Activity-based protein profiling implicates urokinase activation as a key step in human fibrosarcoma intravasation

Biodistribution studies for cell therapy products: Current status and issues

Information on the biodistribution (BD) of cell therapy products (CTPs) is essential for prediction and assessment of their efficacy and toxicity profiles in non-clinical and clinical studies. To conduct BD studies, it is necessary to understand regulatory requirements, implementation status, and analytical methods. This review aimed at surveying international and Japanese trends concerning the BD study for CTPs and the following subjects were investigated, which were considered particularly important: 1) comparison of guidelines to understand the regulatory status of BD studies in a global setting; 2) case studies of the BD study using databases to understand its current status in cell therapy; 3) case studies on quantitative polymerase chain reaction (qPCR) used primarily in non-clinical BD studies for CTPs; and 4) survey of imaging methods used for non-clinical and clinical BD studies. The results in this review will be a useful resource for implementing BD studies.

Advances in chlorin-based photodynamic therapy with nanoparticle delivery system for cancer treatment

Introduction: The treatment of tumors is one of the most difficult problems in the medical field at present. Patients often use a comprehensive therapy that combines surgery, radiotherapy, and chemotherapy. Photodynamic therapy (PDT) has prominent potential for eradicating various cancers. Chlorin-based photosensitizers (PSs), as one of the most utilized photosensitizers, have many advantages over conventional photosensitizers; however, a successful chlorin-based PDT needs multi-functional nano-carriers for selective photosensitizer delivery. The number of researches about nanoparticles designed for improved chlorin-based PSs is increasing in the current era. In this article, we give a brief review focused on the recent research progress in design of chlorin-based nanoparticles for the treatment of malignant tumors with photodynamic therapy.Areas covered: This review focuses on the current nanoparticle platforms for PDT, and describes different strategies to achieve controllable PDT by chlorin-nano-delivery systems. The challenges and prospects of PDT in clinical applications are also discussed.Expert opinions: The requirement for PDT to eradicate cancers has increased exponentially in recent years. The major clinically used photosensitizers are hydrophobic. The main obstacles in effective delivery of PSs are associated with this intrinsic nature. The design of nano-delivery systems to load PSs is pivotal for PSs' widespread use.

Screening of 5- and 6-Substituted Amiloride Libraries Identifies Dual-uPA/NHE1 Active and Single Target-Selective Inhibitors

The K⁺-sparing diuretic amiloride shows off-target anti-cancer effects in multiple rodent models. These effects arise from the inhibition of two distinct cancer targets: the trypsin-like serine protease urokinase-type plasminogen activator (uPA), a cell-surface mediator of matrix degradation and tumor cell invasiveness, and the sodium-hydrogen exchanger isoform-1 (NHE1), a central regulator of transmembrane pH that supports carcinogenic progression. In this study, we co-screened our library of 5- and 6-substituted amilorides against these two targets, aiming to identify single-target selective and dual-targeting inhibitors for use as complementary pharmacological probes. Closely related analogs substituted at the 6-position with pyrimidines were identified as dual-targeting (pyrimidine 24 uPA IC₅₀ = 175 nM, NHE1 IC₅₀ = 266 nM, uPA selectivity ratio = 1.5) and uPA-selective (methoxypyrimidine 26 uPA IC₅₀ = 86 nM, NHE1 IC₅₀ = 12,290 nM, uPA selectivity ratio = 143) inhibitors, while high NHE1 potency and selectivity was seen with 5-morpholino (29 NHE1 IC₅₀ = 129 nM, uPA IC₅₀ = 10,949 nM; NHE1 selectivity ratio = 85) and 5-(1,4-oxazepine) (30 NHE1 IC₅₀ = 85 nM, uPA IC₅₀ = 5715 nM; NHE1 selectivity ratio = 67) analogs. Together, these amilorides comprise a new toolkit of chemotype-matched, non-cytotoxic probes for dissecting the pharmacological effects of selective uPA and NHE1 inhibition versus dual-uPA/NHE1 inhibition.

Small Ones to Fight a Big Problem-Intervention of Cancer Metastasis by Small Molecules

Metastasis represents the most lethal attribute of cancer and critically limits successful therapies in many tumor entities. The clinical need is defined by the fact that all cancer patients, who have or who will develop distant metastasis, will experience shorter survival. Thus, the ultimate goal in cancer therapy is the restriction of solid cancer metastasis by novel molecularly targeted small molecule based therapies. Biomarkers identifying cancer patients at high risk for metastasis and simultaneously acting as key drivers for metastasis are extremely desired. Clinical interventions targeting these key molecules will result in high efficiency in metastasis intervention. In result of this, personalized tailored interventions for restriction and prevention of cancer progression and metastasis will improve patient survival. This review defines crucial biological steps of the metastatic cascade, such as cell dissemination, migration and invasion as well as the action of metastasis suppressors. Targeting these biological steps with tailored therapeutic strategies of intervention or even prevention of metastasis using a wide range of small molecules will be discussed.

Tumor cell intravasation

The process of entering the bloodstream, intravasation, is a necessary step in the development of distant metastases. The focus of this review is on the pathways and molecules that have been identified as being important based on current in vitro and in vivo assays for intravasation. Properties of the vasculature which are important for intravasation include microvessel density and also diameter of the vasculature, with increased intravasation correlating with increased vessel diameter in some tumors. TGFB signaling can enhance intravasation at least in part through induction of EMT, and we discuss other TGFB target genes that are important for intravasation. In addition to TGFB signaling, a number of studies have demonstrated that activation of EGF receptor family members stimulates intravasation, with downstream signaling through PI3K, N-WASP, RhoA, and WASP to induce invadopodia. With respect to proteases, there is strong evidence for contributions by uPA/uPAR, while the roles of MMPs in intravasation may be more tumor specific. Other cells including macrophages, fibroblasts, neutrophils, and platelets can also play a role in enhancing tumor cell intravasation. The technology is now available to interrogate the expression patterns of circulating tumor cells, which will provide an important reality check for the model systems being used. With a better understanding of the mechanisms underlying intravasation, the goal is to provide new opportunities for improving prognosis as well as potentially developing new treatments.

