High expression of the cysteine proteinase legumain in colorectal cancer – Implications for therapeutic targeting

Investigation of prognostic values of immune infiltration and LGMN expression in the microenvironment of osteosarcoma

BACKGROUND

Osteosarcoma (OS), the most common primary malignant bone tumor, predominantly affects children and young adults and is characterized by high invasiveness and poor prognosis. Despite therapeutic advancements, the survival rate remains suboptimal, indicating an urgent need for novel biomarkers and therapeutic targets. This study aimed to investigate the prognostic significance of LGMN expression and immune cell infiltration in the tumor microenvironment of OS.

METHODS

We performed an integrative bioinformatics analysis utilizing the GEO and TARGET-OS databases to identify differentially expressed genes (DEGs) associated with LGMN in OS. We conducted Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) to explore the biological pathways and functions. Additionally, we constructed protein-protein interaction (PPI) networks, a competing endogenous RNA (ceRNA) network, and applied the CIBERSORT algorithm to quantify immune cell infiltration. The diagnostic and prognostic values of LGMN were evaluated using the area under the receiver operating characteristic (ROC) curve and Cox regression analysis. Furthermore, we employed Consensus Clustering Analysis to explore the heterogeneity within OS samples based on LGMN expression.

RESULTS

The analysis revealed significant upregulation of LGMN in OS tissues. DEGs were enriched in immune response and antigen processing pathways, suggesting LGMN's role in immune modulation within the TME. The PPI and ceRNA network analyses provided insights into the regulatory mechanisms involving LGMN. Immune cell infiltration analysis indicated a correlation between high LGMN expression and increased abundance of M2 macrophages, implicating an immunosuppressive role. The diagnostic AUC for LGMN was 0.799, demonstrating its potential as a diagnostic biomarker. High LGMN expression correlated with reduced overall survival (OS) and progression-free survival (PFS). Importantly, Consensus Clustering Analysis identified two distinct subtypes of OS, highlighting the heterogeneity and potential for personalized medicine approaches.

CONCLUSIONS

Our study underscores the prognostic value of LGMN in osteosarcoma and its potential as a therapeutic target. The identification of LGMN-associated immune cell subsets and the discovery of distinct OS subtypes through Consensus Clustering Analysis provide new avenues for understanding the immunosuppressive TME of OS and may aid in the development of personalized treatment strategies. Further validation in larger cohorts is warranted to confirm these findings.

Theranostic Fluorescent Probes

The ability to gain spatiotemporal information, and in some cases achieve spatiotemporal control, in the context of drug delivery makes theranostic fluorescent probes an attractive and intensely investigated research topic. This interest is reflected in the steep rise in publications on the topic that have appeared over the past decade. Theranostic fluorescent probes, in their various incarnations, generally comprise a fluorophore linked to a masked drug, in which the drug is released as the result of certain stimuli, with both intrinsic and extrinsic stimuli being reported. This release is then signaled by the emergence of a fluorescent signal. Importantly, the use of appropriate fluorophores has enabled not only this emerging fluorescence as a spatiotemporal marker for drug delivery but also has provided modalities useful in photodynamic, photothermal, and sonodynamic therapeutic applications. In this review we highlight recent work on theranostic fluorescent probes with a particular focus on probes that are activated in tumor microenvironments. We also summarize efforts to develop probes for other applications, such as neurodegenerative diseases and antibacterials. This review celebrates the diversity of designs reported to date, from discrete small-molecule systems to nanomaterials. Our aim is to provide insights into the potential clinical impact of this still-emerging research direction.

Pigmented Microbial Extract (PMB) from Exiguobacterium Species MB2 Strain (PMB1) and Bacillus subtilis Strain MB1 (PMB2) Inhibited Breast Cancer Cells Growth In Vivo and In Vitro

Breast cancer (BC) continues to be one of the major causes of cancer deaths in women. Progress has been made in targeting hormone and growth factor receptor-positive BCs with clinical efficacy and success. However, little progress has been made to develop a clinically viable treatment for the triple-negative BC cases (TNBCs). The current study aims to identify potent agents that can target TNBCs. Extracts from microbial sources have been reported to contain pharmacological agents that can selectively inhibit cancer cell growth. We have screened and identified pigmented microbial extracts (PMBs) that can inhibit BC cell proliferation by targeting legumain (LGMN). LGMN is an oncogenic protein expressed not only in malignant cells but also in tumor microenvironment cells, including tumor-associated macrophages. An LGMN inhibition assay was performed, and microbial extracts were evaluated for in vitro anticancer activity in BC cell lines, angiogenesis assay with chick chorioallantoic membrane (CAM), and tumor xenograft models in Swiss albino mice. We have identified that PMB from the Exiguobacterium (PMB1), inhibits BC growth more potently than PMB2, from the Bacillus subtilis strain. The analysis of PMB1 by GC-MS showed the presence of a variety of fatty acids and fatty-acid derivatives, small molecule phenolics, and aldehydes. PMB1 inhibited the activity of oncogenic legumain in BC cells and induced cell cycle arrest and apoptosis. PMB1 reduced the angiogenesis and inhibited BC cell migration. In mice, intraperitoneal administration of PMB1 retarded the growth of xenografted Ehrlich ascites mammary tumors and mitigated the proliferation of tumor cells in the peritoneal cavity in vivo. In summary, our findings demonstrate the high antitumor potential of PMB1.

Role of LGMN in tumor development and its progression and connection with the tumor microenvironment

Legumain (LGMN) has been demonstrated to be overexpressed not just in breast, prostatic, and liver tumor cells, but also in the macrophages that compose the tumor microenvironment. This supports the idea that LGMN is a pivotal protein in regulating tumor development, invasion, and dissemination. Targeting LGMN with siRNA or chemotherapeutic medicines and peptides can suppress cancer cell proliferation in culture and reduce tumor growth in vivo. Furthermore, legumain can be used as a marker for cancer detection and targeting due to its expression being significantly lower in normal cells compared to tumors or tumor-associated macrophages (TAMs). Tumor formation is influenced by aberrant expression of proteins and alterations in cellular architecture, but the tumor microenvironment is a crucial deciding factor. Legumain (LGMN) is an in vivo-active cysteine protease that catalyzes the degradation of numerous proteins. Its precise biological mechanism encompasses a number of routes, including effects on tumor-associated macrophage and neovascular endothelium in the tumor microenvironment. The purpose of this work is to establish a rationale for thoroughly investigating the function of LGMN in the tumor microenvironment and discovering novel tumor early diagnosis markers and therapeutic targets by reviewing the function of LGMN in tumor genesis and progression and its relationship with tumor milieu.

Asparaginyl endopeptidase contributes to cetuximab resistance via MEK/ERK signaling in RAS wide-type metastatic colorectal cancer

BACKGROUND

Cetuximab, a monoclonal antibody targeting epidermal growth factor receptor (EGFR), is effective for RAS wild-type metastatic colorectal cancer (mCRC) patients. However, cetuximab resistance often occur and the mechanism has not been fully elucidated. The purpose of this study was to investigate the role of asparaginyl endopeptidase (AEP) in cetuximab resistance.

METHODS

Differentially expressed genes between cetuximab responders and non-responders were identified by analyzing the gene expression profile GSE5851, retrieved from Gene Expression Omnibus (GEO). The potential genes were further validated in cetuximab-resistant CRC cell lines. The expression of AEP in the peripheral blood and tumor tissues of mCRC patients in our hospital were detected by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, respectively. The survival analysis was carried out by Kaplan-Meier method. The function and associated pathways of AEP were further investigated by lentivirus transfection, CCK8 assay, colony formation assay, real-time polymerase chain reaction (qPCR) and western blot.

