Perlecan knockdown in metastatic prostate cancer cells reduces heparin-binding growth factor responses in vitro and tumor growth in vivo

The extracellular matrix component perlecan/HSPG2 regulates radioresistance in prostate cancer cells

Radiotherapy of prostate cancer (PC) can lead to the acquisition of radioresistance through molecular mechanisms that involve, in part, cell adhesion-mediated signaling. To define these mechanisms, we employed a DU145 PC model to conduct a comparative mass spectrometry-based proteomic analysis of the purified integrin nexus, i.e., the cell-matrix junction where integrins bridge assembled extracellular matrix (matrisome components) to adhesion signaling complexes (adhesome components). When parental and radioresistant cells were compared, the expression of integrins was not changed, but cell radioresistance was associated with extensive matrix remodeling and changes in the complement of adhesion signaling proteins. Out of 72 proteins differentially expressed in the parental and radioresistant cells, four proteins were selected for functional validation based on their correlation with biochemical recurrence-free survival. Perlecan/heparan sulfate proteoglycan 2 (HSPG2) and lysyl-like oxidase-like 2 (LOXL2) were upregulated, while sushi repeat-containing protein X-linked (SRPX) and laminin subunit beta 3 (LAMB3) were downregulated in radioresistant DU145 cells. Knockdown of perlecan/HSPG2 sensitized radioresistant DU145 RR cells to irradiation while the sensitivity of DU145 parental cells did not change, indicating a potential role for perlecan/HSPG2 and its associated proteins in suppressing tumor radioresistance. Validation in androgen-sensitive parental and radioresistant LNCaP cells further supported perlecan/HSPG2 as a regulator of cell radiosensitivity. These findings extend our understanding of the interplay between extracellular matrix remodeling and PC radioresistance and signpost perlecan/HSPG2 as a potential therapeutic target and biomarker for PC.

Proteoglycans of basement membranes: Crucial controllers of angiogenesis, neurogenesis, and autophagy

Anti-angiogenic therapy is an established method for the treatment of several cancers and vascular-related diseases. Most of the agents employed target the vascular endothelial growth factor A, the major cytokine stimulating angiogenesis. However, the efficacy of these treatments is limited by the onset of drug resistance. Therefore, it is of fundamental importance to better understand the mechanisms that regulate angiogenesis and the microenvironmental cues that play significant role and influence patient treatment and outcome. In this context, here we review the importance of the three basement membrane heparan sulfate proteoglycans (HSPGs), namely perlecan, agrin and collagen XVIII. These HSPGs are abundantly expressed in the vasculature and, due to their complex molecular architecture, they interact with multiple endothelial cell receptors, deeply affecting their function. Under normal conditions, these proteoglycans exert pro-angiogenic functions. However, in pathological conditions such as cancer and inflammation, extracellular matrix remodeling leads to the degradation of these large precursor molecules and the liberation of bioactive processed fragments displaying potent angiostatic activity. These unexpected functions have been demonstrated for the C-terminal fragments of perlecan and collagen XVIII, endorepellin and endostatin. These bioactive fragments can also induce autophagy in vascular endothelial cells which contributes to angiostasis. Overall, basement membrane proteoglycans deeply affect angiogenesis counterbalancing pro-angiogenic signals during tumor progression, and represent possible means to develop new prognostic biomarkers and novel therapeutic approaches for the treatment of solid tumors.

Proteoglycans in Mechanobiology of Tissues and Organs: Normal Functions and Mechanopathology

Proteoglycans (PGs) are a diverse class of glycoconjugates that serve critical functions in normal mechanobiology and mechanopathology. Both the protein cores and attached glycosaminoglycan (GAG) chains function in mechanically-sensitive processes, and loss of either can contribute to development of pathological conditions. PGs function as key components of the extracellular matrix (ECM) where they can serve as mechanosensors in mechanosensitive tissues including bone, cartilage, tendon, blood vessels and soft organs. The mechanical properties of these tissues depend on the presence and function of PGs, which play important roles in tissue elasticity, osmolarity and pressure sensing, and response to physical activity. Tissue responses depend on cell surface mechanoreceptors that include integrins, CD44, voltage sensitive ion channels, transient receptor potential (TRP) and piezo channels. PGs contribute to cell and molecular interplay in wound healing, fibrosis, and cancer, where they transduce the mechanical properties of the ECM and influence the progression of various context-specific conditions and diseases. The PGs that are most important in mechanobiology vary depending on the tissue and its functions and functional needs. Perlecan, for example, is important in the mechanobiology of basement membranes, cardiac and skeletal muscle, while aggrecan plays a primary role in the mechanical properties of cartilage and joints. A variety of techniques have been used to study the mechanobiology of PGs, including atomic force microscopy, mouse knockout models, and in vitro cell culture experiments with 3D organoid models. These studies have helped to elucidate the tissue-specific roles that PGs play in cell-level mechanosensing and tissue mechanics. Overall, the study of PGs in mechanobiology is yielding fundamental new concepts in the molecular basis of mechanosensing that can open the door to the development of new treatments for a host of conditions related to mechanopathology.

Hypoxia-Induced Biosynthesis of the Extracellular Matrix Molecules, Perlecan and Fibronectin, Promotes the Growth of Pleomorphic Adenoma Cells In Vitro Models

Salivary pleomorphic adenoma is histopathologically characterized by its colorful stroma with myxoid, chondroid, and hyaline appearances, due to enhanced biosynthesis of extracellular matrix (ECM) molecules and poor vascularity. Thus, pleomorphic adenoma cells embedded in the stroma typically survive under hypoxic conditions. We determined the expression kinetics of ECM molecules, such as perlecan and fibronectin (FN), under hypoxia in SM-AP1 cells which are duct epithelial differentiated cells, and in SM-AP4 cells, which are myoepithelial differentiated cells, cloned from pleomorphic adenoma of the parotid gland. We investigated hypoxia-inducible factor-1α (HIF-1α)-inducing pathways through a variety of ECM molecules in association with their cellular proliferation and migration. We observed that hypoxic conditions with elevated HIF-1α protein levels induced increased expression of perlecan and FN in SM-AP cells than in controls. Moreover, perlecan and FN knockdown reduced the proliferation of SM-AP1 and SM-AP4 cells under hypoxia. Further, SM-AP1 cell migration was enhanced by both perlecan and FN knockdown, whereas SM-AP4 cell migration was increased by perlecan knockdown and inhibited by fibronectin knockdown. The results indicated that pleomorphic adenoma cells can survive under hypoxic conditions by promoting cell proliferation via enhanced synthesis of ECM molecules. Overall, ECM molecules may be a new anti-tumor target under hypoxic conditions.

