Matriptase Expression Research Articles

Exosome-Mediated Activation of the Prostasin-Matriptase Serine Protease Cascade in B Lymphoma Cells.

Prostasin and matriptase are extracellular membrane serine proteases with opposing effects in solid epithelial tumors. Matriptase is an oncoprotein that promotes tumor initiation and progression, and prostasin is a tumor suppressor that reduces tumor invasion and metastasis. Previous studies have shown that a subgroup of Burkitt lymphoma have high levels of ectopic matriptase expression but no prostasin. Reducing the matriptase level via small interfering RNAs in B lymphoma cells impeded tumor xenograft growth in mice. Here, we report a novel approach to matriptase regulation in B cancer cells by prostasin via exosomes to initiate a prostasin-matriptase protease activation cascade. The activation and shedding of matriptase were monitored by measuring its quantity and trypsin-like serine protease activity in conditioned media. Sustained activation of the protease cascade in the cells was achieved by the stable expression of prostasin. The B cancer cells with prostasin expression presented phenotypes consistent with its tumor suppressor role, such as reduced growth and increased apoptosis. Prostasin exosomes could be developed as an agent to initiate the prostasin-matriptase cascade for treating B lymphoma with further studies in animal models.

ROS is a master regulator of in vitro matriptase activation.

Matriptase is a type II transmembrane serine protease that is widely expressed in normal epithelial cells and epithelial cancers. Studies have shown that regulation of matriptase expression and activation becomes deranged in several cancers and is associated with poor disease-free survival. Although the central mechanism of its activation has remained unknown, our lab has previously demonstrated that inflammatory conditions such as intracellular pH decrease strongly induces matriptase activation. In this investigation, we first demonstrate clear matriptase activation following Fulvestrant (ICI) and Tykerb (Lapatinib) treatment in HER2-amplified, estrogen receptor (ER)-positive BT474, MDA-MB-361 and ZR-75-30 or single ER-positive MCF7 cells, respectively. This activation modestly involved Phosphoinositide 3-kinase (PI3K) activation and occurred as quickly as six hours post treatment. We also demonstrate that matriptase activation is not a universal hallmark of stress, with Etoposide treated cells showing a larger degree of matriptase activation than Lapatinib and ICI-treated cells. While etoposide toxicity has been shown to be mediated through reactive oxygen species (ROS) and MAPK/ERK kinase (MEK) activity, MEK activity showed no correlation with matriptase activation. Novelly, we demonstrate that endogenous and exogenous matriptase activation are ROS-mediated in vitro and inhibited by N-acetylcysteine (NAC). Lastly, we demonstrate matriptase-directed NAC treatment results in apoptosis of several breast cancer cell lines either alone or in combination with clinically used therapeutics. These data demonstrate the contribution of ROS-mediated survival, its independence of kinase-mediated survival, and the plausibility of using matriptase activation to indicate the potential success of antioxidant therapy.

The serine protease matriptase inhibits migration and proliferation in multiple myeloma cells.

Background: Multiple myeloma (MM) is an incurable malignancy of plasma cells. The serine protease matriptase is frequently dysregulated in human carcinomas, which facilitates tumor progression and metastatic dissemination. The importance of matriptase in hematological malignancies is yet to be clarified. In this study, we aimed to characterize the role of matriptase in MM.Materials and Methods: mRNA expression of matriptase and its inhibitors hepatocyte growth factor activator inhibitor (HAI)-1 and HAI-2 was studied in primary MM cells from patient samples and human myeloma cell lines (HMCLs). We further investigated the effect of matriptase on migration and proliferation of myeloma cells in vitro. By use of the CoMMpass database, we assessed the clinical relevance of matriptase in MM patients.Results: Matriptase was expressed in 96% of patient samples and all HMCLs tested. Overexpression of matriptase in vitro reduced proliferation, and significantly decreased cytokine-induced migration. Conversely, matriptase knockdown significantly enhanced migration. Mechanistically, overexpression of matriptase inhibited activation of Src kinase.Conclusions: Our findings may suggest a novel role of matriptase as a tumor suppressor in MM pathogenesis.

Role of the polycystic kidney disease domain in matriptase chaperone activity and localization of hepatocyte growth factor activator inhibitor-1.