RESULTS

Through bioinformatics analysis, we found that the expression of AEP gene was related to progress free survival (PFS) of mCRC patients treated with cetuximab alone (P = 0.00133). The expression of AEP was significantly higher in the cetuximab-resistant CRC cell lines, as well as in mCRC patients with shorter PFS treated with cetuximab-containing therapy. Furthermore, AEP could decrease the sensitivity of CRC cells to cetuximab in vitro. And the phosphorylation level of MEK and ERK1/2 was increased in AEP overexpression cells. The downregulation of AEP using specific inhibitors could partially restore the sensitivity of CRC cells to cetuximab.

CONCLUSION

The higher expression of AEP could contribute to the shorter PFS of cetuximab treatment in mCRC. The reason might be that AEP could promote the phosphorylation of MEK/ERK protein in the downstream signal pathway of EGFR.

The Mammalian Cysteine Protease Legumain in Health and Disease

The cysteine protease legumain (also known as asparaginyl endopeptidase or δ-secretase) is the only known mammalian asparaginyl endopeptidase and is primarily localized to the endolysosomal system, although it is also found extracellularly as a secreted protein. Legumain is involved in the regulation of diverse biological processes and tissue homeostasis, and in the pathogenesis of various malignant and nonmalignant diseases. In addition to its proteolytic activity that leads to the degradation or activation of different substrates, legumain has also been shown to have a nonproteolytic ligase function. This review summarizes the current knowledge about legumain functions in health and disease, including kidney homeostasis, hematopoietic homeostasis, bone remodeling, cardiovascular and cerebrovascular diseases, fibrosis, aging and senescence, neurodegenerative diseases and cancer. In addition, this review addresses the effects of some marketed drugs on legumain. Expanding our knowledge on legumain will delineate the importance of this enzyme in regulating physiological processes and disease conditions.

Autocrine pro-legumain promotes breast cancer metastasis via binding to integrin αvβ3

Tumor metastasis is the leading cause of cancer-associated mortality. Unfortunately, the underlying mechanism of metastasis is poorly understood. Expression of legumain (LGMN), an endo-lysosomal cysteine protease, positively correlates with breast cancer metastatic progression and poor prognosis. Here, we report that LGMN is secreted in the zymogen form by motile breast cancer cells. Through binding to cell surface integrin αvβ3 via an RGD motif, the autocrine pro-LGMN activates FAK-Src-RhoA signaling in cancer cells and promotes cancer cell migration and invasion independent of LGMN protease activity. Either silencing LGMN expression or mutationally abolishing pro-LGMN‒αvβ3 interaction significantly inhibits cancer cell migration and invasion in vitro and breast cancer metastasis in vivo. Finally, we developed a monoclonal antibody against LGMN RGD motif, which blocks pro-LGMN‒αvβ3 binding, and effectively suppresses cancer cell migration and invasion in vitro and breast cancer metastasis in vivo. Thus, disruption of pro-LGMN‒integrin αvβ3 interaction may be a potentially promising strategy for treating breast cancer metastasis.

Active legumain promotes invasion and migration of neuroblastoma by regulating epithelial-mesenchymal transition

Neuroblastoma (NB) is a commonly occurring malignancy in children. Epithelial-mesenchymal transition (EMT) is an adaptive change in promoting tumor metastasis. As an important factor in regulating tumor metastasis, whether legumain could promote metastasis of NB by EMT is still unexplored. Legumain is the active form of prolegumain, abundant in tumor plasma. So in the current study, different forms of legumain were identified in NB. Second, correlation analysis of N-cadherin and active legumain was identified by western blot analysis. Third, legumain gene amplification or gene knockdown were proceeded to examine the effect of legumain on EMT by scratch and transwell assay; meanwhile, active mature legumain or its asparagine endopeptidase (AEP) inhibitor was also added in. Finally, legumain can be detected differently in NB cells. Changes in legumain could influence NB metastasis by regulating EMT markers (e.g., N-cadherin, vimentin, and slug). Besides, the effect of legumain on EMT by its AEP activity was proved by intervention experiment of AEP gene transfection and gene knockdown experiments or adding recombinant human legumain suspension or specific inhibitor of AEP in NB cells (p < 0.05). These results suggest that legumain can promote invasion and migration of NB by regulating EMT, and EMT of NB is regulated by AEP activity of legumain, which can be inhibited by a specific AEP inhibitor.

Legumain/pH dual-responsive lytic peptide-paclitaxel conjugate for synergistic cancer therapy

After molecule targeted drug, monoclonal antibody and antibody–drug conjugates (ADCs), peptide–drug conjugates (PDCs) have become the next generation targeted anti-tumor drugs due to its properties of low molecule weight, efficient cell penetration, low immunogenicity, good pharmacokinetic and large-scale synthesis by solid phase synthesis. Herein, we present a lytic peptide PTP7-drug paclitaxel conjugate assembling nanoparticles (named PPP) that can sequentially respond to dual stimuli in the tumor microenvironment, which was designed for passive tumor-targeted delivery and on-demand release of a tumor lytic peptide (PTP-7) as well as a chemotherapeutic agent of paclitaxel (PTX). To achieve this, tumor lytic peptide PTP-7 was connected with polyethylene glycol by a peptide substrate of legumain to serve as hydrophobic segments of nanoparticles to protect the peptide from enzymatic degradation. After that, PTX was connected to the amino group of the polypeptide side chain through an acid-responsive chemical bond (2-propionic-3-methylmaleic anhydride, CDM). Therefore, the nanoparticle (PPP) collapsed when it encountered the weakly acidic tumor microenvironment where PTX molecules fell off, and further triggered the cleavage of the peptide substrate by legumain that is highly expressed in tumor stroma and tumor cell surface. Moreover, PPP presents improved stability, improved drug solubility, prolonged blood circulation and significant inhibition ability on tumor growth, which gives a reasonable strategy to accurately deliver small molecule drugs and active peptides simultaneously to tumor sites.

Identification of the Cysteine Protease Legumain as a Potential Chronic Hypoxia-Specific Multiple Myeloma Target Gene

Multiple myeloma (MM) is the second most common hematologic malignancy, which is characterized by clonal proliferation of neoplastic plasma cells in the bone marrow. This microenvironment is characterized by low oxygen levels (1–6% O₂), known as hypoxia. For MM cells, hypoxia is a physiologic feature that has been described to promote an aggressive phenotype and to confer drug resistance. However, studies on hypoxia are scarce and show little conformity. Here, we analyzed the mRNA expression of previously determined hypoxia markers to define the temporal adaptation of MM cells to chronic hypoxia. Subsequent analyses of the global proteome in MM cells and the stromal cell line HS-5 revealed hypoxia-dependent regulation of proteins, which directly or indirectly upregulate glycolysis. In addition, chronic hypoxia led to MM-specific regulation of nine distinct proteins. One of these proteins is the cysteine protease legumain (LGMN), the depletion of which led to a significant growth disadvantage of MM cell lines that is enhanced under hypoxia. Thus, herein, we report a methodologic strategy to examine MM cells under physiologic hypoxic conditions in vitro and to decipher and study previously masked hypoxia-specific therapeutic targets such as the cysteine protease LGMN.