Activity-based protein profiling: an efficient approach to study serine hydrolases and their inhibitors in mammals and microbes

This review focuses on the identification of serine hydrolases and their inhibitors in mammals and microbes with activity-based protein profiling (ABPP).

ShRNA-mediated knock-down of CXCR7 increases TRAIL-sensitivity in MCF-7 breast cancer cells

This study aims to investigate the effects of CXCR7-shRNA on TRAIL-mediated apoptosis and suppression of invasive migration and the underlying mechanisms. (1) We constructed CXCR-7-shRNA lentiviral vectors and confirmed their silencing efficiency in MCF-7 cells by RT-PCR analysis. (2) The effects of CXCR7 and/or TRAIL on cell proliferation were examined by MTT assay. (3) Trans well invasion assay was used to examine the effects of CXCR7 silencing and/or TRAIL on MCF-7 cell invasive migration. (4) Expression of Caspase-3, and Caspase-8, and MMP-2 and MMP-9 proteins was examined by Western blot analysis. (1) Viral titers were 2.95 × 10(8) TU/ml, 3.01 × 10(8) TU/ml, 3.26 × 10(8) TU/ml, and 3.08 × 10(8) TU/ml, respectively. (2) CHXR7 shRNAs markedly decreased CXCR7 mRNA expression in MCF-7 cells, among which CXCR7-shRNA-1 showed significantly higher rate of inhibition (P < 0.05). (3) Combination of TRAIL and CXCR7-shRNA-1 resulted in marked suppression of cell proliferation in time-dependent manner (P < 0.05). (4) Cell invasion capacity was inhibited in each experimental group as compared to blank control group at 48 h post treatments (P < 0.05). Among them, combination of TRAIL and CXCR7-shRNA had the highest inhibitory effect (P < 0.05). (5) Western blot analysis indicated that TRAIL alone does not affect CXCR7 expression, but either TRAIL + CXCR7 shRNA or CXCR7 shRNA alone markedly suppressed CXCR7 protein expression. Furthermore, combination of TRAIL and CXCR-7-shRNA significantly increased Caspase-3 and Caspase-8 expression and decreased MMP-2 and MMP-9 expression (P < 0.05). Knock-down of CXCR-7 expression leads to augmented TRAIL-mediated suppression of MCF-7 cell proliferation and invasion.

Synthesis of novel phosphonic-type activity-based probes for neutrophil serine proteases and their application in spleen lysates of different organisms

Neutrophils are a type of granulocyte important in the "first line of defense" of the innate immune system. Upon activation, they facilitate the destruction of invading microorganisms by the production of superoxide radicals, as well as the release of the enzymatic contents of their lysozymes. These enzymes include specific serine proteases: cathepsin G, neutrophil elastase, proteinase 3, as well as the recently discovered neutrophil serine protease 4 (NSP4). Under normal conditions, the proteolytic activity of neutrophil proteases is tightly regulated by endogenous serpins; however, this mechanism can be subverted during tissue stress, thereby resulting in the uncontrolled activity of serine proteases, which induce chronic inflammation and subsequent pathology. Herein, we describe the development of low-molecular-weight activity-based probes that specifically target the active sites of neutrophil proteases.

Activity-based proteomic and metabolomic approaches for understanding metabolism

There are an increasing number of human pathologies that have been associated with altered metabolism, including obesity, diabetes, atherosclerosis, cancer, and neurodegenerative diseases. Most attention on metabolism has been focused on well-understood metabolic pathways and has largely ignored most of the biochemical pathways that operate in (patho)physiological settings, in part because of the vast landscape of uncharacterized and undiscovered metabolic pathways. One technology that has arisen to meet this challenge is activity-based protein profiling (ABPP) that uses activity-based chemical probes to broadly assess the functional states of both characterized and uncharacterized enzymes. This review will focus on how ABPP, coupled with inhibitor discovery platforms and functional metabolomic technologies, have led to discoveries that have expanded our knowledge of metabolism in health and disease.

Impact of expression of the uPA system in sarcomas

The uPA system mainly comprises the urokinase-type plasminogen activator uPA, the cell-surface receptor uPA receptor and the inhibitor PAI-1. Its clinical and prognostic impact especially in breast cancer is well investigated. In this short report, we summarize the published data describing expression of uPA, PAI-1 and uPA receptor and their relevance to clinical and survival data in sarcomas underlining their impact as tumor biomarkers in this tumor type as well.

Cell surface remodeling by plasmin: a new function for an old enzyme

Plasmin, one of the most potent and reactive serine proteases, is involved in various physiological processes, including embryo development, thrombolysis, wound healing and cancer progression. The proteolytic activity of plasmin is tightly regulated through activation of its precursor, plasminogen, only at specific times and in defined locales as well as through inhibition of active plasmin by its abundant natural inhibitors. By exploiting the plasminogen activating system and overexpressing distinct components of the plasminogen activation cascade, such as pro-uPA, uPAR and plasminogen receptors, malignant cells can enhance the generation of plasmin which in turn, modifies the tumor microenvironment to sustain cancer progression. While plasmin-mediated degradation and modification of extracellular matrix proteins, release of growth factors and cytokines from the stroma as well as activation of several matrix metalloproteinase zymogens, all have been a focus of cancer research studies for decades, the ability of plasmin to cleave transmembrane molecules and thereby to generate functionally important cleaved products which induce outside-in signal transduction, has just begun to receive sufficient attention. Herein, we highlight this relatively understudied, but important function of the plasmin enzyme as it is generated de novo at the interface between cross-talking cancer and host cells.

Protumorigenic activity of plasminogen activator inhibitor-1 through an antiapoptotic function

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is a protease inhibitor but is paradoxically associated with poor outcomes in cancer patients. However, the mechanisms of its effects on tumor cells have not been explored.

METHODS

Endogenous PAI-1 in human tumor cell lines (HT-1080, A549, HCT-116, and MDA-MB-231) was suppressed by small interfering RNAs (siRNAs) and PAI-039, a small molecule inhibitor of PAI-1, and the effects on apoptosis were examined. Tumorigenicity of PAI-1 knockdown (KD) tumor cells was examined in immunodeficient PAI-1 wild-type and knockout (KO) mice (9-15 per group), and event-free survival was analyzed by the Kaplan-Meier method. The effect of PAI-1 suppression on HT-1080 xenotransplanted tumors was evaluated for cell proliferation, apoptosis, and angiogenesis. All statistical tests were two-sided.

