Type II transmembrane serine proteases as potential targets for cancer therapy

Development of ketobenzothiazole-based peptidomimetic TMPRSS13 inhibitors with low nanomolar potency

TMPRSS13, a member of the Type II Transmembrane Serine Proteases (TTSP) family, is involved in cancer progression and in cell entry of respiratory viruses. To date, no inhibitors have been specifically developed toward this protease. In this study, a chemical library of 65 ketobenzothiazole-based peptidomimetic molecules was screened against a proteolytically active form of recombinant TMPRSS13 to identify novel inhibitors. Following an initial round of screening, subsequent synthesis of additional derivatives supported by molecular modelling, uncovered important molecular determinants involved in TMPRSS13 inhibition. One inhibitor, N-0430, achieved low nanomolar affinity towards TMPRSS13 activity in a cellular context. Using a SARS-CoV-2 pseudovirus cell entry model, we further show the ability of N-0430 to block TMPRSS13-dependent entry of the pseudovirus. The identified peptidomimetic inhibitors and the molecular insights of their potency gained from this study will aid in the development of specific TMPRSS13 inhibitors.

TMPRSS4, a type II transmembrane serine protease, as a potential therapeutic target in cancer

Proteases are involved in almost all biological processes, implying their importance for both health and pathological conditions. Dysregulation of proteases is a key event in cancer. Initially, research identified their role in invasion and metastasis, but more recent studies have shown that proteases are involved in all stages of cancer development and progression, both directly through proteolytic activity and indirectly via regulation of cellular signaling and functions. Over the past two decades, a novel subfamily of serine proteases called type II transmembrane serine proteases (TTSPs) has been identified. Many TTSPs are overexpressed by a variety of tumors and are potential novel markers of tumor development and progression; these TTSPs are possible molecular targets for anticancer therapeutics. The transmembrane protease serine 4 (TMPRSS4), a member of the TTSP family, is upregulated in pancreatic, colorectal, gastric, lung, thyroid, prostate, and several other cancers; indeed, elevated expression of TMPRSS4 often correlates with poor prognosis. Based on its broad expression profile in cancer, TMPRSS4 has been the focus of attention in anticancer research. This review summarizes up-to-date information regarding the expression, regulation, and clinical relevance of TMPRSS4, as well as its role in pathological contexts, particularly in cancer. It also provides a general overview of epithelial-mesenchymal transition and TTSPs.

Downregulation of Matriptase Inhibits Porphyromonas gingivalis Lipopolysaccharide-Induced Matrix Metalloproteinase-1 and Proinflammatory Cytokines by Suppressing the TLR4/NF-κB Signaling Pathways in Human Gingival Fibroblasts

Matriptases are cell surface proteolytic enzymes belonging to the type II transmembrane serine protease family that mediate inflammatory skin disorders and cancer progression. Matriptases may affect the development of periodontitis via protease-activated receptor-2 activity. However, the cellular mechanism by which matriptases are involved in periodontitis is unknown. In this study, we examined the antiperiodontitis effects of matriptase on Porphyromonas gingivalis-derived lipopolysaccharide (PG-LPS)-stimulated human gingival fibroblasts (HGFs). Matriptase small interfering RNA-transfected HGFs were treated with PG-LPS. The mRNA and protein levels of proinflammatory cytokines and matrix metalloproteinase 1 (MMP-1) were evaluated using the quantitative real-time polymerase chain reaction (qRT-PCR) and an enzyme-linked immunosorbent assay (ELISA), respectively. Western blot analyses were performed to measure the levels of Toll-like receptor 4 (TLR4)/interleukin-1 (IL-1) receptor-associated kinase (IRAK)/transforming growth factor β-activated kinase 1 (TAK1), p65, and p50 in PG-LPS-stimulated HGFs. Matriptase downregulation inhibited LPS-induced proinflammatory cytokine expression, including the expression of IL-6, IL-8, tumor necrosis factor-α (TNF-α), and IL-Iβ. Moreover, matriptase downregulation inhibited PG-LPS-stimulated MMP-1 expression. Additionally, we confirmed that the mechanism underlying the effects of matriptase downregulation involves the suppression of PG-LPS-induced IRAK1/TAK1 and NF-κB. These results suggest that downregulation of matriptase PG-LPS-induced MMP-1 and proinflammatory cytokine expression via TLR4-mediated IRAK1/TAK1 and NF-κB signaling pathways in HGFs.

TMPRSS13 zymogen activation, surface localization, and shedding is regulated by proteolytic cleavage within the non-catalytic stem region

TMPRSS13 is a member of the type II transmembrane serine protease (TTSP) family. Here we characterize a novel post-translational mechanism important for TMPRSS13 function: proteolytic cleavage within the extracellular TMPRSS13 stem region located between the transmembrane domain and the first site of N-linked glycosylation at asparagine (N)-250 in the scavenger receptor cysteine rich (SRCR) domain. Importantly, the catalytic competence of TMPRSS13 is essential for stem region cleavage, suggesting an autonomous mechanism of action. Site-directed mutagenesis of the 10 basic amino acids (four arginine and six lysine residues) in this region abrogated zymogen activation and catalytic activity of TMPRSS13, as well as phosphorylation, cell surface expression, and shedding. Mutation analysis of individual arginine residues identified R223, a residue located between the low-density lipoprotein receptor class A domain and the SRCR domain, as important for stem region cleavage. Mutation of R223 causes a reduction in the aforementioned functional processing steps of TMPRSS13. These data provide further insight into the roles of different post-translational modifications as regulators of the function and localization of TMPRSS13. Additionally, the data suggest the presence of complex interconnected regulatory mechanisms that may serve to ensure the proper levels of cell-surface and pericellular TMPRSS13-mediated proteolysis under homeostatic conditions.