Genetically-engineered "all-in-one" vaccine platform for cancer immunotherapy

An essential step for cancer vaccination is to break the immunosuppression and elicit a tumor-specific immunity. A major hurdle against cancer therapeutic vaccination is the insufficient immune stimulation of the cancer vaccines and lack of a safe and efficient adjuvant for human use. We discovered a novel cancer immunostimulant, trichosanthin (TCS), that is a clinically used protein drug in China, and developed a well-adaptable protein-engineering method for making recombinant protein vaccines by fusion of an antigenic peptide, TCS, and a cell-penetrating peptide (CPP), termed an “all-in-one” vaccine, for transcutaneous cancer immunization. The TCS adjuvant effect on antigen presentation was investigated and the antitumor immunity of the vaccines was investigated using the different tumor models. The vaccines were prepared via a facile recombinant method. The vaccines induced the maturation of DCs that subsequently primed CD8⁺ T cells. The TCS-based immunostimulation was associated with the STING pathway. The general applicability of this genetic engineering strategy was demonstrated with various tumor antigens (i.e., legumain and TRP2 antigenic peptides) and tumor models (i.e., colon tumor and melanoma). These findings represent a useful protocol for developing cancer vaccines at low cost and time-saving, and demonstrates the adjuvant application of TCS—an old drug for a new application.

Energy Metabolic Plasticity of Colorectal Cancer Cells as a Determinant of Tumor Growth and Metastasis

Metabolic plasticity is the ability of the cell to adjust its metabolism to changes in environmental conditions. Increased metabolic plasticity is a defining characteristic of cancer cells, which gives them the advantage of survival and a higher proliferative capacity. Here we review some functional features of metabolic plasticity of colorectal cancer cells (CRC). Metabolic plasticity is characterized by changes in adenine nucleotide transport across the outer mitochondrial membrane. Voltage-dependent anion channel (VDAC) is the main protein involved in the transport of adenine nucleotides, and its regulation is impaired in CRC cells. Apparent affinity for ADP is a functional parameter that characterizes VDAC permeability and provides an integrated assessment of cell metabolic state. VDAC permeability can be adjusted via its interactions with other proteins, such as hexokinase and tubulin. Also, the redox conditions inside a cancer cell may alter VDAC function, resulting in enhanced metabolic plasticity. In addition, a cancer cell shows reprogrammed energy transfer circuits such as adenylate kinase (AK) and creatine kinase (CK) pathway. Knowledge of the mechanism of metabolic plasticity will improve our understanding of colorectal carcinogenesis.

The Mechanism of Asparagine Endopeptidase in the Progression of Malignant Tumors: A Review

Asparagine endopeptidase (AEP), also called legumain, is currently the only known cysteine protease that specifically cleaves peptide bonds in asparaginyl residue in the mammalian genome. Since 2003, AEP has been reported to be widely expressed in a variety of carcinomas and is considered a potential therapeutic target. In the following years, researchers intensively investigated the substrates of AEP and the mechanism of AEP in partial tumors. With the identification of substrate proteins such as P53, integrin αvβ3, MMP-2, and MMP-9, the biochemical mechanism of AEP in carcinomas is also more precise. This review will clarify the probable mechanisms of AEP in the progression of breast carcinoma, glioblastoma, gastric carcinoma, and epithelial ovarian carcinoma. This review will also discuss the feasibility of targeted therapy with AEP inhibitor (AEPI) in these carcinomas.

Cuprizone and EAE mouse frontal cortex proteomics revealed proteins altered in multiple sclerosis

Two pathophysiological different experimental models for multiple sclerosis were analyzed in parallel using quantitative proteomics in attempts to discover protein alterations applicable as diagnostic-, prognostic-, or treatment targets in human disease. The cuprizone model reflects de- and remyelination in multiple sclerosis, and the experimental autoimmune encephalomyelitis (EAE, MOG1-125) immune-mediated events. The frontal cortex, peripheral to severely inflicted areas in the CNS, was dissected and analyzed. The frontal cortex had previously not been characterized by proteomics at different disease stages, and novel protein alterations involved in protecting healthy tissue and assisting repair of inflicted areas might be discovered. Using TMT-labelling and mass spectrometry, 1871 of the proteins quantified overlapped between the two experimental models, and the fold change compared to controls was verified using label-free proteomics. Few similarities in frontal cortex between the two disease models were observed when regulated proteins and signaling pathways were compared. Legumain and C1Q complement proteins were among the most upregulated proteins in cuprizone and hemopexin in the EAE model. Immunohistochemistry showed that legumain expression in post-mortem multiple sclerosis brain tissue (n = 19) was significantly higher in the center and at the edge of white matter active and chronic active lesions. Legumain was associated with increased lesion activity and might be valuable as a drug target using specific inhibitors as already suggested for Parkinson's and Alzheimer's disease. Cerebrospinal fluid levels of legumain, C1q and hemopexin were not significantly different between multiple sclerosis patients, other neurological diseases, or healthy controls.

Comprehensive molecular and clinicopathological profiling of desmoid tumours

Previous studies have not clearly identified a prognostic factor for desmoid tumours (DT). Whole-exome sequencing (WES) and/or RNA sequencing (RNA-seq) were performed in 64 cases of DT to investigate the molecular profiles in combination with the clinicopathological characteristics. CTNNB1 mutations with specific hotspots were identified in 56 cases (87.5%). A copy number loss in chromosome 6 (chr6) was identified in 14 cases (21.9%). Clustering based on the mRNA expression profiles was predictive of the patients' prognoses. The risk score generated by the expression of a three-gene set (IFI6, LGMN, and CKLF) was a strong prognostic marker for recurrence-free survival (RFS) in our cohort. In risk groups stratified by the expression of IFI6, the hazard ratio for recurrence-free survival in the high-risk group relative to the low-risk group was 12.12 (95% confidence interval: 1.56-94.2; p = 8.0 × 10⁶). In conclusion, CTNNB1 mutations and a chr6 copy number loss are likely the causative mutations underlying the tumorigenesis of DT while the gene expression profiles may help to differentiate patients who would be good candidates for wait-and-see management and those who might benefit from additional systemic or radiation therapies.

Esomeprazole inhibits the lysosomal cysteine protease legumain to prevent cancer metastasis

Legumain is a newly discovered lysosomal cysteine protease that can cleave asparagine bonds and plays crucial roles in regulating immunity and cancer metastasis. Legumain has been shown to be highly expressed in various solid tumors, within the tumor microenvironment and its levels are directly related to tumor metastasis and poor prognosis. Therefore, legumain presents as a potential cancer therapeutic drug target. In this study, we have identified esomeprazole and omeprazole as novel legumain small molecule inhibitors by screening an FDA approved-drug library. These compounds inhibited enzyme activity of both recombinant and endogenous legumain proteins with esomeprazole displaying the highest inhibitory effect. Further molecular docking analysis also indicated that esomeprazole, the S- form of omeprazole had the most stable binding to legumain protein compared to R-omeprazole. Transwell assay data showed that esomeprazole and omeprazole reduced MDA-MB-231 breast cancer cell invasion without effecting cell viability. Moreover, an in vivo orthotopic transplantation nude mouse model study showed that esomeprazole reduced lung metastasis of MDA-MB-231 breast cancer cells. These results indicated that esomeprazole has the exciting potential to be used in anti-cancer therapy by preventing cancer metastasis via the inhibition of legumain enzyme activity. Graphical abstract.

