The Serine Protease Inhibitor Protease Nexin-1 Controls Mammary Cancer Metastasis through LRP-1–Mediated MMP-9 Expression

Concurrently suppressing multidrug resistance and metastasis of breast cancer by co-delivery of paclitaxel and honokiol with pH-sensitive polymeric micelles

To concurrently suppress multidrug resistance (MDR) and metastasis of breast cancer cells, paclitaxel (PTX) and honokiol (HNK) were coencapsulated into pH-sensitive polymeric micelles based on poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) (PEOz-PLA). The physicochemical properties of dual drug-loaded PEOz-PLA micelles were characterized in size, drug loading and in vitro release. The efficiency of MDR reversal for the micelles was testified by synergetic enhancement of cytotoxicity and uptake by MCF-7/ADR cells. The flow cytometry and fluorescence polarization measurement results reinforced the conclusion that down-regulation of P-gp expression and increase of plasma membrane fluidity appeared to be possible mechanisms of MDR reversal by dual drug-loaded PEOz-PLA micelles. Further, the efficient inhibition of tumor metastasis by dual drug-loaded PEOz-PLA micelles was demonstrated by in vitro anti-invasion and anti-migration assessment in MDA-MB-231 cells and in vivo bioluminescence imaging in nude mice. The suppression of MDR and metastasis by the micelles was assigned to synergistic effects of pH-triggered drug release and HNK/PEOz-PLA-aroused P-gp inhibition, and pH-triggered drug release and PTX/HNK-aroused MMPs inhibition, respectively. In conclusion, our findings strengthen the usefulness of co-delivery of PTX and HNK by pH-responsive polymeric micelles for suppression of tumor MDR and metastasis.

STATEMENT OF SIGNIFICANCE

Multidrug resistance (MDR) and metastasis are considered to be two of the major barriers for successful chemotherapy. The combination of a chemotherapeutic drug with a modulator has emerged as a promising strategy for efficiently treating MDR cancer and preventing tumor metastasis. Herein, a dual drug (paclitaxel and honokiol)-loaded pH-sensitive polymeric micelle system based on PEOz-PLA was successfully fabricated to ensure that tumor MDR and metastasis could be concurrently suppressed, therefore achieving distinguishing endo/lysosomal pH from physiological pH by accelerating drug release and then enhancing the cytotoxicity of paclitaxel to drug-resistant tumor cells MCF-7/ADR by increasing cellular uptake of paclitaxel, preventing in vitro invasion and migration for MDA-MB-231 cells and in vivo metastasis in nude mice. Further, the mechanism of MDR reversal by dual drug-loaded PEOz-PLA micelles was elucidated to be down-regulation of P-gp expression and increase of plasma membrane fluidity of MCF-7/ADR cells. The present findings strengthen the usefulness of co-delivery of PTX and HNK by pH-responsive polymeric micelles for suppression of tumor MDR and metastasis.

Identification of Nucleobindin-2 as a Potential Biomarker for Breast Cancer Metastasis Using iTRAQ-based Quantitative Proteomic Analysis

Metastasis is a lethal step in the progression of breast cancer. None of the metastasis-associated biomarkers identified up to now has a definite prognostic value in breast cancer patients. This study was designed to identify biomarkers for breast cancer metastasis and predictors of the prognosis of breast cancer patients. The differentially expressed proteins between 23 paired primary breast tumor and metastatic lymph nodes were identified by quantitative iTRAQ proteomic analysis. Immunohistochemistry was applied to locate and assess the expression of NUCB2 in paired primary breast tumor and metastatic lymph node tissues (n = 106). The relationship between NUCB2 expression and the clinicopathological characteristics of breast cancer patients (n = 189) were analyzed by χ² test. Kaplan-Meier analysis and Cox hazard regression analysis were utilized to investigate the relationship between its expression and prognosis of breast cancer patients. The iTRAQ proteomic results showed that 4,837 confidential proteins were identified, 643 of which were differentially expressed in the primary breast cancer tissues and the paired metastatic lymph nodes. NUCB2 protein was found decreased in paired metastatic lymph nodes (P = 0.000), with the positive expression rate being 82% in primary breast cancer tissues and 47% in paired metastatic lymph nodes, respectively. According to Kaplan-Meier analysis, the overall survival time of patients with positive expression of NUCB2 protein were shorter than those with negative NUCB2 expression (P = 0.004). Cox regression model suggested that NUCB2 was a risk factor of breast cancer patients (P = 0.045, RR = 1.854). We conclude that NUCB2 can be used as a potential biomarker for breast cancer metastasis and a prognostic predictor of breast cancer patients.

Identification of LRP-1 as an endocytosis and recycling receptor for β1-integrin in thyroid cancer cells

LRP-1 is a large endocytic receptor mediating the clearance of various molecules from the extracellular matrix. LRP-1 was reported to control focal adhesion turnover to optimize the adhesion-deadhesion balance to support invasion. To better understand how LRP-1 coordinates cell-extracellular matrix interface, we explored its ability to regulate cell surface integrins in thyroid carcinomas. Using an antibody approach, we demonstrated that β1-integrin levels were increased at the plasma membrane under LRP1 silencing or upon RAP treatment, used as LRP-1 antagonist. Our data revealed that LRP-1 binds with both inactive and active β1-integrin conformations and identified the extracellular ligand-binding domains II or IV of LRP-1 as sufficient to bind β1-integrin. Using a recombinant β1-integrin, we demonstrated that LRP-1 acts as a regulator of β1-integrin intracellular traffic. Moreover, RAP or LRP-1 blocking antibodies decreased up to 36% the number of β1-integrin-containing endosomes. LRP-1 blockade did not significantly affect the levels of β1-integrin-containing lysosomes while decreasing localization of β1-integrin within Rab-11 positive vesicles. Overall, we identified an original molecular process in which LRP-1 acts as a main regulator of β1-integrin internalization and recycling in thyroid cancer cells.

Low-Density Lipoprotein Receptor-Related Protein-1 Signaling in Angiogenesis

Low-density lipoprotein receptor-related protein-1 (LRP1) plays multifunctional roles in lipid homeostasis, signaling transduction, and endocytosis. It has been recognized as an endocytic receptor for many ligands and is involved in the signaling pathways of many growth factors or cytokines. Dysregulation of LRP1-dependent signaling events contributes to the development of pathophysiologic processes such as Alzheimer’s disease, atherosclerosis, inflammation, and coagulation. Interestingly, recent studies have linked LRP1 with endothelial function and angiogenesis, which has been underappreciated for a long time. During zebrafish embryonic development, LRP1 is required for the formation of vascular network, especially for the venous development. LRP1 depletion in the mouse embryo proper leads to angiogenic defects and disruption of endothelial integrity. Moreover, in a mouse oxygen-induced retinopathy model, specific depletion of LRP1 in endothelial cells results in abnormal development of neovessels. These loss-of-function studies suggest that LRP1 plays a pivotal role in angiogenesis. The review addresses the recent advances in the roles of LRP1-dependent signaling during angiogenesis.