Switching mechanism from AR to EGFR signaling via 3-O-sulfated heparan sulfate in castration-resistant prostate cancer

Androgen deprivation therapy is given to suppress prostate cancer growth; however, some cells continue to grow hormone-independently as castration-resistant prostate cancer (CRPC). Sulfated glycosaminoglycans promote ligand binding to receptors as co-receptors, but their role in CRPC remains unknown. Using the human prostate cancer cell line C4-2, which can proliferate in hormone-dependent and hormone-independent conditions, we found that epidermal growth factor (EGF)-activated EGFR-ERK1/2 signaling via 3-O-sulfated heparan sulfate (HS) produced by HS 3-O-sulfotransferase 1 (HS3ST1) is activated in C4-2 cells under hormone depletion. Knockdown of HS3ST1 in C4-2 cells suppressed hormone-independent growth, and inhibited both EGF binding to the cell surface and activation of EGFR-ERK1/2 signaling. Gefitinib, an EGFR inhibitor, significantly suppressed C4-2 cell proliferation and growth of a xenografted C4-2 tumor in castrated mouse. Collectively, our study has revealed a mechanism by which cancer cells switch to hormone-independent growth and identified the key regulator as 3-O-sulfated HS.

Proteoglycans orchestrate remodeling of prostatic cytoarchitecture after androgenic blockade in old gerbils

BACKGROUND

The aim of this study was to evaluate modifications in proteoglycan morphology and composition in the prostatic stroma of 18-month-old gerbils after surgical castration, in association or not with an androgenic blockade.

METHODS

The animals (n = 5) were sorted into groups subjected or not to antiandrogen treatment (flutamide 10 mg/kg/day) administered for the total postsurgery period and euthanized at 7- or 30-day postcastration; the control group consisted of intact animals. Tissue analysis included immunohistochemical assessment (perlecan and chondroitin sulfate) and proteoglycan morphology was analyzed by transmission electron microscopy.

RESULTS

Chondroitin sulfate frequency was increased 7 days postcastration with an androgenic blockade. The presence of these carbohydrates was rare after 30 days of androgenic blockade treatment. There was a significant increase in the amount of perlecan in the prostate stroma from groups subjected to castration plus flutamide for 7 or 30 days. Ultrastructural analysis showed that the incidence of areas occupied by proteoglycans and basement membrane was altered by treatment. In addition, androgenic blockade results in changes in the amount, thickness, and morphology of these structures. At 30 days postcastration, with or without flutamide treatment, larger proteoglycans were common.

CONCLUSIONS

In this study, in particular, the decrease in chondroitin sulfate after the longer period might be understood as a prostatic response to androgenic deprivation, while the high frequency and permanence of perlecan led to the assumption that its modulation could be androgen-independent. Length and form alterations in proteoglycans as well as associations among them and with the basement membrane were dynamic events in the prostate microenvironment.

Molecular mechanism of VEGF and its role in pathological angiogenesis

Over the last seven decades, a significant scientific contribution took place in the delineation of the implications of vascular endothelial-derived growth factor (VEGF) in the processes of angiogenesis. Under pathological conditions, mainly in response to hypoxia or ischemia, elevated VEGF levels promote vascular damage and the growth of abnormal blood vessels. Indeed, the development of VEGF biology has revolutionized our understanding of its role in pathological conditions. Hence, targeting VEGF or VEGF-mediated molecular pathways could be an excellent therapeutic strategy for managing cancers and intraocular neovascular disorders. Although anti-VEGF therapies, such as monoclonal antibodies and small-molecule tyrosine kinase inhibitors, have limited clinical efficacy, they can still significantly improve the overall survival rate. This thus demands further investigation through the development of alternative strategies in the management of VEGF-mediated pathological angiogenesis. This review article focuses on the recent developments toward the delineation of the functional biology of VEGF and the role of anti-VEGF strategies in the management of tumor and eye pathologies. Moreover, therapeutic angiogenesis, an exciting frontier for the treatment of ischemic disorders, is highlighted in this review, including wound healing.

An optimized MALDI MSI protocol for spatial detection of tryptic peptides in fresh frozen prostate tissue

MALDI MS imaging (MSI) is a powerful analytical tool for spatial peptide detection in heterogeneous tissues. Proper sample preparation is crucial to achieve high quality, reproducible measurements. Here we developed an optimized protocol for spatially resolved proteolytic peptide detection with MALDI time-of-flight MSI of fresh frozen prostate tissue sections. The parameters tested included four different tissue washes, four methods of protein denaturation, four methods of trypsin digestion (different trypsin densities, sprayers, and incubation times), and five matrix deposition methods (different sprayers, settings, and matrix concentrations). Evaluation criteria were the number of detected and excluded peaks, percentage of high mass peaks, signal-to-noise ratio, spatial localization, and average intensities of identified peptides, all of which were integrated into a weighted quality evaluation scoring system. Based on these scores, the optimized protocol included an ice-cold EtOH+H2 O wash, a 5 min heating step at 95°C, tryptic digestion incubated for 17h at 37°C and CHCA matrix deposited at a final amount of 1.8 μg/mm2 . Including a heat-induced protein denaturation step after tissue wash is a new methodological approach that could be useful also for other tissue types. This optimized protocol for spatial peptide detection using MALDI MSI facilitates future biomarker discovery in prostate cancer and may be useful in studies of other tissue types.

Application of Proteogenomics to Urine Analysis towards the Identification of Novel Biomarkers of Prostate Cancer: An Exploratory Study

Simple Summary

Prostate cancer (PCa) is one of the most common cancers. Due to the limited and invasive approaches for PCa diagnosis, it is crucial to identify more accurate and non-invasive biomarkers for its detection. The aim of our study was to non-invasively uncover new protein targets for detecting PCa using a proteomics and proteogenomics approach. This work identified several dysregulated mutant protein isoforms in urine from PCa patients, some of them predicted to have a protective or an adverse role in these patients. These results are promising given urine’s non-invasive nature and offers an auspicious opportunity for research and development of PCa biomarkers.

Abstract

To identify new protein targets for PCa detection, first, a shotgun discovery experiment was performed to characterize the urinary proteome of PCa patients. This revealed 18 differentially abundant urinary proteins in PCa patients. Second, selected targets were clinically tested by immunoblot, and the soluble E-cadherin fragment was detected for the first time in the urine of PCa patients. Third, the proteogenome landscape of these PCa patients was characterized, revealing 1665 mutant protein isoforms. Statistical analysis revealed 6 differentially abundant mutant protein isoforms in PCa patients. Analysis of the likely effects of mutations on protein function and PPIs involving the dysregulated mutant protein isoforms suggests a protective role of mutations HSPG2*Q1062H and VASN*R161Q and an adverse role of AMBP*A286G and CD55*S162L in PCa patients. This work originally characterized the urinary proteome, focusing on the proteogenome profile of PCa patients, which is usually overlooked in the analysis of PCa and body fluids. Combined analysis of mass spectrometry data using two different software packages was performed for the first time in the context of PCa, which increased the robustness of the data analysis. The application of proteogenomics to urine proteomic analysis can be very enriching in mutation-related diseases such as cancer.