Evaluation of the anti-cervical cancer effect of a prodrug ：CBZ-AAN-DOX with hypoxic cell culture and tumor-bearing zebrafish models

BACKGROUND

Prodrugs are medications or compounds that, after administration, can be converted into pharmacologically active drugs through metabolism. Unlike conventional drugs, prodrugs have reduced adverse or unintended effects, which could become critical limitations in treatments such as chemotherapy. Previously through computer-aided drug design and chemical synthesis, we have obtained and examined a prodrug N-benzyloxycarbonyl-Ala-Asn-Doxorubicin (CBZ-AAN-DOX). CBZ-AAN-DOX is essentially Doxorubicin that is chemically-modified with tripeptides to target Legumain, a highly expressed protein in cancer cells and is involved in tumor metastasis and tumor microvessel formation. The difficulty to test the safety and efficacy of the prodrug (including the pharmacodynamic parameters of CBZ-AAN-DOX on metastasis and invasion of tumors, as well as cardiac and vascular toxicity) primarily comes from the lack of appropriate experimental models.

METHODS

Human cervical cancer cell lines CaSki under hypoxic conditions were used to evaluate the cell viability by CCK-8 assay after the prodrug treatment. Western blotting method was performed for Legumain protein determination in the cell culture. Wound healing and transwell invasion assays were performed to determine the effects of the prodrug on tumor metastasis and invasion, respectively. Zebrafish models were constructed for toxicity and angiogenesis visual analysis after in vivo treatment with the prodrug.

RESULTS

The CCK-8 results showed that CBZ-AAN-DOX exhibits an IC50 of 28.7 μM in 48 h on CaSki cells that had a lower cell inhibition rate than DOX 80.3 μM for 24 h. Legumain expression was significantly increased in a time-dependent manner in 48 h under hypoxia conditions. The results also showed that 13.9 μM of the prodrug significantly inhibited the migration and invasion of cells and the effects were significantly stronger than that of 41.8 μM of DOX under hypoxia conditions after 48 h. The effects of 160 μM of the prodrug on the survival rate of zebrafish after 72 h and heart-toxicity showed no obvious abnormalities. Cell metastasis and angiogenesis were also inhibited in tumor-bearing zebrafish model.

CONCLUSION

The findings in this study demonstrated that CBZ-AAN-DOX is a promising chemotherapy candidate with low toxicity and high efficiency for cervical cancer. Remarkably, the hypoxic culture model together with the zebrafish model serve as a good system for the evaluation of the toxicity, targeting and impact of the prodrug on tumor invasion and metastasis.

Current insights into the metastasis of epithelial ovarian cancer - hopes and hurdles

BACKGROUND

Ovarian cancer is the most lethal gynecologic cancer and the fifth leading cause of cancer-related mortality in women worldwide. Despite various attempts to improve the diagnosis and therapy of ovarian cancer patients, the survival rate for these patients is still dismal, mainly because most of them are diagnosed at a late stage. Up to 90% of ovarian cancers arise from neoplastic transformation of ovarian surface epithelial cells, and are usually referred to as epithelial ovarian cancer (EOC). Unlike most human cancers, which are disseminated through blood-borne metastatic routes, EOC has traditionally been thought to be disseminated through direct migration of ovarian tumor cells to the peritoneal cavity and omentum via peritoneal fluid. It has recently been shown, however, that EOC can also be disseminated through blood-borne metastatic routes, challenging previous thoughts about ovarian cancer metastasis.

CONCLUSIONS

Here, we review our current understanding of the most updated cellular and molecular mechanisms underlying EOC metastasis and discuss in more detail two main metastatic routes of EOC, i.e., transcoelomic metastasis and hematogenous metastasis. The emerging concept of blood-borne EOC metastasis has led to exploration of the significance of circulating tumor cells (CTCs) as novel and non-invasive prognostic markers in this daunting cancer. We also evaluate the role of tumor stroma, including cancer associated fibroblasts (CAFs), tumor associated macrophages (TAMs), endothelial cells, adipocytes, dendritic cells and extracellular matrix (ECM) components in EOC growth and metastasis. Lastly, we discuss therapeutic approaches for targeting EOC. Unraveling the mechanisms underlying EOC metastasis will open up avenues to the design of new therapeutic options. For instance, understanding the molecular mechanisms involved in the hematogenous metastasis of EOC, the biology of CTCs, and the detailed mechanisms through which EOC cells take advantage of stromal cells may help to find new opportunities for targeting EOC metastasis.

Recent advances in the development of legumain-selective chemical probes and peptide prodrugs

Legumain, which is also known as vacuolar processing enzyme (VPE) or asparaginyl endopeptidase (AEP), is a cysteine protease that was first discovered and characterized in the leguminous seeds of the moth bean in the early 1990s. Later, this enzyme was also detected in higher organisms, including eukaryotes. This pH-dependent protease displays the highest activity in acidic endolysosomal compartments; however, legumain also displays nuclear, cytosolic and extracellular activity when stabilized by other proteins or intramolecular complexes. Based on the results from over 25 years of research, this protease is involved in multiple cellular events, including protein degradation and antigen presentation. Moreover, when dysregulated, this protease contributes to the progression of several diseases, with cancer being the well-studied example. Research on legumain biology was undoubtedly facilitated by the use of small molecule chemical tools. Therefore, in this review, I present the historical perspectives and most current strategies for the development of small molecule substrates, inhibitors and activity-based probes for legumain. These tools are of paramount importance in elucidating the roles of legumain in multiple biological processes. Finally, as this enzyme appears to be a promising molecular target for anticancer therapies, the development of legumain-activated prodrugs is also described.

Asparaginyl endopeptidase may promote liver sinusoidal endothelial cell angiogenesis via PI3K/Akt pathway

BACKGROUND AND AIMS

pathological angiogenesis plays an important role in the progression of chronic liver diseases. Asparaginyl endopeptidase (AEP) participates in tumor angiogenesis and was recently shown to be associated with liver fibrosis. This study aimed to explore the effect of AEP on liver sinusoidal endothelial cell (LSECs) angiogenesis and determine the underlying mechanism.

METHODS

cultured LSECs were infected with lentiviruses in order to suppress AEP expression (AEP-KD1, AEP-KD2). The effect of AEP on LSECs proliferation, apoptosis and migration were subsequently determined by a CCK8 assay, flow cytometry and wound-healing and Transwell assays, respectively, in AEP knocked-down and control LSECs. The expression of the endothelial cell surface markers CD31, CD34 and von Willebrand factor (vWF) were detected by immunofluorescence assay and western blot. The angiogenic factors, vascular endothelial growth factor receptor 2 (VEGFR2) and interleukin 8 (IL 8) were detected by real-time PCR and western blot. The effect of AEP on vessel tube formation by LSECs was examined by Matrigel™ tube-formation assay. Phosphoinositide 3-kinase (PI3K)/Akt expression and phosphorylation were detected by western blot.

RESULTS

AEP was effectively knocked down by lentivirus infection in LSECs. Down-regulation of AEP expression significantly decreased proliferation and migration and increased apoptosis of LSECs. Moreover, expression levels of the endothelial cell surface markers CD31, CD34 and vWF, as well as angiogenic factors VEGFR2 and IL 8, were also reduced after AEP was knocked-down. The vessel tube formation abilities of AEP-KD1 and AEP-KD2 LSECs were significantly inhibited compared with LSECs without AEP knocked-down. Down-regulation of AEP also inhibited the phosphorylation of PI3K and Akt.

CONCLUSION

AEP promotes LSECs angiogenesis in vitro, possibly via the PI3K/Akt pathway. AEP may therefore be a potential therapeutic target for preventing the progression of liver fibrosis.