Aptamer-mediated impairment of EGFR-integrin αvβ3 complex inhibits vasculogenic mimicry and growth of triple-negative breast cancers

Current treatment options for triple-negative breast cancers (TNBCs) is limited by the absence of well-defined biomarkers, excluding a targeted therapy. Notably, epidermal growth factor receptor (EGFR) is overexpressed in a great proportion of TNBCs and is a negative prognostic factor. In clinical trials, however, existing EGFR inhibitors showed disappointing outcome. Oligonucleotide aptamers are a valid alternative to antibodies for diagnostic and therapeutic uses. Here, we prove that, when applied to aggressive TNBC cell lines with unique stem-like plasticity, the anti-EGFR CL4 aptamer, but not erlotinib or cetuximab, prevents the vasculogenic mimicry (VM) capability of the cells and destroys previously formed channels in three-dimensional culture. Notably, we found that CL4 impairs the matrix-induced integrin αvβ3 interaction with EGFR and integrin αvβ3-dependent cell adhesion. Consistently, the aptamer strongly inhibits VM and tumor growth in a xenograft TNBC model. These data suggest that in TNBC cells, EGFR may cooperate with integrin αvβ3 to regulate integrin binding to extracellular ligands required for VM, and EGFR-targeting by CL4 aptamer may counteract this event. Overall, we demonstrate a novel mechanism of action for CL4 related with integrin αvβ3-EGFR interaction, that may help to develop new oligonucleotide-based strategy addressing unmet need for TNBCs therapy.

Inhibition of breast cancer metastasis by paclitaxel-loaded pH responsive poly(β-amino ester) copolymer micelles

Aim: Tumor metastasis is one of the leading causes of insufficient chemotherapy during cancer treatment. In this study, a poly(β-amino ester) derivate was developed to fabricate paclitaxel (PTX) entrapped pH-responsive copolymer micelles for inhibition of breast cancer metastasis. Materials & methods: PTX-loaded micelles were fabricated by thin film hydration method. The inhibition efficacy of the as-prepared micelles was evaluated on MDA-MB-231 cells and tumor bearing mice. Results: PTX-loaded micelles were successfully prepared. Such micelles could promote drug uptake and MDA-MB-231 cell deaths, and suppress tumor metastasis. Conclusion: The pH-responsive PTX-loaded micelles are promising candidates in developing stimuli triggered drug delivery systems in acidic tumor microenvironments with improved inhibitory effects on tumor metastasis.

Regulation of the Extracellular SERPINA5 (Protein C Inhibitor) Penetration Through Cellular Membranes

It is generally accepted that the phospholipid bilayer of the cell membrane is impermeable for proteins and peptides and that these molecules require special mechanisms for their transport from the extra- to the intracellular space. Recently there is increasing evidence that certain proteins/peptides can also directly cross the phospholipid membrane. SERPINA5 (protein C inhibitor) is a secreted protease inhibitor with broad protease reactivity and wide tissue distribution. It binds glycosaminoglycans and certain phospoholipids, which can modulate its inhibitory activity. SERPINA5 has been shown to be internalized by platelets, granulocytes, HL-60 promyelocytic leukemia cells, and by Jurkat lymphoma cells. Once inside the cell it can translocate to the nucleus. There are several indications that SERPINA5 can directly cross the phospholipid bilayer of the cell membrane. In this review we will describe what is known so far about the conditions, as well as the cellular and molecular requirements for SERPINA5 translocation through the cell membrane and for its penetration of pure phospholipid vesicles.

Differential expression of Low density lipoprotein Receptor-related Protein 1 (LRP-1) and matrix metalloproteinase-9 (MMP-9) in prostate gland: From normal to malignant lesions

BACKGROUND

Metalloproteinases (MMPs) are relevant modulators of inflammation, tumor microenvironment, cancer invasion and metastasis. They can be regulated by the Low density lipoprotein Receptor-related Protein 1 (LRP-1), a receptor reported to mediate the clearance of lipoproteins, extracellular matrix (ECM) macromolecules and proteinases. The aim of this study was to evaluate the expression of LRP-1, MMP-2 and MMP-9 across various grades of prostatic diseases as benign prostatic hyperplasia (BPH), BPH plus prostatitis (BPH+P), high grade prostatic intraepithelial neoplasia (HGPIN) and prostate cancer (PCa).

METHODS

LRP-1 was analyzed using immunohistochemistry and MMPs proteolytic activity by zymography in prostate tissues with different prostatic diseases.

RESULTS

LRP-1 was detected in epithelial cells in BPH (16/18), BPH+P (21/21) and HGPIN (6/6), with a staining intensity of 1+, 1+/2+ and 3+, respectively. In PCa, LRP-1 was absent in 19/27 samples while a low expression was observed in 8/27 biopsies. MMP-9 activity was higher and statistically significant in PCa than in BPH (p≤0.01).

CONCLUSION

Considering that LRP-1, by mediating the clearance of MMPs, is involved in the regulation of ECM remodeling and cell migration, we conclude that a decreased expression of LRP-1 could be involved with the increasing activity of MMPs shown in cancers.

SERPINE2/Protease Nexin-1 in vivo multiple functions: Does the puzzle make sense?

Cultures of glial cells and fibroblasts allowed and lead to the identification SERPINE2/Protease Nexin-1 (SERPINE2/PN-1). Cellular, biochemical, immunological and molecular characterization substantiated its variable expression in many organs as a function of development, adult stages, pathological situations or following injury. It is not a circulating serpin, but as other members of the family, its target specificity is influenced by components of the extracellular matrix. The challenges are to identify where and when SERPINE2/PN-1 modulatory action becomes crucial or even possibly specific in a mosaic of feasible in vivo impacts. Data providing correlations are not sufficient to satisfy this aim. Genetically modified mice, or tissue derived thereof, provide interesting in vivo models to identify and study the relevance of this serpin. This review will highlight sometimes-intriguing results indicating a crucial impact of SERPINE2/PN-1, especially in the vasculature, the nervous system or the behavior of cancer cells in vivo. Data presently available will be discussed in an attempt to define general trends in the diversity of SERPINE2/PN-1 modes of action in vivo.