Implication of Hepsin from Primary Tumor in the Prognosis of Colorectal Cancer Patients

Hepsin is a type II transmembrane serine protease whose deregulation promotes tumor invasion by proteolysis of the pericellular components. In colorectal cancer, the implication of hepsin is unknown. Consequently, we aimed to study the correlations between hepsin expression and different clinical-histopathological variables in 169 patients with localized colorectal cancer and 118 with metastases. Tissue microarrays were produced from samples at diagnosis of primary tumors and stained with an anti-hepsin antibody. Hepsin expression was correlated with clinical-histopathological variables by using the chi-square and Kruskal−Wallis tests, Kaplan−Meier and Aalen−Johansen estimators, and Cox and Fine and Gray multivariate models. In localized cancer patients, high-intensity hepsin staining was associated with reduced 5-year disease-free survival (p-value = 0.16). Medium and high intensity of hepsin expression versus low expression was associated with an increased risk of metastatic relapse (hazard ratio 2.83, p-value = 0.035 and hazard ratio 3.30, p-value = 0.012, respectively), being a better prognostic factor than classic histological variables. Additionally, in patients with localized tumor, 5-year thrombosis cumulative incidence increased with the increment of hepsin expression (p-value = 0.038). Medium and high intensities of hepsin with respect to low intensity were associated with an increase in thrombotic risk (hazard ratio 7.71, p-value = 0.043 and hazard ratio 9.02, p-value = 0.028, respectively). This relationship was independent of previous tumor relapse (p-value = 0.036). Among metastatic patients, low hepsin expression was associated with a low degree of tumor differentiation (p-value < 0.001) and with major metastatic dissemination (p-value = 0.023). Hepsin is a potential thrombotic and metastatic biomarker in patients with localized colorectal cancer. In metastatic patients, hepsin behaves in a paradoxical way with respect to differentiation and invasion processes.

Proteases and HPV-Induced Carcinogenesis

Simple Summary

Human papillomavirus (HPV) infection is a sexually transmitted disease with high prevalence worldwide. Although most HPV infections do not lead to cancer, some HPV types are correlated with the majority of cervical cancers, and with some anogenital and oropharyngeal cancers. Moreover, enzymes known as proteases play an essential role in the pathogenic process in HPV-induced carcinogenesis. This review highlights the role of proteases and recent epidemiological data regarding HPV-dependent carcinogenesis.

Abstract

Persistent infection with Human papillomavirus (HPV) is the main etiologic factor for pre-malignant and malignant cervical lesions. Moreover, HPV is also associated with oropharynx and other anogenital carcinomas. Cancer-causing HPV viruses classified as group 1 carcinogens include 12 HPV types, with HPV 16 and 18 being the most prevalent. High-risk HPVs express two oncoproteins, E6 and E7, the products of which are responsible for the inhibition of p53 and pRB proteins, respectively, in human keratinocytes and cellular immortalization. p53 and pRB are pleiotropic proteins that regulate the activity of several signaling pathways and gene expression. Among the important factors that are augmented in HPV-mediated carcinogenesis, proteases not only control processes involved in cellular carcinogenesis but also control the microenvironment. For instance, genetic polymorphisms of matrix metalloproteinase 1 (MMP-1) are associated with carcinoma invasiveness. Similarly, the serine protease inhibitors hepatocyte growth factor activator inhibitor-1 (HAI-1) and -2 (HAI-2) have been identified as prognostic markers for HPV-dependent cervical carcinomas. This review highlights the most crucial mechanisms involved in HPV-dependent carcinogenesis, and includes a section on the proteolytic cascades that are important for the progression of this disease and their impact on patient health, treatment, and survival.

Downregulation of matriptase suppresses the PAR‑2/PLCγ2/PKC‑mediated invasion and migration abilities of MCF‑7 breast cancer cells

Matriptases, members of the type II transmembrane serine protease family, are cell surface proteolytic enzymes that mediate tumor invasion and metastasis. Matriptase is highly expressed in breast cancer and is associated with poor patient outcome. However, the cellular mechanism by which matriptase mediates breast cancer invasion remains unknown. The present study aimed to determine the role of matriptase in the protein kinase C (PKC)‑mediated metastasis of MCF‑7 human breast cancer cells. Matriptase small interfering RNA‑mediated knockdown significantly attenuated the 12‑O‑tetradecanoylphorbol‑13‑acetate (TPA)‑induced invasiveness and migration of MCF‑7 cells, and inhibited the activation of phospholipase C γ2 (PLCγ2)/PKC/MAPK signaling pathways. Matriptase‑knockdown also suppressed the expression of MMP‑9 and inhibited the activation of NF‑κB/activator protein‑1 in MCF‑7 cells. Additionally, GB83 [an inhibitor of protease‑activated receptor‑2 (PAR‑2)] inhibited PKC‑mediated MMP‑9 expression and metastatic ability in MCF‑7 cells. Furthermore, downregulation of matriptase suppressed TPA‑induced MMP‑9 expression and invasiveness via PAR‑2/PLCγ2/PKC/MAPK activation. These findings shed light on the mechanism underlying the role of matriptase in MCF‑7 cell invasion and migration ability, and suggest that matriptase modulation could be a promising therapeutic strategy for preventing breast cancer metastasis.