Pharmacological inhibition of noncanonical EED-EZH2 signaling overcomes chemoresistance in prostate cancer

Rationale: Chemoresistance is a major obstacle in prostate cancer (PCa) treatment. We sought to understand the underlying mechanism of PCa chemoresistance and discover new treatments to overcome docetaxel resistance. Methods: We developed a novel phenotypic screening platform for the discovery of specific inhibitors of chemoresistant PCa cells. The mechanism of action of the lead compound was investigated using computational, molecular and cellular approaches. The in vivo toxicity and efficacy of the lead compound were evaluated in clinically-relevant animal models. Results: We identified LG1980 as a lead compound that demonstrates high selectivity and potency against chemoresistant PCa cells. Mechanistically, LG1980 binds embryonic ectoderm development (EED), disrupts the interaction between EED and enhancer of zeste homolog 2 (EZH2), thereby inducing the protein degradation of EZH2 and inhibiting the phosphorylation and activity of EZH2. Consequently, LG1980 targets a survival signaling cascade consisting of signal transducer and activator of transcription 3 (Stat3), S-phase kinase-associated protein 2 (SKP2), ATP binding cassette B 1 (ABCB1) and survivin. As a lead compound, LG1980 is well tolerated in mice and effectively suppresses the in vivo growth of chemoresistant PCa and synergistically enhances the efficacy of docetaxel in xenograft models. Conclusions: These results indicate that pharmacological inhibition of EED-EZH2 interaction is a novel strategy for the treatment of chemoresistant PCa. LG1980 and its analogues have the potential to be integrated into standard of care to improve clinical outcomes in PCa patients.

Cancer Metastasis: The Role of the Extracellular Matrix and the Heparan Sulfate Proteoglycan Perlecan

Cancer metastasis is the dissemination of tumor cells to new sites, resulting in the formation of secondary tumors. This process is complex and is spatially and temporally regulated by intrinsic and extrinsic factors. One important extrinsic factor is the extracellular matrix, the non-cellular component of tissues. Heparan sulfate proteoglycans (HSPGs) are constituents of the extracellular matrix, and through their heparan sulfate chains and protein core, modulate multiple events that occur during the metastatic cascade. This review will provide an overview of the role of the extracellular matrix in the events that occur during cancer metastasis, primarily focusing on perlecan. Perlecan, a basement membrane HSPG is a key component of the vascular extracellular matrix and is commonly associated with events that occur during the metastatic cascade. Its contradictory role in these events will be discussed and we will highlight the recent advances in cancer therapies that target HSPGs and their modifying enzymes.

Discovery of HSPG2 (Perlecan) as a Therapeutic Target in Triple Negative Breast Cancer

In recent years, there have been significant advances in the treatment of breast cancer resulting in remarkably high survival rates. However, treatment options for metastatic triple negative breast cancer (TNBC) are quite limited due to a lack of identifiable, unique markers. Using a phage display-based whole cell biopanning procedure, we developed two human antibodies that bind to tumor cells with a metastatic TNBC phenotype. Our studies further identified domain 1 of HSPG2 (perlecan) protein as the cognate cell surface antigen bound by the antibody. Immunohistochemistry studies utilizing patient tissue samples revealed significant cell surface expression of HSPG2 in both primary tumors and metastatic lesions. Further, higher HSPG2 expression correlated with poor survival in TNBC. The affinity-matured antibody inhibited the growth of triple negative MDA-MB-231 tumors to a greater extent in nude mice than in NSG mice, pointing to the potential role of natural killer cell-mediated antibody-dependent cell cytotoxicity. This mechanism of action was confirmed through in vitro assays using mouse splenocytes and human peripheral blood mononuclear cells (PBMCs). These results suggest that HSPG2 is a promising target in metastatic TNBC and HSPG2-targeted antibodies could represent a potentially novel class of targeted therapeutics for TNBC.

Perlecan-targeted nanoparticles for drug delivery to triple-negative breast cancer

Aim:

We previously developed two antibodies that bind to a cell surface protein, perlecan, overexpressed in triple-negative breast cancer (TNBC). The goal of this study was to investigate these antibodies as targeting ligands for nanoparticle-mediated drug delivery.

Methods:

Paclitaxel-loaded poly(D,L-lactide-co-glycolide) nanoparticles were functionalized with antibodies using thiol–maleimide chemistry. Effect of antibody functionalization on therapeutic efficacy of drug-loaded nanoparticles was investigated using in vitro and in vivo models of TNBC.

Results:

The antibodies were covalently conjugated to nanoparticles without affecting antibody binding affinity or nanoparticle properties. Perlecan-targeted nanoparticles showed improved cell uptake, retention, cytotoxicity in vitro and enhanced tumor growth inhibition in vivo.

Conclusion:

The data presented here indicates that perlecan-targeted nanoparticles can improve tumor drug delivery to TNBC.

The extracellular matrix as a multitasking player in disease

Extracellular matrices (ECMs) are highly specialized and dynamic three-dimensional (3D) scaffolds into which cells reside in tissues. ECM is composed of a variety of fibrillar components, such as collagens, fibronectin, and elastin, and non-fibrillar molecules as proteoglycans, hyaluronan, and glycoproteins including matricellular proteins. These macromolecular components are interconnected forming complex networks that actively communicate with cells through binding to cell surface receptors and/or matrix effectors. ECMs exert diverse roles, either providing tissues with structural integrity and mechanical properties essential for tissue functions or regulating cell phenotype and functions to maintain tissue homeostasis. ECM molecular composition and structure vary among tissues, and is markedly modified during normal tissue repair as well as during the progression of various diseases. Actually, abnormal ECM remodeling occurring in pathologic circumstances drives disease progression by regulating cell-matrix interactions. The importance of matrix molecules to normal tissue functions is also highlighted by mutations in matrix genes that give rise to genetic disorders with diverse clinical phenotypes. In this review, we present critical and emerging issues related to matrix assembly in tissues and the multitasking roles for ECM in diseases such as osteoarthritis, fibrosis, cancer, and genetic diseases. The mechanisms underlying the various matrix-based diseases are also discussed. Research focused on the highly dynamic 3D ECM networks will help to discover matrix-related causative abnormalities of diseases as well as novel diagnostic tools and therapeutic targets.

Regulatory signaling network in the tumor microenvironment of prostate cancer bone and visceral organ metastases and the development of novel therapeutics

This article describes cell signaling network of metastatic prostate cancer (PCa) to bone and visceral organs in the context of tumor microenvironment and for the development of novel therapeutics. The article focuses on our recent progress in the understanding of: 1) The plasticity and dynamics of tumor–stroma interaction; 2) The significance of epigenetic reprogramming in conferring cancer growth, invasion and metastasis; 3) New insights on altered junctional communication affecting PCa bone and brain metastases; 4) Novel strategies to overcome therapeutic resistance to hormonal antagonists and chemotherapy; 5) Genetic-based therapy to co-target tumor and bone stroma; 6) PCa-bone-immune cell interaction and TBX2-WNTprotein signaling in bone metastasis; 7) The roles of monoamine oxidase and reactive oxygen species in PCa growth and bone metastasis; and 8) Characterization of imprinting cluster of microRNA, in tumor–stroma interaction. This article provides new approaches and insights of PCa metastases with emphasis on basic science and potential for clinical translation. This article referenced the details of the various approaches and discoveries described herein in peer-reviewed publications. We dedicate this article in our fond memory of Dr. Donald S. Coffey who taught us the spirit of sharing and the importance of focusing basic science discoveries toward translational medicine.