The exosomal integrin α5β1/AEP complex derived from epithelial ovarian cancer cells promotes peritoneal metastasis through regulating mesothelial cell proliferation and migration

PURPOSE

Epithelial ovarian cancer (EOC) is one of the most malignant cancers in the gynecologic system. Many patients are diagnosed at an advanced stage with disseminated intra-peritoneal metastases. EOC spreads via both direct extension and trans-coelomic spread. However, the interplay between human peritoneal mesothelial cells (HPMCs) and EOC cells is still ambiguous. We hypothesize that integrins (ITG) in HPMCs may play important roles in EOC metastasis.

METHODS

The expression of different integrin subtypes from HPMCs was assessed using Western blotting. The expression of integrin α5β1 (ITGA5B1) and its co-localization with asparaginyl endopeptidase (AEP) in HPMCs derived from EOC patients (EOC-HPMCs) were assessed using immunofluorescence. The role and mechanism of the exosomal ITGA5B1/AEP complex in HPMCs was assessed using both in vitro and in vivo assays. A retrospective study involving 234 cases was carried out to assess ITGA5B1 and AEP levels in circulating sera and ascites of EOC patients, as well as associations between ITGA5B1/AEP expression and overall survival.

RESULTS

We found that ITGA5B1was highly expressed and co-localized with AEP in EOC cells, and that the exosomal ITGA5B1/AEP complex secreted by EOC cells played an important role in the proliferation and migration of HPMCs. High levels of exosomal ITGA5B1/AEP were also found in circulating sera and ascites of EOC patients, and the expression of ITGA5B1/AEP in EOC tissues was found to be negatively associated with overall survival.

CONCLUSIONS

Our data indicate that EOCs may regulate the function of HPMCs through exosomal ITGA5B1/AEP, which may be crucial for peritoneal metastasis.

Design of a New Peptide Substrate Probe of the Putative Biomarker Legumain with Potential Application in Prostate Cancer Diagnosis Ex Vivo

The lysosomal endoprotease legumain (asparaginyl endoprotease) has been proposed as a putative biomarker in prostate tumours, in which the enzyme is markedly overexpressed. Overexpression, coupled with highly selective specificity for cleavage of substrates at the C-terminus of asparagine (Asn) residues, make legumain an attractive biochemical target for potential diagnosis, prognosis and treatment. We report the design, synthesis, characterisation and preliminary evaluation of a new rhodamine-B (Rho-B)-labelled legumain peptide substrate probe5[Rho-Pro-Ala-Asn-PEG-AQ(4-OH)] and its selective targeting to lysosomes in PC3 prostate cancer cells. Probe5was efficiently activated by recombinant human legumain to afford the high quantum yield reporter fluorophore tripeptide4b(Rho-Pro-Ala-Asn-OH) with concomitant release of intense fluorescence. Furthermore, probe5was activated upon incubation with homogenates derived from fresh-frozen tissue material of prostatectomy specimens. Probe5represents a new viable biochemical tool for probing the activity of legumain with the potential to be used in ex vivo diagnostics in the cancer pathology laboratory.

Legumain-deficient macrophages promote senescence of tumor cells by sustaining JAK1/STAT1 activation

Macrophages serve as the first line of communication between tumors and the rest of the immune system, and understanding the interplay between macrophage and tumor cells is essential for developing novel macrophage-based strategy against tumor. Here, we show that deletion of legumain in macrophages activates senescence of tumor cells. Macrophage derived IL-1β mediates the pro-senescent effect of Lgmn^-/- macrophages since blockage of IL-1β reverses the senescence phenotype in both a coculture model of macrophage and tumor cells and an orthotopic mouse model of breast cancer. Sustained activation of JAK1/STAT1 signaling and increased iNOS were found in the tumor cell-cocultured Lgmn^-/- macrophages, which were necessary for IL-1β expression and secretion. Applying a specific STAT1 agonist mimics the inductive effect of legumain deletion on IL-1β expression in macrophages, and the effect can be blocked via inhibition of iNOS. Legumain and integrin αvβ3 interact to prevent STAT1 signaling in macrophages, and blockage of integrin αvβ3 stimulates STAT1 activation. Therapeutically, transplantation of bone marrow from Lgmn^-/- mice suppresses the malignant growth of tumor by upregulating tumor cell senescence. Therefore, our finding highlights legumain in macrophages as a potential therapeutic target for tumors.

N-Terminomics/TAILS Profiling of Macrophages after Chemical Inhibition of Legumain

Legumain (asparaginyl endopeptidase) is the only protease with a preference for cleavage after asparagine residues. Increased legumain activity is a hallmark of inflammation, neurodegenerative diseases, and cancer, and legumain inhibitors have exhibited therapeutic effects in mouse models of these pathologies. Improved knowledge of its substrates and cellular functions is a requisite to further validation of legumain as a drug target. We, therefore, aimed to investigate the effects of legumain inhibition in macrophages using an unbiased and systematic approach. By shotgun proteomics, we identified 16 094 unique peptides in RAW264.7 cells. Among these, 326 unique peptides were upregulated in response to legumain inhibition, while 241 were downregulated. Many of these proteins were associated with mitochondria and metabolism, especially iron metabolism, indicating that legumain may have a previously unknown impact on related processes. Furthermore, we used N-terminomics/TAILS (terminal amine isotopic labeling of substrates) to identify potential substrates of legumain. We identified three new proteins that are cleaved after asparagine residues, which may reflect legumain-dependent cleavage. We confirmed that frataxin, a mitochondrial protein associated with the formation of iron-sulfur clusters, can be cleaved by legumain. This further asserts a potential contribution of legumain to mitochondrial function and iron metabolism. Lastly, we also identified a potential new cleavage site within legumain itself that may give rise to a 25 kDa form of legumain that has previously been observed in multiple cell and tissue types. Collectively, these data shed new light on the potential functions of legumain and will be critical for understanding its contribution to disease.

Synthesis and evaluation of radioactive/fluorescent peptide probes for imaging of legumain activity

Legumain or asparaginyl endopeptidase is an enzyme overexpressed in some cancers and involved in cancer migration, invasion, and metastasis. We have developed radioiodine- ([¹²⁵I]I-LCP) or fluorescein-labeled peptides (FL-LCP) with a cell-permeable d-Arg nonamer fused to an anionic d-Glu nonamer via a legumain-cleavable linker, to function as peptide probes that measure and monitor legumain activity. Non-cleavable probes of FL-NCP and [¹²⁵I]I-NCP were similarly prepared and evaluated as negative control probes by altering their non-cleavable sequence. Model peptides with the legumain-cleavable or non-cleavable sequence (LCP and NCP, respectively) reacted with recombinant human legumain, and only LCP was digested by this enzyme. [¹²⁵I]I-LCP uptake in legumain-positive HCT116 cells was significantly higher than that of [¹²⁵I]I-NCP (11.2 ± 0.44% vs 1.75 ± 0.06% dose/mg). The accumulation of FL-LCP in the HCT116 cells was rather low (4.75 ± 0.29% dose/mg protein), but not significantly different from the levels of FL-NCP. It is possible that low concentrations of [¹²⁵I]I-LCP (40 pM) can be effectively internalized after legumain cleavage. On the other hand, the cellular uptake of much higher concentrations of the FL-LCP derivative (1 mM) may be restricted by high concentrations of polyanions. The in vivo biodistribution studies in tumor-bearing mice demonstrated that the tumor uptake of [¹²⁵I]I-LCP was 1.34% injected dose per gram (% ID/g) at 30 min. The tumor/blood and tumor/muscle ratios at 30 min were 0.63 and 1.77, respectively, indicating that the [¹²⁵I]I-LCP accumulation in tumors was inadequate for in vivo imaging. Although further structural modifications are necessary to improve pharmacokinetic properties, [¹²⁵I]I-LCP has been demonstrated to be an effective scaffold for the development of nuclear medicine imaging probes to monitor legumain activity in living subjects.