The role of the low-density lipoprotein receptor–related protein 1 (LRP-1) in regulating blood-brain barrier integrity

The blood-brain barrier (BBB) is a protective structure that helps maintaining the homeostasis in cerebral microenvironment by limiting the passage of molecules into the brain. BBB is formed by closely conjugated endothelial cells, with astrocytic endfeet surrounded and extracellular matrix (ECM) consolidated. Numerous neurological diseases can cause disturbance of BBB, leading to brain edema and neurological dysfunctions. The low-density lipoprotein (LDL) receptor–related protein 1 (LRP-1), a member of the LDL receptor gene family, is involved in a lot of important processes in the brain under both physiological and pathological conditions. As a membrane receptor, LRP-1 interacts with a variety of ligands and mediates the internalization of several important substances. LRP-1 is found responsible for inducing the opening of BBB following ischemic attack. It has also been reported that LRP-1 regulates several tight junction proteins and mediates the clearance of major ECM-degrading proteinases. In this review, we briefly discussed the role of LRP-1 in regulating BBB integrity by modulating tight junction proteins, endothelial cells and the remodeling of ECM.

Role of LRP-1 in cancer cell migration in 3-dimensional collagen matrix

The low-density lipoprotein receptor-related protein-1 (LRP-1) is a member of Low Density Lipoprotein Receptor (LDLR) family, which is ubiquitously expressed and which is described as a multifunctional endocytic receptor which mediates the clearance of various extracellular matrix molecules including serine proteinases, proteinase-inhibitor complexes, and matricellular proteins. Several studies showed that high LRP-1 expression promotes breast cancer cell invasiveness, and LRP-1 invalidation leads to cell motility abrogation in both tumor and non-tumor cells. Furthermore, our group has reported that LRP-1 silencing prevents the invasion of a follicular thyroid carcinoma despite increased pericellular proteolytic activities from MMP2 and uPA using a 2D-cell culture model. As the use of 3D culture systems is becoming more and more popular due to their promise as enhanced models of tissue physiology, the aim of the present work is to characterize for the first time how the 3D collagen type I matrix may impact the ability of LRP-1 to regulate the migratory properties of thyroid carcinoma using as a model FTC-133 cells. Our results show that inhibition of LRP-1 activity or expression leads to morphological changes affecting cell-matrix interactions, reorganizations of the actin-cytoskeleton especially by inhibiting FAK activation and increasing RhoA activity and MLC-2 phosphorylation, thus preventing cell migration. Taken together, our results suggest that LRP-1 silencing leads to a decrease of cell migratory capacity in a 3D configuration.

Roles of low-density lipoprotein receptor-related protein 1 in tumors

Low-density lipoprotein receptor-related protein 1 (LRP1, also known as CD91), a multifunctional endocytic and cell signaling receptor, is widely expressed on the surface of multiple cell types such as hepatocytes, fibroblasts, neurons, astrocytes, macrophages, smooth muscle cells, and malignant cells. Emerging in vitro and in vivo evidence demonstrates that LRP1 is critically involved in many processes that drive tumorigenesis and tumor progression. For example, LRP1 not only promotes tumor cell migration and invasion by regulating matrix metalloproteinase (MMP)-2 and MMP-9 expression and functions but also inhibits cell apoptosis by regulating the insulin receptor, the serine/threonine protein kinase signaling pathway, and the expression of Caspase-3. LRP1-mediated phosphorylation of the extracellular signal-regulated kinase pathway and c-jun N-terminal kinase are also involved in tumor cell proliferation and invasion. In addition, LRP1 has been shown to be down-regulated by microRNA-205 and methylation of LRP1 CpG islands. Furthermore, a novel fusion gene, LRP1-SNRNP25, promotes osteosarcoma cell invasion and migration. Only by understanding the mechanisms of these effects can we develop novel diagnostic and therapeutic strategies for cancers mediated by LRP1.

The Matricellular Receptor LRP1 Forms an Interface for Signaling and Endocytosis in Modulation of the Extracellular Tumor Environment

The membrane protein low-density lipoprotein receptor related-protein 1 (LRP1) has been attributed a role in cancer. However, its presumably often indirect involvement is far from understood. LRP1 has both endocytic and signaling activities. As a matricellular receptor it is involved in regulation, mostly by clearing, of various extracellular matrix degrading enzymes including matrix metalloproteinases, serine proteases, protease inhibitor complexes, and the endoglycosidase heparanase. Furthermore, by binding extracellular ligands including growth factors and subsequent intracellular interaction with scaffolding and adaptor proteins it is involved in regulation of various signaling cascades. LRP1 expression levels are often downregulated in cancer and some studies consider low LRP1 levels a poor prognostic factor. On the contrary, upregulation in brain cancers has been noted and clinical trials explore the use of LRP1 as cargo receptor to deliver cytotoxic agents. This mini-review focuses on LRP1's role in tumor growth and metastasis especially by modulation of the extracellular tumor environment. In relation to this role its diagnostic, prognostic and therapeutic potential will be discussed.

SERPINE2 Inhibits IL-1α-Induced MMP-13 Expression in Human Chondrocytes: Involvement of ERK/NF-κB/AP-1 Pathways

OBJECTIVES

Osteoarthritis (OA) is a chronic joint disease, characterized by a progressive loss of articular cartilage. During OA, proinflammatory cytokines, such as interleukin IL-1, induce the expression of matrix metalloproteinases (MMPs) in chondrocytes, contributing thus to the extracellular matrix (ECM) degradation. Members of Serpine family, including plasminogen activator inhibitors have been reported to participate in ECM regulation. The aim of this study was to assess the expression of serpin peptidase inhibitor clade E member 2 (SERPINE2), under basal conditions and in response to increasing doses of IL-1α, in human cultured chondrocytes. We also examined the effects of SERPINE2 on IL-1α-induced MMP-13 expression. For completeness, the signaling pathway involved in this process was also explored.

METHODS

SERPINE2 mRNA and protein expression were evaluated by RT-qPCR and western blot analysis in human T/C-28a2 cell line and human primary chondrocytes. These cells were treated with human recombinant SERPINE2, alone or in combination with IL-1α. ERK 1/2, NFκB and AP-1 activation were assessed by western blot analysis.

RESULTS

Human cultured chondrocytes express SERPINE2 in basal condition. This expression increased in response to IL-1α stimulation. In addition, recombinant SERPINE2 induced a clear inhibition of MMP-13 expression in IL-1α-stimulated chondrocytes. This inhibitory effect is likely regulated through a pathway involving ERK 1/2, NF-κB and AP-1.

CONCLUSIONS

Taken together, these data demonstrate that SERPINE2 might prevent cartilage catabolism by inhibiting the expression of MMP-13, one of the most relevant collagenases, involved in cartilage breakdown in OA.

Serpine2/PN-1 Is Required for Proliferative Expansion of Pre-Neoplastic Lesions and Malignant Progression to Medulloblastoma

Background

Medulloblastomas are malignant childhood brain tumors that arise due to the aberrant activity of developmental pathways during postnatal cerebellar development and in adult humans. Transcriptome analysis has identified four major medulloblastoma subgroups. One of them, the Sonic hedgehog (SHH) subgroup, is caused by aberrant Hedgehog signal transduction due to mutations in the Patched1 (PTCH1) receptor or downstream effectors. Mice carrying a Patched-1 null allele (Ptch1^∆/+) are a good model to study the alterations underlying medulloblastoma development as a consequence of aberrant Hedgehog pathway activity.