Posttranslational modifications of serine protease TMPRSS13 regulate zymogen activation, proteolytic activity, and cell surface localization

TMPRSS13, a member of the type II transmembrane serine protease (TTSP) family, harbors four N-linked glycosylation sites in its extracellular domain. Two of the glycosylated residues are located in the scavenger receptor cysteine-rich (SRCR) protein domain, while the remaining two sites are in the catalytic serine protease (SP) domain. In this study, we examined the role of N-linked glycosylation in the proteolytic activity, autoactivation, and cellular localization of TMPRSS13. Individual and combinatory site-directed mutagenesis of the glycosylated asparagine residues indicated that glycosylation of the SP domain is critical for TMPRSS13 autoactivation and catalytic activity toward one of its protein substrates, the prostasin zymogen. Additionally, SP domain glycosylation-deficient TMPRSS13 displayed impaired trafficking of TMPRSS13 to the cell surface, which correlated with increased retention in the endoplasmic reticulum. Importantly, we showed that N-linked glycosylation was a critical determinant for subsequent phosphorylation of endogenous TMPRSS13. Taken together, we conclude that glycosylation plays an important role in regulating TMPRSS13 activation and activity, phosphorylation, and cell surface localization.

Kallikrein 5 Inhibition by the Lympho-Epithelial Kazal-Type Related Inhibitor Hinders Matriptase-Dependent Carcinogenesis

Head and neck squamous cell carcinoma remains challenging to treat with no improvement in survival rates over the past 50 years. Thus, there is an urgent need to discover more reliable therapeutic targets and biomarkers for HNSCC. Matriptase, a type-II transmembrane serine protease, induces malignant transformation in epithelial stem cells through proteolytic activation of pro-HGF and PAR-2, triggering PI3K-AKT-mTOR and NFKB signaling. The serine protease inhibitor lympho-epithelial Kazal-type-related inhibitor (LEKTI) inhibits the matriptase-driven proteolytic pathway, directly blocking kallikreins in epithelial differentiation. Hence, we hypothesized LEKTI could inhibit matriptase-dependent squamous cell carcinogenesis, thus implicating kallikreins in this process. Double-transgenic mice with simultaneous expression of matriptase and LEKTI under the keratin-5 promoter showed a prominent rescue of K5-Matriptase^+/0 premalignant phenotype. Notably, in DMBA-induced SCC, heterotopic co-expression of LEKTI and matriptase delayed matriptase-driven tumor incidence and progression. Co-expression of LEKTI reverted altered Kallikrein-5 expression observed in the skin of K5-Matriptase^+/0 mice, indicating that matriptase-dependent proteolytic pathway inhibition by LEKTI occurs through kallikreins. Moreover, we showed that Kallikrein-5 is necessary for PAR-2-mediated IL-8 release, YAP1-TAZ/TEAD activation, and matriptase-mediated oral squamous cell carcinoma migration. Collectively, our data identify a third signaling pathway for matriptase-dependent carcinogenesis in vivo. These findings are critical for the identification of more reliable biomarkers and effective therapeutic targets in Head and Neck cancer.

A supramolecular nanocarrier for efficient cancer imaging and therapy by targeting at matriptase

Human serum albumin (HSA), a versatile protein carrier for endogenous and exogenous compounds, is a proven macromolecule to form nanoparticles for drug delivery. To render HSA carrier specificity toward tumors, we designed a recombinant HSA protein fused with Kunitz domain 1 (KD1) of hepatocyte growth factor activator inhibitor type 1, which targets to matriptase, a type II transmembrane serine protease overexpressed on tumor cell surface. The carrier was thus named matriptase targeting carrier (MTC). In this study, we showed that MTC displayed the same inhibitory potency as the KD1 againast matriptase, demonstrating the HSA fusion did not affect the KD1 targeting potency. For tumor optical imaging and ablation, MTC was prepared as nanoparticle drug carrier by a novel method via denaturation and refolding to incorporate photosensitizer, CPZ. This matriptase targeting nanoparticles, CPZ:MTC@NPs, showed high specificity and cytotoxicity for matriptase-overexpressing cancer cells in vitro. In tumor-bearing mice, CPZ:MTC@NPs demonstrated selective accumulation and high retention in matriptase-overexpressing tumor. Under illumination, the nanoparticles significantly reduced tumor volumes (79.6%) as compared to saline control. These findings showed that this supramolecular nanocarrier, a new type of tumor targeting self-assembly nanoparticle, had potential as a highly efficient tumor targeting drug carrier for imaging and therapy.

Cross Talk between COVID-19 and Breast Cancer

Cancer patients are more susceptible to COVID-19; however, the prevalence of COVID-19 in different types of cancer is still inconsistent and inconclusive. Here, we delineate the intricate relationship between breast cancer and COVID-19. Breast cancer and COVID-19 share the involvement of common comorbidities, hormonal signalling pathways, gender differences, rennin- angiotensin system (RAS), angiotensin-converting enzyme-2 (ACE-2), transmembrane protease serine 2 (TMPRSS2) and dipeptidyl peptidase-IV (DPP-IV). We also shed light on the possible effects of therapeutic modalities of COVID-19 on breast cancer outcomes. Briefly, we conclude that breast cancer patients are more susceptible to COVID-19 in comparison with their normal counterparts. Women are more resistant to the occurrence and severity of COVID-19. Increased expressions of ACE2 and TMPRSS2 are correlated with occurrence and severity of COVID-19, but higher expression of ACE2 and lower expression of TMPRSS2 are prognostic markers for overall disease free survival in breast cancer. The ACE2 inhibitors and ibuprofen therapies for COVID-19 treatment may aggravate the clinical condition of breast cancer patients through chemo-resistance and metastasis. Most of the available therapeutic modalities for COVID-19 were also found to exert positive effects on breast cancer outcomes. Besides drugs in clinical trend, TMPRSS2 inhibitors, estrogen supplementation, androgen deprivation and DPP-IV inhibitors may also be used to treat breast cancer patients infected with SARS-CoV-2. However, drug-drug interactions suggest that some of the drugs used for the treatment of COVID-19 may modulate the drug metabolism of anticancer therapies which may lead to adverse drug reaction events.