Hepatocyte growth factor activator inhibitor-1 (HAI-1, also known as SPINT1) is an inhibitor of matriptase, a type-2 transmembrane protease widely expressed in epithelial cells. HAI-1 also functions as a chaperone to maintain the processing and localization of matriptase required for epithelial integrity. However, mechanisms underpinning the chaperone function remain to be elucidated. Here, we show that the first Kunitz domain (KD1) and the adjacent polycystic kidney disease (PKD) domain-like internal domain of HAI-1 are essential for the chaperone function. In HEK293T cells, which do not express endogenous HAI-1 or matriptase, forced matriptase overexpression was unsuccessful unless sufficient HAI-1 was co-expressed. Among mutant HAI-1 constructs, HAI-1 with inactivation mutation in KD1 (HAI-1mKD1) or HAI-1 lacking the PKD domain (HAI-1dPKD) was unable to support matriptase expression, and neither mutant formed a complex with activated matriptase. Matriptase did not localize to the cell surface when co-expressed with HAI-1dPKD. Moreover, HAI-1dPKD accumulated in the cytoplasm of HEK293T and HaCaT cells rather than localizing to the cell surface, presumably due to misfolding as judged by altered antibody recognition. On the other hand, activationlocked and activity-incompetent matriptase were stable and readily overexpressed and localized to the cell surface without HAI-1. Therefore, the observed matriptase instability was caused by its own catalytic activity in the absence of inhibitory HAI-1. The matriptase chaperone function of HAI-1 is thus mediated primarily by the inhibition of undesired intracellular matriptase activity, and the PKD domain is essential for the proper folding and trafficking of inhibitory HAI-1 and its chaperone function.

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

Simple SummaryHead and neck squamous cell carcinomas (HNSCC) are among the most common cancers worldwide. In contrast to the advances in prevention and treatment of other types of cancer, the five-year survival rate for HNSCC is only about 50% and it has not changed for the past 50 years. This poor prognosis is mainly due to a shortage of suitable markers for early detection, delayed diagnosis and/or referral, and ineffectiveness of chemotherapy. The aim of this study was to explore the inhibitory role of LEKTI in matriptase-dependent squamous cell carcinogenesis and to investigate additional players operating in this pathway. We found that Kallikrein-5 is necessary for PAR-2-mediated IL-8 release, YAP1-TAZ/TEAD activation, and matriptase-mediated oral squamous cell carcinoma migration. This knowledge can contribute for the development of future targeted therapy in HNSCC.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 Novel Antibody-Toxin Congujate to Treat Mantle Cell Lymphoma

IntroductionMantle cell lymphoma (MCL), while sensitive to several chemotherapeutic regimens including rituximab, cure rates remain low and new treatments are needed.We have identified a membrane bound “activated” matriptase, as an attractive antigen target for the highly selective delivery of toxins to epithelial tumors and MCL. Matriptase, a member of type II transmembrane serine proteases, is a glycoprotein (80-90 kDa) synthesized as a latent single-chain structure. Activation generates a disulfide-linked-two-chain fully active enzyme through an auto-activation step. Reactive oxygen species (ROS), as well as acidic environments present in tumors can activate matriptase. In addition to roles in initiating carcinogenesis, the enzyme also plays important roles in tumor progression, including invasiveness and metastasis.Importantly, while matriptase is present in a latent form on epithelial cells and B-cells, activated matriptase expression is restricted to the membranes of epithelial tumors and some B-cell malignancies .MethodsMaterials: The M-69 antibody was generated by CY. Bortezomib was from the CINJ pharmacy.Cell Culture: The MCL cells (JeKo-1, Mino, Maver and Z138) were cultured in 1X RPMI Media 1640 (Life Technologies) containing 10% fetal bovine serum (FBS) at 37ºC.Western blotting: The M-69 antibody was used for western analysis and Anti-glyceraldehyde 3-phosphate dehydrogenase (GAPDH) purchased from Millipore was used as a control.Cytotoxicity assay: Cell viability was measured by the trypan blue dye exclusion method using a Vi-Cell XR© cell viability analyzer (Beckman Coulter). The cytotoxicity data were analyzed using GraphPad Prism 4 software (GraphPad Software Inc., CA).Animal studies: NOD/SCID/IL2 receptor gamma chain null (NOD/SCID/IL2gnull, NSG) mice were obtained from the Jackson Laboratory. JeKo-1 MCL cells were used for the xenograft studies. Once tumors were palpable, the mice were treated i.p. with anti-matriptase antibody (M-69) conjugated with MMAE (ADC). Controls used were M-69 antibody alone and saline. In a second experiment mice were treated with the ADC alone, bortezomib alone or the combination. Tumor size and body weights were measured twice a week.ResultsThe linkage of monomethyl auristatin-E (MMAE), a potent tubulin-inhibitor, to M69 used the releasable linker technology which is based on Seattle Genetics' valine-citrulline-PABA linker that is cleavable by cathepsin B in the lysosome, while showing stability in circulation. MALDI-TOF mass spectrometry of the ADC showed a 7000 Da increase of the average M.W. of the antibody that corresponds to an average of 3.5 drug molecules linked to each mAb molecule.MCL (JeKo-1, Mino, Maver and Z138) cell lines were found to overexpress activated matriptase using the M-69 antibody. These cell lines were sensitive to the ADC with IC50s at single digit µg/ml of the conjugate.We elected to use the JeKo-1 cell line for the initial xenograft studies. We found that the 5 mg/kg dose of the ADC weekly produced a better anti-tumor effect (90% growth inhibition) than a 1 mg/kg dose, without any body weight loss. In combination with bortezomib, treatment with the ADC led to some complete responses.ConclusionsThe mouse antibody to human matriptase, M-69, conjugated to MMAE potently inhibited growth of four MCL cell lines and inhibited xenografts of the JeKo-1 MCL in NSG mice alone and produced enhanced effects in combination with bortezomib without significant side effects. DisclosuresRather:Phosplatin Therapeutics: Research Funding. Bertino:Phosplatin Therapeutics: Research Funding.