Results

Transcriptome analysis of human medulloblastomas shows that SERPINE2, also called Protease Nexin-1 (PN-1) is overexpressed in most medulloblastomas, in particular in the SHH and WNT subgroups. As siRNA-mediated lowering of SERPINE2/PN-1 in human medulloblastoma DAOY cells reduces cell proliferation, we analyzed its potential involvement in medulloblastoma development using the Ptch1^∆/+ mouse model. In Ptch1^∆/+ mice, medulloblastomas arise as a consequence of aberrant Hedgehog pathway activity. Genetic reduction of Serpine2/Pn-1 interferes with medulloblastoma development in Ptch1^∆/+ mice, as ~60% of the pre-neoplastic lesions (PNLs) fail to develop into medulloblastomas and remain as small cerebellar nodules. In particular the transcription factor Atoh1, whose expression is essential for development of SHH subgroup medulloblastomas is lost. Comparative molecular analysis reveals the distinct nature of the PNLs in young Ptch1^∆/+Pn-1^Δ/+ mice. The remaining wild-type Ptch1 allele escapes transcriptional silencing in most cases and the aberrant Hedgehog pathway activity is normalized. Furthermore, cell proliferation and the expression of the cell-cycle regulators Mycn and Cdk6 are significantly reduced in PNLs of Ptch1^∆/+Pn-1^Δ/+ mice.

Conclusions

Our analysis provides genetic evidence that aberrant Serpine2/Pn-1 is required for proliferation of human and mouse medulloblastoma cells. In summary, our analysis shows that Serpine2/PN-1 boosts malignant progression of PNLs to medulloblastomas, in which the Hedgehog pathway is activated in a SHH ligand-independent manner.

A model of breast cancer heterogeneity reveals vascular mimicry as a driver of metastasis

Cancer metastasis requires that primary tumour cells evolve the capacity to intravasate into the lymphatic system or vasculature, and extravasate into and colonize secondary sites. Others have demonstrated that individual cells within complex populations show heterogeneity in their capacity to form secondary lesions. Here we develop a polyclonal mouse model of breast tumour heterogeneity, and show that distinct clones within a mixed population display specialization, for example, dominating the primary tumour, contributing to metastatic populations, or showing tropism for entering the lymphatic or vasculature systems. We correlate these stable properties to distinct gene expression profiles. Those clones that efficiently enter the vasculature express two secreted proteins, Serpine2 and Slpi, which were necessary and sufficient to program these cells for vascular mimicry. Our data indicate that these proteins not only drive the formation of extravascular networks but also ensure their perfusion by acting as anticoagulants. We propose that vascular mimicry drives the ability of some breast tumour cells to contribute to distant metastases while simultaneously satisfying a critical need of the primary tumour to be fed by the vasculature. Enforced expression of SERPINE2 and SLPI in human breast cancer cell lines also programmed them for vascular mimicry, and SERPINE2 and SLPI were overexpressed preferentially in human patients that had lung-metastatic relapse. Thus, these two secreted proteins, and the phenotype they promote, may be broadly relevant as drivers of metastatic progression in human cancer.

Extracellular molecules involved in cancer cell invasion

Nowadays it is perfectly clear that understanding and eradicating cancer cell invasion and metastasis represent the crucial, definitive points in cancer therapeutics. During the last two decades there has been a great interest in the understanding of the extracellular molecular mechanisms involved in cancer cell invasion. In this review, we highlight the findings concerning these processes, focusing in particular on extracellular molecules, including extracellular matrix proteins and their receptors, growth factors and their receptors, matrix metalloproteinases and extracellular chaperones. We report the molecular mechanisms underlying the important contribution of this pool of molecules to the complex, multi-step phenomenon of cancer cell invasion.

Exploiting the cytoskeletal filaments of neoplastic cells to potentiate a novel therapeutic approach

Although cytoskeletal-directed agents have been a mainstay in chemotherapeutic protocols due to their ability to readily interfere with the rapid mitotic progression of neoplastic cells, they are all microtubule-based drugs, and there has yet to be any microfilament- or intermediate filament-directed agents approved for clinical use. There are many inherent differences between the cytoskeletal networks of malignant and normal cells, providing an ideal target to attain preferential damage. Further, numerous microfilament-directed agents, and an intermediate filament-directed agent of particular interest (withaferin A) have demonstrated in vitro and in vivo efficacy, suggesting that cytoskeletal filaments may be exploited to supplement chemotherapeutic approaches currently used in the clinical setting. Therefore, this review is intended to expose academics and clinicians to the tremendous variety of cytoskeletal filament-directed agents that are currently available for further chemotherapeutic evaluation. The mechanisms by which microfilament directed- and intermediate filament-directed agents damage malignant cells are discussed in detail in order to establish how the drugs can be used in combination with each other, or with currently approved chemotherapeutic agents to generate a substantial synergistic attack, potentially establishing a new paradigm of chemotherapeutic agents.

The CAP1/Prss8 catalytic triad is not involved in PAR2 activation and protease nexin-1 (PN-1) inhibition

Serine proteases, serine protease inhibitors, and protease-activated receptors (PARs) are responsible for several human skin disorders characterized by impaired epidermal permeability barrier function, desquamation, and inflammation. In this study, we addressed the consequences of a catalytically dead serine protease on epidermal homeostasis, the activation of PAR2 and the inhibition by the serine protease inhibitor nexin-1. The catalytically inactive serine protease CAP1/Prss8, when ectopically expressed in the mouse, retained the ability to induce skin disorders as well as its catalytically active counterpart (75%, n=81). Moreover, this phenotype was completely normalized in a PAR2-null background, indicating that the effects mediated by the catalytically inactive CAP1/Prss8 depend on PAR2 (95%, n=131). Finally, nexin-1 displayed analogous inhibitory capacity on both wild-type and inactive mutant CAP1/Prss8 in vitro and in vivo (64% n=151 vs. 89% n=109, respectively), indicating that the catalytic site of CAP1/Prss8 is dispensable for nexin-1 inhibition. Our results demonstrate a novel inhibitory interaction between CAP1/Prss8 and nexin-1, opening the search for specific CAP1/Prss8 antagonists that are independent of its catalytic activity.

