalloproteinases, in particular meprins α and β, as well as ovastacin, are emerging drug targets. Drug-discovery efforts have led to the development of the first potent and selective inhibitors in the last few years. However, the most recent compounds are based on a highly flexible tertiary amine scaffold that could cause metabolic liabilities or decreased potency due to the entropic penalty upon binding to the target. Thus, the aim of this study was to discover novel conformationally constrained scaffolds as starting points for further inhibitor optimization. Shifting from flexible tertiary amines to rigid heteroaromatic cores resulted in a boost in inhibitory activity. Moreover, some compounds already exhibited higher activity against individual astacin proteinases compared to recently reported inhibitors and also a favorable off-target selectivity profile, thus qualifying them as very suitable chemical probes for target validation.

Research advances of secretory proteins in malignant tumors

Secretory proteins in tumor tissues are important components of the tumor microenvironment. Secretory proteins act on tumor cells or stromal cells or mediate interactions between tumor cells and stromal cells, thereby affecting tumor progression and clinical treatment efficacy. In this paper, recent research advances in secretory proteins in malignant tumors are reviewed.

Mep1a contributes to Ang II-induced cardiac remodeling by promoting cardiac hypertrophy, fibrosis and inflammation

Pathological cardiac remodeling, characterized by excessive deposition of extracellular matrix proteins and cardiac hypertrophy, leads to the development of heart failure. Meprin α (Mep1a), a zinc metalloprotease, previously reported to participate in the regulation of inflammatory response and fibrosis, may also contribute to cardiac remodeling, although whether and how it participates in this process remains unknown. Here, in this work, we investigated the role of Mep1a in pathological cardiac remodeling, as well as the effects of the Mep1a inhibitor actinonin on cardiac remodeling-associated phenotypes. We found that Mep1a deficiency or chemical inhibition both significantly alleviated TAC- and Ang II-induced cardiac remodeling and dysfunction. Mep1a deletion and blocking both attenuated TAC- and Ang II-induced heart enlargement and increases in the thickness of the left ventricle anterior and posterior walls, and reduced expression of pro-hypertrophic markers, including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and myosin heavy chain beta (β-MHC). In addition, Mep1a deletion and blocking significantly inhibited TAC- and Ang II-induced cardiac fibroblast activation and production of extracellular matrix (ECM). Moreover, in Mep1a^-/- mice and treatment with actinonin significantly reduced Ang II-induced infiltration of macrophages and proinflammatory cytokines. Notably, we found that in vitro, Mep1a is expressed in cardiac myocytes and fibroblasts and that Mep1a deletion or chemical inhibition both markedly suppressed Ang II-induced hypertrophy of rat or mouse cardiac myocytes and activation of rat or mouse cardiac fibroblasts. In addition, blocking Mep1a in macrophages reduced Ang II-induced expression of interleukin (IL)-6 and IL-1β, strongly suggesting that Mep1a participates in cardiac remodeling processes through regulation of inflammatory cytokine expression. Mechanism studies revealed that Mep1a mediated ERK1/2 activation in cardiac myocytes, fibroblasts and macrophages and contributed to cardiac remodeling. In light of our findings that blocking Mep1a can ameliorate cardiac remodeling via inhibition of cardiac hypertrophy, fibrosis, and inflammation, Mep1a may therefore serve as a strong potential candidate for therapeutic targeting to prevent cardiac remodeling.