Inhibitors of type II transmembrane serine proteases in the treatment of diseases of the respiratory tract - A review of patent literature

INTRODUCTION

Type II transmembrane serine proteases (TTSPs) of the human respiratory tract generate high interest owing to their ability, among other roles, to cleave surface proteins of respiratory viruses. This step is critical in the viral invasion of coronaviruses, including SARS-CoV-2 responsible for COVID-19, but also influenza viruses and reoviruses. Accordingly, these cell surface enzymes constitute appealing therapeutic targets to develop host-based therapeutics against respiratory viral diseases. Additionally, their deregulated levels or activity has been described in non-viral diseases such as fibrosis, cancer, and osteoarthritis, making them potential targets in these indications.

AREAS COVERED

Areas covered: This review includes WIPO-listed patents reporting small molecules and peptide-based inhibitors of type II transmembrane serine proteases of the respiratory tract.

EXPERT OPINION

Expert opinion: Several TTSPs of the respiratory tract represent attractive pharmacological targets in the treatment of respiratory infectious diseases (notably COVID-19 and influenza), but also against idiopathic pulmonary fibrosis and lung cancer. The current emphasis is primarily on TMPRSS2, matriptase, and hepsin, yet other TTSPs await validation. Compounds listed herein are predominantly peptidomimetic inhibitors, some with covalent reversible mechanisms of action and high potencies. Their selectivity profile, however, are often only partially characterized. Preclinical data are promising and warrant further advancement in the above diseases.

The cell-surface anchored serine protease TMPRSS13 promotes breast cancer progression and resistance to chemotherapy

Breast cancer progression is accompanied by increased expression of extracellular and cell-surface proteases capable of degrading the extracellular matrix as well as cleaving and activating downstream targets. The type II transmembrane serine proteases (TTSPs) are a family of cell-surface proteases that play critical roles in numerous types of cancers. Therefore, the aim of this study was to identify novel and uncharacterized TTSPs with differential expression in breast cancer and to determine their potential roles in progression. Systematic in silico data analysis followed by immunohistochemical validation identified increased expression of the TTSP family member, TMPRSS13 (transmembrane protease, serine 13), in invasive ductal carcinoma patient tissue samples compared to normal breast tissue. To test whether loss of TMPRSS13 impacts tumor progression, TMPRSS13 was genetically ablated in the oncogene-induced transgenic MMTV-PymT tumor model. TMPRSS13 deficiency resulted in a significant decrease in overall tumor burden and growth rate, as well as a delayed formation of detectable mammary tumors, thus suggesting a causal relationship between TMPRSS13 expression and the progression of breast cancer. Complementary studies using human breast cancer cell culture models revealed that siRNA-mediated silencing of TMPRSS13 expression decreases proliferation, induces apoptosis, and attenuates invasion. Importantly, targeting TMPRSS13 expression renders aggressive triple-negative breast cancer cell lines highly responsive to chemotherapy. At the molecular level, knockdown of TMPRSS13 in breast cancer cells led to increased protein levels of the tumor-suppressive protease prostasin. TMPRSS13/prostasin co-immunoprecipitation and prostasin zymogen activation experiments identified prostasin as a potential novel target for TMPRSS13. Regulation of prostasin levels may be a mechanism that contributes to the pro-oncogenic properties of TMPRSS13 in breast cancer. TMPRSS13 represents a novel candidate for targeted therapy in combination with standard of care chemotherapy agents in patients with hormone receptor-negative breast cancer or in patients with tumors refractory to endocrine therapy.

TMPRSS13 promotes cell survival, invasion, and resistance to drug-induced apoptosis in colorectal cancer

Cancer progression is often accompanied by increased levels of extracellular proteases capable of remodeling the extracellular matrix and promoting pro-cancerous signaling pathways by activating growth factors and receptors. The type II transmembrane serine protease (TTSP) family encompasses several proteases that play critical roles in cancer progression; however, the expression or function of the TTSP TMPRSS13 in carcinogenesis has not been examined. In the present study, we found TMPRSS13 to be differentially expressed at both the transcript and protein levels in human colorectal cancer (CRC). Immunohistochemical analyses revealed consistent high expression of TMPRSS13 protein on the cancer cell surface in CRC patient samples; in contrast, the majority of normal colon samples displayed no detectable expression. On a functional level, TMPRSS13 silencing in CRC cell lines increased apoptosis and impaired invasive potential. Importantly, transgenic overexpression of TMPRSS13 in CRC cell lines increased tolerance to apoptosis-inducing agents, including paclitaxel and HA14-1. Conversely, TMPRSS13 silencing rendered CRC cells more sensitive to these agents. Together, our findings suggest that TMPRSS13 plays an important role in CRC cell survival and in promoting resistance to drug-induced apoptosis; we also identify TMPRSS13 as a potential new target for monotherapy or combination therapy with established chemotherapeutics to improve treatment outcomes in CRC patients.