RESULTS

Genetic and pharmacological inhibition of PAI-1 in the four tumor cell lines increased spontaneous apoptosis (mean fold increase relative to control: HT-1080, siRNA#1, mean = 4.0, 95% CI = 2.6 to 5.3, P < .001; siRNA#2, mean = 2.6, 95% CI = 2.4 to 2.9, P < .001, Student t test), which was blocked in the presence of recombinant PAI-1, a caspase-8 inhibitor, or Fas/FasL neutralizing antibodies and was partially attenuated by a plasmin inhibitor-aprotinin. PAI-1 KO mice implanted with PAI-1 KD HT-1080 cells had decreased tumorigenesis and prolonged survival compared with control mice (P = .002, log-rank test), and their tumors exhibited decreased cell proliferation and angiogenesis and increased apoptosis. Furthermore, five of 15 PAI-1 KO mice implanted with PAI-1 KD HT-1080 cells never developed tumors.

CONCLUSIONS

These data suggest that PAI-1 exerts a protective effect against tumor cell apoptosis by a mechanism that, in part, involves plasmin activation and inhibition of Fas/Fas-L-mediated apoptosis and may be a promising therapeutic target.

A novel animal model for in vivo study of liver cancer metastasis

AIM: To establish an animal model with human hepatocyte-repopulated liver for the study of liver cancer metastasis.

METHODS: Cell transplantation into mouse livers was conducted using alpha-fetoprotein (AFP)-producing human gastric cancer cells (h-GCCs) and h-hepatocytes as donor cells in a transgenic mouse line expressing urokinase-type plasminogen activator (uPA) driven by the albumin enhancer/promoter crossed with a severe combined immunodeficient (SCID) mouse line (uPA/SCID mice). Host mice were divided into two groups (A and B). Group A mice were transplanted with h-GCCs alone, and group B mice were transplanted with h-GCCs and h-hepatocytes together. The replacement index (RI), which is the ratio of transplanted h-GCCs and h-hepatocytes that occupy the examined area of a histological section, was estimated by measuring h-AFP and h-albumin concentrations in sera, respectively, as well as by immunohistochemical analyses of h-AFP and human cytokeratin 18 in histological sections.

RESULTS: The h-GCCs successfully engrafted, repopulated, and colonized the livers of mice in group A (RI = 22.0% ± 2.6%). These mice had moderately differentiated adenocarcinomatous lesions with disrupted glandular structures, which is a characteristics feature of gastric cancers. The serum h-AFP level reached 211.0 ± 142.2 g/mL (range, 7.1-324.2 g/mL). In group B mice, the h-GCCs and h-hepatocytes independently engrafted, repopulated the host liver, and developed colonies (RI = 12.0% ± 6.8% and 66.0% ± 12.3%, respectively). h-GCC colonies also showed typical adenocarcinomatous glandular structures around the h-hepatocyte-colonies. These mice survived for the full 56 day-study and did not exhibit any metastasis of h-GCCs in the extrahepatic regions during the observational period. The mice with an h-hepatocyte-repopulated liver possessed metastasized h-GCCs and therefore could be a useful humanized liver animal model for studying liver cancer metastasis in vivo.

CONCLUSION: A novel animal model of human liver cancer metastasis was established using the uPA/SCID mouse line. This model could be useful for in vivo testing of anti-cancer drugs and for studying the mechanisms of human liver cancer metastasis.

CD44 enhances invasion of basal-like breast cancer cells by upregulating serine protease and collagen-degrading enzymatic expression and activity

Introduction

Basal-like breast cancers (BL-BCa) have the worst prognosis of all subgroups of this disease. Hyaluronan (HA) and the HA receptor CD44 have a long-standing association with cell invasion and metastasis of breast cancer. The purpose of this study was to establish the relation of CD44 to BL-BCa and to characterize how HA/CD44 signaling promotes a protease-dependent invasion of breast cancer (BrCa) cells.

Methods

CD44 expression was determined with immunohistochemistry (IHC) analysis of a breast cancer tissue microarray (TMA). In vitro experiments were performed on a panel of invasive BL-BCa cell lines, by using quantitative polymerase chain reaction (PCR), immunoblotting, protease activity assays, and invasion assays to characterize the basis of HA-induced, CD44-mediated invasion.

Results

Expression of the hyaluronan (HA) receptor CD44 associated with the basal-like subgroup in a cohort of 141 breast tumor specimens (P = 0.018). Highly invasive cells of the representative BL-BCa cell line, MDA-MB-231 (MDA-MB-231Hi) exhibited increased invasion through a basement membrane matrix (Matrigel) and collagen. In further experiments, HA-induced promotion of CD44 signaling potentiated expression of urokinase plasminogen activator (uPA) and its receptor uPAR, and underpinned an increased cell-associated activity of this serine protease in MDA-MB-231Hi and a further BL-BCa cell line, Hs578T cells. Knockdown of CD44 attenuated both basal and HA-stimulated uPA and uPAR gene expression and uPA activity. Inhibition of uPA activity by using (a) a gene-targeted RNAi or (b) a small-molecule inhibitor of uPA attenuated HA-induced invasion of MDA-MB-231Hi cells through Matrigel. HA/CD44 signaling also was shown to increase invasion of MDA-MB-231 cells through collagen and to potentiate the collagen-degrading activity of MDA-MB-231Hi cells. CD44 signaling was subsequently shown to upregulate expression of two potent collagen-degrading enzymes, the cysteine protease cathepsin K and the matrix metalloprotease MT1-MMP. RNAi- or shRNA-mediated depletion of CD44 in MDA-MB-231Hi cells decreased basal and HA-induced cathepsin K and MT1-MMP expression, reduced the collagen-degrading activity of the cell, and attenuated cell invasion through collagen. Pharmacologic inhibition of cathepsin K or RNAi-mediated depletion of MT1-MMP also attenuated MDA-MB-231Hi cell invasion through collagen.