Role of meprin metalloproteases in metastasis and tumor microenvironment

A crucial step for tumor cell extravasation and metastasis is the migration through the extracellular matrix, which requires proteolytic activity. Hence, proteases, particularly matrix metalloproteases (MMPs), have been discussed as therapeutic targets and their inhibition should diminish tumor growth and metastasis. The metalloproteases meprin α and meprin β are highly abundant on intestinal enterocytes and their expression was associated with different stages of colorectal cancer. Due to their ability to cleave extracellular matrix (ECM) components, they were suggested as pro-tumorigenic enzymes. Additionally, both meprins were shown to have pro-inflammatory activity by cleaving cytokines and their receptors, which correlates with chronic intestinal inflammation and associated conditions. On the other hand, meprin β was identified as an essential enzyme for the detachment and renewal of the intestinal mucus, important to prevent bacterial overgrowth and infection. Considering this, it is hard to estimate whether high activity of meprins is generally detrimental or if these enzymes have also protective functions in certain cancer types. For instance, for colorectal cancer, patients with high meprin β expression in tumor tissue exhibit a better survival prognosis, which is completely different to prostate cancer. This demonstrates that the very same enzyme may have contrary effects on tumor initiation and growth, depending on its tissue and subcellular localization. Hence, precise knowledge about proteolytic enzymes is required to design the most efficient therapeutic options for cancer treatment. In this review, we summarize the current findings on meprins' functions, expression, and cancer-associated variants with possible implications for tumor progression and metastasis.

LncRNA SLCO4A1-AS1 predicts poor prognosis and promotes proliferation and metastasis via the EGFR/MAPK pathway in colorectal cancer

It is universally acknowledged that long non-coding RNAs (lncRNAs) involved in tumorigenesis in human cancers. However, the function and mechanism of many lncRNAs in colorectal cancer (CRC) remain unclear. By analyzing the two sets of CRC-related gene microarrays data, downloaded from the Gene Expression Omnibus (GEO) database and the lncRNA expression in a set of RNA sequencing data, we found that lncRNA SLCO4A1-AS1 was significantly upregulated in CRC tissues. We then collected CRC tissue samples and verified that SLCO4A1-AS1 is highly expressed in CRC tissues. Furthermore, SLCO4A1-AS1 was also upregulated in the CRC cell line. In situ hybridization results showed that high expression of SLCO4A1-AS1 was associated with poor prognosis in patients with CRC. Next, we found that SLCO4A1-AS1 promoted CRC cell proliferation, migration, and invasion. Results of western blotting assays show that its mechanism may relate to the epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) pathway. Therefore, SLCO4A1-AS1 may be a potential biomarker for CRC prognosis and a new target for colorectal cancer therapy.

O-GlcNAc-induced nuclear translocation of hnRNP-K is associated with progression and metastasis of cholangiocarcinoma

O‐GlcNAcylation is a key post‐translational modification that modifies the functions of proteins. Associations between O‐GlcNAcylation, shorter survival of cholangiocarcinoma (CCA) patients, and increased migration/invasion of CCA cell lines have been reported. However, the specific O‐GlcNAcylated proteins (OGPs) that participate in promotion of CCA progression are poorly understood. OGPs were isolated from human CCA cell lines, KKU‐213 and KKU‐214, using a click chemistry‐based enzymatic labeling system, identified using LC‐MS/MS, and searched against an OGP database. From the proteomic analysis, a total of 21 OGPs related to cancer progression were identified, of which 12 have not been previously reported. Among these, hnRNP‐K, a multifaceted RNA‐ and DNA‐binding protein known as a pre‐mRNA‐binding protein, was one of the most abundantly expressed, suggesting its involvement in CCA progression. O‐GlcNAcylation of hnRNP‐K was further verified by anti‐OGP/anti‐hnRNP‐K immunoprecipitations and sWGA pull‐down assays. The perpetuation of CCA by hnRNP‐K was evaluated using siRNA, which revealed modulation of cyclin D1, XIAP, EMT markers, and MMP2 and MMP7 expression. In native CCA cells, hnRNP‐K was primarily localized in the nucleus; however, when O‐GlcNAcylation was suppressed, hnRNP‐K was retained in the cytoplasm. These data signify an association between nuclear accumulation of hnRNP‐K and the migratory capabilities of CCA cells. In human CCA tissues, expression of nuclear hnRNP‐K was positively correlated with high O‐GlcNAcylation levels, metastatic stage, and shorter survival of CCA patients. This study demonstrates the significance of O‐GlcNAcylation on the nuclear translocation of hnRNP‐K and its impact on the progression of CCA.