Cell surface-anchored serine proteases in cancer progression and metastasis

Over the last two decades, a novel subgroup of serine proteases, the cell surface-anchored serine proteases, has emerged as an important component of the human degradome, and several members have garnered significant attention for their roles in cancer progression and metastasis. A large body of literature describes that cell surface-anchored serine proteases are deregulated in cancer and that they contribute to both tumor formation and metastasis through diverse molecular mechanisms. The loss of precise regulation of cell surface-anchored serine protease expression and/or catalytic activity may be contributing to the etiology of several cancer types. There is therefore a strong impetus to understand the events that lead to deregulation at the gene and protein levels, how these precipitate in various stages of tumorigenesis, and whether targeting of selected proteases can lead to novel cancer intervention strategies. This review summarizes current knowledge about cell surface-anchored serine proteases and their role in cancer based on biochemical characterization, cell culture-based studies, expression studies, and in vivo experiments. Efforts to develop inhibitors to target cell surface-anchored serine proteases in cancer therapy will also be summarized.

Specifically targeting cancer proliferation and metastasis processes: the development of matriptase inhibitors

Matriptase is a type II transmembrane serine protease, which has been suggested to play critical roles in numerous pathways of biological developments. Matriptase is the activator of several oncogenic proteins, including urokinase-type plasminogen activator (uPA), hepatocyte growth factor (HGF) and protease-activated receptor 2 (PAR-2). The activations of these matriptase substrates subsequently lead to the generation of plasmin, matrix metalloproteases (MMPs), and the triggers for many other signaling pathways related to cancer proliferation and metastasis. Accordingly, matriptase is considered an emerging target for the treatments of cancer. Thus far, inhibitors of matriptase have been developed as potential anti-cancer agents, which include small-molecule inhibitors, peptide-based inhibitors, and monoclonal antibodies. This review covers established literature to summarize the chemical and biochemical aspects, especially the inhibitory mechanisms and structure-activity relationships (SARs) of matriptase inhibitors with the goal of proposing the strategies for their future developments in anti-cancer therapy.

The multifaceted roles of tumor-associated proteases and harnessing their activity for prodrug activation

The role of proteases in cancer was originally thought to be limited to the breakdown of basement membranes and extracellular matrix (ECM), thereby promoting cancer cell invasion into surrounding normal tissues. It is now well understood that proteases play a much more complicated role in all stages of cancer progression and that not only tumor cells, but also stromal cells are an important source of proteases in the tumor microenvironment. Among all the proteolytic enzymes potentially associated with cancer, some proteases have taken on heightened importance due to their significant up-regulation and ability to participate at multiple stages of cancer progression and metastasis. In this review, we discuss some of the advances in understanding of the roles of several key proteases from different classes in the development and progression of cancer and the potential to leverage their upregulated activity for the development of novel targeted treatment strategies.

Recent progress on inhibitors of the type II transmembrane serine proteases, hepsin, matriptase and matriptase-2

Members of the type II transmembrane serine proteases (TTSP) family play a vital role in cell growth and development but many are also implicated in disease. Two of the well-studied TTSPs, matriptase and hepsin proteolytically process multiple protein substrates such as the inactive single-chain zymogens pro-HGF and pro-macrophage stimulating protein into the active heterodimeric forms, HGF and macrophage stimulating protein. These two proteases also have many other substrates which are associated with cancer and tumor progression. Another related TTSP, matriptase-2 is expressed in the liver and functions by regulating iron homoeostasis through the cleavage of hemojuvelin and thus is implicated in iron overload diseases. In the present review, we will discuss inhibitor design strategy and Structure activity relationships of TTSP inhibitors, which have been reported in the literature.

Ectopic expression of human airway trypsin-like protease 4 in acute myeloid leukemia promotes cancer cell invasion and tumor growth

Transmembrane serine proteases have been implicated in the development and progression of solid and hematological cancers. Human airway trypsin-like protease 4 (HAT-L4) is a transmembrane serine protease expressed in epithelial cells and exocrine glands. In the skin, HAT-L4 is important for normal epidermal barrier function. Here, we report an unexpected finding of ectopic HAT-L4 expression in neutrophils and monocytes from acute myeloid leukemia (AML) patients. Such expression was not detected in bone marrow cells from normal individuals or patients with chronic myeloid leukemia, acute lymphocytic leukemia and chronic lymphocytic leukemia. In AML patients who underwent chemotherapy, persistent HAT-L4 expression in bone marrow cells was associated with minimal residual disease and poor prognostic outcomes. In culture, silencing HAT-L4 expression in AML-derived THP-1 cells by short hairpin RNAs inhibited matrix metalloproteinase-2 activation and Matrigel invasion. In mouse xenograft models, inhibition of HAT-L4 expression reduced the proliferation and growth of THP-1 cell-derived tumors. Our results indicate that ectopic HAT-L4 expression is a pathological mechanism in AML and that HAT-L4 may be used as a cell surface marker for AML blast detection and targeting.

Membrane-Anchored Serine Proteases and Protease-Activated Receptor-2-Mediated Signaling: Co-Conspirators in Cancer Progression

Pericellular proteolysis provides a significant advantage to developing tumors through the ability to remodel the extracellular matrix, promote cell invasion and migration, and facilitate angiogenesis. Recent advances demonstrate that pericellular proteases can also communicate directly to cells by activation of a unique group of transmembrane G-protein-coupled receptors (GPCR) known as protease-activated receptors (PAR). In this review, we discuss the specific roles of one of four mammalian PARs, namely PAR-2, which is overexpressed in advanced stage tumors and is activated by trypsin-like serine proteases that are highly expressed or otherwise dysregulated in many cancers. We highlight recent insights into the ability of different protease agonists to bias PAR-2 signaling and the newly emerging evidence for an interplay between PAR-2 and membrane-anchored serine proteases, which may co-conspire to promote tumor progression and metastasis. Interfering with these pathways might provide unique opportunities for the development of new mechanism-based strategies for the treatment of advanced and metastatic cancers.