Conclusion

HA-induced CD44 signaling increases a diverse spectrum of protease activity to facilitate the invasion associated with BL-BCa cells, providing new insights into the molecular basis of CD44-promoted invasion.

Reprogramming urokinase into an antibody-recruiting anticancer agent

Synthetic compounds for controlling or creating human immunity have the potential to revolutionize disease treatment. Motivated by challenges in this arena, we report herein a strategy to target metastatic cancer cells for immune-mediated destruction by targeting the urokinase-type plasminogen activator receptor (uPAR). Urokinase-type plasminogen activator (uPA) and uPAR are overexpressed on the surfaces of a wide range of invasive cancer cells and are believed to contribute substantially to the migratory propensities of these cells. The key component of our approach is an antibody-recruiting molecule that targets the urokinase receptor (ARM-U). This bifunctional construct is formed by selectively, covalently attaching an antibody-binding small molecule to the active site of the urokinase enzyme. We demonstrate that ARM-U is capable of directing antibodies to the surfaces of target cancer cells and mediating both antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC) against multiple human cancer cell lines. We believe that the reported strategy has the potential to inform novel treatment options for a variety of deadly, invasive cancers.

Activation of pro-uPA is critical for initial escape from the primary tumor and hematogenous dissemination of human carcinoma cells

Urokinase-type plasminogen activator (uPA) and plasmin have long been implicated in cancer progression. However, the precise contributions of the uPA/plasmin system to specific steps involved in cancer cell dissemination have not been fully established. Herein, we have used a highly disseminating variant of the human PC-3 prostate carcinoma cell line, PC-hi/diss, as a prototype of aggressive carcinomas to investigate the mechanisms whereby pro-uPA activation and uPA-generated plasmin functionally contribute to specific stages of metastasis. The PC-hi/diss cells secrete and activate significant amounts of pro-uPA, leading to efficient generation of plasmin in solution and at the cell surface. In a mouse orthotopic xenograft model, treatment with the specific pro-uPA activation-blocking antibody mAb-112 significantly inhibited local invasion and distant metastasis of the PC-hi/diss cells. To mechanistically examine the uPA/plasmin-mediated aspects of tumor cell dissemination, the anti-pro-uPA mAb-112 and the potent serine protease inhibitor, aprotinin, were used in parallel in a number of in vivo assays modeling various rate-limiting steps in early metastatic spread. Our findings demonstrate that, by generating plasmin, activated tumor-derived uPA facilitates early stages of PC-hi/diss dissemination, specifically the escape from the primary tumor and tumor cell intravasation. Moreover, through a series of in vitro and in vivo analyses, we suggest that PC-hi/diss-invasive escape and dissemination may be enhanced by cleavage of stromal fibronectin by uPA-generated plasmin. Together, our findings point to inhibition of pro-uPA activation at the apex of the uPA/plasmin cascade as a therapy-valid approach to control onset of tumor escape and ensuing metastatic spread.

The pharmacological landscape and therapeutic potential of serine hydrolases

Serine hydrolases perform crucial roles in many biological processes, and several of these enzymes are targets of approved drugs for indications such as type 2 diabetes, Alzheimer's disease and infectious diseases. Despite this, most of the human serine hydrolases (of which there are more than 200) remain poorly characterized with respect to their physiological substrates and functions, and the vast majority lack selective, in vivo-active inhibitors. Here, we review the current state of pharmacology for mammalian serine hydrolases, including marketed drugs, compounds that are under clinical investigation and selective inhibitors emerging from academic probe development efforts. We also highlight recent methodological advances that have accelerated the rate of inhibitor discovery and optimization for serine hydrolases, which we anticipate will aid in their biological characterization and, in some cases, therapeutic validation.

Tumor-recruited neutrophils and neutrophil TIMP-free MMP-9 regulate coordinately the levels of tumor angiogenesis and efficiency of malignant cell intravasation

Tumor-associated neutrophils contribute to neovascularization by supplying matrix metalloproteinase-9 (MMP-9), a protease that has been genetically and biochemically linked to induction of angiogenesis. Specific roles of inflammatory neutrophils and their distinct proMMP-9 in the coordinate regulation of tumor angiogenesis and tumor cell dissemination, however, have not been addressed. We demonstrate that the primary tumors formed by highly disseminating variants of human fibrosarcoma and prostate carcinoma recruit elevated levels of infiltrating MMP-9-positive neutrophils and concomitantly exhibit enhanced levels of angiogenesis and intravasation. Specific inhibition of neutrophil influx by interleukin 8 (IL-8) neutralization resulted in the coordinated diminishment of tumor angiogenesis and intravasation, both of which were rescued by purified neutrophil proMMP-9. However, if neutrophil proMMP-9, naturally devoid of tissue inhibitor of metalloproteinases (TIMP), was delivered in complex with TIMP-1 or in a mixture with TIMP-2, the protease failed to rescue the inhibitory effects of anti-IL8 therapy, indicating that the TIMP-free status of proMMP-9 is critical for facilitating tumor angiogenesis and intravasation. Our findings directly link tumor-associated neutrophils and their TIMP-free proMMP-9 with the ability of aggressive tumor cells to induce the formation of new blood vessels that serve as conduits for tumor cell dissemination. Thus, treatment of cancers associated with neutrophil infiltration may benefit from specific targeting of neutrophil MMP-9 at early stages to prevent ensuing tumor angiogenesis and tumor metastasis.

Mining the Active Proteome of Arabidopsis thaliana

Assigning functions to the >30,000 proteins encoded by the Arabidopsis genome is a challenging task of the Arabidopsis Functional Genomics Network. Although genome-wide technologies like proteomics and transcriptomics have generated a wealth of information that significantly accelerated gene annotation, protein activities are poorly predicted by transcript or protein levels as protein activities are post-translationally regulated. To directly display protein activities in Arabidopsis proteomes, we developed and applied activity-based protein profiling (ABPP). ABPP is based on the use of small molecule probes that react with the catalytic residues of distinct protein classes in an activity-dependent manner. Labeled proteins are separated and detected from proteins gels and purified and identified by mass spectrometry. Using probes of six different chemotypes we have displayed activities of 76 Arabidopsis proteins. These proteins represent over 10 different protein classes that contain over 250 Arabidopsis proteins, including cysteine, serine, and metalloproteases, lipases, acyltransferases, and the proteasome. We have developed methods for identification of in vivo labeled proteins using click chemistry and for in vivo imaging with fluorescent probes. In vivo labeling has revealed additional protein activities and unexpected subcellular activities of the proteasome. Labeling of extracts displayed several differential activities, e.g., of the proteasome during immune response and methylesterases during infection. These studies illustrate the power of ABPP to display the functional proteome and testify to a successful interdisciplinary collaboration involving chemical biology, organic chemistry, and proteomics.

