Binding of urokinase to plasminogen activator inhibitor type-1 mediates cell adhesion and spreading

Quantitative proteomic and metabolomic profiling reveals different osmoregulation mechanisms of tilapia cells coping with different hyperosmotic stress

This study aimed to investigate the different regulatory mechanisms of euryhaline fish under regular hyperosmotic and extreme hyperosmotic stress. The OmB (Oreochromis mossambicus brain) cells were exposed to three treatments: control, regular hyperosmotic stress and extreme hyperosmotic stress. After 12 h exposure, proteomics, metabolomics analyses and integrative analyses were explored. Both kinds of stress lead to lowering cell growth and morphology changes, while under regular hyperosmotic stress, the up-regulated processes related with compatible organic osmolytes synthesis are crucial strategy for the euryhaline fish cell line to survive; On the other hand, under extreme hyperosmotic stress, the processes related with cell apoptosis and cell cycle arrest are dominant. Furthermore, down-regulated pyrimidine metabolism and several ribosomal proteins partially participated in the lowered cell metabolism and increased cell death under both kinds of hyperosmotic stress. The PI3K-Akt and p53 signaling pathways were involved in the stagnant stage of cell cycles and induction of cell apoptosis under both kinds of hyperosmotic stress. However, HIF-1, FoxO, JAK-STAT and Hippo signaling pathways mainly contribute to disrupting the cell cycle, metabolism and induction of cell apoptosis under extreme hyperosmotic stress. SIGNIFICANCE: In the past, the research on fish osmoregulation mainly focused on the transcription factors and ion transporters of osmoregulation, the processes between osmotic sensing and signal transduction, and the associations between signaling pathways and regulation processes have been poorly understood. Investigating fish cell osmoregulation and potential signal transduction pathways is necessary. With the advancements in omics research, it is now feasible to investigate the relationship between environmental stress and molecular responses. In this study, we aimed to explore the signaling pathways and substance metabolism mode during hyper-osmoregulation in OmB cell line, to reveal the key factors that are critical to cell osmoregulation.

Mitochondrial energy metabolism-related gene signature as a prognostic indicator for pancreatic adenocarcinoma

Background: Pancreatic adenocarcinoma (PAAD) is a highly malignant gastrointestinal tumor and is associated with an unfavorable prognosis worldwide. Considering the effect of mitochondrial metabolism on the prognosis of pancreatic cancer has rarely been investigated, we aimed to establish prognostic gene markers associated with mitochondrial energy metabolism for the prediction of survival probability in patients with PAAD. Methods: Gene expression data were obtained from The Cancer Genome Atlas and Gene Expression Omnibus databases, and the mitochondrial energy metabolism-related genes were obtained from the GeneCards database. Based on mitochondrial energy metabolism score (MMs), differentially expressed MMRGs were established for MMs-high and MMs-low groups using ssGSEA. After the univariate Cox and least absolute and selection operator (LASSO) analyses, a prognostic MMRG signature was used in the multivariate Cox proportional regression model. Survival and immune cell infiltration analyses were performed. In addition, a nomogram based on the risk model was used to predict the survival probability of patients with PAAD. Finally, the expression of key genes was verified using quantitative polymerase chain reaction and immunohistochemical staining. Intro cell experiments were performed to evaluated the proliferation and invasion of pancreatic cancer cells. Results: A prognostic signature was constructed consisting of two mitochondrial energy metabolism-related genes (MMP11, COL10A1). Calibration and receiver operating characteristic (ROC) curves verified the good predictability performance of the risk model for the survival rate of patients with PAAD. Finally, immune-related analysis explained the differences in immune status between the two subgroups based on the risk model. The high-risk score group showed higher estimate, immune, and stromal scores, expression of eight checkpoint genes, and infiltration of M0 macrophages, which might indicate a beneficial response to immunotherapy. The qPCR results confirmed high expression of MMP11 in pancreatic cancer cell lines, and IHC also verified high expression of MMP11 in clinical pancreatic ductal adenocarcinoma tissues. In vitro cell experiments also demonstrated the role of MMP11 in cell proliferation and invasion. Conclusion: Our study provides a novel two-prognostic gene signature-based on MMRGs-that accurately predicted the survival of patients with PAAD and could be used for mitochondrial energy metabolism-related therapies in the future.

Cancer selective cell death induction by a bivalent CK2 inhibitor targeting the ATP site and the allosteric αD pocket

Although the involvement of protein kinase CK2 in cancer is well-documented, there is a need for selective CK2 inhibitors suitable for investigating CK2 specific roles in cancer-related biological pathways and further exploring its therapeutic potential. Here, we report the discovery of AB668, an outstanding selective inhibitor that binds CK2 through a bivalent mode, interacting both at the ATP site and an allosteric αD pocket unique to CK2. Using caspase activation assay, live-cell imaging, and transcriptomic analysis, we have compared the effects of this bivalent inhibitor to representative ATP-competitive inhibitors, CX-4945, and SGC-CK2-1. Our results show that in contrast to CX-4945 or SGC-CK2-1, AB668, by targeting the CK2 αD pocket, has a distinct mechanism of action regarding its anti-cancer activity, inducing apoptotic cell death in several cancer cell lines and stimulating distinct biological pathways in renal cell carcinoma.

Novel diagnostic biomarkers of oxidative stress, immune- infiltration characteristics and experimental validation of SERPINE1 in colon cancer

BACKGROUND

Colon cancer (CC) is a prevalent malignant tumor that affects the colon in the gastrointestinal tract. Its aggressive nature, strong invasiveness, and rapid progression make it a significant health concern. In addition, oxidative stress can lead to the production of reactive oxygen species (ROS) that surpass the body's antioxidant defense capacity, causing damage to proteins, lipids, and DNA, potentially promoting tumor development. However, the relationship between CC and oxidative stress requires further investigation.

METHODS

We collected gene expression data and clinical data from 473 CC patients from The Cancer Genome Atlas (TCGA) dataset. Additionally, we obtained 433 oxidative stress genes from Genecards ( https://www.genecards.org/ ). Using univariate, multivariate, and LASSO Cox regression analyses, we developed predictive models for oxidative stress-related genes in CC patients. To validate the models, we utilized data from the Gene Expression Omnibus (GEO) database. We assessed the accuracy of the models through various techniques, including the creation of a nomogram, receiver operating characteristic curve (ROC) analysis, and principal component analysis (PCA). The Cytoscape program was utilized to identify hub genes among differentially expressed genes (DEGs) in tumor patients using the TCGA dataset. Subsequently, we conducted survival analysis, clinical relevance analysis, and immune cell relevance analysis for the intersected genes obtained by combining the hub genes with the genes from the predictive models. Moreover, we investigated the mRNA expression and potential functions of these intersected genes using a range of experimental approaches.

RESULTS

In both the TCGA and GSE17538 datasets, patients classified as high-risk had significantly shorter overall survival compared to those in the low-risk group (TCGA: p < 0.001; GSE17538: p = 0.010). As a result, we decided to further investigate the role of SERPINE1. Our survival analysis revealed that patients with high expression of SERPINE1 had a significantly lower probability of survival compared to those with low expression (p < 0.05). Additionally, our clinical correlation analysis showed a significant relationship between SERPINE1 expression and T, N, and M stages, as well as tumor grade. Furthermore, our immune infiltration correlation analysis demonstrated notable differences in multiple immune cells between the high- and low-expression groups of SERPINE1. To validate our findings, we conducted experimental tests and observed that knocking down SERPINE1 in colon cancer cells resulted in significant reductions in cell viability and proliferation. Interestingly, we also noticed an increase in oxidative stress parameters, such as ROS and MDA levels, while the levels of reduced GSH decreased upon SERPINE1 knockdown. These findings suggest that the antineoplastic effect of silencing SERPINE1 may be associated with the induction of oxidative stress.

CONCLUSION

In conclusion, this study introduces a new approach for the early diagnosis and treatment of CC, and further exploration of SERPINE1 could potentially lead to a significant advancement.

Distribution, Metabolism, and Toxicity of Antimony Species in Wistar Rats. A Bio-Analytical Approach

This work studied the distribution, reactivity, and biological effects of pentavalent or trivalent antimony (Sb(V), Sb(III)) and N-methylglucamine antimonate (NMG-Sb(V)) in Wistar Rats. The expression of fibrosis genes such as α-SMA, PAI-1, and CTGF were determined in Liver, and Kidney tissues. Wistar rats were treated with different concentrations of Sb(V), Sb(III), As(V) and As(III), and MA via intra-peritoneal injections. The results indicated a noteworthy elevation in mRNA levels of plasminogen activator 1 (PAI-1) in the kidneys of rats that were injected. The main accumulation site for Sb(V) was observed to be the liver, from which it is primarily excreted in its reduced form (Sb(III)) through the urine. The generation of Sb(III) in the kidneys has been found to induce damage through the expression of α-SMA and CTGF, and also lead to a higher creatinine clearance compared to As(III).