Metalloproteinase meprin α regulates migration and invasion of human hepatocarcinoma cells and is a mediator of the oncoprotein Reptin

Hepatocellular carcinoma is associated with a high rate of intra-hepatic invasion that carries a poor prognosis. Meprin alpha (Mep1A) is a secreted metalloproteinase with many substrates relevant to cancer invasion. We found that Mep1A was a target of Reptin, a protein that is oncogenic in HCC. We studied Mep1A regulation by Reptin, its role in HCC, and whether it mediates Reptin oncogenic effects.

MepA and Reptin expression was measured in human HCC by qRT-PCR and in cultured cells by PCR, western blot and enzymatic activity measurements. Cell growth was assessed by counting and MTS assay. Cell migration was measured in Boyden chambers and wound healing assays, and cell invasion in Boyden chambers.

Silencing Reptin decreased Mep1A expression and activity, without affecting meprin β. Mep1A, but not meprin β, was overexpressed in a series of 242 human HCC (2.04 fold, p < 0.0001), and a high expression correlated with a poor prognosis. Mep1A and Reptin expressions were positively correlated (r = 0.39, p < 0.0001). Silencing Mep1A had little effect on cell proliferation, but decreased cell migration and invasion of HuH7 and Hep3B cells. Conversely, overexpression of Mep1A or addition of recombinant Mep1A increased migration and invasion. Finally, overexpression of Mep1A restored a normal cell migration in cells where Reptin was depleted.

Mep1A is overexpressed in most HCC and induces HCC cell migration and invasion. Mep1A expression is regulated by Reptin, and Mep1A mediates Reptin-induced migration. Overall, we suggest that Mep1A may be a useful target in HCC.

The Role of Pontin and Reptin in Cellular Physiology and Cancer Etiology

Pontin (RUVBL1, TIP49, TIP49a, Rvb1) and Reptin (RUVBL2, TIP48, TIP49b, Rvb2) are highly conserved ATPases of the AAA+ (ATPases Associated with various cellular Activities) superfamily and are involved in various cellular processes that are important for oncogenesis. First identified as being upregulated in hepatocellular carcinoma and colorectal cancer, their overexpression has since been shown in multiple cancer types such as breast, lung, gastric, esophageal, pancreatic, kidney, bladder as well as lymphatic, and leukemic cancers. However, their exact functions are still quite unknown as they interact with many molecular complexes with vastly different downstream effectors. Within the nucleus, Pontin and Reptin participate in the TIP60 and INO80 complexes important for chromatin remodeling. Although not transcription factors themselves, Pontin and Reptin modulate the transcriptional activities of bona fide proto-oncogenes such as MYC and β-catenin. They associate with proteins involved in DNA damage repair such as PIKK complexes as well as with the core complex of Fanconi anemia pathway. They have also been shown to be important for cell cycle progression, being involved in assembly of telomerase, mitotic spindle, RNA polymerase II, and snoRNPs. When the two ATPases localize to the cytoplasm, they were reported to promote cancer cell invasion and metastasis. Due to their various roles in carcinogenesis, it is not surprising that Pontin and Reptin are proving to be important biomarkers for diagnosis and prognosis of various cancers. They are also current targets for the development of new therapeutic anticancer drugs.

Meprin metalloproteases: Molecular regulation and function in inflammation and fibrosis

The zinc-endopeptidases meprin α and meprin β are extracellular proteases involved in connective tissue homeostasis, intestinal barrier function and immunological processes. Meprins are unique among other extracellular proteases with regard to cleavage specificity and structure. Meprin α and meprin β have a strong preference for negatively charged amino acids around the scissile bond, reflected by cleavage sites identified in procollagen I, the amyloid precursor protein (APP) and the interleukin-6 receptor (IL-6R). In this review we report on recent findings that summarize the complex molecular regulation of meprins, particular folding, activation and shedding. Dysregulation of meprin α and meprin β is often associated with pathological conditions such as neurodegeneration, inflammatory bowel disease and fibrosis. Based on mouse models and patient data we suggest meprins as possible key regulators in the onset and progression of fibrotic disorders, leading to severe diseases such as pulmonary hypertension. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.