Differential subcellular distribution renders HAI-2 a less effective protease inhibitor than HAI-1 in the control of extracellular matriptase proteolytic activity

The integral membrane, Kunitz-type serine protease inhibitors HAI-1 and HAI-2, can suppress the proteolytic activity of the type 2 transmembrane serine protease matriptase with high specificity and potency. High levels of extracellular matriptase proteolytic activity have, however, been observed in some neoplastic B-cells with high levels of endogenous HAI-2, indicating that HAI-2 may be an ineffective matriptase inhibitor at the cellular level. The different effectiveness of the HAIs in the control of extracellular matriptase proteolytic activity is examined here. Upon inducing matriptase zymogen activation in the HAI Teton Daudi Burkitt lymphoma cells, which naturally express matriptase with very low levels of HAI-2 and no HAI-1, nascent active matriptase was rapidly inhibited or shed as an enzymatically active enzyme. With increasing HAI-1 expression, cellular matriptase-HAI-1 complex increased, and extracellular active matriptase decreased proportionally. Increasing HAI-2 expression, however, resulted in cellular matriptase-HAI-2 complex levels reaching a plateau, while extracellular active matriptase remained high. In contrast to this differential effect, both HAI-1 and HAI-2, even at very low levels, were shown to promote the expression and cell-surface translocation of endogenous matriptase. The difference in the suppression of extracellular active matriptase by the two closely related serine protease inhibitors could result from the primarily cell surface expression of HAI-1 compared to the mainly intracellular localization of HAI-2. The HAIs, therefore, resemble one another with respect to promoting matriptase expression and surface translocation but differ in their effectiveness in the control of extracellular matriptase enzymatic activity.

Protease activated receptor 2 and matriptase expression in the joints of cats with and without osteoarthritis.

The aim of this study was to determine the presence of protease-activated receptor 2 (PAR2) and matriptase proteins and quantify PAR2 and matriptase mRNA expression in the articular cartilage and synovial membrane of cats with and without osteoarthritis (OA). A total of 28 articular cartilage samples from adult cats (14 OA and 14 normal), 10 synovial membranes from adult cats (five OA and five normal) and three cartilage samples from 9-week-old fetal cats were used. The presence of PAR2 and matriptase in the cartilage and synovial membrane of the adult samples was detected by immunohistochemical (IHC) staining, while real-time PCR was used for mRNA expression analyses in all samples. PAR2 was detected in all OA and normal articular cartilage and synovial membrane samples but confined to only a few superficial chondrocytes in the normal samples. Matriptase was only detected in OA articular cartilage and synovial membrane samples. PAR2 and matriptase mRNA expression were, however, detected in all cartilage and synovial membrane samples. PAR2 and matriptase mRNA expression levels in OA articular cartilage were five (P <0.001) and 3.3 (P <0.001) times higher than that of the healthy group, respectively. There was no significant difference (P = 0.05) in the OA synovial membrane PAR2 and matriptase mRNA expression compared with the normal samples. Detection of PAR2 and matriptase proteins and gene expression in feline articular tissues is a novel and important finding, and supports the hypothesis that serine proteases are involved in the pathogenesis of feline OA. The consistent presence of PAR2 and matriptase protein in the cytoplasm of OA chondrocytes suggests a possible involvement of proteases in cartilage degradation. Further investigations into the PAR2 and matriptase pathobiology could enhance our understanding of the proteolytic cascades in feline OA, which might lead to the development of novel therapeutic strategies.