Conserved function of the matriptase-prostasin proteolytic cascade during epithelial morphogenesis

Extracellular matrix (ECM) assembly and remodelling is critical during development and organ morphogenesis. Dysregulation of ECM is implicated in many pathogenic conditions, including cancer. The type II transmembrane serine protease matriptase and the serine protease prostasin are key factors in a proteolytic cascade that regulates epithelial ECM differentiation during development in vertebrates. Here, we show by rescue experiments that the Drosophila proteases Notopleural (Np) and Tracheal-prostasin (Tpr) are functional homologues of matriptase and prostasin, respectively. Np mediates morphogenesis and remodelling of apical ECM during tracheal system development and is essential for maintenance of the transepithelial barrier function. Both Np and Tpr degrade the zona pellucida-domain (ZP-domain) protein Dumpy, a component of the transient tracheal apical ECM. Furthermore, we demonstrate that Tpr zymogen and the ZP domain of the ECM protein Piopio are cleaved by Np and matriptase in vitro. Our data indicate that the evolutionarily conserved ZP domain, present in many ECM proteins of vertebrates and invertebrates, is a novel target of the conserved matriptase-prostasin proteolytic cascade.

Epithelial tissue covers the outside of the animal body and lines internal organs. Its disorganization is the source of approximately 90% of all human cancers. Elaboration of the basic epithelial characteristics has led to an understanding of how complex structures such as the branched tubular networks of vertebrate lung or invertebrate tracheal system are organized. Aside from obvious morphological differences, specific compositions of the epithelial extracellular matrix (ECM) have been noted. For example, while the flexible ECM of the vertebrate skin mainly consists of collagen and elastic fibers, the rigid ECM of invertebrates is chitin-based to serve as an inflexible exoskeleton. We show that a central regulator of ECM differentiation and epithelial development in vertebrates, the matriptase-prostasin proteolytic cascade (MPPC), is conserved and essential for both Drosophila ECM morphogenesis and physiology. The functionally conserved components of the MPPC mediate cleavage of zona pellucida-domain (ZP-domain) proteins, which play crucial roles in organizing apical structures of the ECM in both vertebrates and invertebrates. Our data indicate that ZP-proteins are molecular targets of the conserved MPPC and that cleavage within the ZP-domains is a conserved mechanism of ECM development and differentiation.

Matriptase-2: monitoring and inhibiting its proteolytic activity

Matriptase-2 (MT2) is a membrane-anchored proteolytic enzyme. It acts as the proteolytic key regulator in human iron homeostasis. A high expression level can lead to iron overload diseases, whereas mutations in the gene encoding MT2, TMPRSS6, may result in various forms of iron deficiency anemia. Recently, MT2 has been reported as a positive prognostic factor in breast and prostate cancers. However, the exact functions of MT2 in various pathophysiological conditions are still not fully understood. In this review, we describe the synthetic tools designed and synthesized to regulate or monitor MT2 proteolytic activity and present the latest knowledge about the role of MT2 in iron homeostasis and cancer.

Small Peptides as Modulators of Serine Proteases

Serine proteases play critical roles in many physiological and pathological processes, and are proven diagnostic and therapeutic targets in a number of clinical indications. Suppression of the aberrant proteolytic activities of these proteases has been clinically used for the treatments of relevant diseases. Polypeptides with 10-20 residues are of great interests as medicinal modulators of serine proteases, because these peptides demonstrate the characteristics of both small molecule drugs and macromolecular drugs. In this review, we summarized the recent development of peptide-based inhibitors against serine proteases with potent inhibitory and high specificity comparable to monoclonal antibodies. In addition, we also discussed the strategies of enhancing plasma half-life and bioavailability of peptides in vivo, which is the main hurdle that limits the clinical translation of peptide-based drugs. This review advocates new avenue for the development of effective serine protease inhibitors and highlights the prospect of the medicinal use of these inhibitors.

Peptide-Functionalized Hydrogel Cubes for Active Tumor Cell Targeting

Conjugation of bioactive targeting molecules to nano- or micrometer-sized drug carriers is a pivotal strategy to improve their therapeutic efficiency. Herein, we developed pH- and redox-sensitive hydrogel particles with a surface-conjugated cancer cell targeting ligand for specific tumor-targeting and controlled release of the anticancer drug doxorubicin. The poly(methacrylic acid) (PMAA) hydrogel cubes of 700 nm and 2 μm with a hepsin-targeting (IPLVVPL) surface peptide are produced through multilayer polymer assembly on sacrificial cubical mesoporous cores. Direct peptide conjugation to the disulfide-stabilized hydrogels through a thiol-amine reaction does not compromise the structural integrity, hydrophilicity, stability in serum, or pH/redox sensitivity but does affect internalization by cancer cells. The cell uptake kinetics and the ultimate extent of internalization are controlled by the cell type and hydrogel size. The peptide modification significantly promotes the uptake of the 700 nm hydrogels by hepsin-positive MCF-7 cells due to ligand-receptor recognition but has a negligible effect on the uptake of 2 μm PMAA hydrogels. The selectivity of 700 nm IPLVVPL-PMAA hydrogel cubes to hepsin-overexpressing tumor cells is further confirmed by a 3-10-fold higher particle internalization by hepsin-positive MCF-7 and SK-OV-3 compared to that of hepsin-negative PC-3 cells. This work provides a facile method to fabricate enhanced tumor-targeting carriers of submicrometer size and improves the general understanding of particle design parameters for targeted drug delivery.