Brain metastasis-initiating cells: survival of the fittest

Brain metastases (BMs) are the most common brain tumor in adults, developing in about 10% of adult cancer patients. It is not the incidence of BM that is alarming, but the poor patient prognosis. Even with aggressive treatments, median patient survival is only months. Despite the high rate of BM-associated mortality, very little research is conducted in this area. Lack of research and staggeringly low patient survival is indicative that a novel approach to BMs and their treatment is needed. The ability of a small subset of primary tumor cells to produce macrometastases is reminiscent of brain tumor-initiating cells (BTICs) or cancer stem cells (CSCs) hypothesized to form primary brain tumors. BTICs are considered stem cell-like due to their self-renewal and differentiation properties. Similar to the subset of cells forming metastases, BTICs are most often a rare subpopulation. Based on the functional definition of a TIC, cells capable of forming a BM could be considered to be brain metastasis-initiating cells (BMICs). These putative BMICs would not only have the ability to initiate tumor growth in a secondary niche, but also the machinery to escape the primary tumor, migrate through the circulation, and invade the neural niche.

Silibinin and Paclitaxel Cotreatment Significantly Suppress the Activity and Lung Metastasis of Triple Negative 4T1 Mammary Tumor Cell in Mice

The in vitro and in vivo bioactivities of silibinin (SB), paclitaxel (PTX) and SB and PTX in combination (SB+PTX) against murine metastatic mammary 4T1 cancer cell line were investigated. Isobologram and combination index (CI) analyses showed that SB and PTX can function synergistically in the inhibition of 4T1 cell proliferation with a CI value < 1. Both SB and PTX alone or SB+PTX treatment inhibited 4T1 cell migration and motility possibly through downregulation of the serpin protease nexin-1 (PN-1) and N-cadherin expression, inhibition of matrix metalloprotease (MMP)-9 activity, and upregulation of E-cadherin. Flow cytometry and Western blot analyses demonstrated that both drugs deregulated cell-cycle mediators and induced apoptosis in 4T1 cells. A real-time in vivo bioluminescence imaging system to monitor the breast cancer cell metastasis in syngeneic BALB/c mice was established using a stable 4T1^{pGL-COX-2/Luc} cell clone carrying a COX-2 promoter driven-luciferase reporter gene. In vivo study using the allograft 4T1^{pGL-COX-2/Luc} metastatic mouse model indicated that SB co-treated with PTX can significantly suppress lung metastasis of 4T1 cells likely through inhibiting cell proliferation and angiogenesis. Together, this study demonstrates that SB could act synergistically with PTX in 4T1 cells, providing a therapeutic option for highly metastatic triple negative breast cancer.

Acute lymphoid leukemia cells with greater stem cell antigen-1 (Ly6a/Sca-1) expression exhibit higher levels of metalloproteinase activity and are more aggressive in vivo

Stem cell antigen-1 (Ly6a/Sca-1) is a gene that is expressed in activated lymphocytes, hematopoietic stem cells and stem cells of a variety of tissues in mice. Despite decades of study its functions remain poorly defined. These studies explored the impact of expression of this stem cell associated gene in acute lymphoid leukemia. Higher levels of Ly6a/Sca-1 expression led to more aggressive leukemia growth in vivo and earlier death of hosts. Leukemias expressing higher levels of Ly6a/Sca-1 exhibited higher levels of matrix metalloproteinases. The results suggest the hypothesis that the more aggressive behavior of Ly6a/Sca-1 expressing leukemias is due at least in part to greater capacity to degrade microenvironmental stroma and invade tissues.

LDL receptor-related protein-1: a regulator of inflammation in atherosclerosis, cancer, and injury to the nervous system

Low-density lipoprotein receptor-related protein-1 (LRP1) is an endocytic receptor for numerous proteins that are both structurally and functionally diverse. In some cell types, LRP1-mediated endocytosis is coupled to activation of cell signaling. LRP1 also regulates the composition of the plasma membrane and may, thereby, indirectly regulate the activity of other cell-signaling receptors. Given the scope of LRP1 ligands and its multifunctional nature, it is not surprising that numerous biological activities have been attributed to this receptor. LRP1 gene deletion is embryonic-lethal in mice. However, elegant studies using Cre-LoxP recombination have helped elucidate the function of LRP1 in mature normal and pathological tissues. One major theme that has emerged is the role of LRP1 as a regulator of inflammation. In this review, we will describe evidence for LRP1 as a regulator of inflammation in atherosclerosis, cancer, and injury to the nervous system.

Proteomic analysis reveals a proteolytic feedback loop in murine seminal fluid

BACKGROUND

Matrix metalloproteinase 9 (MMP9) has been implicated in extracellular matrix (ECM) remodelling, angiogenesis and inflammation. However, the targets for proteolysis that lead to these physiological consequences are often undefined as is the regulation of MMP9 itself. Therefore, identification of both the potential direct and indirect targets of MMP9 is critical for further understanding the effects of its proteolytic cascades.

METHODS

To study these cascades on a wider scale, transgenic mouse "knock-out" models and ultra-high performance liquid chromatography mass spectroscopy (UPLC-MS(E) ) were used to elucidate the MMP9 targets, inhibitors, and interactors found in mouse seminal vesicle fluid (SVF).

RESULTS

Proteomics analysis of SVF from wild type, mmp9-/- or pn1-/- mice detected differences in serine protease inhibitors (serpins), reproductive proteins, developmental regulators, and cancer proto-oncogenes, including Renin 1/2. Protease nexin 1 (PN1), an ECM-based inhibitor of urokinase, was elevated in the SVF of mmp9-/- mice. We observed that MMP9-mediated N-terminal cleavage of PN1 reduces this serpin's functional activity. Our data also suggest a feedback loop in which inhibition of PN1 is a critical step in permitting greater activity of MMP9.

CONCLUSION

This study extends the degradome of MMP9 and examines components relevant to seminal fluid physiology. PN1 is proposed to be a novel inhibitor of MMP9 activity and a block to collagen cleavage, a frequent antecedent to cancer cell invasion. The interaction of MMP9 with PN1 and other serpins may lead to a better understanding of seminal vesicle function and possible impacts on fertility, as well as provide novel therapeutic targets.

Exosomes and communication between tumours and the immune system: are all exosomes equal?

Communication between cells is particularly important during tumour progression. Communication can take place through direct cell-cell interactions, but also through extracellular secretion of mediators acting at a distance. These mediators can be either soluble molecules or more complex structures called membrane vesicles, enclosing soluble factors within a lipid bilayer. A variety of extracellular membrane vesicles have been described, for instance microvesicles, ectosomes and a subtype called exosomes. The role of exosomes in tumour progression has been studied extensively in the last 10 years. In the present mini-review, we discuss our recent results, first showing the heterogeneity of the vesicles called exosomes and the probable existence of subpopulations of these exosomes, and secondly demonstrating that in vivo secretion of exosomes by some tumours can promote tumour progression, but that such a function cannot be generalized to all tumours and all exosomes.