The Serine Protease Matriptase Acts As a Tumour Suppressor in Multiple Myeloma

Both in newly diagnosed multiple myeloma (MM) and during progression of the disease, malignant plasma cells are found circulating in peripheral blood as well as in the bone marrow (BM). The disseminated nature of MM is strongly dependent on the interplay between the cancer cells and the BM microenvironment, promoting myeloma cell migration in the BM. Matriptase (ST14), a type-II transmembrane serine protease primarily found in epithelial tissues, is overexpressed in a variety of human malignancies and is sufficient to induce tumour formation in mice. Frequently, a concomitant reduction in the levels of its cognate inhibitor hepatocyte growth factor activator inhibitor (HAI)-1 (SPINT1) is observed in carcinomas, while expression and function of the related inhibitor HAI-2 (SPINT2) is yet to be clarified. Dysregulated expression causing increased matriptase proteolytic activity has been associated with cancer growth, survival and metastasis. Here, we show for the first time a role of matriptase as a possible tumour suppressor in myeloma pathogenesis. Gene expression analysis of primary cells from MM patients (n=24) and human myeloma cell lines (n=8) revealed highly variable levels of matriptase, HAI-1 and HAI-2. This observation prompted us to investigate the functional role of matriptase in vitro. We showed that stable overexpression of matriptase in INA-6, a MM cell line with no endogenous ST14 expression, reduced migration by more than 50% in response to the combination of the pro-migratory cytokines stromal cell-derived factor-1 alpha (SDF-1α) and hepatocyte growth factor (HGF, Fig. 1A). Conversely, stable knockdown of matriptase in two MM cell lines with high endogenous matriptase expression (RPMI-8226 and JJN-3) significantly enhanced migration in vitro. Mechanistically, matriptase overexpression blocked activation of Src kinase (Fig. 1B), well-known as a critical player in metastasis formation promoting cancer cell motility, invasiveness and angiogenesis. In agreement with our result, previous studies have demonstrated the activation of Src family kinases (SFK) downstream SDF-1/CXCR4-signaling. Finally, we performed survival analyses in the public available MMRF CoMMpass trial database (release version IA14). Low ST14 expression was associated with significant worse overall survival (P=0.05, Fig. 1C) and progression-free survival (P=0.02, Fig. 1D). Altogether, our data are in marked contrast to the role ascribed to matriptase in epithelial and certain non-epithelial tumours as an oncogenic protein and an unfavourable prognostic marker. In conclusion, these findings suggest a novel role of matriptase as a tumour suppressor in MM pathogenesis. Disclosures Slørdahl: Celgene: Consultancy; Janssen and Celgene: Honoraria.

Abstract 2212: An antibody drug conjugate targeting activated matriptase, exhibits synergistic cytotoxicity with a PARP inhibitor, olaparib in triple negative breast cancer