Sulfonation, an underexploited area: from skeletal development to infectious diseases and cancer

Sulfonation is one of the most abundant cellular reactions modifying a wide range of xenobiotics as well as endogenous molecules which regulate important biological processes including blood clotting, formation of connective tissues, and functionality of secreted proteins, hormones, and signaling molecules. Sulfonation is ubiquitous in all tissues and widespread in nature (plants, animals, and microorganisms). Although sulfoconjugates were discovered over a century ago when, in 1875, Baumann isolated phenyl sulfate in the urine of a patient given phenol as an antiseptic, the significance of sulfonation and its roles in human diseases have been underappreciated until recent years. Here, we provide a current overview of the significance of sulfonation reactions in a variety of biological functions and medical conditions (with emphasis on cancer). We also discuss research areas that warrant further attention if we are to fully understand how deficiencies in sulfonation could impact human health which, in turn, could help define treatments to effect improvements in health.

Proteoglycans remodeling in cancer: Underlying molecular mechanisms

Extracellular matrix is a highly dynamic macromolecular network. Proteoglycans are major components of extracellular matrix playing key roles in its structural organization and cell signaling contributing to the control of numerous normal and pathological processes. As multifunctional molecules, proteoglycans participate in various cell functions during morphogenesis, wound healing, inflammation and tumorigenesis. Their interactions with matrix effectors, cell surface receptors and enzymes enable them with unique properties. In malignancy, extensive remodeling of tumor stroma is associated with marked alterations in proteoglycans' expression and structural variability. Proteoglycans exert diverse functions in tumor stroma in a cell-specific and context-specific manner and they mainly contribute to the formation of a permissive provisional matrix for tumor growth affecting tissue organization, cell-cell and cell-matrix interactions and tumor cell signaling. Proteoglycans also modulate cancer cell phenotype and properties, the development of drug resistance and tumor stroma angiogenesis. This review summarizes the proteoglycans remodeling and their novel biological roles in malignancies with particular emphasis to the underlying molecular mechanisms.

SLC3A2, antigen of mAb 3G9, promotes migration and invasion by upregulating of mucins in gastric cancer

Solute carrier family 3 member 2 (SLC3A2) has been reported to be highly expressed in a variety of carcinomas. However, the function of SLC3A2 in gastric carcinoma (GC) has not been well explored. Monoclonal antibody (mAb) 3G9, generated from immunogen of various human GC cell lines, has been shown to bind to GC tissues specifically. In this study, we identified the target antigen of mAb 3G9 as SLC3A2, and detected the expression profile of SLC3A2 in a panel of gastric cancer cell lines and GC tumor tissues. We found that the increased expression of SLC3A2 was associated with serosal invasion in GC patients. Knockout of SLC3A2 suppressed the migration and invasion of BGC-823 cells in vitro and in vivo, whereas overexpression of SLC3A2 in NCI-N87 cells promoted the migration and invasion in vitro and in vivo. Mechanistic investigations suggested that MUC1, MUC16 and MUC5B were the downstream genes of SLC3A2 in GC cells. Taken together, our data suggested that SLC3A2 promoted the aggressive phenotype of GC by upregulating several mucin genes expression and may serve as a potential biomarker for diagnosis and target therapy.

Perlecan/HSPG2 and matrilysin/MMP-7 as indices of tissue invasion: tissue localization and circulating perlecan fragments in a cohort of 288 radical prostatectomy patients

Prostate cancer (PCa) cells use matrix metalloproteinases (MMPs) to degrade tissue during invasion. Perlecan/HSPG2 is degraded at basement membranes, in reactive stroma and in bone marrow during metastasis. We previously showed MMP-7 efficiently degrades perlecan. We now analyzed PCa tissue and serum from 288 prostatectomy patients of various Gleason grades to decipher the relationship between perlecan and MMP-7 in invasive PCa. In 157 prostatectomy specimens examined by tissue microarray, perlecan levels were 18% higher than their normal counterparts. In Gleason grade 4 tissues, MMP-7 and perlecan immunostaining levels were highly correlated with each other (average correlation coefficient of 0.52) in PCa tissue, regardless of grade. Serial sections showed intense, but non-overlapping, immunostaining for MMP-7 and perlecan at adjacent borders, reflecting the protease-substrate relationship. Using a capture assay, analysis of 288 PCa sera collected at prostatectomy showed elevated levels of perlecan fragments, with most derived from domain IV. Perlecan fragments in PCa sera were associated with overall MMP-7 staining levels in PCa tissues. Domain IV perlecan fragments were present in stage IV, but absent in normal, sera, suggesting perlecan degradation during metastasis. Together, perlecan fragments in sera and MMP-7 in tissues of PCa patients are measures of invasive PCa.

Coexpression and expression quantitative trait loci analyses of the angiogenesis gene-gene interaction network in prostate cancer

BACKGROUND

Prostate cancer (PCa) shows a substantial clinical heterogeneity. The existing risk classification for PCa prognosis based on clinical factors is not sufficient. Although some biomarkers for PCa aggressiveness have been identified, their underlying functional mechanisms are still unclear. We previously reported a gene-gene interaction network associated with PCa aggressiveness based on single nucleotide polymorphism (SNP)-SNP interactions in the angiogenesis pathway. The goal of this study is to investigate potential functional evidence of the involvement of the genes in this gene-gene interaction network.

METHODS

A total of 11 angiogenesis genes were evaluated. The crosstalks among genes were examined through coexpression and expression quantitative trait loci (eQTL) analyses. The study population is 352 Caucasian PCa patients in the Cancer Genome Atlas (TCGA) study. The pairwise coexpressions among the genes of interest were evaluated using the Spearman coefficient. The eQTL analyses were tested using the Kruskal-Wallis test.

RESULTS

Among all within gene and 55 possible pairwise gene evaluations, 12 gene pairs and one gene (MMP16) showed strong coexpression or significant eQTL evidence. There are nine gene pairs with a strong correlation (Spearman correlation ≥0.6, P<1×10^-13). The top coexpressed gene pairs are EGFR-SP1 (r=0.73), ITGB3-HSPG2 (r=0.71), ITGB3-CSF1 (r=0.70), MMP16-FBLN5 (r=0.68), ITGB3-MMP16 (r=0.65), ITGB3-ROBO1 (r=0.62), CSF1-HSPG2 (r=0.61), CSF1-FBLN5 (r=0.6), and CSF1-ROBO1 (r=0.60). One cis-eQTL in MMP16 and five trans-eQTLs (MMP16-ESR1, ESR1-ROBO1, CSF1-ROBO1, HSPG2-ROBO1, and FBLN5-CSF1) are significant with a false discovery rate q value less than 0.2.

CONCLUSIONS

These findings provide potential biological evidence for the gene-gene interactions in this angiogenesis network. These identified interactions between the angiogenesis genes not only provide information for PCa etiology mechanism but also may serve as integrated biomarkers for building a risk prediction model for PCa aggressiveness.