Case-only design identifies interactions of genetic risk variants at SIGLEC5 and PLG with the lncRNA CTD-2353F22.1 implying the importance of periodontal wound healing for disease aetiology

AIM

The basis of phenotypic variation of periodontitis is genetic variability. Disease relevant effects of individual risk alleles are considered to result from genetic interactions. We investigated gene × gene (G×G) interactions of suggestive periodontitis susceptibility alleles.

MATERIALS AND METHODS

We used the case-only design and investigated single-nucleotide polymorphism (SNPs) that showed associations in our recent genome-wide association study (GWAS) and GWAS meta-analysis with p < 5 × 10^-6 . CRISPR-dCas9 gene activation followed by RNA-sequencing and gene-set enrichment analyses elucidated differentially expressed genes and gene networks. With the databases of SNPInspector and Transfac professional, luciferase reporter gene assays and antibody electrophoretic mobility shift experiments, we analysed allele-specific effects on transcription factor binding.

RESULTS

SNPs at the genes sialic acid binding Ig-like lectin 5 (SIGLEC5) and plasminogen (PLG) showed G×G interactions with rs1122900 at the long non-coding RNA (lncRNA) CTD-2353F22. Associated chromatin cis-activated CTD-2353F22.1 6.5-fold (p = .003), indicating CTD-2353F22.1 as target gene of this interaction. CTD-2353F22.1 regulated GADD45A (p_adj  < 4.9 × 10^-11 , log₂ fold change (FC) = -0.55), THBS1, SERPINE1 and Tissue Factor F3 (p_adj  < 5 × 10^-7 , log₂ FC ≥ -0.35) and the gene set "angiogenesis" (area under the curve = 0.71, p_adj  = 8.2 × 10^-5 ). rs1122900 effect C-allele decreased reporter gene activity (5.5-fold, p = .0003) and PRDM14 binding (76%).

CONCLUSIONS

CTD-2353F22.1 mediates interaction of SIGLEC5 and PLG, together with genes that function in periodontal wound healing.

Proteomic characterisation of prostate cancer intercellular communication reveals cell type-selective signalling and TMSB4X-dependent fibroblast reprogramming

BACKGROUND

In prostate cancer, the tumour microenvironment (TME) represents an important regulator of disease progression and response to treatment. In the TME, cancer-associated fibroblasts (CAFs) play a key role in tumour progression, however the mechanisms underpinning fibroblast-cancer cell interactions are incompletely resolved. Here, we address this by applying cell type-specific labelling with amino acid precursors (CTAP) and mass spectrometry (MS)-based (phospho)proteomics to prostate cancer for the first time.

METHODS

Reciprocal interactions between PC3 prostate cancer cells co-cultured with WPMY-1 prostatic fibroblasts were characterised using CTAP-MS. Signalling network changes were determined using Metascape and Enrichr and visualised using Cytoscape. Thymosin β4 (TMSB4X) overexpression was achieved via retroviral transduction and assayed by ELISA. Cell motility was determined using Transwell and random cell migration assays and expression of CAF markers by indirect immunofluorescence.

RESULTS

WPMY-1 cells co-cultured with PC3s demonstrated a CAF-like phenotype, characterised by enhanced PDGFRB expression and alterations in signalling pathways regulating epithelial-mesenchymal transition, cytoskeletal organisation and cell polarisation. In contrast, co-cultured PC3 cells exhibited more modest network changes, with alterations in mTORC1 signalling and regulation of the actin cytoskeleton. The expression of the actin binding protein TMSB4X was significantly decreased in co-cultured WPMY-1 fibroblasts, and overexpression of TMSB4X in fibroblasts decreased migration of co-cultured PC3 cells, reduced fibroblast motility, and protected the fibroblasts from being educated to a CAF-like phenotype by prostate cancer cells.

CONCLUSIONS

This study highlights the potential of CTAP-MS to characterise intercellular communication within the prostate TME and identify regulators of cellular crosstalk such as TMSB4X.

Analysis of the Hypoxic Response in a Mouse Cortical Collecting Duct-Derived Cell Line Suggests That Esrra Is Partially Involved in Hif1α-Mediated Hypoxia-Inducible Gene Expression in mCCDcl1 Cells

The kidney is strongly dependent on a continuous oxygen supply, and is conversely highly sensitive to hypoxia. Controlled oxygen gradients are essential for renal control of solutes and urine-concentrating mechanisms, which also depend on various hormones including aldosterone. The cortical collecting duct (CCD) is part of the aldosterone-sensitive distal nephron and possesses a key function in fine-tuned distal salt handling. It is well known that aldosterone is consistently decreased upon hypoxia. Furthermore, a recent study reported a hypoxia-dependent down-regulation of sodium currents within CCD cells. We thus investigated the possibility that cells from the cortical collecting duct are responsive to hypoxia, using the mouse cortical collecting duct cell line mCCDcl1 as a model. By analyzing the hypoxia-dependent transcriptome of mCCDcl1 cells, we found a large number of differentially-expressed genes (3086 in total logFC< −1 or >1) following 24 h of hypoxic conditions (0.2% O2). A gene ontology analysis of the differentially-regulated pathways revealed a strong decrease in oxygen-linked processes such as ATP metabolic functions, oxidative phosphorylation, and cellular and aerobic respiration, while pathways associated with hypoxic responses were robustly increased. The most pronounced regulated genes were confirmed by RT-qPCR. The low expression levels of Epas1 under both normoxic and hypoxic conditions suggest that Hif-1α, rather than Hif-2α, mediates the hypoxic response in mCCDcl1 cells. Accordingly, we generated shRNA-mediated Hif-1α knockdown cells and found Hif-1α to be responsible for the hypoxic induction of established hypoxically-induced genes. Interestingly, we could show that following shRNA-mediated knockdown of Esrra, Hif-1α protein levels were unaffected, but the gene expression levels of Egln3 and Serpine1 were significantly reduced, indicating that Esrra might contribute to the hypoxia-mediated expression of these and possibly other genes. Collectively, mCCDcl1 cells display a broad response to hypoxia and represent an adequate cellular model to study additional factors regulating the response to hypoxia.

Interacting Effects of Sea Louse (Lepeophtheirus salmonis) Infection and Formalin-Killed Aeromonas salmonicida on Atlantic Salmon Skin Transcriptome

Lepeophtheirus salmonis (sea lice) and bacterial co-infection threatens wild and farmed Atlantic salmon performance and welfare. In the present study, pre-adult L. salmonis-infected and non-infected salmon were intraperitoneally injected with either formalin-killed Aeromonas salmonicida bacterin (ASAL) or phosphate-buffered saline (PBS). Dorsal skin samples from each injection/infection group (PBS/no lice, PBS/lice, ASAL/no lice, and ASAL/lice) were collected at 24 h post-injection and used for transcriptome profiling using a 44K salmonid microarray platform. Microarray results showed no clear inflammation gene expression signatures and revealed extensive gene repression effects by pre-adult lice (2,189 down and 345 up-regulated probes) in the PBS-injected salmon (PBS/lice vs. PBS/no lice), which involved basic cellular (e.g., RNA and protein metabolism) processes. Lice repressive effects were not observed within the group of ASAL-injected salmon (ASAL/lice vs. ASAL/no lice); on the contrary, the observed skin transcriptome changes –albeit of lesser magnitude (82 up and 1 down-regulated probes)– suggested the activation in key immune and wound healing processes (e.g., neutrophil degranulation, keratinocyte differentiation). The molecular skin response to ASAL was more intense in the lice-infected (ASAL/lice vs. PBS/lice; 272 up and 11 down-regulated probes) than in the non-infected fish (ASAL/no lice vs. PBS/no lice; 27 up-regulated probes). Regardless of lice infection, the skin’s response to ASAL was characterized by the putative activation of both antibacterial and wound healing pathways. The transcriptomic changes prompted by ASAL+lice co-stimulation (ASAL/lice vs. PBS/no lice; 1878 up and 3120 down-regulated probes) confirmed partial mitigation of lice repressive effects on fundamental cellular processes and the activation of pathways involved in innate (e.g., neutrophil degranulation) and adaptive immunity (e.g., antibody formation), as well as endothelial cell migration. The qPCR analyses evidenced immune-relevant genes co-stimulated by ASAL and lice in an additive (e.g., mbl2b, bcl6) and synergistic (e.g., hampa, il4r) manner. These results provided insight on the physiological response of the skin of L. salmonis-infected salmon 24 h after ASAL stimulation, which revealed immunostimulatory properties by the bacterin with potential applications in anti-lice treatments for aquaculture. As a simulated co-infection model, the present study also serves as a source of candidate gene biomarkers for sea lice and bacterial co-infection.