Transcriptome analysis reveals TMPRSS6 isoforms with distinct functionalities

TMPRSS6 (matriptase-2) is a type II transmembrane serine protease involved in iron homoeostasis. At the cell surface of hepatocytes, TMPRSS6 cleaves haemojuvelin (HJV) and regulates the BMP/SMAD signalling pathway leading to production of hepcidin, a key regulator of iron absorption. Although four TMPRSS6 human isoforms and three mice Tmprss6 isoforms are annotated in databases (Ensembl and RefSeq), their relative expression or activity has not been studied. Analyses of RNA-seq data and RT-PCR from human tissues reveal that TMPRSS6 isoform 1 (TMPRSS6-1) and 3 are mostly expressed in human testis while TMPRSS6-2 and TMPRSS6-4 are the main transcripts expressed in human liver, testis and pituitary. Furthermore, we confirm the existence and analyse the relative expression of three annotated mice Tmprss6 isoforms. Using heterologous expression in HEK293 and Hep3B cells, we show that all human TMPRSS6 isoforms reach the cell surface but only TMPRSS6-1 undergoes internalization. Moreover, truncated TMPRSS6-3 or catalytically altered TMPRSS6-4 interact with HJV and prevent its cleavage by TMPRSS6-2, suggesting their potential role as dominant negative isoforms. Taken together, our results highlight the importance of understanding the precise function of each TMPRSS6 isoforms both in human and in mouse.

Serine peptidase inhibitor Kunitz type 2 (SPINT2) in cancer development and progression

Understanding the molecular basis and mechanisms involved in neoplastic transformation and progression is important for the development of novel selective target therapeutic strategies. Hepatocyte growth factor (HGF)/c-MET signaling plays an important role in cell proliferation, survival, migration and motility of cancer cells. Serine peptidase inhibitor Kunitz type 2 (SPINT2) binds to and inactivates the HGF activator (HGFA), behaving as an HGFA inhibitor (HAI) and impairing the conversion of pro-HGF into bioactive HGF. The scope of the present review is to recapitulate and review the evidence of SPINT2 participation in cancer development and progression, exploring the clinical, biological and functional descriptions of the involvement of this protein in diverse neoplasias. Most studies are in agreement as to the belief that, in a large range of human cancers, the SPINT2 gene promoter is frequently methylated, resulting in the epigenetic silence of this gene. Functional assays indicate that SPINT2 reactivation ameliorates the malignant phenotype, specifically reducing cell viability, migration and invasion in diverse cancer cell lines. In sum, the SPINT2 gene is epigenetically silenced or downregulated in human cancers, altering the balance of HGF activation/inhibition ratio, which contributes to cancer development and progression.

Membrane-Anchored Serine Proteases: Host Cell Factors in Proteolytic Activation of Viral Glycoproteins

Over one third of all known proteolytic enzymes are serine proteases. Among these, the trypsin-like serine proteases comprise one of the best characterized subfamilies due to their essential roles in blood coagulation, food digestion, fibrinolysis, or immunity. Trypsin-like serine proteases possess primary substrate specificity for basic amino acids. Most of the well-characterized trypsin-like proteases such as trypsin, plasmin, or urokinase are soluble proteases that are secreted into the extracellular environment. At the turn of the millennium, a number of novel trypsin-like serine proteases have been identified that are anchored in the cell membrane, either by a transmembrane domain at the N- or C-terminus or via a glycosylphosphatidylinositol (GPI) linkage. Meanwhile more than 20 membrane-anchored serine proteases (MASPs) have been identified in human and mouse, and some of them have emerged as key regulators of mammalian development and homeostasis. Thus, the MASP corin and TMPRSS6/matriptase-2 have been demonstrated to be the activators of the atrial natriuretic peptide (ANP) and key regulator of hepcidin expression, respectively. Furthermore, MASPs have been recognized as host cell factors activating respiratory viruses including influenza virus as well as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses. In particular, transmembrane protease serine S1 member 2 (TMPRSS2) has been shown to be essential for proteolytic activation and consequently spread and pathogenesis of a number of influenza A viruses in mice and as a factor associated with severe influenza virus infection in humans.

This review gives an overview on the physiological functions of the fascinating and rapidly evolving group of MASPs and a summary of the current knowledge on their role in proteolytic activation of viral fusion proteins.

Analyzing the Type II Transmembrane Serine Protease Hepsin-Dependent Basement Membrane Remodeling in 3D Cell Culture

Breakdown of the basement membrane is a key step that precedes tumor invasion, and accumulating evidence suggests a key role for the type II transmembrane proteases (TTSPs) in that process. Overexpression of a TTSP hepsin characterizes many solid cancers, including prostate, breast, and ovarian cancer, and in experimental tumor models, the elevated proteolytic activity of hepsin simultaneously activates several growth factors and cleaves basement membrane protein laminin-332, which is an essential component of the cell-basement membrane junction hemidesmosome. These hepsin-dependent molecular events associate with dramatic loss of basement membrane integrity in mouse tumor models and in three-dimensional (3D) epithelial culture. In particular, the 3D culture systems offer unprecedented possibilities to clarify the mechanistic basis of destructive interactions between out-of-control serine protease activity and the basement membrane structure. Here, we describe how to establish 3D mammary epithelial culture in an exogenous basement membrane-free egg white matrix and provide a protocol for quantitative analysis of the impact of hepsin on laminin-332 and its hemidesmosomal receptor α6-integrin by means of confocal microscopy imaging. These protocols were established to facilitate studies aiming to decipher the exact role of oncogenic proteases in tumor invasion processes and to identify novel therapeutic agents able to intervene these cancer critical processes.