Prostate cancer cells specifically reorganize epithelial cell-fibroblast communication through proteoglycan and junction pathways

Microenvironment and stromal fibroblasts are able to inhibit tumor cell proliferation both through secreted signaling molecules and direct cell-cell interactions but molecular mechanisms of these effects remain unclear. In this study, we investigated a role of cell-cell contact-related molecules (protein ECM components, proteoglycans (PGs) and junction-related molecules) in intercellular communications between the human TERT immortalized fibroblasts (BjTERT fibroblasts) and normal (PNT2) or cancer (LNCaP, PC3, DU145) prostate epithelial cells. It was shown that BjTERT-PNT2 cell coculture resulted in significant decrease of both BjTERT and PNT2 proliferation rates and reorganization of transcriptional activity of cell-cell contact-related genes in both cell types. Immunocytochemical staining revealed redistribution of DCN and LUM in PNT2 cells and significant increase of SDC1 at the intercellular contact zones between BjTERT and PNT2 cells, suggesting active involvement of the PGs in cell-cell contacts and contact inhibition of cell proliferation. Unlike to PNT2 cells, PC3 cells did not respond to BjTERT in terms of PGs expression, moderately increased transcriptional activity of junctions-related genes (especially tight junction) and failed to establish PC3-BjTERT contacts. At the same time, PC3 cells significantly down-regulated junctions-related genes (especially focal adhesions and adherens junctions) in BjTERT fibroblasts resulting in visible preference for homotypic PC3-PC3 over heterotypic PC3-BjTERT contacts and autonomous growth of PC3 clones. Taken together, the results demonstrate that an instructing role of fibroblasts to normal prostate epithelial cells is revoked by cancer cells through deregulation of proteoglycans and junction molecules expression and overall disorganization of fibroblast-cancer cell communication.

Differential immunohistochemical expression profiles of perlecan-binding growth factors in epithelial dysplasia, carcinoma in situ, and squamous cell carcinoma of the oral mucosa

The intercellular deposit of perlecan, a basement-membrane type heparan sulfate proteoglycan, is considered to function as a growth factor reservoir and is enhanced in oral epithelial dysplasia and carcinoma in situ (CIS). However, it remains unknown which types of growth factors function in these perlecan-enriched epithelial conditions. The aim of this study was to determine immunohistochemically which growth factors were associated with perlecan in normal oral epithelia and in different epithelial lesions from dysplasia and CIS to squamous cell carcinoma (SCC). Eighty-one surgical tissue specimens of oral SCC containing different precancerous stages, along with ten of normal mucosa, were examined by immunohistochemistry for growth factors. In normal epithelia, perlecan and growth factors were not definitely expressed. In epithelial dysplasia, VEGF, SHH, KGF, Flt-1, and Flk-1were localized in the lower half of rete ridges (in concordance with perlecan, 33-100%), in which Ki-67 positive cells were densely packed. In CIS, perlecan and those growth factors/receptors were more strongly expressed in the cell proliferating zone (63-100%). In SCC, perlecan and KGF disappeared from carcinoma cells but emerged in the stromal space (65-100%), while VEGF, SHH, and VEGF receptors remained positive in SCC cells (0%). Immunofluorescence showed that the four growth factors were shown to be produced by three oral SCC cell lines and that their signals were partially overlapped with perlecan signals. The results indicate that perlecan and its binding growth factors are differentially expressed and function in specific manners before (dysplasia/CIS) and after (SCC) invasion of dysplasia/carcinoma cells.

Transcriptional activation by NFκB increases perlecan/HSPG2 expression in the desmoplastic prostate tumor microenvironment

Perlecan/HSPG2, a heparan sulfate proteoglycan typically found at tissue borders including those separating epithelia and connective tissue, increases near sites of invasion of primary prostatic tumors as previously shown for other proteins involved in desmoplastic tissue reaction. Studies of prostate cancer cells and stromal cells from both prostate and bone, the major site for prostate cancer metastasis, showed that cancer cells and a subset of stromal cells increased production of perlecan in response to cytokines present in the tumor microenvironment. In silico analysis of the HSPG2 promoter revealed two conserved NFκB binding sites, in addition to the previously reported SMAD3 binding sites. By systematically transfecting cells with a variety of reporter constructs including sequences up to 2.6 kb from the start site of transcription, we identified an active cis element in the distal region of the HSPG2 promoter, and showed that it functions in regulating transcription of HSPG2. Treatment with TNF-α and/or TGFβ1 identified TNF-α as a major cytokine regulator of perlecan production. TNF-α treatment also triggered p65 nuclear translocation and binding to the HSPG2 regulatory region in stromal cells and cancer cells. In addition to stromal induction of perlecan production in the prostate, we identified a matrix-secreting bone marrow stromal cell type that may represent the source for increases in perlecan in the metastatic bone marrow environment. These studies implicate perlecan in cytokine-mediated, innate tissue responses to cancer cell invasion, a process we suggest reflects a modified wound healing tissue response co-opted by prostate cancer cells.

The role of perlecan and endorepellin in the control of tumor angiogenesis and endothelial cell autophagy

During tumor growth and angiogenesis there is a dynamic remodeling of tissue architecture often accompanied by the release of extracellular matrix constituents full of biological activity. One of the key constituents of the tumor microenvironment is the large heparan sulfate proteoglycan perlecan. This proteoglycan, strategically located at cell surfaces and within basement membranes, is a well-defined pro-angiogenic molecule when intact. However, when partially processed by proteases released during cancer remodeling and invasion, the C-terminal fragment of perlecan, known as endorepellin, has opposite effects than its parent molecule. Endorepellin is a potent inhibitor of angiogenesis by exerting a dual receptor antagonism by simultaneously engaging VEGFR2 and α2β1 integrin. Signaling through the α2β1 integrin leads to actin disassembly and block of endothelial cell migration, necessary for capillary morphogenesis. Signaling through the VEGFR2 induces dephosphorylation of the receptor via activation of SHP-1 and suppression of downstream proangiogenic effectors, especially attenuating VEGFA expression. A novel and emerging role of endorepellin is its ability to evoke autophagy by activating Peg3 and various canonical autophagic markers. This effect is specific for endothelial cells as these are the primary cells expressing both VEGFR2 and α2β1 integrin. Thus, an endogenous fragment of a ubiquitous proteoglycan can regulate both angiogenesis and autophagy through a dual receptor antagonism. The biological properties of this natural endogenous protein place endorepellin as a potential therapeutic agent against cancer or diseases where angiogenesis is prominent.

Agrin and perlecan mediate tumorigenic processes in oral squamous cell carcinoma

Oral squamous cell carcinoma is the most common type of cancer in the oral cavity, representing more than 90% of all oral cancers. The characterization of altered molecules in oral cancer is essential to understand molecular mechanisms underlying tumor progression as well as to contribute to cancer biomarker and therapeutic target discovery. Proteoglycans are key molecular effectors of cell surface and pericellular microenvironments, performing multiple functions in cancer. Two of the major basement membrane proteoglycans, agrin and perlecan, were investigated in this study regarding their role in oral cancer. Using real time quantitative PCR (qRT-PCR), we showed that agrin and perlecan are highly expressed in oral squamous cell carcinoma. Interestingly, cell lines originated from distinct sites showed different expression of agrin and perlecan. Enzymatically targeting chondroitin sulfate modification by chondroitinase, oral squamous carcinoma cell line had a reduced ability to adhere to extracellular matrix proteins and increased sensibility to cisplatin. Additionally, knockdown of agrin and perlecan promoted a decrease on cell migration and adhesion, and on resistance of cells to cisplatin. Our study showed, for the first time, a negative regulation on oral cancer-associated events by either targeting chondroitin sulfate content or agrin and perlecan levels.