Oxidized/deamidated-ceruloplasmin dysregulates choroid plexus epithelial cells functionality and barrier properties via RGD-recognizing integrin binding

Choroid plexus epithelial cells (CPEpiCs) determine the composition of cerebrospinal fluid (CSF) and constitute the blood-CSF barrier (BCSFB), functions that are altered in neurodegenerative diseases. In Parkinson's disease (PD) the pathological environment oxidizes and deamidates the ceruloplasmin, a CSF-resident ferroxidase, which undergoes a gain of RGD-recognizing integrin binding property, that may result in signal transduction. We investigated the effects that oxidized/deamidated ceruloplasmin (Cp-ox/de) may exert on CPEpiCs functions. Through RGD-recognizing integrins binding, Cp-ox/de mediates CPEpiCs adhesion and intracellular signaling, resulting in cell proliferation inhibition and alteration of the secretome profile in terms of proteins related to cell-extracellular matrix interaction. Oxidative conditions, comparable to those found in the CSF of PD patients, induced CPEpiCs barrier leakage, allowing Cp-ox/de to cross it, transducing integrins-mediated signal that further worsens BCSFB integrity. This mechanism might contribute to PD pathological processes altering CSF composition and aggravating the already compromised BCSFB function.

Extracellular matrix: an important regulator of cell functions and skeletal muscle development

Extracellular matrix (ECM) is a kind of connective tissue in the cell microenvironment, which is of great significance to tissue development. ECM in muscle fiber niche consists of three layers: the epimysium, the perimysium, and the endomysium (basal lamina). These three layers of connective tissue structure can not only maintain the morphology of skeletal muscle, but also play an important role in the physiological functions of muscle cells, such as the transmission of mechanical force, the regeneration of muscle fiber, and the formation of neuromuscular junction. In this paper, detailed discussions are made for the structure and key components of ECM in skeletal muscle tissue, the role of ECM in skeletal muscle development, and the application of ECM in biomedical engineering. This review will provide the reader with a comprehensive overview of ECM, as well as a comprehensive understanding of the structure, physiological function, and application of ECM in skeletal muscle tissue.

SILAC-Based Quantification of TGFBR2-Regulated Protein Expression in Extracellular Vesicles of Microsatellite Unstable Colorectal Cancers

Microsatellite unstable (MSI) colorectal cancers (CRCs) are characterized by mutational inactivation of Transforming Growth Factor Beta Receptor Type 2 (TGFBR2). TGFBR2-deficient CRCs present altered target gene and protein expression. Such cellular alterations modulate the content of CRC-derived extracellular vesicles (EVs). EVs function as couriers of proteins, nucleic acids, and lipids in intercellular communication. At a qualitative level, we have previously shown that TGFBR2 deficiency causes overall alterations in the EV protein content. To deepen the basic understanding of altered protein dynamics, this work aimed to determine TGFBR2-dependent EV protein signatures in a quantitative manner. Using a stable isotope labeling with amino acids in cell culture (SILAC) approach for mass spectrometry-based quantification, 48 TGFBR2-regulated proteins were identified in MSI CRC-derived EVs. Overall, TGFBR2 deficiency caused upregulation of several EV proteins related to the extracellular matrix and nucleosome as well as downregulation of proteasome-associated proteins. The present study emphasizes the general overlap of proteins between EVs and their parental CRC cells but also highlights the impact of TGFBR2 deficiency on EV protein composition. From a clinical perspective, TGFBR2-regulated quantitative differences of protein expression in EVs might nominate novel biomarkers for liquid biopsy-based MSI typing in the future.

Proteome profiling of triple negative breast cancer cells overexpressing NOD1 and NOD2 receptors unveils molecular signatures of malignant cell proliferation

Background

Triple negative breast cancer (TNBC) is a malignancy with very poor prognosis, due to its aggressive clinical characteristics and lack of response to receptor-targeted drug therapy. In TNBC, immune-related pathways are typically upregulated and may be associated with a better prognosis of the disease, encouraging the pursuit for immunotherapeutic options. A number of immune-related molecules have already been associated to the onset and progression of breast cancer, including NOD1 and NOD2, innate immune receptors of bacterial-derived components which activate pro-inflammatory and survival pathways. In the context of TNBC, overexpression of either NOD1or NOD2 is shown to reduce cell proliferation and increase clonogenic potential in vitro. To further investigate the pathways linking NOD1 and NOD2 signaling to tumorigenesis in TNBC, we undertook a global proteome profiling of TNBC-derived cells ectopically expressing each one of these NOD receptors.

Results

We have identified a total of 95 and 58 differentially regulated proteins in NOD1- and NOD2-overexpressing cells, respectively. We used bioinformatics analyses to identify enriched molecular signatures aiming to integrate the differentially regulated proteins into functional networks. These analyses suggest that overexpression of both NOD1 and NOD2 may disrupt immune-related pathways, particularly NF-κB and MAPK signaling cascades. Moreover, overexpression of either of these receptors may affect several stress response and protein degradation systems, such as autophagy and the ubiquitin-proteasome complex. Interestingly, the levels of several proteins associated to cellular adhesion and migration were also affected in these NOD-overexpressing cells.

Conclusions

Our proteomic analyses shed new light on the molecular pathways that may be modulating tumorigenesis via NOD1 and NOD2 signaling in TNBC. Up- and downregulation of several proteins associated to inflammation and stress response pathways may promote activation of protein degradation systems, as well as modulate cell-cycle and cellular adhesion proteins. Altogether, these signals seem to be modulating cellular proliferation and migration via NF-κB, PI3K/Akt/mTOR and MAPK signaling pathways. Further investigation of altered proteins in these pathways may provide more insights on relevant targets, possibly enabling the immunomodulation of tumorigenesis in the aggressive TNBC phenotype.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5523-6) contains supplementary material, which is available to authorized users.

Mechanisms of plasminogen activator inhibitor 1 action in stromal remodeling and related diseases

Plasminogen activator inhibitor type 1 (PAI-1) is the main physiologic inhibitor of fibrinolysis. However, it is also involved in many physiological processes such as extracellular matrix (ECM) proteolysis and remodeling, cell adhesion, motility, and apoptosis, angiogenesis, etc. The aim of the study was to summarize current knowledge and gain insights into the mechanisms of PAI-1 action in the processes of stromal remodeling and diseases with considerable matrix pathologies (atherosclerosis, tissue fibrosis, cancer metastasis, pregnancy related complications, etc). As a component of an early cellular response to injury, PAI-1 reacts with membrane surface proteins and participates in the initiation of intracellular signaling, specifically cytoskeletal reorganization and motility. Complexity of ECM homeostasis resides in varying relation of the plasminogen system components and other matrix constituents. Inflammatory mediators (transforming growth factor-β and interferon-γ) and hormones (angiotensin II) are in the close interdependent relation with PAI-1. Also, special attention is devoted to the role of increased PAI-1 concentrations due to the common 4G/5G polymorphism. Some of the novel mechanisms of ECM modification consider PAI-1 dependent stabilization of urokinase mediated cell adhesion, control of the vascular endothelial cadherin trafficking and interaction with endothelial cells proteasome, its relation to matrix metalloproteinase 2 and osteopontin, and oxidative inhibition by myeloperoxidase. Targeting and/or alteration of PAI-1 functions might bring benefit to the future therapeutic approaches in diseases where ECM undergoes substantial remodeling.

Plasminogen activator inhibitor-1 is an independent prognostic factor of ovarian cancer and IMD-4482, a novel plasminogen activator inhibitor-1 inhibitor, inhibits ovarian cancer peritoneal dissemination

In the present study, the therapeutic potential of targeting plasminogen activator inhibitor-1 (PAI-1) in ovarian cancer was tested. Tissues samples from 154 cases of ovarian carcinoma were immunostained with anti-PAI-1 antibody, and the prognostic value was analyzed. Among the samples, 67% (104/154) showed strong PAI-1 expression; this was significantly associated with poor prognosis (progression-free survival: 20 vs. 31 months, P = 0.0033). In particular, among patients with stage II-IV serous adenocarcinoma, PAI-1 expression was an independent prognostic factor. The effect of a novel PAI-1 inhibitor, IMD-4482, on ovarian cancer cell lines was assessed and its therapeutic potential was examined using a xenograft mouse model of ovarian cancer. IMD-4482 inhibited in vitro cell adhesion to vitronectin in PAI-1-positive ovarian cancer cells, followed by the inhibition of extracellular signal-regulated kinase and focal adhesion kinase phosphorylation through dissociation of the PAI-urokinase receptor complex from integrin αVβ3. IMD-4482 caused G0/G1 cell arrest and inhibited the proliferation of PAI-1-positive ovarian cancer cells. In the xenograft model, IMD-4482 significantly inhibited peritoneal dissemination with the reduction of PAI-1 expression and the inhibition of focal adhesion kinase phosphorylation. Collectively, the functional inhibition of PAI-1 significantly inhibited ovarian cancer progression, and targeting PAI-1 may be a potential therapeutic strategy in ovarian cancer.