Resveratrol enhances antitumor activity of TRAIL in prostate cancer xenografts through activation of FOXO transcription factor

BACKGROUND

Resveratrol (3, 4', 5 tri-hydroxystilbene), a naturally occurring polyphenol, exhibits anti-inflammatory, antioxidant, cardioprotective and antitumor activities. We have recently shown that resveratrol can enhance the apoptosis-inducing potential of TRAIL in prostate cancer cells through multiple mechanisms in vitro. Therefore, the present study was designed to validate whether resveratrol can enhance the apoptosis-inducing potential of TRAIL in a xenograft model of prostate cancer.

METHODOLOGY/PRINCIPAL FINDINGS

Resveratrol and TRAIL alone inhibited growth of PC-3 xenografts in nude mice by inhibiting tumor cell proliferation (PCNA and Ki67 staining) and inducing apoptosis (TUNEL staining). The combination of resveratrol and TRAIL was more effective in inhibiting tumor growth than single agent alone. In xenografted tumors, resveratrol upregulated the expressions of TRAIL-R1/DR4, TRAIL-R2/DR5, Bax and p27(/KIP1), and inhibited the expression of Bcl-2 and cyclin D1. Treatment of mice with resveratrol and TRAIL alone inhibited angiogenesis (as demonstrated by reduced number of blood vessels, and VEGF and VEGFR2 positive cells) and markers of metastasis (MMP-2 and MMP-9). The combination of resveratrol with TRAIL further inhibited number of blood vessels in tumors, and circulating endothelial growth factor receptor 2-positive endothelial cells than single agent alone. Furthermore, resveratrol inhibited the cytoplasmic phosphorylation of FKHRL1 resulting in its enhanced activation as demonstrated by increased DNA binding activity.

CONCLUSIONS/SIGNIFICANCE

These data suggest that resveratrol can enhance the apoptosis-inducing potential of TRAIL by activating FKHRL1 and its target genes. The ability of resveratrol to inhibit tumor growth, metastasis and angiogenesis, and enhance the therapeutic potential of TRAIL suggests that resveratrol alone or in combination with TRAIL can be used for the management of prostate cancer.

Activity-based protein profiling for biochemical pathway discovery in cancer

Large-scale profiling methods have uncovered numerous gene and protein expression changes that correlate with tumorigenesis. However, determining the relevance of these expression changes and which biochemical pathways they affect has been hindered by our incomplete understanding of the proteome and its myriad functions and modes of regulation. Activity-based profiling platforms enable both the discovery of cancer-relevant enzymes and selective pharmacological probes to perturb and characterize these proteins in tumour cells. When integrated with other large-scale profiling methods, activity-based proteomics can provide insight into the metabolic and signalling pathways that support cancer pathogenesis and illuminate new strategies for disease diagnosis and treatment.

Activity-based proteomics of enzyme superfamilies: serine hydrolases as a case study

Genome sequencing projects have uncovered thousands of uncharacterized enzymes in eukaryotic and prokaryotic organisms. Deciphering the physiological functions of enzymes requires tools to profile and perturb their activities in native biological systems. Activity-based protein profiling has emerged as a powerful chemoproteomic strategy to achieve these objectives through the use of chemical probes that target large swaths of enzymes that share active-site features. Here, we review activity-based protein profiling and its implementation to annotate the enzymatic proteome, with particular attention given to probes that target serine hydrolases, a diverse superfamily of enzymes replete with many uncharacterized members.

Co-detection of members of the urokinase plasminogen activator system in tumour tissue and serum correlates with a poor prognosis for soft-tissue sarcoma patients

Background:

The urokinase plasminogen activator (uPA) system is one of the best-investigated protease systems, both under physiological and pathological conditions, including various types of cancer. However, effects of co-expression of members of the uPA system in soft-tissue sarcoma (STS) patients at the protein level in both tumour tissue and serum have not been investigated yet.

Methods:

We examined 82 STS patients for protein levels of uPA, PAI-1and uPAR in tumour tissue and serum by ELISA.

Results:

A significant correlation between high antigen levels of uPA, PAI-1 or uPAR in tumour tissue, and of uPAR in serum, with poor outcome of STS patients was found for the first time. Most strikingly, we observed an additive effect of combined uPA, PAI-1 or uPAR levels in tumour tissue extracts with uPAR levels in serum on patients’ prognosis. High uPA/uPAR, PAI-1/uPAR and uPAR/uPAR antigen levels in tumour tissue/serum were associated with a 5.9-fold, 5.8-fold and 6.2-fold increased risk of tumour-related death (P=0.003, 0.001 and 0.002, respectively) compared with those patients who displayed low levels of the respective marker combination.

Conclusion:

As expression of members of the uPA system in tumour tissue and serum is additively correlated with prognosis of STS patients, our results suggest that combinations of these biomarkers can identify STS patients with a higher risk of tumour-related death.

