p11 regulates extracellular plasmin production and invasiveness of HT1080 fibrosarcoma cells

BRD4L cooperates with MYC to block local tumor invasion via suppression of S100A10

Targeted therapy based on BRD4 and MYC shows promise due to their well-researched oncogenic functions in cancer, but their tumor-suppressive roles are less understood. In this study, we employ a systematic approach to delete exons that encode the low-complexity domain (LCD) of BRD4L in cells by using CRISPR-Cas9. In particular, the deletion of exon 14 (BRD4-E14) results in cellular morphological changes towards spindle-shaped and loosely packed. BRD4-E14 deficient cells show increased cell migration and reduced cell adhesion. The expression of S100A10 was significantly increased in cells lacking E14. BRD4L binds with MYC via the E14-encoded region of the LCD to inhibit the expression of S100A10. In cancer tissues, there is a positive correlation between BRD4 and MYC, while both of these proteins are negatively associated with S100A10 expression. Finally, knocking out the BRD4-E14 region or MYC promotes tumor growth in vivo. Together, these data support a tumor-suppressive role of BRD4L and MYC in some contexts. This discovery emphasizes the significance of a discreetly design and precise patient recruitment in clinical trials that testing cancer therapy based BRD4 and MYC.

Identification and characterization of calreticulin as a novel plasminogen receptor

Calreticulin (CRT) was originally identified as a key calcium-binding protein of the endoplasmic reticulum. Subsequently, CRT was shown to possess multiple intracellular functions, including roles in calcium homeostasis and protein folding. Recently, several extracellular functions have been identified for CRT, including roles in cancer cell invasion and phagocytosis of apoptotic and cancer cells by macrophages. In the current report, we uncover a novel function for extracellular CRT and report that CRT functions as a plasminogen-binding receptor that regulates the conversion of plasminogen to plasmin. We show that human recombinant or bovine tissue-derived CRT dramatically stimulated the conversion of plasminogen to plasmin by tissue plasminogen activator or urokinase-type plasminogen activator. Surface plasmon resonance analysis revealed that CRT-bound plasminogen (KD = 1.8 μM) with moderate affinity. Plasminogen binding and activation by CRT were inhibited by ε-aminocaproic acid, suggesting that an internal lysine residue of CRT interacts with plasminogen. We subsequently show that clinically relevant CRT variants (lacking four or eight lysines in carboxyl-terminal region) exhibited decreased plasminogen activation. Furthermore, CRT-deficient fibroblasts generated 90% less plasmin and CRT-depleted MDA MB 231 cells also demonstrated a significant reduction in plasmin generation. Moreover, treatment of fibroblasts with mitoxantrone dramatically stimulated plasmin generation by WT but not CRT-deficient fibroblasts. Our results suggest that CRT is an important cellular plasminogen regulatory protein. Given that CRT can empower cells with plasmin proteolytic activity, this discovery may provide new mechanistic insight into the established role of CRT in cancer.

Recent Advances in Molecular and Cellular Functions of S100A10

S100A10 (p11, annexin II light chain, calpactin light chain) is a multifunctional protein with a wide range of physiological activity. S100A10 is unique among the S100 family members of proteins since it does not bind to Ca2+, despite its sequence and structural similarity. This review focuses on studies highlighting the structure, regulation, and binding partners of S100A10. The binding partners of S100A10 were collated and summarized.

S100A10 Promotes Pancreatic Ductal Adenocarcinoma Cells Proliferation, Migration and Adhesion through JNK/LAMB3-LAMC2 Axis

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive tumors, characterized by diagnosis at an advanced stage and a poor prognosis. As a member of the S100 protein family, S100A10 regulates multiple biological functions related to cancer progression and metastasis. However, the role of S100A10 in PDAC is still not completely elucidated. In this study, we reported that S100A10 was significantly up-regulated in PDAC tissue and associated with a poor prognosis by integrated bioinformatic analysis and human PDAC tissue samples. In vitro, down-regulation of S100A10 reduced the proliferation, migration, and adhesion of PDAC cell lines, whereas up-regulation of S100A10 showed the opposite effect. Furthermore, LAMB3 was proved to be activated by S100A10 using RNA-sequencing and western blotting. The effect of LAMB3 on the proliferation, migration, and adhesion of PDAC cells was similar to that of S100A10. Up-regulation or down-regulation of LAMB3 could reverse the corresponding effect of S100A10. Moreover, we validated S100A10 activates LAMB3 through the JNK pathway, and LAMB3 was further proved to interact with LAMC2. Mice-bearing orthotopic pancreatic tumors showed that S100A10 knocked-down PANC-1 cells had a smaller tumor size than the control group. In conclusion, S100A10 promotes PDAC cells proliferation, migration, and adhesion through JNK/LAMB3-LAMC2 axis.

The ANXA2/S100A10 Complex—Regulation of the Oncogenic Plasminogen Receptor

The generation of the serine protease plasmin is initiated by the binding of its zymogenic precursor, plasminogen, to cell surface receptors. The proteolytic activity of plasmin, generated at the cell surface, plays a crucial role in several physiological processes, including fibrinolysis, angiogenesis, wound healing, and the invasion of cells through both the basement membrane and extracellular matrix. The seminal observation by Albert Fischer that cancer cells, but not normal cells in culture, produce large amounts of plasmin formed the basis of current-day observations that plasmin generation can be hijacked by cancer cells to allow tumor development, progression, and metastasis. Thus, the cell surface plasminogen-binding receptor proteins are critical to generating plasmin proteolytic activity at the cell surface. This review focuses on one of the twelve well-described plasminogen receptors, S100A10, which, when in complex with its regulatory partner, annexin A2 (ANXA2), forms the ANXA2/S100A10 heterotetrameric complex referred to as AIIt. We present the theme that AIIt is the quintessential cellular plasminogen receptor since it regulates the formation and the destruction of plasmin. We also introduce the term oncogenic plasminogen receptor to define those plasminogen receptors directly activated during cancer progression. We then discuss the research establishing AIIt as an oncogenic plasminogen receptor-regulated during EMT and activated by oncogenes such as SRC, RAS, HIF1α, and PML-RAR and epigenetically by DNA methylation. We further discuss the evidence derived from animal models supporting the role of S100A10 in tumor progression and oncogenesis. Lastly, we describe the potential of S100A10 as a biomarker for cancer diagnosis and prognosis.

Plasmin and Plasminogen System in the Tumor Microenvironment: Implications for Cancer Diagnosis, Prognosis, and Therapy

Simple Summary

In this review, we present a detailed discussion of how the plasminogen-activation system is utilized by tumor cells in their unrelenting attack on the tissues surrounding them. Plasmin is an enzyme which is responsible for digesting several proteins that hold the tissues surrounding solid tumors together. In this process tumor cells utilize the activity of plasmin to digest tissue barriers in order to leave the tumour site and spread to other parts of the body. We specifically focus on the role of plasminogen receptor—p11 which is an important regulatory protein that facilitates the conversion of plasminogen to plasmin and by this means promotes the attack by the tumour cells on their surrounding tissues.