Komodo dragon-inspired synthetic peptide DRGN-1 promotes wound-healing of a mixed-biofilm infected wound

Cationic antimicrobial peptides are multifunctional molecules that have a high potential as therapeutic agents. We have identified a histone H1-derived peptide from the Komodo dragon (Varanus komodoensis), called VK25. Using this peptide as inspiration, we designed a synthetic peptide called DRGN-1. We evaluated the antimicrobial and anti-biofilm activity of both peptides against Pseudomonas aeruginosa and Staphylococcus aureus. DRGN-1, more than VK25, exhibited potent antimicrobial and anti-biofilm activity, and permeabilized bacterial membranes. Wound healing was significantly enhanced by DRGN-1 in both uninfected and mixed biofilm (Pseudomonas aeruginosa and Staphylococcus aureus)-infected murine wounds. In a scratch wound closure assay used to elucidate the wound healing mechanism, the peptide promoted the migration of HEKa keratinocyte cells, which was inhibited by mitomycin C (proliferation inhibitor) and AG1478 (epidermal growth factor receptor inhibitor). DRGN-1 also activated the EGFR-STAT1/3 pathway. Thus, DRGN-1 is a candidate for use as a topical wound treatment. Wound infections are a major concern; made increasingly complicated by the emerging, rapid spread of bacterial resistance. The novel synthetic peptide DRGN-1 (inspired by a peptide identified from Komodo dragon) exhibits pathogen-directed and host-directed activities in promoting the clearance and healing of polymicrobial (Pseudomonas aeruginosa & Staphylococcus aureus) biofilm infected wounds. The effectiveness of this peptide cannot be attributed solely to its ability to act upon the bacteria and disrupt the biofilm, but also reflects the peptide’s ability to promsote keratinocyte migration. When applied in a murine model, infected wounds treated with DRGN-1 healed significantly faster than did untreated wounds, or wounds treated with other peptides. The host-directed mechanism of action was determined to be via the EGFR-STAT1/3 pathway. The pathogen-directed mechanism of action was determined to be via anti-biofilm activity and antibacterial activity through membrane permeabilization. This novel peptide may have potential as a future therapeutic for treating infected wounds.

A synthetic peptide based on a natural molecule found in the Komodo dragon promotes healing of biofilm-infected wounds. Peptides are small protein-like molecules. Monique van Hoek, Barney Bishop and colleagues at George Mason University in Virginia, USA, isolated a natural peptide with some antimicrobial properties from Komodo dragon plasma. They designed a modified synthetic version with rearranged amino acids, named DRGN-1 in recognition of the “Komodo dragon” peptide that inspired it. In preliminary trials, DRGN-1 enhanced the healing of biofilm-infected wounds in mice, and was more effective than the natural peptide. This may be due to both bacterial- and host-directed effects. DRGN-1 reduced biofilm and bacterial number while increasing wound closure. The authors suggest DRGN-1 could be developed into a therapeutic agent that may treat the biofilm-infected wounds that are increasingly resistant to conventional antibiotics.

Tetraspanins Function as Regulators of Cellular Signaling

Tetraspanins are molecular scaffolds that distribute proteins into highly organized microdomains consisting of adhesion, signaling, and adaptor proteins. Many reports have identified interactions between tetraspanins and signaling molecules, finding unique downstream cellular consequences. In this review, we will explore these interactions as well as the specific cellular responses to signal activation, focusing on tetraspanin regulation of adhesion-mediated (integrins/FAK), receptor-mediated (EGFR, TNF-α, c-Met, c-Kit), and intracellular signaling (PKC, PI4K, β-catenin). Additionally, we will summarize our current understanding for how tetraspanin post-translational modifications (palmitoylation, N-linked glycosylation, and ubiquitination) can regulate signal propagation. Many of the studies outlined in this review suggest that tetraspanins offer a potential therapeutic target to modulate aberrant signal transduction pathways that directly impact a host of cellular behaviors and disease states.