RBBP9: a tumor-associated serine hydrolase activity required for pancreatic neoplasia

Pancreatic cancer is one of the most lethal malignancies. To discover functionally relevant modulators of pancreatic neoplasia, we performed activity-based proteomic profiling on primary human ductal adenocarcinomas. Here, we identify retinoblastoma-binding protein 9 (RBBP9) as a tumor-associated serine hydrolase that displays elevated activity in pancreatic carcinomas. Whereas RBBP9 is expressed in normal and malignant tissues at similar levels, its elevated activity in tumor cells promotes anchorage-independent growth in vitro as well as pancreatic carcinogenesis in vivo. At the molecular level, RBBP9 activity overcomes TGF-beta-mediated antiproliferative signaling by reducing Smad2/3 phosphorylation, a previously unknown role for a serine hydrolase in cancer biology. Conversely, loss of endogenous RBBP9 or expression of mutationally inactive RBBP9 leads to elevated Smad2/3 phosphorylation, implicating this serine hydrolase as an essential suppressor of TGF-beta signaling. Finally, RBBP9-mediated suppression of TGF-beta signaling is required for E-cadherin expression as loss of the serine hydrolase activity leads to a reduction in E-cadherin levels and a concomitant decrease in the integrity of tumor cell-cell junctions. These data not only define a previously uncharacterized serine hydrolase activity associated with epithelial neoplasia, but also demonstrate the potential benefit of functional proteomics in the identification of new therapeutic targets.

Nonproteolytic induction of catalytic activity into the single-chain form of urokinase-type plasminogen activator by dipeptides

Serine proteases are initially synthesized as single-chain proenzymes with activities that are many orders of magnitude lower than those of the mature enzyme. Proteolytic cleavage of an exposed loop liberates a new amino terminus that inserts into a hydrophobic pocket and forms a stabilizing salt bridge with a ubiquitously conserved aspartate residue, resulting in a conformational change organizing the mature oxyanion hole. In a decisive 1976 work, Huber and Bode [Bode, W., and Huber, R. (1976) FEBS Lett. 68, 231-236] demonstrated that peptides sequentially similar to the new amino terminus in combination with a catalytic site inhibitor could specifically induce a trypsin-like conformation in trypsinogen. We now demonstrate that an Ile-Ile or Ile-Val dipeptide can induce limited enzyme activity in the single-chain zymogen form of urokinase-type plasminogen activator (uPA) or its K158A variant, which cannot be activated proteolytically. Furthermore, the slow formation of a covalent serpin-protease complex between single-chain uPA and PAI-1 is significantly accelerated in the presence of specific dipeptide sequences. The technique of using a dipeptide mimic as a surrogate for the liberated amino terminus further provides a novel means by which to covalently label the immature active site of single-chain uPA with a fluorescent probe, permitting fluorescence approaches for direct observations of conformational changes within the protease domain during zymogen activation. These data demonstrate the structural plasticity of the protease domain, reinforce the notion of "molecular sexuality", and provide a novel way of studying conformational changes of zymogens during proteolytic activation.

Comparative analysis of metastasis variants derived from human prostate carcinoma cells: roles in intravasation of VEGF-mediated angiogenesis and uPA-mediated invasion

To analyze the process of tumor cell intravasation, we used the human tumor-chick embryo spontaneous metastasis model to select in vivo high (PC-hi/diss) and low (PC-lo/diss) disseminating variants from the human PC-3 prostate carcinoma cell line. These variants dramatically differed in their intravasation and dissemination capacities in both chick embryo and mouse spontaneous metastasis models. Concomitant with enhanced intravasation, PC-hi/diss exhibited increased angiogenic potential in avian and murine models. PC-hi/diss angiogenesis and intravasation were dependent on increased secretion of vascular endothelial growth factor (VEGF), since treating developing tumors with a function-blocking anti-VEGF antibody simultaneously inhibited both processes without affecting primary tumor growth. PC-hi/diss cells were also more migratory and invasive, suggestive of heightened ability to escape from primary tumors due to matrix-degrading activity. Consistent with this suggestion, PC-hi/diss cells produced more of the serine protease urokinase-type plasminogen activator (uPA) as compared with PC-lo/diss. The functional role of uPA in PC-hi/diss dissemination was confirmed by inhibition of invasion, angiogenesis, and intravasation with specific function-blocking antibodies that prevented uPA activation and blocked uPA activity. These processes were similarly sensitive to aprotinin, a potent inhibitor of serine proteases, including uPA-generated plasmin. Thus, our comparison of the PC-3 intravasation variants points to key roles for the uPA-plasmin system in PC-hi/diss intravasation, possibly via (1) promoting tumor cell matrix invasion and (2) facilitating development of VEGF-dependent angiogenic blood vessels.

Diversity of serine hydrolase activities of unchallenged and botrytis-infected Arabidopsis thaliana

Activity-based protein profiling is a powerful method to display enzyme activities in proteomes and provides crucial information on enzyme activity rather than protein or transcript abundance. We applied activity-based protein profiling using fluorophosphonate-based probes to display the activities of Ser hydrolases in the model plant Arabidopsis thaliana. Multidimensional protein identification technology and in-gel analysis of fluorophosphonate-labeled leaf extracts revealed over 50 Ser hydrolases, including dozens of proteases, esterases, and lipases, representing over 10 different enzyme families. Except for some well characterized Ser hydrolases like subtilases TPP2 and ARA12, prolyl oligopeptidase acylamino acid-releasing enzyme, serine carboxypeptidase-like SNG1 and BRS1, carboxylesterase-like CXE12, methylesterases MES2 and MES3, and S-formylglutathione hydrolase, the majority of these serine hydrolases have not been described before. We studied transiently expressed SNG1 and investigated plants infected with the fungal pathogen Botrytis cinerea. Besides the down-regulation of several Arabidopsis Ser hydrolase activities during Botrytis infection, we detected the activities of Botrytis-derived cutinases and lipases, which are thought to contribute to pathogenicity.

A novel mode of intervention with serine protease activity: targeting zymogen activation

Serine proteases are secreted from cells as single-chain zymogens, typically having activities orders of magnitude lower than those of the mature two-chain enzymes. Activation occurs by a conformational change initiated by cleavage of a specific peptide bond. We have derived a monoclonal antibody (mAb-112) which binds with subnanomolar affinity to pro-uPA, the zymogen form of urokinase-type plasminogen activator (uPA). We mapped the epitope of the antibody to the autolysis loop, one of the structural elements known to change conformation during zymogen activation. A mechanistic evaluation with biophysical methods elucidated a novel bifunctional inhibitory mechanism whereby mAb-112 not only delays the proteolytic conversion of single-chain pro-uPA into the two-chain form but also subsequently averts the conformational transition to a mature protease by sequestering the two-chain form in a zymogen-like, noncatalytic state. Functional studies employing two variants of human HT-1080 cells, exhibiting high and low levels of dissemination in a chorioallantoic membrane assay, demonstrate that mAb-112 is an effective inhibitor of tumor cell intravasation. These findings show that pharmacological interference with zymogen activation is a plausible and robust means to regulate uPA activity and the downstream effects of plasminogen activation in the spread of cancer and other processes of pathological tissue remodeling. A strategy that targets regions related to pro-enzyme activation likely provide a unique inhibitor-protease interaction surface and is, thus, expected to enhance the chances of engineering high inhibitor specificity. Our results provide new information about the structural flexibility underlying the equilibrium between active and inactive forms of serine proteases.