Abstract

The tumor microenvironment (TME) is now being widely accepted as the key contributor to a range of processes involved in cancer progression from tumor growth to metastasis and chemoresistance. The extracellular matrix (ECM) and the proteases that mediate the remodeling of the ECM form an integral part of the TME. Plasmin is a broad-spectrum, highly potent, serine protease whose activation from its precursor plasminogen is tightly regulated by the activators (uPA, uPAR, and tPA), the inhibitors (PAI-1, PAI-2), and plasminogen receptors. Collectively, this system is called the plasminogen activation system. The expression of the components of the plasminogen activation system by malignant cells and the surrounding stromal cells modulates the TME resulting in sustained cancer progression signals. In this review, we provide a detailed discussion of the roles of plasminogen activation system in tumor growth, invasion, metastasis, and chemoresistance with specific emphasis on their role in the TME. We particularly review the recent highlights of the plasminogen receptor S100A10 (p11), which is a pivotal component of the plasminogen activation system.

S100A10 Has a Critical Regulatory Function in Mammary Tumor Growth and Metastasis: Insights Using MMTV-PyMT Oncomice and Clinical Patient Sample Analysis

Simple Summary

The key challenges that face patients during breast cancer therapy is the metastatic spread and aggressiveness of the disease. Thus, the goal of current breast cancer research is to discover new therapeutic and diagnostic targets that limit the aggressive spread of the cancer. In this study, we investigated the role of protein S100A10 (p11) in breast tumor growth, progression, and metastasis using mouse cancer models and patient tumor sample analysis. We have demonstrated in our previous studies that p11 is critical for the function of a proteolytic enzyme–plasmin, which aids in the digestion of the tissues surrounding the tumor and allows the escape of the cancer cells from the breast tissue to organs such as the lungs and bone. Here, we present evidence that genetic deletion of p11 results in smaller and less aggressive mammary tumors in mice. We also observed that the cancer spread to the lungs is dramatically reduced in the absence of p11 gene in mice. Subsequent analysis of breast cancer patient tissues showed a correlation between higher p11 expression and both poor survival and aggressive cancer.

Abstract

S100A10 (p11) is a plasminogen receptor that regulates cellular plasmin generation by cancer cells. In the current study, we used the MMTV-PyMT mouse breast cancer model, patient tumor microarray, and immunohistochemical (IHC) analysis to investigate the role of p11 in oncogenesis. The genetic deletion of p11 resulted in significantly decreased tumor onset, growth rate, and spontaneous pulmonary metastatic burden in the PyMT/p11-KO (knock-out) mice. This phenotype was accompanied by substantial reduction in Ki67 positivity, macrophage infiltration, decreased vascular density in the primary tumors, and decrease in invasive carcinoma and pulmonary metastasis. Surprisingly, IHC analysis of wild-type MMTV-PyMT mice failed to detect p11 expression in the tumors or metastatic tumor cells and loss of p11 did not decrease plasmin generation in the PyMT tumors and cells. Furthermore, tumor cells expressing p11 displayed dramatically reduced lung metastasis when injected into p11-depleted mice, further strengthening the stromal role of p11 in tumor growth and metastasis. Transcriptome analysis of the PyMT tumors from p11-KO mice showed marked reduction in genes such as Areg, Muc1, and S100a8 involved in breast cancer development, progression, and inflammation. The PyMT/p11-KO tumors displayed a remarkable increase in inflammatory cytokines such as interleukin (Il)-6, Il-10, and interferon (Ifn)-γ. Gene expression profiling and IHC of primary breast cancer samples showed that p11 mRNA and protein levels were significantly higher in tumor tissues compared to normal mammary tissue. P11 mRNA expression was significantly associated with poor patient prognosis and significantly elevated in high grade, triple negative (TN) tumors, and tumors with high proliferative index. This is the first study examining the crucial role of p11 in breast tumor development and metastasis, thus emphasizing its potential as a diagnostic and prognostic biomarker in breast cancer.

Development of an immune-related prognostic model for pediatric acute lymphoblastic leukemia patients

Background

Acute lymphoblastic leukemia (ALL) is the most common hematological malignancy in pediatrics, and immune‐related genes (IRGs) play crucial role in its development. Our study aimed to identify prognostic immune biomarkers of pediatric ALL and construct a risk assessment model.

Methods

Pediatric ALL patients’ gene expression data were downloaded from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) database. We screened differentially expressed IRGs (DEIRGs) between the relapse and non‐relapse groups. Cox regression analysis was used to identify optimal prognostic genes, then, a risk model was constructed, and its accuracy was verified in different cohorts.

Results

We screened 130 DEIRGs from 251 pediatric ALL samples. The top three pathways that DEIRGs may influence tumor progression are NABA matrisome‐associated, chemotaxis, and antimicrobial humoral response. A set of 84 prognostic DEIRGs was identified by using univariate Cox analysis. Then, Lasso regression and multivariate Cox regression analysis screened four optimal genes (PRDX2, S100A10, RORB, and SDC1), which were used to construct the prognostic risk model. The risk score was calculated and the survival analysis results showed that high‐risk score was associated with poor overall survival (OS) (p = 3.195 × 10⁻⁷). The time‐dependent survival receiver operating characteristic curves showed good prediction accuracy (Area Under Curves for 3‐year, 5‐year OS were 0.892 and 0.89, respectively). And the predictive performance of our risk model was successfully verified in testing cohort and entire cohort.

Conclusions

Our prognostic risk model can effectively divide pediatric ALL patients into high‐risk and low‐risk groups, which may help predict clinical prognosis and optimize individualized treatment.

Modulation of Ion Channels and Receptors by p11 (S100A10)

p11 (S100A10, annexin II light chain, calpactin I light chain) is a multifunctional protein that forms a heterotetrameric complex with Annexin A2, particularly at cell membranes. p11, alone or together with Annexin A2, interacts with several ion channels and receptors and regulates their cellular localization and function. Altered levels of p11 are implicated in the pathophysiology of several forms of cancer, psychiatric disorders, and neurodegeneration. Via interactions with ion channels and receptors, p11 modulates therapeutic actions of drugs targeting brain disorders. By serving as a plasminogen receptor, p11 plays an important role in plasmin generation, fibrinolysis, angiogenesis, tumor progression, and metastasis. Here, we review mechanisms whereby p11 regulates functions of ion channels and receptors in health and disease states.

Identification and Analysis of Dysfunctional Genes and Pathways in CD8+ T Cells of Non-Small Cell Lung Cancer Based on RNA Sequencing

Lung cancer, the most common of malignant tumors, is typically of the non-small cell (NSCLC) type. T-cell-based immunotherapies are a promising and powerful approach to treating NSCLCs. To characterize the CD8⁺ T cells of non-small cell lung cancer, we re-analyzed the published RNA-Seq gene expression profiles of 36 CD8⁺ T cell isolated from tumor (TIL) samples and 32 adjacent uninvolved lung (NTIL) samples. With an advanced Monte Carlo method of feature selection, we identified the CD8⁺ TIL specific expression patterns. These patterns revealed the key dysfunctional genes and pathways in CD8⁺ TIL and shed light on the molecular mechanisms of immunity and use of immunotherapy.