Human airway trypsin-like protease, a serine protease involved in respiratory diseases

More than 2% of all human genes are coding for a complex system of more than 700 proteases and protease inhibitors. Among them, serine proteases play extraordinary, diverse functions in different physiological and pathological processes. The human airway trypsin-like protease (HAT), also referred to as TMPRSS11D and serine 11D, belongs to the emerging family of cell surface proteolytic enzymes, the type II transmembrane serine proteases (TTSPs). Through the cleavage of its four major identified substrates, HAT triggers specific responses, notably in epithelial cells, within the pericellular and extracellular environment, including notably inflammatory cytokine production, inflammatory cell recruitment, or anticoagulant processes. This review summarizes the potential role of this recently described protease in mediating cell surface proteolytic events, to highlight the structural features, proteolytic activity, and regulation, including the expression profile of HAT, and discuss its possible roles in respiratory physiology and disease.

Paramyxoviruses activation by host proteases in cultures of normal and cancer cells

Multiplication of paramyxovirus Sendai and Newcastle disease virus (NDV) was studied in cultures of normal and tumor cells. Production of noninfectious virus with uncleaved F0 was observed in canine kidney cell line MDCK (line H) and its derivatives carrying tetracycline-regulated expression of transmembrane protease HAT or TMPRSS2 with trypsin-like cleavage specificity. Under tetracycline induction, a cleavage F0 (65 kD)>F1 (50 kD)+F2(15 kD) and production of infectious virus were observed in these cell cultures. Under tetracycline induction, the additional subunit 38K (m.w. 38 kDa) of the F protein was detected both in infected MDCK-HAT cells and in newly synthesized Sendai virus in addition to F0, F1 and F2, indicating thereby a second HAT-sensitive proteolytic site in the F0 molecule. Highly infectious virus containing cleaved F1+F2 was produced in cultures of cancer cells Caco-2 and H1299. Virus Sendai synthesized in H1299 cells contained 38 K subunit indicating a cleavage of the F0 at a second site by H1299 host cell proteases. Levels of cleaved F1+F2 and infectious virions were higher at the late stage of infection in cancer cells, suggesting thus the induction of virus-activating proteases in Caco-2 and H1299 cells under infection with paramyxoviruses. NDV virus was found to induce more rapid death of cancer cells Caco-2 than Sendai virus. Cooperatively, the obtained data show that cancer cells in distinction to nonmalignant cells can synthesize protease(s) activating infectivity of paramyxoviruses. Thus, they are more vulnerable to paramyxovirus infection than normal cells.

The Transmembrane Serine Protease HAT-like 4 Is Important for Epidermal Barrier Function to Prevent Body Fluid Loss

Membrane-bound proteases are essential for epidermal integrity. Human airway trypsin-like protease 4 (HAT-L4) is a type II transmembrane serine protease. Currently, its biochemical property, cellular distribution and physiological function remain unknown. Here we examined HAT-L4 expression and function in vitro and in vivo. In Western analysis, HAT-L4 expressed in transfected CHO cells appeared as a 48-kDa protein. Flow cytometry confirmed HAT-L4 expression on the cell surface with the expected membrane topology. RT-PCR and immunostaining experiments indicated that HAT-L4 was expressed in epithelial cells and exocrine glands in tissues including skin, esophagus, trachea, tongue, eye, bladder, testis and uterus. In the skin, HAT-L4 expression was abundant in keratinocytes and sebaceous glands. We generated HAT-L4 knockout mice by disrupting the Tmprss11f gene encoding HAT-L4. HAT-L4 knockout mice were viable and fertile. No defects were found in HAT-L4 knockout mice in hair growth, wound healing, water repulsion and body temperature regulation. Compared with wild-type controls, HAT-L4-deficient newborn mice had greater body fluid loss and higher mortality in a trans-epidermal body fluid loss test. In metabolic studies, HAT-L4-deficient adult mice drank water more frequently than wild-type controls did. These results indicate that HAT-L4 is important in epidermal barrier function to prevent body fluid loss.

The role of type II transmembrane serine protease-mediated signaling in cancer

Pericellular proteases have long been implicated in carcinogenesis. Previous research focused on these proteins, primarily as extracellular matrix (ECM) protein-degrading enzymes which allowed cancer cells to breach the basement membrane and invade surrounding tissue. However, recently, there has been a shift in the view of cell surface proteases, including serine proteases, as proteolytic modifiers of particular targets, including growth factors and protease-activated receptors, which are critical for the activation of oncogenic signaling pathways. Of the 176 human serine proteases currently identified, a subset of 17, known as type II transmembrane serine proteases (TTSPs). Many have been shown to be relevant to cancer progression since they were first identified as a family around the turn of the century. To this end, altered expression of TTSPs appeared as a trademark of several tumor types. However, the substrates and underlying signaling pathways remained unclear. Localization of these proteins to the cell surface places them in the unique position to mediate signal transduction between the cell and its surrounding environment. Many of the TTSPs have already been shown to play key roles in processes such as postnatal development, tissue homeostasis, and tumor progression, which share overlapping molecular mechanisms. In this review, we summarize the current knowledge regarding the role of the TTSP family in pro-oncogenic signaling.