Identification of the Duck Egg White N-Glycoproteome and Insight into the Course of Biological Evolution

Protein glycosylation is a ubiquitous posttranslational modification that modulates protein properties, thereby influencing bioactivities within a system. Duck egg white (DEW) proteins exhibit diverse biological properties compared with their chicken egg white (CEW) counterparts, which might be related to glycosylation. N-Glycoproteome analysis of DEW was conducted, and a total of 231 N-glycosites from 68 N-glycoproteins were identified. Gene ontology analysis was used to elucidate the biofunctions of DEW N-glycoproteins and compare them with those of CEW, which showed that the differences mostly involved molecular functions and biological processes. The biological functions of DEW N-glycoproteins were illuminated through bioinformatics analysis and comparison with CEW orthologues, which showed different allergenicities and antibacterial abilities. These divergences might be initiated by specific alterations in glycosylation, which can enhance the proteolysis resistance and protein steric hindrance. These results provide new insights for discovering the effects of N-glycosylation on biofunctions during the divergence of homologous proteins.

Degradomics in Biomarker Discovery

The upregulation of protease expression and proteolytic activity is implicated in numerous pathological conditions such as neurodegeneration, cancer, cardiovascular and autoimmune diseases, and bone degeneration. During disease progression, various proteases form characteristic patterns of cleaved proteins and peptides, which can affect disease severity and course of progression. It has been shown that qualitative and quantitative monitoring of cleaved protease substrates can provide relevant prognostic, diagnostic, and therapeutic information. As proteolytic fragments and peptides generated in the affected tissue are commonly translocated to blood, urine, and other proximal fluids, their possible application as biomarkers is the subject of ongoing research. The field of degradomics has been established to enable the global identification of proteolytic events on the organism level, utilizing proteomic approaches and sample preparation techniques that facilitate the detection of proteolytic processing of protease substrates in complex biological samples. In this review, some of the latest developments in degradomic methodologies used for the identification and validation of biologically relevant proteolytic events and their application in the search for clinically relevant biomarker candidates are presented. The current state of degradomics in clinics is discussed and the future perspectives of the field are outlined.

Fabrication of chitosan based nanocomposite with legumain sensitive properties using charge driven self-assembly strategy

Chitosan (CS) based nanoparticles (NPs) have several advantages in delivering drugs. They are usually prepared in a micro-emulsion solvent system but this route can leave significant levels of potentially harmful organic solvent residue in the NPs. In this study, we prepared CS based nanocomposites using charge driven self-assembly in an aqueous buffer, thus avoiding the use of organic solvents. Doxorubicin (DOX) was covalently attached to positive charged CS with a legumain substrate peptide to confer targeted drug release property, since legumain is often overexpressed in tumors or tumor associated micro environments. This DOX prodrug solution interacted with negative charged methoxyl poly (ethylene glycol)-block-poly (glutamic acid) copolymer (PEG-PGA) in an aqueous buffer forming nanocomposite with a regular morphology. The particle size and zeta potential of these NPs was regulated by the addition of different PEG-PGA concentrations into the DOX prodrug solution. Due to its potential for legumain triggered release, this DOX NP exhibited enhanced cytotoxicity against choroidal melanoma cell line (Mum-2C) and reduced cytotoxicity on normal human corneal epithelial cells (HCEC), suggesting a good potential for enhanced targeted delivery of chemotherapeutic agents. A chitosan based nanocomposite with legumain sensitive properties are rapidly controllable prepared in aqueous buffer by charge driven self-assembly strategy, without using micro-emulsion solvent system and cross-linking agents.

Development of a selected reaction monitoring mass spectrometry-based assay to detect asparaginyl endopeptidase activity in biological fluids

Cancer Biomarkers have the capability to improve patient outcomes. They have potential applications in diagnosis, prognosis, monitoring of disease progression and measuring response to treatment. This type of information is particularly useful in the individualisation of treatment regimens. Biomarkers may take many forms but considerable effort has been made to identify and quantify proteins in biological fluids. However, a major challenge in measuring protein in biological fluids, such as plasma, is the sensitivity of the assay and the complex matrix of proteins present. Furthermore, determining the effect of proteases in disease requires measurement of their activity in biological fluids as quantification of the protein itself may not provide sufficient information. To date little progress has been made towards monitoring activity of proteases in plasma. The protease asparaginyl endopeptidase has been implicated in diseases such as breast cancer, leukaemia and dementia. Here we describe a new approach to sensitively and in a targeted fashion quantify asparaginyl endopeptidase activity in plasma using a synthetic substrate peptide protected from nonspecific hydrolysis using D-amino acids within the structure. Our selected reaction monitoring approach enabled asparaginyl endopeptidase activity to be measured in human plasma with both a high dynamic range and sensitivity. This manuscript describes a paradigm for future development of assays to measure protease activities in biological fluids as biomarkers of disease.

Asparaginyl endopeptidase promotes the invasion and metastasis of gastric cancer through modulating epithelial-to-mesenchymal transition and analysis of their phosphorylation signaling pathways

Asparaginyl endopeptidase (AEP) is a lysosomal protease often overexpressed in gastric cancer. AEP was expressed higher in peritoneal metastatic loci than in primary gastric cancer. Then we overexpressed AEP or knocked it down with a lentiviral vector in gastric cancer cell lines and detected the cell cycle arrest and the changes of the invasive and metastatic ability in vitro and in vivo. When AEP was knocked-down, the proliferative, invasive and metastatic capacity of gastric cancer cells were inhibited, and the population of sub-G1 cells increased. AEP knockdown led to significant decrease of expression of transcription factor Twist and the mesenchymal markers N-cadherin, ß-catenin and Vimentin and to increased expression of epithelial marker E-cadherin. These results showed that AEP could promote invasion and metastasis by modulating EMT. We used phosphorylation-specific antibody microarrays to investigate the mechanism how AEP promotes gastric cancer invasion and metastasis, and found that the phosphorylation level of AKT and MAPK signaling pathways was decreased significantly if AEP was knocked-down. Therefore, AKT and MAPK signaling pathways took part in the modulation.

Legumain-cleavable 4-arm poly(ethylene glycol)-doxorubicin conjugate for tumor specific delivery and release

Traditional chemotherapy strategy exists undesirable toxic side-effects to normal tissues due to the low selectively to cancer cells of micromolecule cytotoxic drugs. One considered method to realizing the targeted delivery and increasing the specificity to tumor tissues of the cytotoxic drug is to transporting and discharging it through an environment-sensitive mechanism. In this study, a novel enzyme-sensitive polymer-doxorubicin conjugate was designed to delivery chemotherapeutic drug in a tumor-specific behavior and selectively activated in tumor tissue. Briefly, doxorubicin (DOX) was conjugated to carboxyl-terminated 4-arm poly(ethylene glycol) through a tetrapeptide linker, alanine-alanine-asparagine-leucine (AANL), which was one of the substrates of legumain, an asparaginyl endopeptidase that was found presented in plants, mammals and also highly expressed in human tumor tissues. Hereinafter, the polymer-DOX conjugate was termed as 4-arm PEG-AANL-DOX. Dynamic laser scattering (DLS) and transmission electron microscopy (TEM) measurements indicated that the 4-arm PEG-AANL-DOX could self-assemble into micelles in aqueous solution. Drug release and in vitro cytotoxicity studies revealed that the 4-arm PEG-AANL-DOX could be cleaved by legumain. Ex vivo DOX fluorescence imaging measurements demonstrated that the 4-arm PEG-AANL-DOX had an improved tumor-targeting delivery as compared with the free DOX·HCl. In vivo studies on nude mice bearing MDA-MB-435 tumors revealed that the 4-arm PEG-AANL-DOX had a comparable anticancer efficacy with the free DOX·HCl but without DOX-related toxicities to normal tissues as measured by body weight change and histological assessments, indicating that the 4-arm PEG-AANL-DOX had an improved therapeutic index for cancer therapy.