Critical role and its underlying molecular events of the plasminogen receptor, S100A10 in malignant tumor and non-tumor diseases

S100A10 is a small molecular weight protein expressed in the cytoplasm of many cells and one of the members of the S100 protein family that binds calcium and forms the largest subgroup of EF-hand proteins. The regulatory processes of S100A10 are complicated. S100A10 participates in the regulation of a variety of tumor and non-tumor diseases through cascade reactions with multitudinous signaling molecules. In malignant tumors, such as acute promyelocytic leukemia (APL) and lung cancer, S100A10 is likely involved in their progression, including invasion and metastasis through the regulation of plasmin production and subsequent plasmin-dependent stimulation of other proteases, such as matrix metalloproteinase (MMP)-2 and -9. Both the plasmin and MMPs are capable of inducing degradation of the extracellular matrix (ECM) and basement membrane, which is a critical step for tumor progression. In non-tumor diseases, the distribution of S100A10 in the brain and its interaction with 5-hydroxytryptamine 1B (5-HT1B) receptor, an important mediator in the central nervous system that maintains a dynamic balance of the neurotransmitters, correlates with depression-like behavior. S100A10 also participates in inflammatory responses through the regulation of peripheral macrophage migration to the inflammatory sites, which depends on the generation of plasmin and other proteinases at the surface of macrophages. Considerable attention should be paid to understand the significant role of S100A10 in the modulation of malignant tumor and non-tumor diseases.

Multiple functions of S100A10, an important cancer promoter

The S100 group of calcium binding proteins is composed of 21 members that exhibit tissue/cell specific expressions. These S100 proteins bind a diverse range of targets and regulate multiple cellular processes, including proliferation, migration and differentiation. S100A10, also known as p11, binds mainly to annexin A2 and mediates the conversion of plasminogen to an active protease, plasmin. Higher S100A10 expression has been reported to link to worse outcome and/or chemoresistance in a number of cancer types in lung, breast, ovary, pancreas, gall bladder and colorectum and leukemia although some discrepancy was reported. In this review, we focused on the roles of the S100A10 in cancer. We summarized its biological functions, role in cancer progression, prognostic value and targeting of S100A10 for cancer therapy.

S100A10 and Cancer Hallmarks: Structure, Functions, and its Emerging Role in Ovarian Cancer

S100A10, which is also known as p11, is located in the plasma membrane and forms a heterotetramer with annexin A2. The heterotetramer, comprising of two subunits of annexin A2 and S100A10, activates the plasminogen activation pathway, which is involved in cellular repair of normal tissues. Increased expression of annexin A2 and S100A10 in cancer cells leads to increased levels of plasmin—which promotes the degradation of the extracellular matrix—increased angiogenesis, and the invasion of the surrounding organs. Although many studies have investigated the functional role of annexin A2 in cancer cells, including ovarian cancer, S100A10 has been less studied. We recently demonstrated that high stromal annexin A2 and high cytoplasmic S100A10 expression is associated with a 3.4-fold increased risk of progression and 7.9-fold risk of death in ovarian cancer patients. Other studies have linked S100A10 with multidrug resistance in ovarian cancer; however, no functional studies to date have been performed in ovarian cancer cells. This article reviews the current understanding of S100A10 function in cancer with a particular focus on ovarian cancer.

CPT1A-mediated succinylation of S100A10 increases human gastric cancer invasion

Gastric cancer (GC) is a malignancy of the lining of the stomach and is prone to distant metastasis, which involves a variety of complex molecules. The S100 proteins are a family of calcium-binding cytosolic proteins that possess a wide range of intracellular and extracellular functions and play pivotal roles in the invasion and migration of tumour cells. Among these, S100A10 is known to be overexpressed in GC. Lysine succinylation, a recently identified form of protein post-translational modification, is an important regulator of cellular processes. Here, we demonstrated that S100A10 was succinylated at lysine residue 47 (K47), and levels of succinylated S100A10 were increased in human GC. Moreover, K47 succinylation of S100A10 was stabilized by suppression of ubiquitylation and subsequent proteasomal degradation. Furthermore, carnitine palmitoyltransferase 1A (CPT1A) was found to function as a lysine succinyltransferase that interacts with S100A10. Succinylation of S100A10 is regulated by CPT1A, while desuccinylation is regulated by SIRT5. Overexpression of a succinylation mimetic mutant, K47E S100A10, increased cell invasion and migration. Taken together, this study reveals a novel mechanism of S100A10 accumulation mediated by succinylation in GC, which promotes GC progression and is regulated by the succinyltransferase CPT1A and SIRT5-mediated desuccinylation.

S100A10, a novel biomarker in pancreatic ductal adenocarcinoma

Pancreatic cancer is arguably the deadliest cancer type. The efficacy of current therapies is often hindered by the inability to predict patient outcome. As such, the development of tools for early detection and risk prediction is key for improving outcome and quality of life. Here, we introduce the plasminogen receptor S100A10 as a novel predictive biomarker and a driver of pancreatic tumor growth and invasion. We demonstrated that S100A10 mRNA and protein are overexpressed in human pancreatic tumors compared to normal ducts and nonductal stroma. S100A10 mRNA and methylation status were predictive of overall survival and recurrence-free survival across multiple patient cohorts. S100A10 expression was driven by promoter methylation and the oncogene KRAS. S100A10 knockdown reduced surface plasminogen activation, invasiveness, and in vivo growth of pancreatic cancer cell lines. These findings delineate the clinical and functional contribution of S100A10 as a biomarker in pancreatic cancer.

Regulation of cell surface protease receptor S100A10 by retinoic acid therapy in acute promyelocytic leukemia (APL)☆

S100A10 (p11), a member of the S100 family of small dimeric EF-hand-type Ca²⁺-binding proteins, plays a role in a variety of both intracellular and extracellular processes. Previous studies have suggested that p11 is intrinsically unstable and requires binding to annexin A2 (p36) to prevent its rapid ubiquitylation and degradation. Our laboratory has shown that p11 levels are stimulated by the expression of the oncoprotein, PML/RARα. Furthermore, treatment of the APL cell line, NB4 with all-trans retinoic acid (ATRA) causes the rapid loss of p36 and p11 protein. However, the mechanism by which ATRA regulates p11 levels has not been established. Here, we show that the proteasomal inhibitor, lactacystin reversed the ATRA-dependent loss of p11, but did not cause an accumulation of ubiquitylated forms of p11, suggesting that ATRA promotes the proteasomal degradation of p11 in an ubiquitin-independent manner. ATRA treatment of MCF-7 breast cancer cells reduced p11 but not p36 transcript and protein levels, thus indicating that ATRA can regulate p11 levels independently of PML/RARα and p36. Overexpression of p36 upregulated p11 protein but not mRNA levels, indicating that p36 affects p11 post translationally. The forced expression of ubiquitin and p11 in 293 T cells resulted in ubiquitylation of p11 that was blocked by mutagenesis of lysine 57. This study highlights the complex regulation of p11 by retinoid signaling and challenges the hypothesis that ubiquitin-mediated proteasomal degradation of p11 represents a universal mechanism of regulation of this protein.

Cell surface protease activation during RAS transformation: Critical role of the plasminogen receptor, S100A10

The link between oncogenic RAS expression and the acquisition of the invasive phenotype has been attributed to alterations in cellular activities that control degradation of the extracellular matrix. Oncogenic RAS-mediated upregulation of matrix metalloproteinase 2 (MMP-2), MMP-9 and urokinase-type plasminogen activator (uPA) is critical for invasion through the basement membrane and extracellular matrix. The uPA converts cell surface-bound plasminogen to plasmin, a process that is regulated by the binding of plasminogen to specific receptors on the cell surface, however, the identity of the plasminogen receptors that function in this capacity is unclear. We have observed that transformation of cancer cells with oncogenic forms of RAS increases plasmin proteolytic activity by 2- to 4-fold concomitant with a 3-fold increase in cell invasion. Plasminogen receptor profiling revealed RAS-dependent increases in both S100A10 and cytokeratin 8. Oncogenic RAS expression increased S100A10 gene expression which resulted in an increase in S100A10 protein levels. Analysis with the RAS effector-loop mutants that interact specifically with Raf, Ral GDS pathways highlighted the importance of the RalGDS pathways in the regulation of S100A10 gene expression. Depletion of S100A10 from RAS-transformed cells resulted in a loss of both cellular plasmin generation and invasiveness. These results strongly suggest that increases in cell surface levels of S100A10, by oncogenic RAS, plays a critical role in RAS-stimulated plasmin generation, and subsequently, in the invasiveness of oncogenic RAS expressing cancer cells.