Meprin Metalloproteases Generate Biologically Active Soluble Interleukin-6 Receptor to Induce Trans-Signaling

Soluble Interleukin-6 receptor (sIL-6R) mediated trans-signaling is an important pro-inflammatory stimulus associated with pathological conditions, such as arthritis, neurodegeneration and inflammatory bowel disease. The sIL-6R is generated proteolytically from its membrane bound form and A Disintegrin And Metalloprotease (ADAM) 10 and 17 were shown to perform ectodomain shedding of the receptor in vitro and in vivo. However, under certain conditions not all sIL-6R could be assigned to ADAM10/17 activity. Here, we demonstrate that the IL-6R is a shedding substrate of soluble meprin α and membrane bound meprin β, resulting in bioactive sIL-6R that is capable of inducing IL-6 trans-signaling. We determined cleavage within the N-terminal part of the IL-6R stalk region, distinct from the cleavage site reported for ADAM10/17. Interestingly, meprin β can be shed from the cell surface by ADAM10/17 and the observation that soluble meprin β is not capable of shedding the IL-6R suggests a regulatory mechanism towards trans-signaling. Additionally, we observed a significant negative correlation of meprin β expression and IL-6R levels on human granulocytes, providing evidence for in vivo function of this proteolytic interaction.

MEP1A contributes to tumor progression and predicts poor clinical outcome in human hepatocellular carcinoma

Although many staging classifications have been proposed for hepatocellular carcinoma (HCC), determining a patient's prognosis in clinical practice is a challenge due to the molecular diversity of HCC. We investigated the relationship between MEP1A, a candidate oncogene, and clinical outcomes of HCC patients; furthermore, we explored the role of MEP1A in HCC. In this report, it was demonstrated by quantitative real-time polymerase chain reaction that MEP1A messenger RNA levels were significantly elevated in HCC tumor tissues compared with matched adjacent nonneoplastic tissues and nonmalignant liver disease tissues. Immunohistochemical analyses of tissue samples from two independent groups of 394 HCC patients showed that positive expression of MEP1A in tumor cells was an independent and significant risk factor affecting survival after curative resection in both cohort 1 (hazard ratio = 2.05, 95% confidence interval 1.427-2.946; P < 0.001) and cohort 2 (hazard ratio = 1.89, 95% confidence interval 1.260-2.833; P = 0.002). Analysis of Barcelona Clinic Liver Cancer stage 0-A subgroup further showed that patients with positive MEP1A expression in tumor cells had poorer surgical prognoses than those with negative MEP1A expression in tumor cells (cohort 1 P = 0.001, cohort 2 P < 0.001). Both in vitro and in vivo assays showed that MEP1A promoted HCC cell proliferation, migration, and invasion. Further analyses found that MEP1A played an important role in regulating cytoskeletal events and induced epithelial-mesenchymal transition in HCC cells.

CONCLUSION

MEP1A is a novel prognostic predictor in HCC and plays an important role in the development and progression of HCC.