JMJD3 and NF-κB-dependent activation of Notch1 gene is required for keratinocyte migration during skin wound healing

It has been shown that epigenetic regulation plays an important role in skin wound healing. We previously found that histone H3K27me3 demethylase JMJD3 regulates inflammation and cell migration in keratinocyte wound healing. In this study, we identified Notch1 as a direct target of JMJD3 and NF-κB in wounded keratinocytes using in vitro cell and in vivo animal models. We found that Notch1 is up-regulated in the wound edge and its expression is dependent on JMJD3 and NF-κB in wounded keratinocytes. We also found that Notch1 activates the expression of RhoU and PLAU gene, which are critical regulators of cell migration. Consistently, depletion or inactivation of Notch1 resulted in decreased filopodia formation, increased focal adhesion and actin stress fiber, leading to reduced keratinocyte migration and skin wound healing. Thus, our findings provide the molecular mechanism involving JMJD3/NF-κB-Notch pathway in keratinocyte wound healing.

Transforming growth factor-Beta and urokinase-type plasminogen activator: dangerous partners in tumorigenesis-implications in skin cancer

Transforming growth factor-beta (TGF-β) is a pleiotropic factor, with several different roles in health and disease. TGF-β has been postulated as a dual factor in tumor progression, since it represses epithelial tumor development in early stages, whereas it stimulates tumor progression in advanced stages. During tumorigenesis, cancer cells acquire the capacity to migrate and invade surrounding tissues and to metastasize different organs. The urokinase-type plasminogen activator (uPA) system, comprising uPA, the uPA cell surface receptor, and plasminogen-plasmin, is involved in the proteolytic degradation of the extracellular matrix and regulates key cellular events by activating intracellular signal pathways, which together allow cancer cells to survive, thus, enhancing cell malignance during tumor progression. Due to their importance, uPA and its receptor are tightly transcriptionally regulated in normal development, but are deregulated in cancer, when their activity and expression are related to further development of cancer. TGF-β regulates uPA expression in cancer cells, while uPA, by plasminogen activation, may activate the secreted latent TGF-β, thus, producing a pernicious cycle which contributes to the enhancement of tumor progression. Here we review the specific roles and the interplay between TGF-β and uPA system in cancer cells and their implication in skin cancer.

Matrix-bound PAI-1 supports cell blebbing via RhoA/ROCK1 signaling

The microenvironment of a tumor can influence both the morphology and the behavior of cancer cells which, in turn, can rapidly adapt to environmental changes. Increasing evidence points to the involvement of amoeboid cell migration and thus of cell blebbing in the metastatic process; however, the cues that promote amoeboid cell behavior in physiological and pathological conditions have not yet been clearly identified. Plasminogen Activator Inhibitor type-1 (PAI-1) is found in high amount in the microenvironment of aggressive tumors and is considered as an independent marker of bad prognosis. Here we show by immunoblotting, activity assay and immunofluorescence that, in SW620 human colorectal cancer cells, matrix-associated PAI-1 plays a role in the cell behavior needed for amoeboid migration by maintaining cell blebbing, localizing PDK1 and ROCK1 at the cell membrane and maintaining the RhoA/ROCK1/MLC-P pathway activation. The results obtained by modeling PAI-1 deposition around tumors indicate that matrix-bound PAI-1 is heterogeneously distributed at the tumor periphery and that, at certain spots, the elevated concentrations of matrix-bound PAI-1 needed for cancer cells to undergo the mesenchymal-amoeboid transition can be observed. Matrix-bound PAI-1, as a matricellular protein, could thus represent one of the physiopathological requirements to support metastatic formation.

SMAD3 is essential for transforming growth factor-β1-induced urokinase type plasminogen activator expression and migration in transformed keratinocytes

Transforming growth factor-β1 (TGF-β1) stimulates the extracellular matrix degrading proteases expression and cell migration in order to enhance cancer cells malignancy. In the present study, we analysed the role of TGF-β1-induced Smad3 activation in the urokinase type plasminogen activator (uPA) production, as well as in cell migration and E-cadherin downregulation in transformed PDV keratinocyte cell line. TGF-β1 signalling was interfered by the chemical inhibitor of the TGF-β1-receptor 1 (ALK5), SB505124, and the specific Smad3 inhibitor, SiS3. Our results showed that TGF-β1 stimulates uPA expression directly through ALK5 activation. The inhibition of Smad3 strongly reduced the capacity of TGF-β1 to stimulate uPA expression, in parallel decreasing the uPA inhibitor plasminogen activator inhibitor type 1 (PAI-1) expression. In addition, the transient expression of dominant negative Smad3 mutant inhibited the TGF-β1-induced uPA promoter transactivation. Moreover, Smad3-/- mouse embryonic fibroblasts were refractory to the induction of uPA by TGF-β1. The inhibition of both ALK5 and Smad3 dramatically blocked the TGF-β1-stimulated E-cadherin downregulation, F-actin reorganisation and migration of PDV cells. Taken together, our results suggest that the TGF-β1-induced activation of Smad3 is the critical step for the uPA upregulation and E-cadherin downregulation, which are the key events preceding the induction of cell migration by TGF-β1 in transformed cells.

A tiny touch: activation of cell signaling pathways with magnetic nanoparticles

Magnetic nanoparticles can be coated with specific ligands that enable them to bind to receptors on a cell's surface. When a magnetic field is applied, it pulls on the particles so that they deliver nanoscale forces at the ligand-receptor bond. It has been observed that mechanical stimulation in this manner can activate cellular signaling pathways that are known as mechanotransduction pathways. Integrin receptors, stretch-activated ion channels, focal adhesions, and the cytoskeleton are key players in activating these pathways, but there is still much we do not know about how these mechanosensors work. Current evidence indicates that applied forces at these structures can activate Ca(2+) signaling, Src family protein kinase, MAPK, and RhoGTPase pathways. The techniques of magnetic twisting and magnetic tweezers, which use magnetic particles to apply forces to cells, afford a fine degree of control over how cells are stimulated and hold much promise in elucidating the fundamentals of mechanotransduction. The particles are generally not harmful to cellular health, and their nanoscale dimensions make them advantageous for probing a cell's molecular-scale sensory structures. This review highlights the basic aspects of magnetic nanoparticles, magnetic particle techniques and the structures and pathways that are involved in mechanotransduction.

mTOR mediates human trophoblast invasion through regulation of matrix-remodeling enzymes and is associated with serine phosphorylation of STAT3

The intracellular signaling molecule mammalian target of rapamycin (mTOR) is essential for cell growth and proliferation. It is involved in mouse embryogenesis, murine trophoblast outgrowth and linked to tumor cell invasiveness. In order to assess the role of mTOR in human trophoblast invasion we analyzed the in vitro invasiveness of HTR-8/SVneo immortalized first-trimester trophoblast cells in conjunction with enzyme secretion upon mTOR inhibition and knockdown of mTOR protein expression. Additionally, we also tested the capability of mTOR to trigger signal transducer and activator of transcription (STAT)-3 by its phosphorylation status. Rapamycin inhibited mTOR kinase activity as demonstrated with a lower phosphorylation level of the mTOR substrate p70 S6 kinase (S6K). With the use of rapamycin and siRNA-mediated mTOR knockdown we could show that cell proliferation, invasion and secretion of matrix-metalloproteinases (MMP)-2 and -9, urokinase-like plasminogen activator (uPA) and its major physiological uPA inhibitor (PAI)-1 were inhibited. While tyrosine phosphorylation of STAT3 was unaffected by mTOR inhibition and knockdown, serine phosphorylation was diminished. We conclude that mTOR signaling is one major mechanism in a tightly regulated network of intracellular signal pathways including the JAK/STAT system to regulate invasion in human trophoblast cells by secretion of enzymes that remodel the extra-cellular matrix (ECM) such as MMP-2, -9, uPA and PAI-1. Dysregulation of mTOR may contribute to pregnancy-related pathologies caused through impaired trophoblast invasion.

PAI-1 and functional blockade of SNAI1 in breast cancer cell migration

Introduction

Snail, a family of transcriptional repressors implicated in cell movement, has been correlated with tumour invasion. The Plasminogen Activation (PA) system, including urokinase plasminogen activator (uPA), its receptor and its inhibitor, plasminogen activator inhibitor type 1(PAI-1), also plays a key role in cancer invasion and metastasis, either through proteolytic degradation or by non-proteolytic modulation of cell adhesion and migration. Thus, Snail and the PA system are both over-expressed in cancer and influence this process. In this study we aimed to determine if the activity of SNAI1 (a member of the Snail family) is correlated with expression of the PA system components and how this correlation can influence tumoural cell migration.