LRP-1: a checkpoint for the extracellular matrix proteolysis

Low-density lipoprotein receptor-related protein-(LRP-1) is a large endocytic receptor that binds more than 35 ligands and exhibits signaling properties. Proteinases capable of degrading extracellular matrix (ECM), called matrix proteinases in this paper, are mainly serine proteinases: the activators of plasminogen into plasmin, tissue-type (tPA) and urokinase-type (uPA) plasminogen activators, and the members of the matrix metalloproteinase (MMP) family. LRP-1 is responsible for clearing matrix proteinases, complexed or not with inhibitors. This paper attempts to summarize some aspects on the cellular and molecular bases of endocytic and signaling functions of LRP-1 that modulate extra- and pericellular levels of matrix proteinases.

Genes regulated in metastatic osteosarcoma: evaluation by microarray analysis in four human and two mouse cell line systems

Osteosarcoma (OS) is a rare bone neoplasm that affects mainly adolescents. It is associated with poor prognosis in case of metastases formation. The search for metastasis predicting markers is therefore imperative to optimize treatment strategies for patients at risk and important for the search of new drugs for the treatment of this devastating disease. Here, we have analyzed by microarray the differential gene expression in four human and two mouse OS cell line systems consisting of parental cell lines with low metastatic potential and derivatives thereof with increased metastatic potential. Using two osteoblastic cell line systems, the most common OS phenotype, we have identified forty-eight common genes that are differentially expressed in metastatic cell lines compared to parental cells. The identified subset of metastasis relevant genes in osteoblastic OS overlapped only minimally with differentially expressed genes in the other four preosteoblast or nonosteoblastic cell line systems. The results imply an OS phenotype specific expression pattern of metastasis regulating proteins and form a basis for further investigation of gene expression profiles in patients' samples combined with survival analysis with the aim to optimize treatment strategies to develop new drugs and to consequently improve the survival of patients with the most common form of osteoblastic OS.

Protease nexin 1 inhibits hedgehog signaling in prostate adenocarcinoma

Prostate adenocarcinoma (CaP) patients are classified into low-, intermediate-, and high-risk groups that reflect relative survival categories. While there are accepted treatment regimens for low- and high-risk patients, intermediate-risk patients pose a clinical dilemma, as treatment outcomes are highly variable for these individuals. A better understanding of the factors that regulate the progression of CaP is required to delineate risk. For example, aberrant activation of the Hedgehog (Hh) pathway is implicated in CaP progression. Here, we identify the serine protease inhibitor protease nexin 1 (PN1) as a negative regulator of Hh signaling in prostate. Using human CaP cell lines and a mouse xenograft model of CaP, we demonstrate that PN1 regulates Hh signaling by decreasing protein levels of the Hh ligand Sonic (SHH) and its downstream effectors. Furthermore, we show that SHH expression enhanced tumor growth while overexpression of PN1 inhibited tumor growth and angiogenesis in mice. Finally, using comparative genome hybridization, we found that genetic alterations in Hh pathway genes correlated with worse clinical outcomes in intermediate-risk CaP patients, indicating the importance of this pathway in CaP.

Role of plasminogen activator inhibitor-1 in urokinase's paradoxical in vivo tumor suppressing or promoting effects

Tumor proteases and inhibitors have been associated with paradoxical effects on tumor progression in preclinical and clinical settings. We previously reported that urokinase (uPA) overexpression delays tumor progression in mammary cancer. This study aimed to determine the role of plasminogen activator inhibitor-1 (PAI-1) on uPA's paradoxical in vivo effects. Using syngeneic murine models, we found that stable uPA overexpression promoted in vivo growth of colon tumors (MC-38) naturally expressing high PAI-1, whereas growth inhibition was observed in renal tumors (RENCA) expressing lower PAI-1 levels. In murine mammary carcinoma (4T1), uPA overexpression shifted the uPA/PAI-1 balance in favor of the protease, resulting in significantly reduced tumor growth and metastases in vivo. Conversely, increased tumor progression was observed in stable PAI-1 overexpressing 4T1 tumors as compared with uPA-overexpressing and control tumors. These effects were associated with downregulation of metastases promoting genes in uPA-overexpressing tumors, such as metalloproteinases, CXCL-1, c-Fos, integrin α-5, VEGF-A, PDGF-α, and IL-1β. In PAI-1-overexpressing tumors, many of the above genes were upregulated. PAI-1 overexpressing tumors had increased total and new tumor microvessels, and increased tumor cell proliferation, whereas the opposite effects were found in uPA-overexpressing tumors. Finally, PAI-1 downregulation led to significant inhibition of 4T1 tumor growth and metastases in vivo. In conclusion, uPA's dual effects on tumor progression occur in the context of its interactions with endogenous PAI-1 expression. Our studies uncover novel mechanisms of in vivo tumor control by modulation of the balance between tumor proteases and inhibitors, which may be exploited therapeutically.

Rab27a supports exosome-dependent and -independent mechanisms that modify the tumor microenvironment and can promote tumor progression

During progression from single cancer cells to a tumor mass and metastases, tumor cells send signals that can subvert their tissue microenvironment. These signals involve soluble molecules and various extracellular vesicles, including a particular type termed exosomes. The specific roles of exosomes secreted in the tumor microenvironment, however, is unclear. The small GTPases RAB27A and RAB27B regulate exocytosis of multivesicular endosomes, which lead to exosome secretion, in human HeLa cells. Here, we used mouse models to show that Rab27a blockade in mammary carcinoma cells decreased secretion of exosomes characterized by endocytic markers, but also of matrix metalloproteinase 9, which is not associated with exosomes. Rab27a blockade resulted in decreased primary tumor growth and lung dissemination of a metastatic carcinoma (4T1), but not of a nonmetastatic carcinoma (TS/A). Local growth of 4T1 tumors required mobilization of a population of neutrophil immune cells induced by Rab27a-dependent secretion of exosomes together with a specific combination of cytokines and/or metalloproteinases. Our findings offer in vivo validation of the concept that exosome secretion can exert key pathophysiologic roles during tumor formation and progression, but they also highlight the idiosyncratic character of the tumor context.

LRP-1--CD44, a new cell surface complex regulating tumor cell adhesion

The low-density lipoprotein receptor-related protein 1 (LRP-1) is a large endocytic receptor mediating the clearance of various molecules from the extracellular matrix. In the field of cancer, LRP-1-mediated endocytosis was first associated with antitumor properties. However, recent results suggested that LRP-1 may coordinate the adhesion-deadhesion balance in malignant cells to support tumor progression. Here, we observed that LRP-1 silencing or RAP (receptor-associated protein) treatment led to accumulation of CD44 at the tumor cell surface. Moreover, we evidenced a tight interaction between CD44 and LRP-1, not exclusively localized in lipid rafts. Overexpression of LRP-1-derived minireceptors indicated that the fourth ligand-binding cluster of LRP-1 is required to bind CD44. Labeling of CD44 with EEA1 and LAMP-1 showed that internalized CD44 is routed through early endosomes toward lysosomes in a LRP-1-dependent pathway. LRP-1-mediated internalization of CD44 was highly reduced under hyperosmotic conditions but poorly affected by membrane cholesterol depletion, revealing that it proceeds mostly via clathrin-coated pits. Finally, we demonstrated that CD44 silencing abolishes RAP-induced tumor cell attachment, revealing that cell surface accumulation of CD44 under LRP-1 blockade is mainly responsible for the stimulation of tumor cell adhesion. Altogether, our data shed light on the LRP-1-mediated internalization of CD44 that appeared critical to define the adhesive properties of tumor cells.