Activity-based protein profiling: from enzyme chemistry to proteomic chemistry

Genome sequencing projects have provided researchers with a complete inventory of the predicted proteins produced by eukaryotic and prokaryotic organisms. Assignment of functions to these proteins represents one of the principal challenges for the field of proteomics. Activity-based protein profiling (ABPP) has emerged as a powerful chemical proteomic strategy to characterize enzyme function directly in native biological systems on a global scale. Here, we review the basic technology of ABPP, the enzyme classes addressable by this method, and the biological discoveries attributable to its application.

DLC1 suppresses distant dissemination of human hepatocellular carcinoma cells in nude mice through reduction of RhoA GTPase activity, actin cytoskeletal disruption and down-regulation of genes involved in metastasis

The process of cell dissemination from the primary tumors to distant sites is the most harmful event during cancer progression, and the leading cause of cancer death. We have previously demonstrated that restoration of DLC1 tumor suppressor gene expression in the DLC1-negative Focus and 7703K human hepatocellular carcinoma (HCC) cell lines induced caspase-3 mediated apoptosis, reduced cell growth in vitro and tumorigenicity in vivo and diminished the ability to migrate through Matrigel, a property suggestive of metastatic potential in vivo. We now show that subcutaneous tumors developing after inoculation of Focus and 7703K cells into nude mice disseminate cells to liver and lung, and this process is markedly suppressed by restoration of DLC1 expression. Inhibition of tumor cell dissemination was associated with lower levels of RhoA activity, an increase in rounded cells and a reduction in actin stress fibers and focal adhesion molecules that are of critical importance in cancer cell invasion and metastasis. In addition, DLC1 down-regulated the expression of osteopontin and matrix metalloproteinase-9, which are highly up-regulated in most primary HCC with associated metastases. These observations implicate the DLC1 gene in suppression of HCC cell dissemination and identify novel cellular and genetic alterations that contribute to prevention of metastasis, a life-threatening event in cancer progression.

Cell surface proteomics identifies molecules functionally linked to tumor cell intravasation

In order to better understand the molecular and cellular determinants of tumor cell intravasation, our laboratory has generated a pair of congenic human HT-1080 fibrosarcoma variants (i.e. HT-hi/diss and HT-lo/diss) differing 50-100-fold in their ability to intravasate and disseminate. To investigate the molecular differences underlying the distinct dissemination capacities of these HT-1080 variants, we performed a comparative analysis of the cell surface proteomes of HT-hi/diss and HT-lo/diss. Cell membrane proteins were enriched by biotinylation and avidin precipitation and analyzed by tandem mass spectrometry employing multidimensional protein identification technology. By this approach, 47 cell surface-associated molecules were identified as differentially expressed between the HT-1080 intravasation variants. From these candidates, four targets (i.e. TIMP-2, NCAM-1, JAM-C, and tissue factor (TF)) were selected for further biochemical validation and in vivo functional verification. Western blot analysis of the cell surface enriched fractions confirmed the proteomic array data, demonstrating that, in vitro, TIMP-2 protein was increased in the HT-lo/diss variant, whereas NCAM-1, JAM-C, and TF levels were increased in the HT-hi/diss variant. Corresponding in vivo differences in levels of TIMP-2, JAM-C, and TF were demonstrated in primary tumors grown in the chick embryo. Finally, functional inhibition of one selected protein (i.e. TF) by small interfering RNA silencing or ligation with a function-blocking antibody significantly reduced HT-hi/diss intravasation, thus clearly implicating TF in the early steps of tumor cell dissemination. Overall, our cell surface proteomic analysis provides a powerful tool for identification of specific cell membrane molecules that contribute functionally to intravasation and metastasis in vivo.

Application of activity-based probes to the study of enzymes involved in cancer progression

Many tumor cells have elevated levels of hydrolytic and proteolytic enzymes, presumably to aid in key processes such as angiogenesis, cancer cell invasion, and metastasis. Functional roles of enzymes in cancer progression are difficult to study using traditional genomic and proteomic methods because the activities of these enzymes are often regulated by post-translational mechanisms. Thus, methods that allow for the direct monitoring of enzyme activity in a physiologically relevant environment are required to better understand the roles of specific players in the complex process of tumorigenesis. This review highlights advances in the field of activity-based proteomics, which uses small molecules known as activity-based probes (ABPs) that covalently bind to the catalytic site of target enzymes. We discuss the application of ABPs to cancer biology, especially to the discovery of tumor biomarkers, the screening of enzyme inhibitors, and the imaging of enzymes implicated in cancer.

Curcumin sensitizes TRAIL-resistant xenografts: molecular mechanisms of apoptosis, metastasis and angiogenesis

BACKGROUND

We have recently shown that curcumin (a diferuloylmethane, the yellow pigment in turmeric) enhances apoptosis-inducing potential of TRAIL in prostate cancer PC-3 cells, and sensitizes TRAIL-resistant LNCaP cells in vitro through multiple mechanisms. The objectives of this study were to investigate the molecular mechanisms by which curcumin sensitized TRAIL-resistant LNCaP xenografts in vivo.

METHODS

Prostate cancer TRAIL-resistant LNCaP cells were implanted in Balb c nude mice to examine the effects of curcumin and/or TRAIL on tumor growth and genes related to apoptosis, metastasis and angiogenesis.