Methods

We compared the invasive breast cancer cell-line MDA-MB-231 expressing SNAI1 (MDA-mock) with its derived clone expressing a dominant-negative form of SNAI1 (SNAI1-DN). Expression of PA system mRNAs was analysed by cDNA microarrays and real-time quantitative RT-PCR. Wound healing assays were used to determine cell migration. PAI-1 distribution was assessed by immunostaining.

Results

We demonstrated by both cDNA microarrays and real-time quantitative RT-PCR that the functional blockade of SNAI1 induces a significant decrease of PAI-1 and uPA transcripts. After performing an in vitro wound-healing assay, we observed that SNAI1-DN cells migrate more slowly than MDA-mock cells and in a more collective manner. The blockade of SNAI1 activity resulted in the redistribution of PAI-1 in SNAI1-DN cells decorating large lamellipodia, which are commonly found structures in these cells.

Conclusions

In the absence of functional SNAI1, the expression of PAI-1 transcripts is decreased, although the protein is redistributed at the leading edge of migrating cells in a manner comparable with that seen in normal epithelial cells.

RNAi-mediated downregulation of urokinase plasminogen activator receptor inhibits proliferation, adhesion, migration and invasion in oral cancer cells

RNA interference (RNAi) has emerged as an effective method to target specific genes for silencing. Overexpression of urokinase-type plasminogen activator receptor (uPAR) has been implicated in progression and metastasis of oral cancer. In our study, RNAi was introduced to downregulate the expression of uPAR in the highly malignant oral squamous cell carcinoma (OSCC) cells. Our data demonstrated that siRNA targeting of uPAR leads to the efficient and specific inhibition of endogenous uPAR mRNA and protein expression as determined by quantitative real-time RT-PCR and Western blotting. Furthermore, simultaneous silencing of uPAR resulted in a dramatic reduction of tumor cell proliferation activity, adhesion, migration and invasion in vitro compared to the controls. These findings provide further evidence for the involvement of uPAR in a variety of cancer key cellular events as a versatile signaling orchestrator, and suggest that RNAi-directed targeting of uPAR can be used as a potent and specific therapeutic tool for the treatment of oral cancer, especially in inhibiting and/or preventing cancer cell invasion and metastasis.

The plasminogen activator inhibitor "paradox" in cancer

Proteolysis in general and specifically the plasminogen activating system regulated by urokinase (uPA) its specific receptor, the GPI membrane anchored urokinase receptor (uPAR) and the specific plasminogen activator inhibitor 1 (PAI-1) plays a major role in tumorigenesis, tumor progression, tumor invasion and metastasis formation. This is exemplified by a body of published work showing a positive correlation between the expression of uPA or uPAR in several tumors and their malignancy. It is generally assumed that such a "pro-malignant" effect of the uPA-uPAR system is mediated by increased local proteolysis thus favoring tumor invasion, by a pro-angiogenic effect of this system and also by uPA-uPAR signaling towards the tumor thereby shifting the tumor phenotype to a more "malignant" one. However, when tumor patients are analyzed for long term survival, those with high levels of the inhibitor of the system, PAI-1 have a much worse prognosis than those with lower PAI-1 levels. This indicates that increased overall proteolysis alone cannot be made responsible for the adverse effects of the plasminogen activating system in tumors. Moreover, it becomes increasingly evident that components of the fibrinolytic system secreted by the tumor cells themselves are not solely responsible for a correlation between the plasminogen activating system and tumor malignancy; components of the plasminogen activating system secreted by stroma cells or cells of the immune system such as macrophages contribute also to the impact of fibrinolysis on malignancy. This review summarizes the evidence for the role of plasminogen activator inhibitor-1 in mediating the malignant phenotype and possible mechanism thereby trying to explain the "PAI-1 paradox in cancer" on a molecular level.

SERPINE1 (PAI-1) is deposited into keratinocyte migration "trails" and required for optimal monolayer wound repair

Cutaneous tissue injury, both in vivo and in vitro, initiates activation of a "wound repair" transcriptional program. One such highly induced gene encodes plasminogen activator inhibitor type-1 (PAI-1, SERPINE1). PAI-1-GFP, expressed as a fusion protein under inducible control of +800 bp of the wound-activated PAI-1 promoter, prominently "marked" keratinocyte migration trails during the real-time of monolayer scrape-injury repair. Addition of active recombinant PAI-1 to wounded wild-type keratinocyte monolayers as well as to PAI-1(-/-) MEFs and PAI-1(-/-) keratinocytes significantly stimulated directional motility above basal levels in all cell types. PAI-1 expression knockdown or antibody-mediated functional inhibition, in contrast, effectively attenuated injury repair. The defect in wound-associated migratory activity as a consequence of antisense-mediated PAI-1 down-regulation was effectively reversed by addition of recombinant PAI-1 immediately after scrape injury. One possible mechanism underlying the PAI-1-dependent motile response may involve fine control of the keratinocyte substrate detachment/re-attachment process. Exogenous PAI-1 significantly enhanced keratinocyte spread cell "footprint" area while PAI-1 neutralizing antibodies, but not control non-immune IgG, effectively inhibited spreading with apoptotic hallmarks evident within 24 h. Importantly, PAI-1 not only stimulated keratinocyte adhesion and wound-initiated planar migration but also rescued keratinocytes from plasminogen-induced substrate detachment/anoikis. The early transcriptional response of the PAI-1 gene to monolayer trauma and its prominence in the injury repair genetic signature are consistent with its function as both a survival factor and regulator of the time course of epithelial migration as part of the cutaneous injury response program.

uPA dependent and independent mechanisms of wound healing by C-phycocyanin

Wound repair requires both recruitment and well co-ordinated actions of many cell types including inflammatory cells, endothelial cells, epithelial cells and importantly fibroblast cells. Urokinase-type plasminogen activator (uPA) system plays a vital role in wound healing phenomenon. We have previously demonstrated that C-phycocyanin (C-pc), a biliprotein from blue-green algae, transcriptionally regulates uPA through cAMP-dependent protein kinase A (PKA) pathway. To date, a role for C-pc in wound-healing scenario is not elucidated. This study was designed to examine the wound-healing property of C-pc in relation to fibroblast proliferation and migration. C-pc increased fibroblast proliferation in a dose-dependent manner. It also enhanced G1 phase of cell cycle and increased the expressions of cyclin-dependent kinases 1 and 2, which facilitate cell cycle progression, in a uPA-independent manner. In vitro wound healing and migration assays revealed the pro-migratory properties of C-pc. Short-interference RNA studies demonstrated that uPA was necessary for C-pc-induced fibroblast migration. C-pc also significantly elevated the expressions of chemokines (MDC, RANTES, Eotaxin, GRO α, ENA78 and TARC) and Rho-GTPases (Cdc 42 and Rac 1) in a uPA-dependent manner. Pre-treatment of C-pc-stimulated cells with pharmacological inhibitor of PI-3K (LY294002) annulled the expression of GTPases implying that Rac 1 and Cdc 42 were induced through PI-3K pathway. C-pc-induced cellular migration towards wounded area was also negatively affected by PI-3K inhibition. In vivo wound-healing experiments in mice validated our finding that C-pc accelerates wound healing. Our data provides conclusive evidence of a novel therapeutic usage for C-pc as a wound-healing agent. C-pc is a food and drug administration (FDA)-approved health supplement. We believe this compound can also be beneficial in healing of internal wounds, such as ulcers.

Dual role for plasminogen activator inhibitor type 1 as soluble and as matricellular regulator of epithelial alveolar cell wound healing

Epithelium repair, crucial for restoration of alveolo-capillary barrier integrity, is orchestrated by various cytokines and growth factors. Among them keratinocyte growth factor plays a pivotal role in both cell proliferation and migration. The urokinase plasminogen activator (uPA) system also influences cell migration through proteolysis during epithelial repair. In addition, the complex formed by uPAR-uPA and matrix-bound plasminogen activator inhibitor type-1 (PAI-1) exerts nonproteolytic roles in various cell types. Here we present new evidence about the dual role of PAI-1 under keratinocyte growth factor stimulation using an in vitro repair model of rat alveolar epithelial cells. Besides proteolytic involvement of the uPA system, the availability of matrix-bound-PAI-1 is also required for an efficient healing. An unexpected decrease of healing was shown when PAI-1 activity was blocked. However, the proteolytic action of uPA and plasmin were still required. Moreover, immediately after wounding, PAI-1 was dramatically increased in the newly deposited matrix at the leading edge of wounds. We thus propose a dual role for PAI-1 in epithelial cell wound healing, both as a soluble inhibitor of proteolysis and also as a matrix-bound regulator of cell migration. Matrix-bound PAI-1 could thus be considered as a new member of the matricellular protein family.