Prognostic Roles of mRNA Expression of S100 in Non-Small-Cell Lung Cancer

The S100 protein family is involved in cancer cell invasion and metastasis, but its prognostic value in non-small-cell lung cancer (NSCLC) has not been elucidated. In the present study we investigated the prognostic role of mRNA expression of each individual S100 in NSCLC patients through the Kaplan-Meier plotter (KM plotter) database. Expression of 14 members of the S100 family correlated with overall survival (OS) for all NSCLC patients; 18 members were associated with OS in adenocarcinoma, but none were associated with OS in squamous cell carcinoma. In particular, high mRNA expression level of S100B was associated with better OS in NSCLC patients. The prognostic value of S100 according to smoking status, pathological grades, clinical stages, and chemotherapeutic treatment of NSCLC was further assessed. Although the results should be further verified in clinical trials our findings provide new insights into the prognostic roles of S100 proteins in NSCLC and might promote development of S100-targeted inhibitors for the treatment of NSCLC.

Hedgehog signaling stimulates Tenascin C to promote invasion of pancreatic ductal adenocarcinoma cells through Annexin A2

Pancreatic adenocarcinoma (PDA) is characterized by a dense desmoplastic reaction that comprises 60-90% of the tumor, while only 10-40% of the tumor is composed of malignant epithelial cells. This desmoplastic reaction is composed of stromal fibroblast cells, extracellular matrix proteins, and immune cells. Accumulating evidence has suggested that the stromal and epithelial cell compartments interact during the pathogenesis of this disease. Therefore, it is important to identify the signaling pathways responsible for this interaction to better understand the mechanisms by which PDA invades and metastasizes. Here, we show that secreted stromal factors induce invasion of PDA cells. Specifically, hedgehog signaling from the tumor cells induces tenascin C (TnC) secretion from the stromal cells that acts back upon the tumor cells in a paracrine fashion to induce the invasion of PDA cells through its' receptor annexin A2 (AnxA2). Therefore, blocking the interaction between TnC and AnxA2 has the potential to prevent liver metastasis in PDA.

Mechanism of plasmin generation by S100A10

Plasminogen (Pg) is cleaved to form plasmin by the action of specific plasminogen activators such as the tissue plasminogen activator (tPA). Although the interaction of tPA and Pg with the surface of the fibrin clot has been well characterised, their interaction with cell surface Pg receptors is poorly understood. S100A10 is a cell surface Pg receptor that plays a key role in cellular plasmin generation. In the present report, we have utilised domain-switched/deleted variants of tPA, truncated plasminogen variants and S100A10 site-directed mutant proteins to define the regions responsible for S100A10-dependent plasmin generation. In contrast to the established role of the finger domain of tPA in fibrin-stimulated plasmin generation, we show that the kringle-2 domain of tPA plays a key role in S100A10-dependent plasmin generation. The kringle-1 domain of plasminogen, indispensable for fibrin-binding, is also critical for S100A10-dependent plasmin generation. S100A10 retains activity after substitution or deletion of the carboxyl-terminal lysine suggesting that internal lysine residues contribute to its plasmin generating activity. These studies define a new paradigm for plasminogen activation by the plasminogen receptor, S100A10.

Disruption of Annexin II /p11 Interaction Suppresses Leukemia Cell Binding, Homing and Engraftment, and Sensitizes the Leukemia Cells to Chemotherapy

The bone marrow microenvironment plays an important role in acute lymphoblastic leukemia (ALL) cell proliferation, maintenance, and resistance to chemotherapy. Annexin II (ANX2) is abundantly expressed on bone marrow cells and complexes with p11 to form ANX2/p11-hetero-tetramer (ANX2T). We present evidence that p11 is upregulated in refractory ALL cell lines and patient samples. A small molecule inhibitor that disrupts ANX2/p11 interaction (ANX2T inhibitor), an anti-ANX2 antibody, and knockdown of p11, abrogated ALL cell adhesion to osteoblasts, indicating that ANX2/p11 interaction facilitates binding and retention of ALL cells in the bone marrow. Furthermore, ANX2T inhibitor increased the sensitivity of primary ALL cells co-cultured with osteoblasts to dexamethasone and vincristine induced cell death. Finally, in an orthotopic leukemia xenograft mouse model, the number of ALL cells homing to the bone marrow was reduced by 40-50% in mice injected with anti-ANX2 antibody, anti-p11 antibody or ANX2T inhibitor compared to respective controls. In a long-term engraftment assay, the percentage of ALL cells in mouse blood, bone marrow and spleen was reduced in mice treated with agents that disrupt ANX2/p11 interaction. These data show that disruption of ANX2/p11 interaction results in reduced ALL cell adhesion to osteoblasts, increased ALL cell sensitization to chemotherapy, and suppression of ALL cell homing and engraftment.

Metal ion mediated transition from random coil to β-sheet and aggregation of Bri2-23, a natural inhibitor of Aβ aggregation

Soft metal ion binding enforces critical rearrangement of the structure of Bri2-23, a natural inhibitor of Aβ aggregation, thus shifting its solution behavior to a self aggregating system.

On the contribution of S100A10 and annexin A2 to plasminogen activation and oncogenesis: an enduring ambiguity

ABSTRACT 

Plasminogen receptors are becoming increasingly relevant in regulating many diseases such as cancer, stroke and inflammation. However, controversy has emerged concerning the putative role of some receptors, in particular annexin A2, in binding plasminogen. Several reports failed to account for the effects of annexin A2 on the stability and conformation of its binding partner S100A10. This has created an enduring ambiguity as to the actual function of annexin A2 in plasmin regulation. Supported by a long line of evidence, we conclude that S100A10, and not annexin A2, is the primary plasminogen receptor within the annexin A2-S100A10 complex and contributes to the plasmin-mediated effects that were originally ascribed to annexin A2.

Dynamic reciprocity: the role of annexin A2 in tissue integrity

Interactions between cells and the extracellular matrix are integral to tissue development, remodelling and pathogenesis. This is underlined by bi-directional flow of information signalling, referred to as dynamic reciprocity. Annexin A2 is a complex and multifunctional protein that belongs to a large family of Ca(2+)-dependent anionic phospholipid and membrane-binding proteins. It has been implicated in diverse cellular processes at the nuclear, cytoplasmic and extracellular compartments including Ca(2+)-dependent regulation of endocytosis and exocytosis, focal adhesion dynamics, transcription and translation, cell proliferation, oxidative stress and apoptosis. Most of these functions are mediated by the annexin A2-S100A10 heterotetramer (AIIt) via its ability to simultaneously interact with cytoskeletal, membrane and extracellular matrix components, thereby mediating regulatory effects of extracellular matrix adhesion on cell behaviour and vice versa. While Src kinase-mediated phosphorylation of filamentous actin-bound AIIt results in membrane-cytoskeletal remodelling events which control cell polarity, cell morphology and cell migration, AIIt at the cell surface can bind to a number of extracellular matrix proteins and catalyse the activation of serine and cysteine proteases which are important in facilitating tissue remodelling during tissue repair, neoangiogenesis and pathological situations. This review will focus on the role of annexin A2 in regulating tissue integrity through intercellular and cell-extracellular matrix interaction. Annexin A2 is differentially expressed in various tissue types as well as in many pathologies, particularly in several types of cancer. These together suggest that annexin A2 acts as a central player during dynamic reciprocity in tissue homeostasis.