Urinary signatures of Renal Cell Carcinoma investigated by peptidomic approaches

Renal Cell Carcinoma (RCC) is typically asymptomatic and surgery usually increases patient's lifespan only for early stage tumours. Moreover, solid renal masses cannot be confidently differentiated from RCC. Therefore, markers to distinguish malignant kidney tumours and for their detection are needed. Two different peptide signatures were obtained by a MALDI-TOF profiling approach based on urine pre-purification by C8 magnetic beads. One cluster of 12 signals could differentiate malignant tumours (n = 137) from benign renal masses and controls (n = 153) with sensitivity of 76% and specificity of 87% in the validation set. A second cluster of 12 signals distinguished clear cell RCC (n = 118) from controls (n = 137) with sensitivity and specificity values of 84% and 91%, respectively. Most of the peptide signals used in the two models were observed at higher abundance in patient urines and could be identified as fragments of proteins involved in tumour pathogenesis and progression. Among them: the Meprin 1α with a pro-angiogenic activity, the Probable G-protein coupled receptor 162, belonging to the GPCRs family and known to be associated with several key functions in cancer, the Osteopontin that strongly correlates to tumour stages and invasiveness, the Phosphorylase b kinase regulatory subunit alpha and the SeCreted and TransMembrane protein 1.

Transforming growth factor alpha promotes osteosarcoma metastasis by ICAM-1 and PI3K/Akt signaling pathway

Osteosarcoma is the most common primary malignancy of bone and is characterized by a high malignant and metastatic potential. Transforming growth factor alpha (TGF-α) is classified as the EGF (epidermal growth factor)-like family, which is involved in cancer cellular activities such as proliferation, motility, migration, adhesion and invasion abilities. However, the effect of TGF-α on human osteosarcoma is largely unknown. We found that TGF-α increased the cell migration and expression of intercellular adhesion molecule-1 (ICAM-1) in human osteosarcoma cells. Transfection of cells with ICAM-1 siRNA reduced TGF-α-mediated cell migration. We also found that the phosphatidylinositol 3'-kinase (PI3K)/Akt/NF-κB pathway was activated after TGF-α treatment, and TGF-α-induced expression of ICAM-1 and cell migration was inhibited by the specific inhibitors and siRNAs of PI3K, Akt, and NF-κB cascades. In addition, knockdown of TGF-α expression markedly decreased cell metastasis in vitro and in vivo. Our results indicate that TGF-α/EGFR interaction elicits PI3K and Akt activation, which in turn activates NF-κB, resulting in the expression of ICAM-1 and contributing the migration of human osteosarcoma cells.

From wavy hair to naked proteins: the role of transforming growth factor alpha in health and disease

Since its discovery in 1978 and cloning in 1984, transforming growth factor-alpha (TGF-α, TGFA) has been one of the most extensively studied EGF receptor (EGFR) ligands. In this review, we provide a historical perspective on TGFA-related studies, highlighting what we consider important advances related to its function in normal and disease states.

Meprin-β regulates production of pro-inflammatory factors via a disintegrin and metalloproteinase-10 (ADAM-10) dependent pathway in macrophages

Inflammatory response plays an important role not only in the normal physiology but also in the pathology such as atherosclerosis. Meprin, an astacin metalloproteinase, has exhibited proinflammatory effects in vivo and in vitro studies. Here, we tried to further investigate the proinflammatory potential of meprin-β and the possible underlying mechanisms in primary human peripheral blood macrophages. In our current study, ELISA assay revealed that meprin-β increased the production of pro-inflammatory cytokines, including interleukin-1β (IL-1β), interleukin-18 and interleukin-6 (IL-6) in macrophages. However, meprin-β shows no effects on the level of ligands of epidermal growth factor receptor (EGFR), and the activation of EGFR. The molecular mechanism was associated with activation of a disintegrin and metalloproteinase 10 (ADAM10) and the phosphorylation of IκB. Further analysis of upstream mechanisms showed that activation of NF-κB by meprin-β was mediated by inhibiting ADAM10-downstream extracellular signal regulated kinase (ERK1/2) pathway. Taken together, these results indicated that meprin-β exhibited pro-inflammatory effects by targeting activating ADAM10, leading to ERK1/2-mediated activation of NF-κB in macrophages, and this would make meprin-β a strong candidate for further study as proinflammatory target.