Abstract Matriptase, is a serine protease type II transmembrane protein. Matriptase forms a cognate pair with its Kunitz type endogenous inhibitor HAI-1 and is commonly deregulated and ubiquitously expressed in a variety of human carcinomas and in particular, breast cancer. This enzyme activity is regulated by binding to its endogenous inhibitors (HAI-1 or 2). Previously, we reported the synthesis and anti-tumor studies of a novel antibody drug conjugate (ADC) targeting activated matriptase of tumor cells (Oncotarget, 2018,9(40):25983). The activated matriptase-specific monoclonal antibody (M69) was conjugated with a potent anti-mitotic toxin, monomethyl auristatin-E (MMAE) via a lysosomal protease (cathepsin B) -cleavable dipeptide linker. The ADC was found to be potent and selective against multiple activated matriptase-positive epithelial carcinoma cell lines including triple negative breast cancer (TNBC), as well as alone and in combination with bortezomib in Mantle cell lymphoma (Frontiers in Oncology, 2019,9:258). In-vivo studies showed that the ADC has potent anti-tumor effects alone or in combination with cisplatin or carboplatin against TNBC xenografts and a primary human TNBC (PDX), respectively. The chimeric ADC (mouse-human chimera) also evoked an immune response against TNBC xenografts in humanized mouse models. Here, we report the sensitivity of TNBC tumors with and without a BRCA mutation to ADC alone or in combination with a PARP inhibitor, Olaparib. We analyzed the mutational status of BRCA1, BRAC2, p53 and activated matriptase expression of four TNBC cell lines (MDA-MB-468, MDA-MB-231, HCC1806 and MDA-MB-436). All of the cell lines had p53 mutations. The MDA-MB-468 cell line with a mutation in BRCA 2, and expression of activated matriptase was the most sensitive cell line to both olaparib and the chimeric MMAE ADC, and the combination of them resulted in marked synergistic cell kill. The MDA-MB-436 cell line with a splice site mutation in BCRA1 was less sensitive to both treatments, but there was modest synergy when the two drugs were combined. In contrast the MDA-MB-231 cell line without a BRCA mutation was much less sensitive to the ADC or olaparib, and the combination did not show synergy. The HCC1806 cell line with wt BRCA was sensitive to the ADC and olaparib, but the combination resulted in antagonistic effects. Triple negative breast cancers with a BRAC2 mutation and overexpression of activated matriptase may be a subset of breast cancers that may benefit from the combination of our novel ADC and a PARP inhibitor. Citation Format: Gulam M. Rather, Zoltan Szekely, Joseph R. Bertino. An antibody drug conjugate targeting activated matriptase, exhibits synergistic cytotoxicity with a PARP inhibitor, olaparib in triple negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2212.

Expression of protease activating receptor-2 (PAR-2) is positively correlated with the recurrence of non-muscle invasive bladder cancer: an immunohistochemical analysis.

Background: Matriptase, which is a Type II transmembrane serine protease, has the potential to activate several growth factors, including pro-hepatocyte growth factor (HGF). A G protein-coupled transmembrane cell-surface receptor and a protease-activated receptor 2 (PAR-2) are also required for activation by matriptase. Activation of PAR-2 has been reported to induce the progression of various cancers. In a previous study, we evaluated the correlation between upregulation of MET phosphorylation with high matriptase expression and worse prognosis in patients with muscle invasive bladder cancer; however, expression of PAR-2, matriptase and MET in non-muscle invasive bladder cancer (NMIBC) has not been evaluated.Materials and methods: We retrospectively analyzed the expression of PAR-2, matriptase and MET using 55 paraffin-embedded specimens obtained from patients with NMIBC by immunohistochemistry.Results: MET was significantly expressed in high-grade urothelial carcinoma (UC) and pathological T1 cancers. High expression of PAR-2 was significantly associated with a worse recurrence rate in NMIBC. In subgroup analysis, the expression of PAR-2 was also correlated with high recurrence rate in low-grade UC. In addition, expression of matriptase tended to correlate with worse recurrence rate in high-grade UC.Conclusion: Increased expression of PAR-2 was significantly correlated with worse recurrence rate in patients with NMIBC. In addition, expression of matriptase also indicated a tendency toward recurrence in high-grade UC, suggesting an important role of matriptase-induced PAR-2 activation in NMIBC.

Overexpression of matriptase in tumor stroma is a poor prognostic indicator of extrahepatic bile duct cancer.