Extracellular matrix protein 1 regulates cell proliferation and trastuzumab resistance through activation of epidermal growth factor signaling

INTRODUCTION

Extracellular matrix protein 1 (ECM1) is a secreted glycoprotein with putative functions in cell proliferation, angiogenesis and differentiation. Expression of ECM1 in several types of carcinoma suggests that it may promote tumor development. In this study, we investigated the role of ECM1 in oncogenic cell signaling in breast cancer, and potential mechanisms for its effects.

METHODS

In order to find out the functional role of ECM1, we used the recombinant human ECM1 and viral transduction systems which stably regulated the expression level of ECM1. We examined the effect of ECM1 on cell proliferation and cell signaling in vitro and in vivo. Moreover, tissues and sera of patients with breast cancer were used to confirm the effect of ECM1.

RESULTS

ECM1 protein was increased in trastuzumab-resistant (TR) cells, in association with trastuzumab resistance and cell proliferation. Through physical interaction with epidermal growth factor receptor (EGFR), ECM1 potentiated the phosphorylation of EGFR and extracellular signal-regulated kinase upon EGF treatment. Moreover, ECM1-induced galectin-3 cleavage through upregulation of matrix metalloproteinase 9 not only improved mucin 1 expression, but also increased EGFR and human epidermal growth factor receptor 3 protein stability as a secondary signaling.

CONCLUSIONS

ECM1 has important roles in both cancer development and trastuzumab resistance in breast cancer through activation of EGFR signaling.

Insidious changes in stromal matrix fuel cancer progression

Reciprocal interactions between tumor and stromal cells propel cancer progression and metastasis. A complete understanding of the complex contributions of the tumor stroma to cancer progression necessitates a careful examination of the extracellular matrix (ECM), which is largely synthesized and modulated by cancer-associated fibroblasts. This structurally supportive meshwork serves as a signaling scaffold for a myriad of biologic processes and responses favoring tumor progression. The ECM is a repository for growth factors and cytokines that promote tumor growth, proliferation, and metastasis through diverse interactions with soluble and insoluble ECM components. Growth factors activated by proteases are involved in the initiation of cell signaling pathways essential to invasion and survival. Various transmembrane proteins produced by the cancer stroma bind the collagen and fibronectin-rich matrix to induce proliferation, adhesion, and migration of cancer cells, as well as protease activation. Integrins are critical liaisons between tumor cells and the surrounding stroma, and with their mechano-sensing ability, induce cell signaling pathways associated with contractility and migration. Proteoglycans also bind and interact with various matrix proteins in the tumor microenvironment to promote cancer progression. Together, these components function to mediate cross-talk between tumor cells and fibroblasts ultimately to promote tumor survival and metastasis. These stromal factors, which may be expressed differentially according to cancer stage, have prognostic utility and potential. This review examines changes in the ECM of cancer-associated fibroblasts induced through carcinogenesis, and the impact of these changes on cancer progression. The implication is that cancer progression, even in epithelial cancers, may be based in large part on changes in signaling from cancer-associated stromal cells. These changes may provide early prognostic indicators to further stratify patients during treatment or alter the timing of their follow-up visits and observations.

The mutational landscape of adenoid cystic carcinoma

Adenoid cystic carcinomas (ACCs) are among the most enigmatic of human malignancies. These aggressive salivary cancers frequently recur and metastasize despite definitive treatment, with no known effective chemotherapy regimen. Here, we determined the ACC mutational landscape and report the exome or whole genome sequences of 60 ACC tumor/normal pairs. These analyses revealed a low exonic somatic mutation rate (0.31 non-silent events/megabase) and wide mutational diversity. Interestingly, mutations selectively involved chromatin state regulators, such as SMARCA2, CREBBP, and KDM6A, suggesting aberrant epigenetic regulation in ACC oncogenesis. Mutations in genes central to DNA damage and protein kinase A signaling also implicate these processes. We observed MYB-NFIB translocations and somatic mutations in MYB-associated genes, solidifying these aberrations as critical events. Lastly, we identified recurrent mutations in the FGF/IGF/PI3K pathway that may potentially offer new avenues for therapy (30%). Collectively, our observations establish a molecular foundation for understanding and exploring new treatments for ACC.

SNP-SNP interaction network in angiogenesis genes associated with prostate cancer aggressiveness

Angiogenesis has been shown to be associated with prostate cancer development. The majority of prostate cancer studies focused on individual single nucleotide polymorphisms (SNPs) while SNP-SNP interactions are suggested having a great impact on unveiling the underlying mechanism of complex disease. Using 1,151 prostate cancer patients in the Cancer Genetic Markers of Susceptibility (CGEMS) dataset, 2,651 SNPs in the angiogenesis genes associated with prostate cancer aggressiveness were evaluated. SNP-SNP interactions were primarily assessed using the two-stage Random Forests plus Multivariate Adaptive Regression Splines (TRM) approach in the CGEMS group, and were then re-evaluated in the Moffitt group with 1,040 patients. For the identified gene pairs, cross-evaluation was applied to evaluate SNP interactions in both study groups. Five SNP-SNP interactions in three gene pairs (MMP16+ ROBO1, MMP16+ CSF1, and MMP16+ EGFR) were identified to be associated with aggressive prostate cancer in both groups. Three pairs of SNPs (rs1477908+ rs1387665, rs1467251+ rs7625555, and rs1824717+ rs7625555) were in MMP16 and ROBO1, one pair (rs2176771+ rs333970) in MMP16 and CSF1, and one pair (rs1401862+ rs6964705) in MMP16 and EGFR. The results suggest that MMP16 may play an important role in prostate cancer aggressiveness. By integrating our novel findings and available biomedical literature, a hypothetical gene interaction network was proposed. This network demonstrates that our identified SNP-SNP interactions are biologically relevant and shows that EGFR may be the hub for the interactions. The findings provide valuable information to identify genotype combinations at risk of developing aggressive prostate cancer and improve understanding on the genetic etiology of angiogenesis associated with prostate cancer aggressiveness.

Silencing SOX2 induced mesenchymal-epithelial transition and its expression predicts liver and lymph node metastasis of CRC patients

SOX2 is an important stem cell marker and plays important roles in development and carcinogenesis. However, the role of SOX2 in Epithelial-Mesenchymal Transition has not been investigated. We demonstrated, for the first time, that SOX2 is involved in the Epithelial-Mesenchymal Transition (EMT) process as knock downof SOX2 in colorectal cancer (CRC) SW620 cells induced a Mesenchymal-Epithelial Transition (MET) process with recognized changes in the expression of key genes involved in the EMT process including E-cadherin and vimentin. In addition, we provided a link between SOX2 activity and the WNT pathway by showing that knock down of SOX2 reduced the WNT pathway activity in colorectal cancer (CRC) cells. We further demonstrated that SOX2 is involved in cell migration and invasion in vitro and in metastasis in vivo for CRC cells, and that the process might be mediated through the MMP2 activity. Finally, an IHC analysis of 44 cases of colorectal cancer patients suggested that SOX2 is a prognosis marker for metastasis of colorectal cancers.