IMAC fractionation in combination with LC-MS reveals H2B and NIF-1 peptides as potential bladder cancer biomarkers

Improvement in bladder cancer (BC) management requires more effective diagnosis and prognosis of disease recurrence and progression. Urinary biomarkers attract special interest because of the noninvasive means of urine collection. Proteomic analysis of urine entails the adoption of a fractionation methodology to reduce sample complexity. In this study, we applied immobilized metal affinity chromatography in combination with high-resolution LC-MS/MS for the discovery of native urinary peptides potentially associated with BC aggressiveness. This approach was employed toward urine samples from patients with invasive BC, noninvasive BC, and benign urogenital diseases. A total of 1845 peptides were identified, corresponding to a total of 638 precursor proteins. Specific enrichment for proteins involved in nucleosome assembly and for zinc-finger transcription factors was observed. The differential expression of two candidate biomarkers, histone H2B and NIF-1 (zinc finger 335) in BC, was verified in independent sets of urine samples by ELISA and by immunohistochemical analysis of BC tissue. The results collectively support changes in the expression of both of these proteins with tumor progression, suggesting their potential role as markers for discriminating BC stages. In addition, the data indicate a possible involvement of NIF-1 in BC progression, likely as a suppressor and through interactions with Sox9 and HoxA1.

The metalloproteases meprin α and meprin β: unique enzymes in inflammation, neurodegeneration, cancer and fibrosis

The metalloproteases meprin α and meprin β exhibit structural and functional features that are unique among all extracellular proteases. Although meprins were discovered more than 30 years ago, their precise substrates and physiological roles have been elusive. Both enzymes were originally found to be highly expressed in kidney and intestine, which focused research on these particular tissues and associated pathologies. Only recently it has become evident that meprins exhibit a much broader expression pattern, implicating functions in angiogenesis, cancer, inflammation, fibrosis and neurodegenerative diseases. Different animal models, as well as proteomics approaches for the identification of protease substrates, have helped to reveal more precise molecular signalling events mediated by meprin activity, such as activation and release of pro-inflammatory cytokines. APP (amyloid precursor protein) is cleaved by meprin β in vivo, reminiscent of the β-secretase BACE1 (β-site APP-cleaving enzyme 1). The subsequent release of Aβ (amyloid β) peptides is thought to be the major cause of the neurodegenerative Alzheimer's disease. On the other hand, ADAM10 (a disintegrin and metalloprotease domain 10), which is the constitutive α-secretase, was shown to be activated by meprin β, which is itself shed from the cell surface by ADAM10. In skin, both meprins are overexpressed in fibrotic tumours, characterized by massive accumulation of fibrillar collagens. Indeed, procollagen III is processed to its mature form by meprin α and meprin β, an essential step in collagen fibril assembly. The recently solved crystal structure of meprin β and the unique cleavage specificity of these proteases identified by proteomics will help to generate specific inhibitors that could be used as therapeutics to target meprins under certain pathological conditions.

Epidermal growth factor regulates hematopoietic regeneration after radiation injury

The mechanisms which regulate HSC regeneration following myelosuppressive injury are not well understood. We identified epidermal growth factor (EGF) to be highly enriched in the bone marrow (BM) serum of mice bearing deletion of Bak and Bax in Tie2⁺ cells (Tie2Cre;Bak1^−/−;Bax^fl/− mice), which displayed radioprotection of the HSC pool and 100% survival following lethal dose total body irradiation (TBI). BM HSCs from wild type mice expressed functional EGFR and systemic administration of EGF promoted the recovery of the HSC pool in vivo and the improved survival of mice following TBI. Conversely, administration of erlotinib, an EGFR antagonist, significantly decreased both HSC regeneration and mice survival following TBI. VavCre;EGFR^fl/+ mice also demonstrated delayed recovery of BM stem/progenitor cells following TBI compared to VavCre;EGFR^+/+ mice. Mechanistically, EGF reduced radiation-induced apoptosis of HSCs and mediated this effect via repression of the proapoptotic protein, PUMA. EGFR signaling regulates HSC regeneration following myelosuppressive injury.