Joining S100 proteins and migration: for better or for worse, in sickness and in health

The vast diversity of S100 proteins has demonstrated a multitude of biological correlations with cell growth, cell differentiation and cell survival in numerous physiological and pathological conditions in all cells of the body. This review summarises some of the reported regulatory functions of S100 proteins (namely S100A1, S100A2, S100A4, S100A6, S100A7, S100A8/S100A9, S100A10, S100A11, S100A12, S100B and S100P) on cellular migration and invasion, established in both culture and animal model systems and the possible mechanisms that have been proposed to be responsible. These mechanisms involve intracellular events and components of the cytoskeletal organisation (actin/myosin filaments, intermediate filaments and microtubules) as well as extracellular signalling at different cell surface receptors (RAGE and integrins). Finally, we shall attempt to demonstrate how aberrant expression of the S100 proteins may lead to pathological events and human disorders and furthermore provide a rationale to possibly explain why the expression of some of the S100 proteins (mainly S100A4 and S100P) has led to conflicting results on motility, depending on the cells used.

Annexin A2: its molecular regulation and cellular expression in cancer development

Annexin A2 (ANXA2) orchestrates multiple biologic processes and clinical associations, especially in cancer progression. The structure of ANXA2 affects its cellular localization and function. However, posttranslational modification and protease-mediated N-terminal cleavage also play critical roles in regulating ANXA2. ANXA2 expression levels vary among different types of cancers. With some cancers, ANXA2 can be used for the detection and diagnosis of cancer and for monitoring cancer progression. ANXA2 is also required for drug-resistance. This review discusses the feasibility of ANXA2 which is active in cancer development and can be a therapeutic target in cancer management.

New insights into the role of Plg-RKT in macrophage recruitment

Plasminogen (PLG) is the zymogen of plasmin, the major enzyme that degrades fibrin clots. In addition to its binding and activation on fibrin clots, PLG also specifically interacts with cell surfaces where it is more efficiently activated by PLG activators, compared with the reaction in solution. This results in association of the broad-spectrum proteolytic activity of plasmin with cell surfaces that functions to promote cell migration. Here, we review emerging data establishing a role for PLG, plasminogen receptors and the newly discovered plasminogen receptor, Plg-RKT, in macrophage recruitment in the inflammatory response, and we address mechanisms by which the interplay between PLG and its receptors regulates inflammation.

Plasminogen-stimulated inflammatory cytokine production by airway smooth muscle cells is regulated by annexin A2

Plasminogen has a role in airway inflammation. Airway smooth muscle (ASM) cells cleave plasminogen into plasmin, a protease with proinflammatory activity. In this study, the effect of plasminogen on cytokine production by human ASM cells was investigated in vitro. Levels of IL-6 and IL-8 in the medium of ASM cells were increased by incubation with plasminogen (5-50 μg/ml) for 24 hours (P < 0.05; n = 6-9), corresponding to changes in the levels of cytokine mRNA at 4 hours. The effects of plasminogen were attenuated by α2-antiplasmin (1 μg/ml), a plasmin inhibitor (P < 0.05; n = 6-12). Exogenous plasmin (5-15 mU/ml) also stimulated cytokine production (P < 0.05; n = 6-8) in a manner sensitive to serine-protease inhibition by aprotinin (10 KIU/ml). Plasminogen-stimulated cytokine production was increased in cells pretreated with basic fibroblast growth factor (300 pM) in a manner associated with increases in urokinase plasminogen activator expression and plasmin formation. The knockdown of annexin A2, a component of the putative plasminogen receptor comprised of annexin A2 and S100A10, attenuated plasminogen conversion into plasmin and plasmin-stimulated cytokine production by ASM cells. Moreover, a role for annexin A2 in airway inflammation was demonstrated in annexin A2-/- mice in which antigen-induced increases in inflammatory cell number and IL-6 levels in the bronchoalveolar lavage fluid were reduced (P < 0.01; n = 10-14). In conclusion, plasminogen stimulates ASM cytokine production in a manner regulated by annexin A2. Our study shows for the first time that targeting annexin A2-mediated signaling may provide a novel therapeutic approach to the treatment of airway inflammation in diseases such as chronic asthma.

Plasminogen receptors: the first quarter century

The interaction of plasminogen with cell surfaces results in promotion of plasmin formation and retention on the cell surface. This results in arming cell surfaces with the broad-spectrum proteolytic activity of plasmin. Over the past quarter century, key functional consequences of the association of plasmin with the cell surface have been elucidated. Physiologic and pathophysiologic processes with plasmin-dependent cell migration as a central feature include inflammation, wound healing, oncogenesis, metastasis, myogenesis, and muscle regeneration. Cell surface plasmin also participates in neurite outgrowth and prohormone processing. Furthermore, plasmin-induced cell signaling also affects the functions of inflammatory cells, via production of cytokines, reactive oxygen species, and other mediators. Finally, plasminogen receptors regulate fibrinolysis. In this review, we highlight emerging data that shed light on longstanding controversies and raise new issues in the field. We focus on (1) the impact of the recent X-ray crystal structures of plasminogen and the development of antibodies that recognize cell-induced conformational changes in plasminogen on our understanding of the interaction of plasminogen with cells; (2) the relationship between apoptosis and plasminogen binding to cells; (3) the current status of our understanding of the molecular identity of plasminogen receptors and the discovery of a structurally unique novel plasminogen receptor, Plg-RKT; (4) the determinants of the interplay between distinct plasminogen receptors and cellular functions; and (5) new insights into the role of colocalization of plasminogen and plasminogen activator receptors on the cell surface.

Annexin A2 heterotetramer: structure and function

Annexin A2 is a pleiotropic calcium- and anionic phospholipid-binding protein that exists as a monomer and as a heterotetrameric complex with the plasminogen receptor protein, S100A10. Annexin A2 has been proposed to play a key role in many processes including exocytosis, endocytosis, membrane organization, ion channel conductance, and also to link F-actin cytoskeleton to the plasma membrane. Despite an impressive list of potential binding partners and regulatory activities, it was somewhat unexpected that the annexin A2-null mouse should show a relatively benign phenotype. Studies with the annexin A2-null mouse have suggested important functions for annexin A2 and the heterotetramer in fibrinolysis, in the regulation of the LDL receptor and in cellular redox regulation. However, the demonstration that depletion of annexin A2 causes the depletion of several other proteins including S100A10, fascin and affects the expression of at least sixty-one genes has confounded the reports of its function. In this review we will discuss the annexin A2 structure and function and its proposed physiological and pathological roles.