Bile duct cancer is known to contain numerous fibroblasts, and reported to recruit cancer- associated fibroblasts by secreting platelet-derived growth factor-D (PDGF-D) which needs serine proteases, such as matriptase, to behave as a ligand. However, their expression pattern, and prognostic value have not been clarified. In this study, we investigated the clinicopathological significance of PDGF-D and matriptase expression in patients with extrahepatic bile duct cancer. The samples were obtained from 256 patients who underwent the surgical resection between 1991 and 2015, and the expression levels of PDGF-D and matriptase were evaluated immunohistochemically. Staining intensities and distribution were scored, and finally classified into low and high expression groups in cancer cells and stroma respectively. High expression of matriptase in the cancer stroma was detected in 91 tumors (40%). The high stromal matriptase expression was significantly associated with shorter recurrence-free survival (RFS) and overall survival (OS) (P = 0.0027 and 0.0023, respectively). Multivariate analyses also demonstrated that the stromal matriptase expression level was an independent influential factor in RFS (P = 0.0050) and OS (P = 0.0093). Our findings suggest that the high stromal matriptase expression was strongly associated with tumor progression, recurrence and poor outcomes in patients with extrahepatic bile duct cancer.

Matriptase-Induced Phosphorylation of MET is Significantly Associated with Poor Prognosis in Invasive Bladder Cancer; an Immunohistochemical Analysis.

Hepatocyte growth factor (HGF) plays an important role in cancer progression via phosphorylation of MET (c-met proto-oncogene product, receptor of HGF). HGF-zymogen (pro-HGF) must be processed for activation by HGF activators including matriptase, which is a type II transmembrane serine protease and the most efficient activator. The enzymatic activity is tightly regulated by HGF activator inhibitors (HAIs). Dysregulated pro-HGF activation (with upregulated MET phosphorylation) is reported to promote cancer progression in various cancers. We retrospectively analyzed the expression of matriptase, phosphorylated-MET (phospho-MET) and HAI-1 in tumor specimens obtained from patients with invasive bladder cancer by immunohistochemistry. High expression of phospho-MET and increased expression of matriptase were significantly associated with poor prognosis, and high matriptase/low HAI-1 expression showed poorer prognosis. Furthermore, high expression of matriptase tended to correlate with phosphorylation of MET. Increased expression of matriptase may induce the ligand-dependent activation of MET, which leads to poor prognosis in patients with invasive bladder cancer.

Expression and Clinical Significances of HGFA, Matriptase, HAI-1 and HAI-2 in Acute Myeloid Leukemia

To investigate the expression and clinical significances of HGFA, Matriptase, HAI-1 and HAI-2 in patients with acute myeloid leukemia (AML). The bone marrow samples from 91 AML patients, 41 AML patients in complete remission, and 32 normal controls were collected. Real time fluorescence quantitative RT-PCR (qRT-PCR) was used to detect the mRNA expressions levels of HGFA, Matriptase, HAI-1, HAI-2 . The expressions of these genes were compared among AML untreated group, the complete remission group and the healthy control group. The correlation of their expression with clinical characteristics was analyzed. The level of HGFA in the AML untreated group was higher than that in the healthy control group（P<0.05）, while the HAI-2 mRNA level was lower than that in the healthy control group（P<0.05）. The mRNA levels of HAI-1 and Matriptase were not changed significantly in all groups. The HAI-2 mRNA expression level was significantly lower in the high white blood cell group (P<0.05). The abnormal activation of HGF/c-Met signaling system in AML may result from the increase of HGFA expression and the decrease of HAI-2 expression of the upstream regulatory factors.

Abstract 3444: EGFR-dependent matriptase activation in ErbB2-amplified breast cancer

Abstract Of the nearly 250,000 new breast cancer cases expected annually, nearly 25% will have ErbB2 (HER2) gene amplification, which is associated with increased growth signaling, more aggressive disease, and poor patient prognosis. Matriptase is a type II transmembrane serine protease that plays a role in normal epithelial cell biology. The expression and activation of matriptase are tightly regulated in normal cells partly through co-expression with endogenous inhibitor, HAI-1, which rapidly inhibits the protease, once activated, by the formation of a high affinity complex. Matriptase has oncogenic potential when its regulation is deranged and it activates downstream substrates known to play a role in tumor progression such as pro-HGF. ErbB2 activity can regulate matriptase activity in prostate cancer and so we set out to elucidate the relationship between ErbB2 and matriptase in ErbB2-amplified breast cancer. SKBR3, AU565, and ErbB2 transfected MCF7 cells (MB7) were used to explore the relationship between ErbB2 levels and matriptase activation as they express higher levels of ErbB2 compared with MCF7 cells. Under standard growth conditions, high level of ErbB2 activation was associated with extensive matriptase activation. Activation of ErbB2 by stimulating EGFR with EGF resulted in increased matriptase activation. Inhibition of ErbB2 activity by serum deprivation or Lapatinib (a dual ErbB2 and EGFR kinase inhibitor) treatment resulted in decreased matriptase activation. Treatment with Lapatinib or the EGFR-specific inhibitor, Gefitinib, blocked matriptase activation whereas the ErbB2 inhibitor, AG825, has no effect. Using inhibitors of downstream signaling pathways, EGFR-induced matriptase activation was shown to be mediated by PI3K signaling. Further elucidation of the pathway is ongoing. In summary, our data suggest that EGFR signaling in this context modulates matriptase activation, which may also contribute to breast cancer progression. Citation Format: Darius Gaymon. EGFR-dependent matriptase activation in ErbB2-amplified breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3444.