STATEMENT OF SIGNIFICANCE

Herein we describe the construction of a novel tumor environment-sensitive delivery system through the instruction of a legumain-cleavable linkage to a polymer-DOX conjugate (4-arm PEG-AANL-DOX). This particular design strategy allows for polymer-DOX conjugates to be delivered in a tumor-specific manner and selectively activable in tumor microenvironment so that it can combine the advantages of tumor-specific delivery and tumor intracellular microenvironment-triggered release systems.

Molecular imaging of the tumor microenvironment

The tumor microenvironment plays a critical role in tumor initiation, progression, metastasis, and resistance to therapy. It is different from normal tissue in the extracellular matrix, vascular and lymphatic networks, as well as physiologic conditions. Molecular imaging of the tumor microenvironment provides a better understanding of its function in cancer biology, and thus allowing for the design of new diagnostics and therapeutics for early cancer diagnosis and treatment. The clinical translation of cancer molecular imaging is often hampered by the high cost of commercialization of targeted imaging agents as well as the limited clinical applications and small market size of some of the agents. Because many different cancer types share similar tumor microenvironment features, the ability to target these biomarkers has the potential to provide clinically translatable molecular imaging technologies for a spectrum of cancers and broad clinical applications. There has been significant progress in targeting the tumor microenvironment for cancer molecular imaging. In this review, we summarize the principles and strategies of recent advances made in molecular imaging of the tumor microenvironment, using various imaging modalities for early detection and diagnosis of cancer.

The expression of asparaginyl endopeptidase promotes growth potential in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most common and lethal cancer-related death among females in the world. Asparaginyl endopeptidase (AEP) is a member of C13 family peptidases and expressed in the extracellular matrix and tumor cells. The aim of this article is to explore the function of asparaginyl endopeptidase in epithelial ovarian cancer. The expression of AEP was examined in 20 EOC samples, 3 EOC metastasis samples, 6 fallopian tube metastasis samples, 4 peritoneum metastasis samples and 20 benign ovarian tumor samples by immunohistochemistry. The expression of AEP was also evaluated in serum and ascites of EOC patients by elisa. And we used a lentiviral vector to overexpress AEP in human epithelial ovarian cancer cell lines SKOV3ip and detected the function of AEP-SKOV3ip cells both in vitro and in vivo. The growth of AEP-SKOV3ip cells was observed by MTT, migration and tube formation assays in vitro. Additionally, the subcutaneous mice model was used to identify the tumor growth and metastasis in vivo. Mice tumors were stained for CD31 to determine the microvessel density (MVD). We demonstrated that AEP was highly expressed in the EOC patient tissues and ascites. The AEP transfected SKOV3ip cells could both promote tumor growth in vitro and in vivo. The MVD in AEP-SKOV3ip group was higher than that in NC-SKOV3ip group. Therefore, our results demonstrated that AEP could induce EOC growth and progressionboth in vitro and in vivo.

Asparaginyl endopeptidase improves the resistance of microtubule-targeting drugs in gastric cancer through IQGAP1 modulating the EGFR/JNK/ERK signaling pathway

PURPOSE

In recent years, understanding of the role of asparaginyl endopeptidase (AEP) in tumorigenesis has steadily increased. In this study, we investigated whether AEP expression correlates with sensitivity to chemotherapeutic drugs in gastric cancer and explored the mechanism.

PATIENTS AND METHODS

AEP expression in the serum of patients' peripheral blood was measured by enzyme-linked immunosorbent assay. Patient survival time was evaluated using univariate and multivariate analyses. Mass spectrometry and co-immunoprecipitation assays were utilized to discover proteins that interact with AEP. Gastric cancer cell lines were established, in which AEP was overexpressed or knocked out using lentiviral CRISPR. The proliferative abilities of these cell lines in response to chemotherapy agents were evaluated using the Cell Counting Kit-8 method. Gene expression changes in these lines were assessed by real-time polymerase chain reaction and Western blot.

RESULTS

Patients with low expression of AEP were significantly more likely to have a good prognosis and experience complete response or partial response after treatment with docetaxel/S-1 regimen. Mass spectrum analysis showed that several proteins in the focal adhesion and mitogen-activated protein kinase signaling pathways interacted with AEP. IQGAP1 was confirmed to be one of the proteins interacting with AEP, and its protein level increased when AEP was knocked out. AEP knockout decreased resistance to microtubule inhibitors, including paclitaxel, docetaxel, and T-DM1. The expression levels of MDR1, p-EGFR, p-JNK, p-ERK, and p-Rac1/cdc42 were decreased in AEP knockout gastric cancer cell lines, and inhibitors of both JNK and ERK could block AEP-induced expression of MDR1.

CONCLUSION

AEP was not only a prognostic factor but also a predictive marker. AEP knockout could inhibit the activity of the EGFR/JNK/ERK signaling pathway and improve sensitivity to microtubule inhibitors through interacting with IQGAP1.

Development of a smart activity-based probe to detect subcellular activity of asparaginyl endopeptidase in living cells

A smart activity-based probe that generates a turn-on fluorescence signal in response to enzyme activity was developed, allowing dynamic imaging of subcellular enzyme activity in living cells.

The Agaricus blazei-Based Mushroom Extract, Andosan™, Protects against Intestinal Tumorigenesis in the A/J Min/+ Mouse

BACKGROUND

The novel A/J Min/+ mouse, which is a model for human Familial Adenomatous Polyposis (FAP), develops spontaneously multiple adenocarcinomas in the colon as well as in the small intestine. Agaricus blazei Murill (AbM) is an edible Basidiomycetes mushroom that has been used in traditional medicine against cancer and other diseases. The mushroom contains immunomodulating β-glucans and is shown to have antitumor effects in murine cancer models. Andosan™ is a water extract based on AbM (82%), but it also contains the medicinal Basidiomycetes mushrooms Hericeum erinaceus and Grifola frondosa.

METHODS AND FINDINGS

Tap water with 10% Andosan™ was provided as the only drinking water for 15 or 22 weeks to A/J Min/+ mice and A/J wild-type mice (one single-nucleotide polymorphism (SNP) difference), which then were exsanguinated and their intestines preserved in formaldehyde and the serum frozen. The intestines were examined blindly by microscopy and also stained for the tumor-associated protease, legumain. Serum cytokines (pro- and anti-inflammatory, Th1-, Th2 -and Th17 type) were measured by Luminex multiplex analysis. Andosan™ treated A/J Min/+ mice had a significantly lower number of adenocarcinomas in the intestines, as well as a 60% significantly reduced intestinal tumor load (number of tumors x size) compared to control. There was also reduced legumain expression in intestines from Andosan™ treated animals. Moreover, Andosan™ had a significant cytotoxic effect correlating with apoptosis on the human cancer colon cell line, Caco-2, in vitro. When examining serum from both A/J Min/+ and wild type mice, there was a significant increase in anti-tumor Th1 type and pro-inflammatory cytokines in the Andosan™ treated mice.