Matrix metalloproteinases in tumorigenesis: an evolving paradigm

Proteases are crucial for development, tissue remodeling, and tumorigenesis. Matrix metalloproteinases (MMPs) family, in particular, consists of more than 20 members with unique substrates and diverse function. The expression and activity of MMPs in a variety of human cancers have been intensively studied. MMPs have well-recognized roles in the late stage of tumor progression, invasion, and metastasis. However, increasing evidence demonstrates that MMPs are involved earlier in tumorigenesis, e.g., in malignant transformation, angiogenesis, and tumor growth both at the primary and metastatic sites. Recent studies also suggest that MMPs play complex roles in tumor progression. While most MMPs promote tumor progression, some of them may protect the host against tumorigenesis in a context-dependent manner. MMPs have been chosen as promising targets for cancer therapy on the basis of their aberrant up-regulation in malignant tumors and their ability to promote cancer metastasis. Although preclinical studies testing the efficacy of MMP suppression in tumor models were so encouraging, the results of clinical trials in cancer patients have been rather disappointing. Here, we review the complex roles of MMPs and their endogenous inhibitors such as tissue inhibitors of metalloproteinase in tumorigenesis and strategies in suppressing MMPs.

Inhibition of cyclo-oxygenase 2 reduces tumor metastasis and inflammatory signaling during blockade of vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) blockade is an effective therapy for human cancer, yet virtually all neoplasms resume primary tumor growth or metastasize during therapy. Mechanisms of progression have been proposed to include genes that control vascular remodeling and are elicited by hypoperfusion, such as the inducible enzyme cyclooxygenase-2 (COX-2). We have previously shown that COX-2 inhibition by the celecoxib analog SC236 attenuates perivascular stromal cell recruitment and tumor growth. We therefore examined the effect of combined SC236 and VEGF blockade, using the metastasizing orthotopic SKNEP1 model of pediatric cancer. Combined treatment perturbed tumor vessel remodeling and macrophage recruitment, but did not further limit primary tumor growth as compared to VEGF blockade alone. However, combining SC236 and VEGF inhibition significantly reduced the incidence of lung metastasis, suggesting a distinct effect on prometastatic mechanisms. We found that SC236 limited tumor cell viability and migration in vitro, with effects enhanced by hypoxia, but did not change tumor proliferation or matrix metalloproteinase expression in vivo. Gene set expression analysis (GSEA) indicated that the addition of SC236 to VEGF inhibition significantly reduced expression of gene sets linked to macrophage mobilization. Perivascular recruitment of macrophages induced by VEGF blockade was disrupted in tumors treated with combined VEGF- and COX-2-inhibition. Collectively, these findings suggest that during VEGF blockade COX-2 may restrict metastasis by limiting both prometastatic behaviors in individual tumor cells and mobilization of macrophages to the tumor vasculature.

Spatiotemporal expression of SERPINE2 in the human placenta and its role in extravillous trophoblast migration and invasion

BACKGROUND

SERPINE2, one of the potent serpins belonging to the plasminogen activator (PA) system, is involved in the tissue remodeling. We previously demonstrated the expression patterns of Serpine2 in the mouse placenta and uterus, indicating that Serpine2 is a major PA inhibitor in the placenta and uterus during the estrous cycle, pregnancy, and lactation. In this study, we further investigated the expression pattern of SERPINE2 in the human placenta and explored possible functional roles of SERPINE2 in regulating trophoblast activity.

METHODS

Placental tissues from various trimesters were collected for real-time reverse-transcription polymerase chain reaction quantification. Immunohistochemical staining was performed in placental tissues to assure localization of SERPINE2. SERPINE2 small interfering (si) RNA was applied to suppress its expression in villous explants and extravillous trophoblast-like 3A cells. Subsequent experiments to evaluate SERPINE2 levels, villous outgrowth, trophoblast invasion, and tube formation were performed.

RESULTS

SERPINE2 messenger RNA was detected in the human placenta during pregnancy with the highest levels in the third trimester. The SERPINE2 protein was present in villous syncytiotrophoblasts and trophoblasts of chorionic villi for anti-SERPINE2 immunostaining. Extravillous trophoblasts in the chorionic plate and basal plate confronting the invasive face of anchoring villi were also positive. In most decidual cells, SERPINE2 was observed in the cytoplasm. In addition, fibrinoid deposit was weakly immunoreactive. Introduction of SERPINE2 siRNA into villous explants and trophoblast cells led to significantly reduced villous outgrowth, and trophoblastic migration and invasion. Moreover, capillary-like network formation of 3A cells in Matrigel was greatly attenuated by SERPINE2 siRNA and SERPINE2 antiserum.

CONCLUSIONS

These data identify the temporal and spatial SERPINE2 distribution in the human placenta and suggest its possible role in modulating tissue remodeling of extravillous trophoblasts in the placenta during pregnancy.

The serine protease inhibitor serpinE2 is a novel target of ERK signaling involved in human colorectal tumorigenesis

BACKGROUND

Among the most harmful of all genetic abnormalities that appear in colorectal cancer (CRC) development are mutations of KRAS and its downstream effector BRAF as they result in abnormal extracellular signal-related kinase (ERK) signaling. In a previous report, we had shown that expression of a constitutive active mutant of MEK1 (caMEK) in normal rat intestinal epithelial cells (IECs) induced morphological transformation associated with epithelial to mesenchymal transition, growth in soft agar, invasion and metastases in nude mice. Results from microarrays comparing control to caMEK-expressing IECs identified the gene encoding for serpinE2, a serine protease inhibitor, as a potential target of activated MEK1.

RESULTS

1- RT-PCR and western blot analyses confirmed the strong up-regulation of serpinE2 expression and secretion by IECs expressing oncogenic MEK, Ras or BRAF. 2- Interestingly, serpinE2 mRNA and protein were also markedly enhanced in human CRC cells exhibiting mutation in KRAS and BRAF. 3- RNAi directed against serpinE2 in caMEK-transformed rat IECs or in human CRC cell lines HCT116 and LoVo markedly decreased foci formation, anchorage-independent growth in soft agarose, cell migration and tumor formation in nude mice. 4- Treatment of CRC cell lines with U0126 markedly reduced serpinE2 mRNA levels, indicating that expression of serpinE2 is likely dependent of ERK activity. 5- Finally, Q-PCR analyses demonstrated that mRNA levels of serpinE2 were markedly increased in human adenomas in comparison to healthy adjacent tissues and in colorectal tumors, regardless of tumor stage and grade.