[The PAI-1 swing: microenvironment and cancer cell migration]

Cancer is a complex and dynamic process caused by a cellular dysfunction leading to a whole organ or even organism vital perturbation. To better understand this process, we need to study each one of the levels involved, which allows the scale change, and to integrate this knowledge. A matricellular protein, PAI-1, is able to induce in vitro cell behaviour modifications, morphological changes, and to promote cell migration. PAI-1 influences the mesenchymo-amaeboid transition. This matricellular protein should be considered as a potential 'launcher' of the metastatic process acting at the molecular, cellular, tissular levels and, as a consequence, at the organism's level.

Maggots and wound healing: an investigation of the effects of secretions from Lucilia sericata larvae upon the migration of human dermal fibroblasts over a fibronectin-coated surface

Lucilia sericata larvae, or greenbottle fly maggots, placed within chronic wounds have been observed to remove necrotic tissue and infection. They are also believed to actively promote granulation tissue formation. Interactions between fibroblasts and the surrounding extracellular matrix play a crucial role in tissue formation, influencing fibroblast proliferation, migration, and tissue remodeling. For example, the strength of cell adhesion to surfaces coated with extracellular matrix influences cell motility. L. sericata larval excretory/secretory products having previously been shown to modify fibroblast adhesion to collagen and particularly fibronectin, it was hypothesized that these products would alter fibroblast migration. This was investigated using a two-dimensional in vitro wound assay, time-lapse digital photography, enzyme class-specific substrates and inhibitors, and gel electrophoresis. Results showed that L. sericata excretory/secretory products promoted fibroblast migration upon a fibronectin-coated surface. This was related to the degradation of fibronectin by serine proteinases within maggot excretion/secretions. The presence of a metalloproteinase activity may also have played a role. Thus, a possible mechanism by which maggots enhance tissue formation within wounds may be via the promotion of fibroblast motility, providing for a wider distribution of viable fibroblasts.

Angiostatin's molecular mechanism: aspects of specificity and regulation elucidated

Tumor growth requires the development of new vessels that sprout from pre-existing normal vessels in a process known as "angiogenesis" [Folkman (1971) N Engl J Med 285:1182-1186]. These new vessels arise from local capillaries, arteries, and veins in response to the release of soluble growth factors from the tumor mass, enabling these tumors to grow beyond the diffusion-limited size of approximately 2 mm diameter. Angiostatin, a naturally occurring inhibitor of angiogenesis, was discovered based on its ability to block tumor growth in vivo by inhibiting the formation of new tumor blood vessels [O'Reilly et al. (1994a) Cold Spring Harb Symp Quant Biol 59:471-482]. Angiostatin is a proteolytically derived internal fragment of plasminogen and may contain various members of the five plasminogen "kringle" domains, depending on the exact sites of proteolysis. Different forms of angiostatin have measurably different activities, suggesting that much remains to be elucidated about angiostatin biology. A number of groups have sought to identify the native cell surface binding site(s) for angiostatin, resulting in at least five different binding sites proposed for angiostatin on the surface of endothelial cells (EC). This review will consider the data supporting all of the various reported angiostatin binding sites and will focus particular attention on the angiostatin binding protein identified by our group: F(1)F(O) ATP synthase. There have been several developments in the quest to elucidate the mechanism of action of angiostatin and the regulation of its receptor. The purpose of this review is to describe the highlights of research on the mechanism of action of angiostatin, its' interaction with ATP synthase on the EC surface, modulators of its activity, and issues that should be explored in future research related to angiostatin and other anti-angiogenic agents.

The kringle domain of urokinase-type plasminogen activator potentiates LPS-induced neutrophil activation through interaction with {alpha}V{beta}3 integrins

Urokinase plasminogen activator (uPA) is a serine protease that catalyzes the conversion of plasminogen to plasmin. In addition, uPA has been shown to have proinflammatory properties, particularly in potentiating lipopolysaccharide (LPS)-induced neutrophil responses. To explore the mechanisms by which uPA exerts these effects, we examined the ability of specific uPA domains to increase cytokine expression in murine and human neutrophils stimulated with LPS. Whereas the addition of intact uPA to neutrophils cultured with LPS increased mRNA and protein levels of interleukin-1beta, macrophage-inflammatory protein-2, and tumor necrosis factor alpha, deletion of the kringle domain (KD) from uPA resulted in loss of these potentiating effects. Addition of purified uPA KD to LPS-stimulated neutrophils increased cytokine expression to a degree comparable with that produced by single-chain uPA. Inclusion of the arginine-glycine-aspartic but not the arginine-glycine-glutamic peptide to neutrophil cultures blocked uPA kringle-induced potentiation of proinflammatory responses, demonstrating that interactions between the KD and integrins were involved. Antibodies to alpha(V) or beta(3) integrins or to the combination of alpha(V)beta(3) prevented uPA kringle-induced enhancement of expression of proinflammatory cytokines and also of adhesion of neutrophils to the uPA KD. These results demonstrate that the KD of uPA, through interaction with alpha(V)beta(3) integrins, potentiates neutrophil activation.

Plasminogen activator inhibitor-1 (PAI-1) stimulates human corneal epithelial cell adhesion and migration in vitro

In addition to its role as an inhibitor of urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) is hypothesized to regulate epithelial cell adhesion and migration. We have previously reported that PAI-1 may be an important regulatory factor of the uPA system in cornea. The purpose of this study was to extend those observations by determining the effect of exogenous PAI-1 on the migration and adhesion of human corneal epithelial cells (HCEC) in vitro. The expression of PAI-1 in non-transformed early passage HCEC was confirmed by immunofluorescence microscopy and Western blot analysis. Colorimetric assays coupled with function-inhibiting antibody studies using the matrix assembled in situ by cultured cells demonstrate that immobilized PAI-1 serves as an efficient substrate for HCEC adhesion. HCEC attachment to PAI-1 is comparable to that of laminin-10, a known strong adhesion protein for epithelial cells. In addition to serving as an adhesion substrate, PAI-1 also functions as a chemotactic agent for corneal epithelium. Additionally it promotes the random migration of HCEC, from an initial cell cluster, along a culture substrate. Our results in corneal epithelium are consistent with reports from other investigators showing that PAI-1 facilitates both epithelial adhesion and migration. From our studies we conclude that PAI-1 may play a dual role in corneal wound healing. Initially PAI-1 may function to stimulate migration and facilitate the reepithelialization of the wound bed. Post-reepithelization, PAI-1 may ensure corneal epithelial cell adhesion to matrix to promote successful wound healing.

RNAi-mediated inhibition of cathepsin B and uPAR leads to decreased cell invasion, angiogenesis and tumor growth in gliomas

RNA interference (RNAi) provides a powerful method for gene silencing in eukaryotic cells, including proliferating mammalian cells. Here, we determined whether RNAi could be utilized to inhibit the expression of proteases implicated in the extracellular matrix degradation, which is characteristic of tumor progression. We have previously shown that antisense stable clones of uPAR and cathepsin B were less invasive and did not form tumors when injected intracranially ex vivo. Since antisense-mediated gene silencing does not completely inhibit the translation of target mRNA and high molar concentrations of antisense molecules are required to achieve gene silencing, we used the RNAi approach to silence uPAR and cathepsin B in this study. We found that the expression of double-stranded RNA leads to the efficient and specific inhibition of endogenous uPAR and cathepsin B protein expression in glioma cell lines as determined by Western blotting. We also found the RNAi of uPAR and cathepsin B reduces glioma cell invasion and angiogenesis in in vitro and in vivo models. Intratumoral injections of plasmid vectors expressing hpRNA for uPAR and cathepsin B resulted in the regression of pre-established intracranial tumors. Further, RNAi for uPAR and cathepsin B inhibited cell proliferation and reduced the levels of pERK and pFAK compared to controls. Taken together, our findings indicate for the first time that RNAi operates in human glioma cells with potential application for cancer gene therapy.

Thrombospondin 1: a multifunctional protein implicated in the regulation of tumor growth

Thrombospondins belong to a family of extracellular matrix (ECM) proteins widely found from embryonic to adult tissues. The modular structure of thrombospondins contains a series of peptide sequences implicated in a multiplicity of biological functions. Extracellular matrix undergoes important alterations under proteolysis that occurs in pathological processes like tumorigenesis. An elevated secretion of thrombospondin 1 (TSP1) is often observed in tumors and is sometimes considered as a predictive factor. However, the role of TSP1 in cancer progression remains controversial and must be carefully apprehended. The regulation of cell adhesion, proliferation, apoptosis by TSP1 is examined in the present review and it is clear from the literature and from our investigations that TSP1 presents both stimulatory and inhibitory effects. The exposition of cryptic sites upon conformational changes can partially explain this contradiction. More interestingly, the analysis of TSP1-directed intracellular signaling pathways activated through specific receptors or supramolecular receptors docking systems may be useful to discriminate the precise function of TSP1 in tumor progression. The central role played by TSP1 in the control of matrix-degrading enzyme activation and catabolism reveals attractive tracks of research and highlights the involvement of the lipoprotein receptor-related protein (LRP) receptor in these events. Therefore, TSP1-derived peptides constitute a source of potentially active matrikins which could provide essential tools in cancer therapy.