CONCLUSIONS

The results from this mouse model for colorectal cancer shows significant protection of orally administered Andosan™ against development of intestinal cancer. This is supported by the finding of less legumain in intestines of Andosan™ treated mice and increased systemic Th1 cytokine response. The mechanism is probably both immuno-modulatory and growth inhibition of tumor cells by induction of apoptosis.

MiRNA-Embedded ShRNAs for Radiation-Inducible LGMN Knockdown and the Antitumor Effects on Breast Cancer

Legumain (LGMN) is highly expressed in breast cancer (BC) and other solid tumors and is a potential anticancer target. Here we investigate the anti-tumor effects of short hairpin RNAs (shRNAs) targeting LGMN embedded in a microRNA-155 (miR-155) architecture, which is driven by a radiation-inducible chimeric RNA polymerase II (Pol II) promoter. Lentiviral vectors were generated with the chimeric promoter which controlled the expression of downstream shRNA-miR-155 cassette. Fluorescence was observed by using confocal microscopy. Real-time quantitative PCR and Western blotting were used to determine the expression level of LGMN, MMP2, and MMP9. Furthermore, the proliferation and invasive ability of BC cells was analyzed via plate colony formation and invasion assays. Here we demonstrated that the chimeric promoter could be effectively induced by radiation treatment. Furthermore, the shRNA-miR-155 cassette targeting LGMN could be effectively activated by the chimeric promoter. Radiation plus knockdown of LGMN impairs colony formation and dampens cell migration and invasion in BC cells. Inhibition of LGMN downregulates MMP2 and MMP9 expression in BC cells. Pol II-driven shRNA-miR-155 could effectively suppress the growth and invasiveness of BC cells, and that the interference effects could be regulated by radiation doses. Moreover, knockdown of LGMN alleviates the aggressive phenotype of BC cells through modulating MMPs expression.

Legumain is activated in macrophages during pancreatitis

Pancreatitis is an inflammatory disease of the pancreas characterized by dysregulated activity of digestive enzymes, necrosis, immune infiltration, and pain. Repeated incidence of pancreatitis is an important risk factor for pancreatic cancer. Legumain, a lysosomal cysteine protease, has been linked to inflammatory diseases such as atherosclerosis, stroke, and cancer. Until now, legumain activation has not been studied during pancreatitis. We used a fluorescently quenched activity-based probe to assess legumain activation during caerulein-induced pancreatitis in mice. We detected activated legumain by ex vivo imaging, confocal microscopy, and gel electrophoresis. Compared with healthy controls, legumain activity in the pancreas of caerulein-treated mice was increased in a time-dependent manner. Legumain was localized to CD68(+) macrophages and was not active in pancreatic acinar cells. Using a small-molecule inhibitor of legumain, we found that this protease is not essential for the initiation of pancreatitis. However, it may serve as a biomarker of disease, since patients with chronic pancreatitis show strongly increased legumain expression in macrophages. Moreover, the occurrence of legumain-expressing macrophages in regions of acinar-to-ductal metaplasia suggests that this protease may influence reprogramming events that lead to inflammation-induced pancreatic cancer.

Pathophysiological roles of proteases in gastrointestinal disease

Gastrointestinal diseases, such as irritable bowel syndrome, inflammatory bowel disease, and colorectal cancer, affect a large proportion of the population and are associated with many unpleasant symptoms. Although the causes of these diseases remain largely unknown, there is increasing evidence to suggest that dysregulated protease activity may be a contributing factor. Proteases are enzymes that cleave other proteins, and their activity is normally very tightly regulated. During disease, however, the balance between proteases and their inhibitors is often shifted, leading to altered spatial and temporal control of substrate cleavage. Evaluating protease levels in normal physiology and disease has relied heavily on the use of chemical tools. Although these tools have greatly advanced the field, they are not without caveats. This review provides an introduction to these tools, their application in the gut, and a summary of the current knowledge on the contribution of protease activity to gastrointestinal disease.

Proteases in cancer drug delivery

Whereas protease inhibitors have been developed successfully against hypertension and viral infections, they have failed thus far as cancer drugs. With advances in cancer profiling we now better understand that the tumor "degradome" (i.e. the repertoire of proteases and their natural inhibitors and interaction partners) forms a complex network in which specific nodes determine the global outcome of manipulation of the protease web. However, knowing which proteases are active in the tumor micro-environment, we may tackle cancers with the use of Protease-Activated Prodrugs (PAPs). Here we exemplify this concept for metallo-, cysteine and serine proteases. PAPs not only exist as small molecular adducts, containing a cleavable substrate sequence and a latent prodrug, they are presently also manufactured as various types of nanoparticles. Although the emphasis of this review is on PAPs for treatment, it is clear that protease activatable probes and nanoparticles are also powerful tools for imaging purposes, including tumor diagnosis and staging, as well as visualization of tumor imaging during microsurgical resections.

Clinicopathologic significance of legumain overexpression in cancer: a systematic review and meta-analysis

Since reports on the clinical significance of legumain in cancer have shown inconsistent results, we systematically evaluated clinical indicators of legumain in cancer. We searched the Cochrane Library, PubMed, Embase, and EBSCO databases and the Wangfang and CNKI databases in China by using "legumain" and ("neoplasms" OR "cancer") as search terms. We included case-controlled studies of legumain and cancer. The quality of the studies was evaluated by using Lichtenstein's guidelines, and valid data was extracted for analysis. In total, 10 articles were included in this study. Meta-analysis showed that legumain was overexpressed in cancer compared with in normal tissue and was higher in stage III-IV disease than in I-II disease. Moreover, legumain overexpression was correlated with poor prognosis and clinical stage. Furthermore, Cancer Genome Atlas data showed that among patients with rectal cancer, those with tumors overexpressing legumain had shorter overall survival than those in the low expression group (P < 0.05). Legumain appears to be involved in tumor development and deterioration; thus, it can potentially be developed into both a marker for monitoring and diagnosing tumors and a therapeutic target.

Structure and function of legumain in health and disease

The last years have seen a steady increase in our understanding of legumain biology that is driven from two largely uncoupled research arenas, the mammalian and the plant legumain field. Research on legumain, which is also referred to as asparaginyl endopeptidase (AEP) or vacuolar processing enzyme (VPE), is slivered, however. Here we summarise recent important findings and put them into a common perspective. Legumain is usually associated with its cysteine endopeptidase activity in lysosomes where it contributes to antigen processing for class II MHC presentation. However, newly recognized functions disperse previously assumed boundaries with respect to their cellular compartmentalisation and enzymatic activities. Legumain is also found extracellularly and even translocates to the cytosol and the nucleus, with seemingly incompatible pH and redox potential. These different milieus translate into changes of legumain's molecular properties, including its (auto-)activation, conformational stability and enzymatic functions. Contrasting its endopeptidase activity, legumain can develop a carboxypeptidase activity which remains stable at neutral pH. Moreover, legumain features a peptide ligase activity, with intriguing mechanistic peculiarities in plant and human isoforms. In pathological settings, such as cancer or Alzheimer's disease, the proper association of legumain activities with the corresponding cellular compartments is breached. Legumain's increasingly recognized physiological and pathological roles also indicate future research opportunities in this vibrant field.