Dysregulated HAI-2 Plays an Important Role in Renal Cell Carcinoma Bone Metastasis through Ligand-Dependent MET Phosphorylation.

MET, a c-met proto-oncogene product and hepatocyte growth factor (HGF) receptor, is known to play an important role in cancer progression, including bone metastasis. In a previous study, we reported increased expression of MET and matriptase, a novel activator of HGF, in bone metastasis. In this study, we employed a mouse model of renal cell carcinoma (RCC) bone metastasis to clarify the significance of the HGF/MET signaling axis and the regulator of HGF activator inhibitor type-2 (HAI-2). Luciferase-transfected 786-O cells were injected into the left cardiac ventricle of mice to prepare the mouse model of bone metastasis. The formation of bone metastasis was confirmed by whole-body bioluminescent imaging, and specimens were extracted. Expression of HGF/MET-related molecules was analyzed. Based on the results, we produced HAI-2 stable knockdown 786-O cells, and analyzed invasiveness and motility. Expression of HGF and matriptase was increased in bone metastasis compared with the control, while that of HAI-2 was decreased. Furthermore, we confirmed increased phosphorylation of MET in bone metastasis. The expression of matriptase was upregulated, and both invasiveness and motility were increased significantly by knockdown of HAI-2. The significance of ligand-dependent MET activation in RCC bone metastasis is considered, and HAI-2 may be an important regulator in this system.

Effect of a synthetic inhibitor of urokinase plasminogen activator on the migration and invasion of human cervical cancer cells in vitro.

As a notable feature of malignant tumors, invasion and metastasis are important events in the process of tumor progression. Amiloride, a synthetic inhibitor of urokinase plasminogen activator (uPA), is involved in these events. To evaluate the therapeutic value of amiloride in cervical cancer, HeLa cells were used as in vitro cellular models. The migration and invasion abilities of HeLa cells, in addition to the mRNA expression of matriptase, uPA, uPA receptor and 72 kDa type IV collagenase (MMP-2), were detected using scratch assays, Transwell chamber assays and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The results of RT-qPCR demonstrated that the mRNA expression of uPA and MMP-2 in HeLa cells was downregulated significantly in a dose-dependent manner when incubated with various concentrations of amiloride for 24 h. The migration distance of HeLa cells was significantly shorter at 6, 12 and 24 h following incubation with amiloride (P<0.01), and there was a positive correlation between cell migratory ability and cellular uPA protein expression level (r=0.955, P<0.01). The number of HeLa cells that penetrated the Matrigel following incubation for 24 h with different concentrations of amiloride decreased significantly compared with the control group, indicating that cell invasiveness was positively correlated with the protein expression level of uPA in the cells (r=0.993, P<0.01). The present study demonstrated that amiloride was able to specifically inhibit the mRNA expression levels of uPA in HeLa cells, and sequentially downregulate the mRNA expression of downstream MMP-2 in the uPA system, thereby suppressing the migratory and invasive ability of HeLa cells. Therefore, amiloride may be a promising therapeutic target for the treatment of cervical cancer.

Regulation of matriptase and HAI-1 system, a novel therapeutic target in human endometrial cancer cells.