RESULTS

Curcumin inhibited growth of LNCaP xenografts in nude mice by inducing apoptosis (TUNEL staining) and inhibiting proliferation (PCNA and Ki67 staining), and sensitized these tumors to undergo apoptosis by TRAIL. In xenogrfated tumors, curcumin upregulated the expression of TRAIL-R1/DR4, TRAIL-R2/DR5, Bax, Bak, p21/WAF1, and p27/KIP1, and inhibited the activation of NFkappaB and its gene products such as cyclin D1, VEGF, uPA, MMP-2, MMP-9, Bcl-2 and Bcl-XL. The regulation of death receptors and members of Bcl-2 family, and inactivation of NFkappaB may sensitize TRAIL-resistant LNCaP xenografts. Curcumin also inhibited number of blood vessels in tumors, and circulating endothelial growth factor receptor 2-positive endothelial cells in mice.

CONCLUSION

The ability of curcumin to inhibit tumor growth, metastasis and angiogenesis, and enhance the therapeutic potential of TRAIL suggests that curcumin alone or in combination with TRAIL can be used for prostate cancer prevention and/or therapy.

An integrated high-performance liquid chromatography-mass spectrometry system for the activity-dependent analysis of matrix metalloproteases

Matrix metalloproteases (MMPs) comprise a family of enzymes that play important roles in mediating angiogenesis, the remodelling of tissues and in cancer metastasis. Consequently, they are attractive targets for therapeutic intervention in chronic inflammation, cancer and neurological disorders. In order to study MMPs in body fluids in an activity-dependent manner, we have developed an automated, integrated system comprising an immobilized inhibitor cartridge for activity-dependent enrichment, an immobilized trypsin reactor for rapid on-line proteolysis and a capillary or nanoLC-MS system for separation and identification of the obtained peptide fragments. This targeted proteomics system was optimized with respect to recovery and evaluated through the analysis of urine samples that were spiked with recombinant MMP-12. MMP-12 specific peptide fragments were easily detected in a nanoLC-MS analysis of 500 microL crude urine spiked at a level of 8 nM. These results show the feasibility of selective, activity-dependent enrichment of MMPs from a non-treated biofluid at low nM concentrations.

Functional analysis of matrix metalloproteinases and tissue inhibitors of metalloproteinases differentially expressed by variants of human HT-1080 fibrosarcoma exhibiting high and low levels of intravasation and metastasis

The role of tumor-derived matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) in cancer cell dissemination was analyzed by employing two variants of human HT-1080 fibrosarcoma, HT-hi/diss and HT-lo/diss, which differ by 50-100-fold in their ability to intravasate and metastasize in the chick embryo. HT-hi/diss and HT-lo/diss were compared by quantitative reverse transcription-PCR and Western blot analyses for mRNA and protein expression of nine MMPs (MMP-1, -2, -3, -7, -8, -9, -10, -13, and -14) and three TIMPs (TIMP-1, -2, and -3) in cultured cells in vitro and in primary tumors in vivo. MMP-1 and MMP-9 were more abundant in the HT-hi/diss variant, both in cultures and in tumors, whereas the HT-lo/diss variant consistently expressed higher levels of MMP-2, TIMP-1, and TIMP-2. Small interfering RNA-mediated down-regulation of MMP-2 and TIMP-2 increased intravasation of HT-lo/diss cells. Coordinately, treatment of the developing HT-hi/diss tumors with recombinant TIMP-1 and TIMP-2 significantly reduced HT-hi/diss cell intravasation. However, a substantial increase of HT-hi/diss dissemination was observed upon small interfering RNA-mediated down-regulation of three secreted MMPs, including the interstitial collagenase MMP-1 and the two gelatinases, MMP-2 and MMP-9, but not the membrane-tethered MMP-14. The addition of recombinant pro-MMP-9 protein to the HT-hi/diss tumors reversed the increased intravasation of HT-hi/diss cells, in which MMP-9 was stably down-regulated by short hairpin RNA interference. This rescue did not occur if the pro-MMP-9 was stoichiometrically complexed with TIMP-1, pointing to a direct role of the MMP-9 enzyme in regulation of HT-hi/diss intravasation. Collectively, these findings demonstrate that tumor-derived MMPs may have protective functions in cancer cell intravasation, i.e. not promoting but rather catalytically interfering with the early stages of cancer dissemination.

Antimetastatic activity of insulin-like growth factor binding protein-3 in lung cancer is mediated by insulin-like growth factor-independent urokinase-type plasminogen activator inhibition

Insulin-like growth factor binding protein-3 (IGFBP-3), a major IGF-binding protein in human serum, regulates the growth of non-small cell lung cancer (NSCLC) cells through IGF-dependent and IGF-independent mechanisms. However, the role of IGFBP-3 in lung cancer metastasis is not well known. In the present study, we showed that noncytotoxic doses of adenoviral or recombinant IGFBP-3 significantly decreased the migration and invasion of H1299 and A549 NSCLC cells. Furthermore, treatment of human lung fibroblasts with recombinant IGFBP-3 suppressed their ability to stimulate the invasion of H1299 cells. Overexpression of IGFBP-3 markedly reduced lung metastasis of A549 cells in an experimental animal model system and prolonged the survival time of the animals. Urokinase-type plasminogen activator (uPA) inhibitor treatment or uPA small interfering RNA transfection of A549 and H1299 cells resulted in a significant decrease in invasion. Corresponding ELISA, Western blot, gelatin zymogram, and semiquantitative reverse transcription-PCR analyses revealed that IGFBP-3 reduced the expression of uPA mRNA through IGF-independent mechanisms. The specific role of uPA in anti-invasive activity of IGFBP-3 was further confirmed in NSCLC cells, in which uPA expression/activity was suppressed by the transfection with synthetic small interfering RNA or by the treatment with uPA inhibitor or induced by the infection with an adenoviral vector. IGFBP-3 also decreased the expression/activity of matrix metalloproteinase-2 through IGF-dependent but uPA-independent pathways. Taken together, our data suggest that IGFPB-3 effectively block uPA- and matrix metalloproteinase-2-stimulated invasion pathways, ultimately reducing lung cancer cell metastasis. Our findings indicate that IGFBP-3 may be a promising anti-invasive and antimetastatic therapeutic agent in lung cancer.