CONCLUSIONS

Our data indicate that serpinE2 is up-regulated by oncogenic activation of Ras, BRAF and MEK1 and contributes to pro-neoplastic actions of ERK signaling in intestinal epithelial cells. Hence, serpinE2 may be a potential therapeutic target for colorectal cancer treatment.

Matrix metalloproteinase-9 regulates tumor cell invasion through cleavage of protease nexin-1

Matrix metalloproteinase-9 (MMP-9) expression is known to enhance the invasion and metastasis of tumor cells. In previous work based on a proteomic screen, we identified the serpin protease nexin-1 (PN-1) as a potential target of MMP-9. Here, we show that PN-1 is a substrate for MMP-9 and establish a link between PN-1 degradation by MMP-9 and regulation of invasion. PN-1 levels increased in prostate carcinoma cells after downregulation of MMP-9 and in tissues of MMP-9-deficient mice, consistent with PN-1 degradation by MMP-9. We identified three MMP-9 cleavage sites in PN-1 and showed that mutations in those sites made PN-1 more resistant to MMP-9. Urokinase plasminogen activator (uPA) is inhibited by PN-1. MMP-9 augmented uPA activity in the medium of PC3-ML cells by degrading PN-1. Prostate cancer cells, overexpressing PN-1 or treated with MMP-9 shRNA, had reduced cell invasion in Matrigel. PN-1 siRNA restored uPA activity and the invasive capacity. PN-1 mutated in the serpin inhibitory domain, the reactive center loop, failed to inhibit uPA and to reduce Matrigel invasion. This study shows a novel molecular pathway in which MMP-9 regulates uPA activity and tumor cell invasion through cleavage of PN-1.

LRP-1 promotes cancer cell invasion by supporting ERK and inhibiting JNK signaling pathways

Background

The low-density lipoprotein receptor-related protein-1 (LRP-1) is an endocytic receptor mediating the clearance of various extracellular molecules involved in the dissemination of cancer cells. LRP-1 thus appeared as an attractive receptor for targeting the invasive behavior of malignant cells. However, recent results suggest that LRP-1 may facilitate the development and growth of cancer metastases in vivo, but the precise contribution of the receptor during cancer progression remains to be elucidated. The lack of mechanistic insights into the intracellular signaling networks downstream of LRP-1 has prevented the understanding of its contribution towards cancer.

Methodology/Principal Findings

Through a short-hairpin RNA-mediated silencing approach, we identified LRP-1 as a main regulator of ERK and JNK signaling in a tumor cell context. Co-immunoprecipitation experiments revealed that LRP-1 constitutes an intracellular docking site for MAPK containing complexes. By using pharmacological agents, constitutively active and dominant-negative kinases, we demonstrated that LRP-1 maintains malignant cells in an adhesive state that is favorable for invasion by activating ERK and inhibiting JNK. We further demonstrated that the LRP-1-dependent regulation of MAPK signaling organizes the cytoskeletal architecture and mediates adhesive complex turnover in cancer cells. Moreover, we found that LRP-1 is tethered to the actin network and to focal adhesion sites and controls ERK and JNK targeting to talin-rich structures.

Conclusions

We identified ERK and JNK as the main molecular relays by which LRP-1 regulates focal adhesion disassembly of malignant cells to support invasion.

SERPINB3 induces epithelial-mesenchymal transition

Epithelial-mesenchymal transition is believed to facilitate invasion and metastasis formation of epithelial tumour cells. SERPINB3 is a serine protease inhibitor, physiologically found in normal squamous epithelium but over-expressed in epithelial tumours and known to inhibit apoptosis. We tested the hypothesis that SERPINB3 has a role in invasion by modulating the epithelial-mesenchymal transition programme, using morphological, molecular and cell biology techniques on HepG2 cell clones transfected with the human SERPINB3 gene. The paracrine effect of this serpin was determined by the addition of exogenous recombinant SERPINB3 protein to HepG2 and MDCK cell line. SERPINB3 expression leads to changes in transfected cells morphology, characterized by clusters of loosely connected cells with elongated shape. Ultrastructural analysis confirmed the decrease of desmosomal junctions and widening of intercellular spaces. These alterations were associated with a reduction of E-cadherin and an increase of beta-catenin, with a parallel increase of cell proliferation. SERPINB3 clones, untransfected HepG2 and MDCK cells treated with exogenous SERPINB3 expressed vimentin, undetectable in controls. SERPINB3 induced significant cell scattering, migration and invasiveness in untransfected cells. These effects were not dependent on the anti-protease activity of the protein, as documented by the results obtained with an active loop-deleted recombinant SERPINB3 protein. Scatter activity was inhibited by an anti-SERPINB3 antibody in a dose-dependent manner and SERPINB3-transfected cells formed a significantly higher number of colonies on soft agar than controls. In conclusion, the observed results indicate that SERPINB3 induces deregulation of adhesion processes and increases the invasiveness potential supported by features of epithelial-mesenchymal transition, acting at both the autocrine and the paracrine level.

Impaired fear extinction in mice lacking protease nexin-1

The serine protease inhibitor protease-nexin-1 (PN-1) has been shown to modulate N-methyl-d-aspartate receptor (NMDAR)-mediated synaptic currents and NMDAR-dependent long-term potentiation of synaptic transmission. Here, we analysed the role of PN-1 in the acquisition and extinction of classical auditory fear conditioning, two distinct forms of learning that both depend on NMDAR activity in the amygdala. Immunostaining revealed that PN-1 is expressed throughout the amygdala, primarily in gamma-aminobutyric acid containing neurons of the central amygdala and intercalated cell masses (ITCs) and in glia. Fear extinction was severely impaired in mice lacking PN-1 (PN-1 KO). Consistent with a role for the basal nucleus of the amygdala in fear extinction, we found that, compared with wild-type (WT) littermate controls, PN-1 KO mice exhibited decreased numbers of Fos-positive neurons in the basal nucleus after extinction. Moreover, immunoblot analysis of laser-microdissected amygdala sub-nuclei revealed specific extinction-induced increases in the level of phosphorylated alpha-calcium/calmodulin protein kinase II in the medial ITCs and in the lateral subdivision of the central amygdala in WT mice. These responses were altered in PN-1 KO mice. Together, these data indicate that lack of extinction in PN-1 KO mice is associated with distinct changes in neuronal activity across the circuitry of the basal and central nuclei and the ITCs, supporting a differential impact on fear extinction of these amygdala substructures. They also suggest a new role for serine protease inhibitors such as PN-1 in modulating fear conditioning and extinction.