The effects of specific and non-specific regulation of matriptase on endometrial cancer cells in vitro were investigated. Messenger ribonucleic acid (mRNA) and protein expression of matriptase and hepatocyte growth factor activator inhibitor-1 (HAI-1) in RL-952, HEC-1A, and HEC-1B endometrial cancer cells were detected by real-time quantitative PCR (RT-qPCR) and western blot. The cells were infected with lentivirus-mediated small-interfering RNA (siRNA) targeted on matriptase (MA-siRNA) or treated with different cisplatin (DDP) concentrations. After treatment, invasion, migration, and cellular apoptosis were analyzed. Matriptase mRNA and protein expression significantly decreased to 80% after infection with MA-siRNA (P < 0.01), and scratch and trans-well chamber assays showed significant inhibition of invasiveness and metastasis. Upon incubation with cisplatin at concentrations higher than the therapeutic dose for 24 h, the expressions of matriptase and HAI-1 significantly decreased (P < 0.001). Moreover, the invasiveness, metastasis, and survival rate of HEC-1A and RL-952 endometrial cancer cells were significantly decreased (P < 0.001) due to the down-regulation of matriptase and HAI-1 upon increasing cisplatin concentration. However, a slight increase in matriptase and HAI-1 expression was observed in cells treated with low cisplatin concentration (P = 0.01). Moreover, matriptase expression was associated with metastasis and invasiveness. Down-regulation of matriptase by specific Ma-SiRNA or non-specific cisplatin in matriptase/HAI-1–positive endometrial cancer cells showed promising therapeutic features.

Abstract 4615: Development of an antibody-drug conjugate with broad anticancer activity

Abstract Treatment for patients with advanced solid tumors that include triple negative breast cancer (TNBC), non-small cell lung cancer (NSCLC), and castrate resistant prostate cancer (CRPC), as well as Mantle Cell Lymphoma (MCL), while increasing survival is not curative. We have identified a membrane bound protease, “activated” matriptase, as an attractive target antigen for highly selective antibody delivery of cytotoxins as activated matriptase expression is restricted to epithelial tumors and some B-cell lymphomas. We generated a novel ADC by linking M69, a mouse antibody specific to activated matriptase, to monomethyl auristatin E (MMAE) via a PEGylated, releasable di-peptide linker as a proof-of-principle prototype. Both in cell lines and in human xenograft models of TNBC, NSCLC, CRPC and MCL, the conjugate was found to exhibit potent anticancer activity against all of these tumor types without toxicity. Encouraged by these results, we are also exploring the use of this ADC against gastric and pancreatic cancer, and in combination with chemotherapy and immunotherapy. As this is a mouse antibody, we are also generating a chimeric antibody for toxicity studies in primates. Citation Format: Siang-Yo Lin, Zoltan Szekely, Chen-Yong Lin, Joseph R. Bertino, Gulam Mohmad Rather. Development of an antibody-drug conjugate with broad anticancer activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4615. doi:10.1158/1538-7445.AM2017-4615

Inflammatory cytokines down-regulate the barrier-protective prostasin-matriptase proteolytic cascade early in experimental colitis

Compromised gastrointestinal barrier function is strongly associated with the progressive and destructive pathologies of the two main forms of irritable bowel disease (IBD), ulcerative colitis (UC), and Crohn's disease (CD). Matriptase is a membrane-anchored serine protease encoded by suppression of tumorigenicity-14 (ST14) gene, which is critical for epithelial barrier development and homeostasis. Matriptase barrier-protective activity is linked with the glycosylphosphatidylinositol (GPI)-anchored serine protease prostasin, which is a co-factor for matriptase zymogen activation. Here we show that mRNA and protein expression of both matriptase and prostasin are rapidly down-regulated in the initiating inflammatory phases of dextran sulfate sodium (DSS)-induced experimental colitis in mice, and, significantly, the loss of these proteases precedes the appearance of clinical symptoms, suggesting their loss may contribute to disease susceptibility. We used heterozygous St14 hypomorphic mice expressing a promoter-linked β-gal reporter to show that inflammatory colitis suppresses the activity of the St14 gene promoter. Studies in colonic T84 cell monolayers revealed that barrier disruption by the colitis-associated Th2-type cytokines, IL-4 and IL-13, down-regulates matriptase as well as prostasin through phosphorylation of the transcriptional regulator STAT6 and that inhibition of STAT6 with suberoylanilide hydroxamic acid (SAHA) restores protease expression and reverses cytokine-induced barrier dysfunction. Both matriptase and prostasin are significantly down-regulated in colonic tissues from human subjects with active ulcerative colitis or Crohn's disease, implicating the loss of this barrier-protective protease pathway in the pathogenesis of irritable bowel disease.