Plasmin activity in the porcine airways is enhanced during experimental infection with Mycoplasma hyopneumoniae, is positively correlated with proinflammatory cytokine levels and is ameliorated by vaccination

In Mycoplasma hyopneumoniae (Mhp) infection of swine, the host immune response is considered a major driver of lung pathology; however the underlying inflammatory mechanisms are not well understood. The serine protease plasmin is being increasingly recognised as a significant player in inflammatory processes. Here we compare plasmin activity in tracheobronchial lavage fluid (TBLF) from pigs experimentally challenged with Mhp that were either unvaccinated (n=10), or vaccinated with the commercial vaccine Suvaxyn(®) M.hyo (n=10). TBLF collected immediately prior to challenge and at 21 d and 35 d post-challenge was also assayed for levels of proinflammatory cytokines (TNF-α, IL-1β and IL-6), and for bacterial load (by qPCR). Clinical signs, pathology, cytokine analyses and qPCR all indicated that vaccinated pigs had significantly reduced disease relative to unvaccinated animals. Plasmin activity increased significantly in TBLF collected at 21 d post-challenge compared to pre-challenge TBLF in unvaccinated (P<0.01), but not vaccinated animals (P>0.05). A significant correlation was observed between bacterial load and plasmin activity in the 21 d (r=0.66; P<0.01) and the 35 d post-challenge samples, (r=0.62; P<0.01). Plasmin activity was also significantly correlated with levels of TNF-α, IL-1β and IL-6 at 21 d (r=0.78, P<0.0001; r=0.77, P<0.0001; r=0.64, P<0.005) and with TNF-α and IL-1β at 35 d post-challenge (r=0.77, P<0.0001; r=0.74, P<0.0005). Our results indicate that plasminogen is activated to plasmin in the respiratory tract of pigs as part of the host inflammatory response to Mhp infection and that this effect is ameliorated by vaccination.

Plasminogen receptors and their role in the pathogenesis of inflammatory, autoimmune and malignant disease

Plasminogen is the proenzyme of plasmin, the key protease of the fibrinolytic system, but its role is not limited to fibrinolysis regulation. Plasminogen binds not only to fibrin, but also to different receptors on cell surfaces, including the heterotetrameric complex Annexin A2-S100A10, enolase-1, histone H2B and the plasminogen receptor Plg-R(KT) . These receptors localize plasmin generation to the cell surface and provide a broad spectrum of reactions including proteolytic activity, cell migration and recruitment as well as signaling pathway activation. These plasminogen-binding proteins are involved in both physiologic and pathologic processes such as inflammation, thrombosis and cancer. Thus, plasminogen is at the center of a complex tightly controlled and regulated system where plasminogen-binding proteins have a crucial role, suggesting new therapeutic and diagnostic strategies. This review will discuss currently available information on plasminogen receptors, particularly their mechanisms of action and their roles in inflammatory, autoimmune and malignant disease.

The biochemistry and regulation of S100A10: a multifunctional plasminogen receptor involved in oncogenesis

The plasminogen receptors mediate the production and localization to the cell surface of the broad spectrum proteinase, plasmin. S100A10 is a key regulator of cellular plasmin production and may account for as much as 50% of cellular plasmin generation. In parallel to plasminogen, the plasminogen-binding site on S100A10 is highly conserved from mammals to fish. S100A10 is constitutively expressed in many cells and is also induced by many diverse factors and physiological stimuli including dexamethasone, epidermal growth factor, transforming growth factor-α, interferon-γ, nerve growth factor, keratinocyte growth factor, retinoic acid, and thrombin. Therefore, S100A10 is utilized by cells to regulate plasmin proteolytic activity in response to a wide diversity of physiological stimuli. The expression of the oncogenes, PML-RARα and KRas, also stimulates the levels of S100A10, suggesting a role for S100A10 in pathophysiological processes such as in the oncogenic-mediated increases in plasmin production. The S100A10-null mouse model system has established the critical role that S100A10 plays as a regulator of fibrinolysis and oncogenesis. S100A10 plays two major roles in oncogenesis, first as a regulator of cancer cell invasion and metastasis and secondly as a regulator of the recruitment of tumor-associated cells, such as macrophages, to the tumor site.

Sanguisorba minor extract suppresses plasmin-mediated mechanisms of cancer cell migration

BACKGROUND

Sanguisorba minor, as well as several other edible herbs and vegetables, has been used extensively in traditional medicine. The observed beneficial effects can be attributed at least in part to the direct modulation of several enzymatic activities by its polyphenolic constituents.

METHODS

The ethanol extract of Sanguisorba minor was characterized by reversed-phase liquid chromatography, and most relevant analytes were identified by multiple stage mass spectrometry. The whole extract and the most relevant isolated constituents were tested for their ability to modulate the activity of human plasmin both toward a synthetic substrate and in human breast cancer cell culture models. Kinetic and equilibrium parameters were obtained by a concerted spectrophotometric and biosensor-based approach.

RESULTS

Quercetin-3-glucuronide was recognized as the compound mainly responsible for the in vitro plasmin inhibition by S. minor extract, with an inhibition constant in the high nanomolar range; in detail, our approach based on bioinformatic, enzymatic and binding analyses classified the inhibition as competitive. Most interestingly, cell-based assays showed that this flavonoid was effective in suppressing plasmin-induced loss of cancer cell adhesion.

GENERAL SIGNIFICANCE

Our results show that the extract from Sanguisorba minor limits plasmin-mediated tumor cell motility in vitro, mostly due to quercetin-3-glucuronide. This glucuronated flavonoid is a promising template for rational designing of anticancer drugs to be used in the treatment of pathological states involving the unregulated activity of plasmin.

The role of the annexin A2 heterotetramer in vascular fibrinolysis

The vascular endothelial cells line the inner surface of blood vessels and function to maintain blood fluidity by producing the protease plasmin that removes blood clots from the vasculature, a process called fibrinolysis. Plasminogen receptors play a central role in the regulation of plasmin activity. The protein complex annexin A2 heterotetramer (AIIt) is an important plasminogen receptor at the surface of the endothelial cell. AIIt is composed of 2 molecules of annexin A2 (ANXA2) bound together by a dimer of the protein S100A10. Recent work performed by our laboratory allowed us to clarify the specific roles played by ANXA2 and S100A10 subunits within the AIIt complex, which has been the subject of debate for many years. The ANXA2 subunit of AIIt functions to stabilize and anchor S100A10 to the plasma membrane, whereas the S100A10 subunit initiates the fibrinolytic cascade by colocalizing with the urokinase type plasminogen activator and receptor complex and also providing a common binding site for both tissue-type plasminogen activator and plasminogen via its C-terminal lysine residue. The AIIt mediated colocalization of the plasminogen activators with plasminogen results in the rapid and localized generation of plasmin to the endothelial cell surface, thereby regulating fibrinolysis.

Regulation of fibrinolysis by S100A10 in vivo

Endothelial cells form the inner lining of vascular networks and maintain blood fluidity by inhibiting blood coagulation and promoting blood clot dissolution (fibrinolysis). Plasmin, the primary fibrinolytic enzyme, is generated by the cleavage of the plasma protein, plasminogen, by its activator, tissue plasminogen activator. This reaction is regulated by plasminogen receptors at the surface of the vascular endothelial cells. Previous studies have identified the plasminogen receptor protein S100A10 as a key regulator of plasmin generation by cancer cells and macrophages. Here we examine the role of S100A10 and its annexin A2 binding partner in endothelial cell function using a homozygous S100A10-null mouse. Compared with wild-type mice, S100A10-null mice displayed increased deposition of fibrin in the vasculature and reduced clearance of batroxobin-induced vascular thrombi, suggesting a role for S100A10 in fibrinolysis in vivo. Compared with wild-type cells, endothelial cells from S100A10-null mice demonstrated a 40% reduction in plasminogen binding and plasmin generation in vitro. Furthermore, S100A10-deficient endothelial cells demonstrated impaired neovascularization of Matrigel plugs in vivo, suggesting a role for S100A10 in angiogenesis. These results establish an important role for S100A10 in the regulation of fibrinolysis and angiogenesis in vivo, suggesting S100A10 plays a critical role in endothelial cell function.