Age-related changes in the mitotic and metabolic characteristics of muscle-derived cells

Age-related sarcopenia could partly result from cumulative repeated episodes of incomplete repair and regeneration. We hypothesized that mitotic and metabolic events associated with satellite cell activation and proliferation could be altered with aging. Muscle-derived cells (mdc) were isolated from gastrocnemius and quadriceps muscles of young (3 wk old), adult (9 mo old), and old (24 mo old) Sprague-Dawley male rats (n = 10/group). The mdc from young growing rats started to proliferate earlier compared with adult and old animals. Cell cycle duration was significantly reduced with aging from 36.5 +/- 3.2 to 28.0 +/- 2.2 h. However, the proportion of noncycling (G0 phase) and cycling (G1 + S + G2 + M phases) cultured mdc was statistically unchanged among the three age groups. Significantly lower increase in c-met and proliferating cell nuclear antigen expression were observed in cultured mdc of old rats upon serum stimulation. Major changes in the expression of citrate synthase, lactate dehydrogenase, proteasome, caspase 3, plasminogen activators (PAs), and matrix metalloproteinase 2-9 (MMP2-9) were observed upon serum stimulation, but no age-related difference was noted. However, when measured on crushed muscle extracts, PAs and MMP2-9 enzyme activities were significantly decreased with aging. Our results show that cellular and biochemical events associated with the control of mdc activation and proliferation occur with aging. These alterations may participate in the accumulation of repeated episodes of incomplete repair and regeneration throughout the life span, thus contributing to the loss of skeletal muscle mass and function with aging.

Cytoskeletal mechanics in adherent human airway smooth muscle cells: probe specificity and scaling of protein-protein dynamics

We probed elastic and loss moduli in the adherent human airway smooth muscle cell through a variety of receptor systems, each serving as a different molecular window on cytoskeletal dynamics. Coated magnetic microbeads were attached to the cell surface via coating-receptor binding. A panel of bead coatings was investigated: a peptide containing the sequence RGD, vitronectin, urokinase, activating antibody against beta(1)-integrin, nonactivating antibody against beta(1)-integrin, blocking antibody against beta(1)-integrin, antibody against beta(1)-integrin, and acetylated low-density lipoprotein. An oscillatory mechanical torque was applied to the bead, and resulting lateral displacements were measured at baseline, after actin disruption by cytochalasin D, or after contractile activation by histamine. As expected, mechanical moduli depended strongly on bead type and bead coating, differing at the extremes by as much as two orders of magnitude. In every case, however, elastic and loss moduli increased with frequency f as a weak power law, f( x-1). Moreover, with few exceptions, data could be scaled such that elastic and frictional responses depended solely on the power law exponent x. Taken together, these data suggest that power law behavior represents a generic feature of underlying protein-protein dynamics.

Transforming growth factor-beta1 produced by ovarian cancer cell line HRA stimulates attachment and invasion through an up-regulation of plasminogen activator inhibitor type-1 in human peritoneal mesothelial cells

The processes of ovarian cancer dissemination are characterized by altered local proteolysis, cellular proliferation, cell attachment, and invasion, suggesting that the urokinase-type plasminogen activator (uPA) and its specific inhibitor (plasminogen activator inhibitor type-1 (PAI-1)) could be involved in the pathogenesis of peritoneal dissemination. We showed previously that expression of uPA and PAI-1 in the human ovarian cancer cell line HRA can be down-regulated by exogenous bikunin (bik), a Kunitz-type protease inhibitor, via suppression of transforming growth factor-beta1 (TGF-beta1) up-regulation and that overexpression of the bik gene can specifically suppress the in vivo growth and peritoneal dissemination of HRA cells in an animal model. We hypothesize that the plasminogen activator system in mesothelial cells can be modulated by HRA cells. To test this hypothesis, we used complementary techniques in mesothelial cells to determine whether uPA and PAI-1 expression are altered by exposure to culture media conditioned by HRA cells. Here we show the following: 1) that expression of PAI-1, but not uPA, was markedly induced by culture media conditioned by wild-type HRA cells but not by bik transfected clones; 2) that by antibody neutralization the effect appeared to be mediated by HRA cell-derived TGF-beta1; 3) that exogenous TGF-beta1 specifically enhanced PAI-1 up-regulation at the mRNA and protein level in mesothelial cells in a time- and concentration-dependent manner, mainly through MAPK-dependent activation mechanism; and 4) that mesothelial cell-derived PAI-1 may promote tumor invasion possibly by enhancing cell-cell interaction. This represents a novel pathway by which tumor cells can regulate the plasminogen activator system-dependent cellular responses in mesothelial cells that may contribute to formation of peritoneal dissemination of ovarian cancer.

Decreased plasminogen activator inhibitor-1 secretion in hypoxic corneal epithelial cells is associated with increased urokinase plasminogen activator activity

The aim of this study was to determine the effects of hypoxia on mRNA levels, cell-associated and -secreted protein concentration, activity, and protein complex formation of urokinase-type plasminogen activator, its receptor, and plasminogen activator inhibitor type-1 in corneal epithelium. Non-transformed human corneal epithelial cells were cultured in 20% oxygen (normoxic conditions) or 2% oxygen (hypoxic conditions) for 1, 3, 5, or 7 days. Relative changes in mRNA levels of plasminogen activator, receptor, and plasminogen activator inhibitor-1 were determined using a cDNA expression array, chemiluminescence, and densitometry. Protein concentrations were determined using enzyme linked immunosorbent assays. Activity assays were also used. Protein complex formation was assayed using cell surface biotinylation, immunoprecipitation, and Western blot analysis. Hypoxic corneal epithelial cells demonstrated no significant differences in plasminogen activator or receptor mRNA. Cell-associated plasminogen activator and membrane-associated receptor protein levels were unchanged. In contrast decreases in mRNA and secreted plasminogen activator inhibitor-1 protein were observed in hypoxic cells. Concurrently, increased cell-associated plasminogen activator activity was observed in hypoxic cells. The formation of plasminogen activator/receptor/plasminogen activator inhibitor-1 complex at the cell surface was not inhibited by hypoxia. However, in hypoxic cells less plasminogen activator inhibitor-1 was associated with receptor. It is concluded that in corneal epithelium cultured in 2% oxygen plasminogen activator inhibitor-1 may be an important regulatory factor of the plasminogen activator system resulting in increased urokinase plasminogen activator activity.

Role of plasminogen activators during healing after uterine serosal lesioning in the rat

OBJECTIVE

Study the expression pattern of tissue-type (t-PA) and urokinase-type (u-PA) plasminogen activators during uterine serosal healing after lesioning in a rat model.

DESIGN

Descriptive study with an adhesion model using reverse transcriptase-polymerase chain reaction (PCR) and immuncytochemical techniques.

SETTING

Academic medical center.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Expression profiles of t-PA and u-PA were examined in the uteroperitoneal adhesion tissues of rat from the time of injury until day 7 after surgery using relative abundance reverse transcriptase-PCR and immunocytochemical techniques.

RESULT(S)

The t-PA transcript levels dropped in uteroperitoneal tissues by 6 hours after surgery and remained low until day 5. Thereafter, a rapid up-regulation of this transcript was observed at day 7. In contrast, the u-PA transcript levels demonstrated a biphasic profile during the progression of adhesion development with peaks at 2 and 5 days after surgery. Immunocytochemical staining demonstrated expression of these plasminogen activators in the newly formed blood vessels.

CONCLUSION(S)

Altered levels of t-PA and u-PA transcripts and its expression in newly formed blood vessels during healing and adhesion development indicate involvement of these plasminogen activators in serosal healing and adhesion development.

CD44 stimulation by fragmented hyaluronic acid induces upregulation of urokinase-type plasminogen activator and its receptor and subsequently facilitates invasion of human chondrosarcoma cells

It has been established that fragmented hyaluronic acid (HA), but not native high molecular weight HA, can induce angiogenesis, cell proliferation and migration. We have studied the outside-in signal transduction pathways responsible for fragmented HA-mediated cancer cell invasion. In our study, we have studied the effects of CD44 stimulation by ligation with HA upon the expression of matrix metalloproteinases (MMPs)-2 and -9 as well as urokinase-type plasminogen activator (uPA), its receptor (uPAR) and its inhibitor (PAI-1) and the subsequent induction of invasion of human chondrosarcoma cell line HCS-2/8. Our study indicates that (i) CD44 stimulation by fragmented HA upregulates expression of uPA and uPAR mRNA and protein but does not affect MMPs secretion or PAI-1 mRNA expression; (ii) the effects of HA fragments are critically HA size dependent: high molecular weight HA is inactive, but lower molecular weight fragmented HA (Mr 3.5 kDa) is active; (iii) cells can bind avidly Mr 3.5 kDa fragmented HA through a CD44 molecule, whereas cells do not effectively bind higher Mr HA; (iv) a fragmented HA induces phosphorylation of MAP kinase proteins (MEK1/2, ERK1/2 and c-Jun) within 30 min; (v) CD44 is critical for the response (activation of MAP kinase and upregulation of uPA and uPAR expression); and (vi) cell invasion induced by CD44 stimulation with a fragmented HA is inhibited by anti-CD44 mAb, MAP kinase inhibitors, neutralizing anti-uPAR pAb, anti-catalytic anti-uPA mAb or amiloride. Therefore, our study represents the first report that CD44 stimulation induced by a fragmented HA results in activation of MAP kinase and, subsequently, enhances uPA and uPAR expression and facilitates invasion of human chondrosarcoma cells.