Antithetic roles of proteoglycans in cancer

Proteoglycans (PGs), a family of complex post-translationally sculptured macromolecules, are fundamental regulators of most normal and aberrant cellular functions. The unparalleled structural-functional diversity of PGs endows them with the ability to serve as critical mediators of the tumor cells' interaction with the host microenvironment, while directly contributing to the organization and dynamic remodeling of this milieu. Despite their indisputable importance during embryonic development and in the adult organism, and their frequent dysregulation in tumor lesions, their precise involvement in tumorigenesis awaits a more decisive demonstration. Particularly challenging is to ascertain to what extent selected PGs may catalyze tumor progression and to what extent they may inhibit it, implying antithetic functions of individual PGs. Integrated efforts are needed to consolidate the routine use of PGs in the clinical monitoring of cancer patients and to broaden the exploitation of these macromolecules as therapeutic targets. Several PGs have the required attributes to be contemplated as effective antigens for immunotherapeutic approaches, while the tangible results obtained in recent clinical trials targeting the NG2/CSPG4 transmembrane PG urge further development of PG-based cancer treatment modalities.

Role of heparan sulfate 2-o-sulfotransferase in prostate cancer cell proliferation, invasion, and growth factor signaling

Heparan-sulfate proteoglycans (HSPGs) are required for maximal growth factor signaling in prostate cancer progression. The degree of sulfate modification on the covalently attached heparan sulfate (HS) chains is one of the determining factors of growth factor-HSPG interactions. Sulfate groups are transferred to HS chains via a series of O-sulfotransferases. In the present study, we demonstrate that Heparan sulfate 2-O-sulfotransferase (2OST) is essential for maximal proliferation and invasion of prostate cancer cells in the LNCaP-C4-2B model. We also show that a decrease in invasion due to 2OST siRNA is associated with an increase in actin and E-cadherin accumulation at the cell surface. 2OST expression correlates with increasing metastatic potential in this model. We demonstrate that 2OST expression is upregulated by the stress-inducible transcription factors HIF1α, ATF2, and NFκB. Chromatin immunoprecipitation analysis suggests that HIF1α and ATF2 act directly on the 2OST promoter, while NFκB acts indirectly.

Endorepellin, the angiostatic module of perlecan, interacts with both the α2β1 integrin and vascular endothelial growth factor receptor 2 (VEGFR2): a dual receptor antagonism

Endorepellin, the C-terminal module of perlecan, negatively regulates angiogenesis counter to its proangiogenic parental molecule. Endorepellin (the C-terminal domain V of perlecan) binds the α2β1 integrin on endothelial cells and triggers a signaling cascade that leads to disruption of the actin cytoskeleton. Here, we show that both perlecan and endorepellin bind directly and with high affinity to both VEGF receptors 1 and 2, in a region that differs from VEGFA-binding site. In both human and porcine endothelial cells, this interaction evokes a physical down-regulation of both the α2β1 integrin and VEGFR2, with concurrent activation of the tyrosine phosphatase SHP-1 and downstream attenuation of VEGFA transcription. We demonstrate that endorepellin requires both the α2β1 integrin and VEGFR2 for its angiostatic activity. Endothelial cells that express α2β1 integrin but lack VEGFR2, do not respond to endorepellin treatment. Thus, we provide a new paradigm for the activity of an antiangiogenic protein and mechanistically explain the specificity of endorepellin for endothelial cells, the only cells that simultaneously express both receptors. We hypothesize that a mechanism such as dual receptor antagonism could operate for other angiostatic fragments.

The effect of proteoglycans inhibited on the neurotropic growth of salivary adenoid cystic carcinoma

OBJECTIVE

To evaluate the relationship between inhibition of proteoglycans which secreted by salivary adenoid cystic carcinoma cell line (SACC-83) and the neurotropic ability of the tumor cells.

METHODS

The expression vector of short hairpin RNA (shRNA-WJ4) targeting xylosyltransferase-I gene was constructed and transfected into SACC-83 cells (group SACC83-WJ4), shRNA-HK used as negative control was transfected into SACC-83 cells (group SACC-83-HK), SACC-83 cells without transfection was used as black control (group SACC-83). The xylosyltransferase-I gene expression was measured by real-time PCR. The content of proteoglycans was detected by Blyscan Assay Kit. The effect of down-regulated proteoglycans on the perineural invasion of nude mice was observed. All data were analyzed by the software spss 13.0.

RESULTS

The results showed that the transfected efficiency of shRNA was 43.3%. The expression of xylosyltransferase-I was inhibited by 43.0% 48 h after transfection of shRNA-WJ4. The content of proteoglycans was down-regulated by 30.25% 48 h after transfection. In the neurotropic experiment in vivo of nude mice, the rate of perineural invasion of group SACC-83-WJ4 was 33.33%, significantly lower than that of the negative control (100%) and the black control (100%) (P < 0.05).

CONCLUSION

Xylosyltransferase-I gene of SACC cells was silenced by RNA interference technology, proteoglycans secretion was reduced and neurotropic invasion behavior of SACC was inhibited obviously.

Proteoglycans in cancer biology, tumour microenvironment and angiogenesis

Proteoglycans, key molecular effectors of cell surface and pericellular microenvironments, perform multiple functions in cancer and angiogenesis by virtue of their polyhedric nature and their ability to interact with both ligands and receptors that regulate neoplastic growth and neovascularization. Some proteoglycans such as perlecan, have pro- and anti-angiogenic activities, whereas other proteoglycans, such as syndecans and glypicans, can also directly affect cancer growth by modulating key signalling pathways. The bioactivity of these proteoglycans is further modulated by several classes of enzymes within the tumour microenvironment: (i) sheddases that cleave transmembrane or cell-associated syndecans and glypicans, (ii) various proteinases that cleave the protein core of pericellular proteoglycans and (iii) heparanases and endosulfatases which modify the structure and bioactivity of various heparan sulphate proteoglycans and their bound growth factors. In contrast, some of the small leucine-rich proteoglycans, such as decorin and lumican, act as tumour repressors by physically antagonizing receptor tyrosine kinases including the epidermal growth factor and the Met receptors or integrin receptors thereby evoking anti-survival and pro-apoptotic pathways. In this review we will critically assess the expanding repertoire of molecular interactions attributed to various proteoglycans and will discuss novel proteoglycan functions modulating cancer progression, invasion and metastasis and how these factors regulate the tumour microenvironment.