Gene therapy vectors with enhanced transfection based on hydrogels modified with affinity peptides

Regenerative strategies for damaged tissue aim to present biochemical cues that recruit and direct progenitor cell migration and differentiation. Hydrogels capable of localized gene delivery are being developed to provide a support for tissue growth, and as a versatile method to induce the expression of inductive proteins; however, the duration, level, and localization of expression is often insufficient for regeneration. We thus investigated the modification of hydrogels with affinity peptides to enhance vector retention and increase transfection within the matrix. PEG hydrogels were modified with lysine-based repeats (K4, K8), which retained approximately 25% more vector than control peptides. Transfection increased 5- to 15-fold with K8 and K4 respectively, over the RDG control peptide. K8- and K4-modified hydrogels bound similar quantities of vector, yet the vector dissociation rate was reduced for K8, suggesting excessive binding that limited transfection. These hydrogels were subsequently applied to an in vitro co-culture model to induce NGF expression and promote neurite outgrowth. K4-modified hydrogels promoted maximal neurite outgrowth, likely due to retention of both the vector and the NGF. Thus, hydrogels modified with affinity peptides enhanced vector retention and increased gene delivery, and these hydrogels may provide a versatile scaffold for numerous regenerative medicine applications.

Regulation of S100A10 by the PML-RAR-α oncoprotein

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia that results from the expression of the promyelocytic leukemia–retinoic acid receptor α (PML-RAR-α) oncoprotein. It is characterized by severe hemorrhagic complications due in part to excessive fibrinolysis, resulting from the excessive generation of the fibrinolytic enzyme, plasmin, at the cell surface of the PML cells. The treatment of patients with all-trans retinoic acid (ATRA) effectively ameliorates the disease by promoting the destruction of the PML-RAR-α oncoprotein. In the present study we show for the first time that the plasminogen receptor, S100A10, is present on the extracellular surface of APL cells and is rapidly down-regulated in response to all-trans retinoic acid. The loss of S100A10 is concomitant with a loss in fibrinolytic activity. Furthermore, the induced expression of the PML-RAR-α oncoprotein increased the expression of cell surface S100A10 and also caused a dramatic increase in fibrinolytic activity. Depletion of S100A10 by RNA interference effectively blocked the enhanced fibrinolytic activity observed after induction of the PML-RAR-α oncoprotein. These experiments show that S100A10 plays a crucial role in the generation of plasmin leading to fibrinolysis, thus providing a link to the clinical hemorrhagic phenotype of APL.

DLC1 interaction with S100A10 mediates inhibition of in vitro cell invasion and tumorigenicity of lung cancer cells through a RhoGAP-independent mechanism

The DLC1 gene encodes a Rho GTPase-activating protein (RhoGAP) that functions as a tumor suppressor in several common human cancers. The multidomain structure of DLC1 enables interaction with a number of other proteins. Here we report that the proinflammatory protein S100A10 (also known as p11), a key cell surface receptor for plasminogen which regulates pericellular proteolysis and tumor cell invasion, is a new binding partner of DLC1 in human cells. We determined that the 2 proteins colocalize in the cell cytoplasm and that their binding is mediated by central sequences in the central domain of DLC1 and the C-terminus of S100A10. Because the same S100A10 sequence also mediates binding to Annexin 2, we found that DLC1 competed with Annexin 2 for interaction with S100A10. DLC1 binding to S100A10 did not affect DLC1's RhoGAP activity, but it decreased the steady-state level of S100A10 expression in a dose-dependent manner by displacing it from Annexin 2 and making it accessible to ubiquitin-dependent degradation. This process attenuated plasminogen activation and resulted in inhibition of in vitro cell migration, invasion, colony formation, and anchorage-independent growth of aggressive lung cancer cells. These results suggest that a novel GAP-independent mechanism contributes to the tumor suppressive activity of DLC1, and highlight the importance and complexity of protein-protein interactions involving DLC1 in certain cancers.

Secretion of extracellular hsp90alpha via exosomes increases cancer cell motility: a role for plasminogen activation

Background

Metastasis is a multi-step process that is responsible for the majority of deaths in cancer patients. Current treatments are not effective in targeting metastasis. The molecular chaperone hsp90α is secreted from invasive cancer cells and activates MMP-2 to enhance invasiveness, required for the first step in metastasis.

Methods

We analyzed the morphology and motility of invasive cancer cells that were treated with exogenous exosomes in the presence or absence of hsp90α. We performed mass spectrometry and immunoprecipitation to identify plasminogen as a potential client protein of extracellular hsp90α. Plasmin activation assays and migration assays were performed to test if plasminogen is activated by extracellular hsp90α and has a role in migration.

Results

We found that hsp90α is secreted in exosomes in invasive cancer cells and it contributes to their invasive nature. We identified a novel interaction between hsp90α and tissue plasminogen activator that together with annexin II, also found in exosomes, activates plasmin. Extracellular hsp90α promotes plasmin activation as well as increases plasmin dependent cell motility.

Conclusions

Our data indicate that hsp90α is released by invasive cancer cells via exosomes and implicates hsp90α in activating plasmin, a second protease that acts in cancer cell invasion.

S100A10 regulates plasminogen-dependent macrophage invasion

The plasminogen activation system plays an integral role in the migration of macrophages in response to an inflammatory stimulus, and the binding of plasminogen to its cell-surface receptor initiates this process. Although previous studies from our laboratory have shown the importance of the plasminogen receptor S100A10 in cancer cell plasmin production, the potential role of this protein in macrophage migration has not been investigated. Using thioglycollate to induce a peritoneal inflammatory response, we demonstrate, for the first time, that compared with wild-type (WT) mice, macrophage migration across the peritoneal membrane into the peritoneal cavity in S100A10-deficient (S100A10(-/-)) mice was decreased by up to 53% at 24, 48, and 72 hours. Furthermore, the number of S100A10-deficient macrophages that infiltrated Matrigel plugs was reduced by 8-fold compared with their WT counterpart in vivo. Compared with WT macrophages, macrophages from S100A10(-/-) mice demonstrated a 50% reduction in plasmin-dependent invasion across a Matrigel barrier and a 45% reduction in plasmin generation in vitro. This loss in plasmin-dependent invasion was in part the result of a decreased generation of plasmin and a decreased activation of pro-MMP-9 by S100A10-deficient macrophages. This study establishes a direct involvement of S100A10 in macrophage recruitment in response to inflammatory stimuli.

Thrombomodulin suppresses invasiveness of HT1080 tumor cells by reducing plasminogen activation on the cell surface through activation of thrombin-activatable fibrinolysis inhibitor

Cell malignancy is negatively correlated with the expression of thrombomodulin (TM), a thrombin receptor expressed on the surface of various cells, including tumor cells. TM accelerates thrombin-activatable fibrinolysis inhibitor (TAFI) activation catalyzed by thrombin. The active form of TAFI (TAFIa) contributes to inhibition of plasmin formation through its carboxypeptidase B (CPB)-like activity. Here, we examined whether TM- and tumor cell-dependent TAFI activation participates in controlling pericellular fibrinolysis and cell invasion. Human fibrosarcoma HT1080 cells retained the ability to activate both prothrombin and plasminogen, but did not express TM. HT1080 cells mediated activation of TAFI in plasma in the presence of soluble-type TM (sTM) through cell-dependent prothrombin activation. HT1080 cells stably expressing TM (TM-HT1080) mediated plasma TAFI activation without added sTM, but HT1080 (wild-type) and Mock-transfected HT1080 cells (Mock) did not. Production of TAFIa suppressed cell-mediated plasminogen activation. Matrigel invasion by wild-type and Mock cells was enhanced two-fold by diluted plasma (10%), whereas the plasma-induced invasion of TM-HT1080 cells (65% of wild-type invasion) was lower than those of wild-type and Mock cells. Cell invasion by TM-HT1080 was partially enhanced by addition of a TAFIa/CPB inhibitor. These results suggest that TM suppresses pericellular fibrinolysis and plasma-induced tumor cell invasion, and that it is mediated, at least in part, by plasma TAFI activation.