Characterisation of the lumenal domain of TGN38 and effects of elevated expression of TGN38 on glycoprotein secretion

The TGN-localised, type I integral membrane protein TGN38 has previously been suggested to play a role as a cargo transporter within mammalian cells. We have undertaken a series of experiments designed to address this hypothesis, and, in so doing, have partially characterised the glycosylation status of the lumenal domain of TGN38. We find that elevated expression of different regions of the lumenal domain of TGN38 has no reproducible effect on secretion from stably transfected NRK cells expressing the different lumenal domain constructs; neither does it affect the gross morphology of organelles of the secretory and endocytic pathways. However, we observed that, whilst elevated expression of full-length TGN38 in stably transfected NRK cells does not have any significant effect on the morphology of organelles of the secretory and endocytic pathways, it does lead to a change in the pattern of protein secretion from these cells. In particular, elevated expression of full-length TGN38 led to increased secretion of a 48-kDa glycoprotein identified as plasminogen activator inhibitor-1.

Fibrillar collagen regulation of plasminogen activator inhibitor-1 is involved in altered smooth muscle cell migration

OBJECTIVE

Vascular smooth muscle cells (SMCs) cultured on polymerized type I collagen fibrils are arrested in the G1 phase of the cell cycle, and their phenotypic markers and pattern of expressed genes are markedly altered. In this study, we examined polymerized collagen regulation of plasminogen activator inhibitor (PAI)-1 and its involvement in SMC migration.

METHODS AND RESULTS

We demonstrate that secretion and cell surface accumulation of PAI-1 are suppressed in SMCs cultured on polymerized collagen compared with SMCs cultured on monomer collagen. SMCs replated on vitronectin after culture on monomer collagen result in PAI-1 accumulation at focal adhesions and colocalization with alpha(v)beta3 integrins. In contrast, polymerized collagen inhibits PAI-1 accumulation at focal adhesions when the SMCs are replated on vitronectin. Furthermore, for SMCs cultured on polymerized collagen, platelet-derived growth factor-stimulated migration on vitronectin is enhanced by PAI-1, with its function counteracted by urinary plasminogen activator. Finally, exogenous addition of PAI-1 appears to partly restore platelet-derived growth factor-stimulated alpha(v)beta3-dependent SMC migration that is specifically suppressed by polymerized collagen.

CONCLUSIONS

Polymerized type I collagen fibrils dynamically regulate PAI-1, which may be involved in altered alpha(v)beta3 integrin-dependent SMC migration.

Human breast adenocarcinoma cell lines promote angiogenesis by providing cells with uPA-PAI-1 and by enhancing their expression

During angiogenesis, endothelial cells use uPA and PAI-1 to migrate and degrade the basement membrane surrounding capillary blood vessels. Invasive tumor cells produce a large amount of uPA that could bind uPAR present at the endothelial cell surface to facilitate their invasion. To verify this hypothesis, endothelial cells were incubated with conditioned medium (CM) from two breast cancer cell lines (MCF7 and MDA MB 231 cells). Within a short incubation period (30 min) with both CM, an increase of uPA, PAI-1 and uPA-PAI-1 complex was detected in endothelial cell layer as assessed by casein zymography, ELISA and uPA immunostaining. The extent of this enhancement was related to the levels of uPA secreted by tumor cells (high in MDA MB 231 cells and low in MCF7 cells). After 2 hr of incubation, the CM from both tumor cells upregulated uPA and PAI-1 mRNA levels in endothelial cells in a time-dependent manner. The uPA increase in the cell layer could not be attributable to an increase of uPAR level. Only the CM from highly invasive MDA MB 231 cells increased the angiogenic morphotype of endothelial cells assessed in a collagen gel. A single addition of amino-terminal fragment of uPA (ATF) was able to abolish the angiogenic effect induced by MDA MB 231 cell CM. Our data demonstrate that the interactions occurring between breast tumor cells and endothelial cells can modulate tumor angiogenesis at least by two mechanisms: an increase of uPA and PAI-1 cell surface-binding and of their expression by endothelial cells.

Proteolytic events of wound-healing--coordinated interactions among matrix metalloproteinases (MMPs), integrins, and extracellular matrix molecules

During wound-healing, cells are required to migrate rapidly into the wound site via a proteolytically generated pathway in the provisional matrix, to produce new extracellular matrix, and, subsequently, to remodel the newly formed tissue matrix during the maturation phase. Two classes of molecules cooperate closely to achieve this goal, namely, the matrix adhesion and signaling receptors, the integrins, and matrix-degrading and -processing enzymes, the matrix metalloproteinases (MMPs). There is now substantial experimental evidence that blocking key molecules of either group will prevent or seriously delay wound-healing. It has been known for some time now that cell adhesion by means of the integrins regulates the expression of MMPs. In addition, certain MMPs can bind to integrins or other receptors on the cell surface involved in enzyme activation, thereby providing a mechanism for localized matrix degradation. By proteolytically modifying the existing matrix molecules, the MMPs can then induce changes in cell behavior and function from a state of rest to migration. During wound repair, the expression of integrins and MMPs is simultaneously up-regulated. This review will focus on those aspects of the extensive knowledge of fibroblast and keratinocyte MMPs and integrins in biological processes that relate to wound-healing.

Promigratory effect of plasminogen activator inhibitor-1 on invasive breast cancer cell populations

The urokinase-type plasminogen activator (uPA) system is a dynamic complex in which the membrane receptor uPAR binds uPA that binds the plasminogen activator inhibitor (PAI)-1 localized in the extracellular matrix, resulting in endocytosis of the whole complex by the low-density lipoprotein receptor-related protein (LRP). High expression of PAI-1 is paradoxically associated with marked tumor spreading and poor prognosis. We previously reported a nonproteolytic role of the [uPAR:uPA:PAI-1:LRP] complex operative in cell migration. Here we explored whether matrix PAI-1 could be used as a migration support by human breast cancer cells. We showed that the uPA system and LRP are localized at filopodia of invasive cells, and that formation/internalization of the [uPAR:uPA:PAI-1:LRP] complex is required for attachment and migration of cancer cells on plastic and on a PAI-1 coat. PAI-1 increased both filopodia formation and migration of cancer cells suggesting a chemokine-like activity. Migration velocity, expression of the uPA system, use of the [uPAR:uPA:PAI-1:LRP] complex to migrate, and promigratory effects of PAI-1 paralleled cancer cell invasiveness. Phenotyping and functional analysis of invasive cancer cell subclones indicated that different cell subpopulations may use different strategies to migrate depending on both the environment and their expression of the uPA system, some of them taking advantage of abundant available PAI-1.

Effect of hypoxia on cellular adhesion to vitronectin and fibronectin

Cellular invasion of extracellular matrix (ECM) occurs during normal and pathological settings. For cells to invade, they must adhere to the underlying substratum, break down barrier molecules, and detach from the substratum prior to migrating through the ECM. We previously demonstrated that incubation under reduced oxygen levels increases the in vitro invasiveness of trophoblast and breast carcinoma cells, an effect linked to elevated expression of the cell surface receptor for urokinase-type plasminogen activator (uPAR). This study examined the role of oxygen, integrins and the urokinase-type plasminogen activator (uPA) system on the adhesion of trophoblast and breast carcinoma cells to the ECM molecules vitronectin and fibronectin. Compared to exposure to 20 and 5% oxygen, exposure to 1% oxygen decreased adhesion of these cells to vitronectin and fibronectin, an effect that was reversible by re-exposure to 20% oxygen. Incubation in 1% oxygen also resulted in reduced expression of surface alpha(5) integrin. Furthermore, adhesion to vitronectin and fibronectin was reduced by compounds that interfere with integrin function, such as EDTA, anti-integrin antibodies, or by antibodies that interfere with the binding of pro-uPA to uPAR, soluble uPAR, soluble vitronectin, phosphatidylinositol-specific phospholipase C, as well as plasminogen activator inhibitor-1. These findings suggest an important role for oxygen in the regulation of cellular invasion, possibly in part through its effects on integrin and uPAR-mediated mechanisms of adhesion.