Epigenetic deregulation of multiple S100 gene family members by differential hypomethylation and hypermethylation events in medulloblastoma

Deregulated expression of genes encoding members of the S100 family of calcium-binding proteins has been associated with the malignant progression of multiple tumour types. Using a pharmacological expression reactivation approach, we screened 16 S100 genes for evidence of epigenetic regulation in medulloblastoma, the most common malignant brain tumour of childhood. Four family members (S100A2, S100A4, S100A6 and S100A10) demonstrated evidence of upregulated expression in multiple medulloblastoma cell lines, following treatment with the DNA methyltransferase inhibitor, 5′-aza-2′-deoxycytidine. Subsequent analysis revealed methylation of critical CpG sites located within these four genes in an extended cell line panel. Assessment of these genes in the non-neoplastic cerebellum (from which medulloblastomas develop) revealed strong somatic methylation affecting S100A2 and S100A4, whereas S100A6 and S100A10 were unmethylated. Assessed against these normal tissue-specific methylation states, S100A6 and S100A10 demonstrated tumour-specific hypermethylation in medulloblastoma primary tumours (5 out of 40 and 4 out of 35, respectively, both 12%) and cell lines (both 7 out of 9, 78%), which was associated with their transcriptional silencing. Moreover, S100A6 hypermethylation was significantly associated with the aggressive large cell/anaplastic morphophenotype (P=0.026). In contrast, pro-metastatic S100A4 displayed evidence of hypomethylation relative to the normal cerebellum in a significant proportion primary tumours (7 out of 41, 17%) and cell lines (3 out of 9, 33%), which was associated with its elevated expression. In summary, these data characterise complex patterns of somatic methylation affecting S100 genes in the normal cerebellum and demonstrate their disruption causing epigenetic deregulation of multiple S100 family members in medulloblastoma development. Epigenetic events affecting S100 genes have potential clinical utility and merit further investigation as molecular biomarkers for this disease.

Evaluation of S100A10, annexin II and B-FABP expression as markers for renal cell carcinoma

This study aimed to analyze expression of S100A10, annexin II and B-FABP genes in renal cell carcinoma (RCC) and their potential value as tumor markers. Furthermore, any correlation between the gene expression and prognostic indicators of RCC was analyzed. Expression of each gene was estimated by RT-PCR in the non-neoplastic (normal) and tumorous parts of resected kidney samples. Also, each antigen was immunostained in RCC and normal kidney tissues. Expression of the S100A10 gene averaged 2.5-fold higher in the tumor than that in the normal tissues (n = 47), after standardization against that of beta-actin. However, expression of annexin II, a natural ligand of S100A10, was only 1.64-fold higher. In the tissue sections of RCC, S100A10 and annexin II were immunostained in membranes. In the normal renal epithelia, however, both antigens were stained in the Bowman's capsule and the tubules from Henle's loop through the collecting duct system, but not in the proximal tubules, from where most RCC are derived. In contrast, expression of the B-FABP gene was 20-fold higher in the tumor. No B-FABP was immunohistochemically detected in normal kidney sections, but it was stained in the cytoplasm of RCC tissue sections. S100A10 and B-FABP genes were overexpressed regardless of nuclear grade and stage of RCC. Immunopositivity in RCC tissues (n = 13) was 100% for S100A10 and annexin II, and 70% for B-FABP; however, no clear relationship was observed in either antigen with nuclear grade and stage. It was found that all three performed well as RCC markers. B-FABP was most specific to RCC, as it was expressed little in normal kidney tissues.

Role of Annexin-II in GI cancers: interaction with gastrins/progastrins

The role of the gastrin peptide hormones (G17, G34) and their precursors (progastrins, PG; gly-extended gastrin, G-gly), in gastrointestinal (GI) cancers has been extensively reviewed in recent years [W. Rengifo-Cam, P. Singh, Role of progastrins and gastrins and their receptors in GI and pancreatic cancers: targets for treatment, Curr. Pharm. Des. 10 (19) (2004) 2345-2358; M. Dufresne, C. Seva, D. Fourmy, Cholecystokinin and gastrin receptors, Physiol. Rev. 86 (3) (2006) 805-847; A. Ferrand, T.C. Wang, Gastrin and cancer: a review, Cancer Lett. 238 (1) (2006) 15-29]. A possible important role of progastrin peptides in colon carcinogenesis has become evident from experiments with transgenic mouse models [W. Rengifo-Cam, P. Singh, (2004); A. Ferrand, T.C. Wang, (2006)]. It is now known that growth stimulatory and co-carcinogenic effects of gastrin/PG peptides are mediated by both proliferative and anti-apoptotic effects of the peptides on target cells [H. Wu, G.N. Rao, B. Dai, P. Singh, Autocrine gastrins in colon cancer cells Up-regulate cytochrome c oxidase Vb and down-regulate efflux of cytochrome c and activation of caspase-3, J. Biol. Chem. 275 (42) (2000) 32491-32498; H. Wu, A. Owlia, P. Singh, Precursor peptide progastrin(1-80) reduces apoptosis of intestinal epithelial cells and upregulates cytochrome c oxidase Vb levels and synthesis of ATP, Am. J. Physiol. Gastrointest. Liver Physiol. 285 (6) (2003) G1097-G1110]. Several receptor subtypes have been described that mediate growth effects of gastrin peptides [W. Rengifo-Cam, P. Singh (2004); M. Dufresne, C. Seva, D. Fourmy, (2006)]. Recently, we identified Annexin II as a high affinity binding protein for gastrin/PG peptides [P. Singh, H. Wu, C. Clark, A. Owlia, Annexin II binds progastrin and gastrin-like peptides, and mediates growth factor effects of autocrine and exogenous gastrins on colon cancer and intestinal epithelial cells, Oncogene (2006), doi:10.1038/sj.onc.1209798]. Importantly, the expression of Annexin II was required for mediating growth stimulatory effects of gastrin and PG peptides on intestinal epithelial and colon cancer cells [P. Singh, H. Wu, C. Clark, A. Owlia, Annexin II binds progastrin and gastrin-like peptides, and mediates growth factor effects of autocrine and exogenous gastrins on colon cancer and intestinal epithelial cells, Oncogene (2006), doi:10.1038/sj.onc.1209798], suggesting that Annexin-II may represent the elusive novel receptor for gastrin/PG peptides. The importance of this finding in relation to the structure and function of Annexin-II, especially in GI cancers, is described below. Since this surprising finding represents a new front in our understanding of the mechanisms involved in mediating growth effects of gastrin/PG peptides in GI cancers, our current understanding of the role of Annexin-II in proliferation and metastasis of cancer cells is additionally reviewed.