Amphiphilic block co-polyesters bearing pendant cyclic ketal groups as nanocarriers for controlled release of camptothecin

Amphiphilic block co-polymers consisting of hydrophilic poly(ethylene glycol) and hydrophobic polyester bearing pendent cyclic ketals were synthesized by ring-opening co-polymerization of ε-caprolactone (CL) and 1,4,8-trioxaspiro-[4,6]-9-undecanone (TSU) using α-hydroxyl, ω-methoxy, poly(ethylene glycol) as the initiator and stannous octoate as the catalyst. Compositional analyses indicate that TSU was randomly distributed in the hydrophobic blocks. When the TSU content in the co-polymers increased, the polymer crystallinity decreased progressively and the glass transition temperature increased accordingly. The hydrophobic, anticancer drug, camptothecin (CPT), was successfully encapsulated in the block copolymer nanoparticles. The CPT encapsulation efficiency and release kinetics were strongly dependent on the co-polymer composition and crystallinity. CPT release from nanoparticles constructed from co-polymers containing 0, 39 and 100 mol% TSU in the hydrophobic block followed the same trend, with an initial burst of approx. 40% within one day followed by a moderate and slow release lasting up to 7 days. At a TSU content of 14 mol%, CPT was released in a continuous and controlled fashion with a reduced initial burst and a 73% cumulative release by day 7. The in vitro cytoxicity assay showed that the blank nanoparticles were not toxic to the cultured bone metastatic prostate cancer cells (C4-2B). Compared to the free drug, the encapsulated CPT was more effective in inducing apoptotic responses in C4-2B cells. Modulating the physical characteristics of the amphiphilic co-polymers via co-polymerization offers a facile method for controlling the bioavailability of anticancer drugs, ultimately increasing effectiveness and minimizing toxicity.

Proteoglycans: master modulators of paracrine fibroblast-carcinoma cell interactions

Reciprocal interactions between tumor and stromal cells govern carcinoma growth and progression. Signaling functions between these cell types in the tumor microenvironment are largely carried out by secreted growth factors and cytokines. This review discusses how proteoglycans, which are abundantly present in normal and neoplastic tissues, modulate paracrine growth factor signaling events. General principles of proteoglycan involvement in paracrine signaling include stromal induction, core protein processing by proteases and growth factor binding via proteoglycan glycosaminoglycan chains or core protein domains.

Structure-function analysis of VEGF receptor activation and the role of coreceptors in angiogenic signaling

Vascular endothelial growth factors (VEGFs) constitute a family of six polypeptides, VEGF-A, -B, -C, -D, -E and PlGF, that regulate blood and lymphatic vessel development. VEGFs specifically bind to three type V receptor tyrosine kinases (RTKs), VEGFR-1, -2 and -3, and to coreceptors such as neuropilins and heparan sulfate proteoglycans (HSPG). VEGFRs are activated upon ligand-induced dimerization mediated by the extracellular domain (ECD). A study using receptor constructs carrying artificial dimerization-promoting transmembrane domains (TMDs) showed that receptor dimerization is necessary, but not sufficient, for receptor activation and demonstrates that distinct orientation of receptor monomers is required to instigate transmembrane signaling. Angiogenic signaling by VEGF receptors also depends on cooperation with specific coreceptors such as neuropilins and HSPG. A number of VEGF isoforms differ in binding to coreceptors, and ligand-specific signal output is apparently the result of the specific coreceptor complex assembled by a particular VEGF isoform. Here we discuss the structural features of VEGF family ligands and their receptors in relation to their distinct signal output and angiogenic potential.

Basement membrane proteoglycans: modulators Par Excellence of cancer growth and angiogenesis

Proteoglycans located in basement membranes, the nanostructures underling epithelial and endothelial layers, are unique in several respects. They are usually large, elongated molecules with a collage of domains that share structural and functional homology with numerous extracellular matrix proteins, growth factors and surface receptors. They mainly carry heparan sulfate side chains and these contribute not only to storing and preserving the biological activity of various heparan sulfate-binding cytokines and growth factors, but also in presenting them in a more "active configuration" to their cognate receptors. Abnormal expression or deregulated function of these proteoglycans affect cancer and angiogenesis, and are critical for the evolution of the tumor microenvironment. This review will focus on the functional roles of the major heparan sulfate proteoglycans from basement membrane zones: perlecan, agrin and collagen XVIII, and on their roles in modulating cancer growth and angiogenesis.

Perlecan regulates developmental angiogenesis by modulating the VEGF-VEGFR2 axis

Using the zebrafish, we previously identified a central function for perlecan during angiogenic blood vessel development. Here, we explored the nature of perlecan function during developmental angiogenesis. A close examination of individual endothelial cell behavior revealed that perlecan is required for proper endothelial cell migration and proliferation. Because these events are largely mediated by VEGF-VEGFR2 signaling, we investigated the relationship between perlecan and the VEGF pathway. We discovered that perlecan knockdown caused an abnormal increase and redistribution of total VEGF-A protein suggesting that perlecan is required for the appropriate localization of VEGF-A. Importantly, we linked perlecan function to the VEGF pathway by efficiently rescuing the perlecan morphant phenotype by microinjecting VEGF-A(165) protein or mRNA. Combining the strategic localization of perlecan throughout the vascular basement membrane along with its growth factor-binding ability, we hypothesized a major role for perlecan during the establishment of the VEGF gradient which provides the instructive cues to endothelial cells during angiogenesis. In support of this hypothesis we demonstrated that human perlecan bound in a heparan sulfate-dependent fashion to VEGF-A(165). Moreover, perlecan enhanced VEGF mediated VEGFR2 activation of human endothelial cells. Collectively, our results indicate that perlecan coordinates developmental angiogenesis through modulation of VEGF-VEGFR2 signaling events. The identification of angiogenic factors, such as perlecan, and their role in vertebrate development will not only enhance overall understanding of the molecular basis of angiogenesis, but may also provide new insight into angiogenesis-based therapeutic approaches.

Systems biology of vascular endothelial growth factors

Several cytokine families have roles in the development, maintenance, and remodeling of the microcirculation. Of these, the vascular endothelial growth factor (VEGF) family is one of the best studied and one of the most complex. Five VEGF ligand genes and five cell-surface receptor genes are known in the human, and each of these may be transcribed as multiple splice isoforms to generate an extensive family of proteins, many of which are subject to further proteolytic processing. Using the VEGF family as an example, we describe the current knowledge of growth-factor expression, processing, and transport in vivo. Experimental studies and computational simulations are being used to measure and predict the activity of these molecules, and we describe avenues of research that seek to fill the remaining gaps in our understanding of VEGF family behavior.

Novel interactions of perlecan: unraveling perlecan's role in angiogenesis

Perlecan, a highly conserved and ubiquitous basement membrane heparan sulfate proteoglycan, is essential for life, inasmuch as its absence results in embryonic lethality in mice and C. elegans, and neonatal lethality in humans. Perlecan plays an essential role in vasculogenesis and chondrogenesis, as well as in pathological states where these processes are maladapted. Although a large body of evidence supports a pro-angiogenic role for perlecan, recent findings suggests that portions of the perlecan protein core can be antiangiogenic, requiring a further evaluation of the functioning of this complex molecule. This review is focused on the genetics of mammalian and nonmammalian perlecan, the elucidation of its novel interacting partners and its role in angiogenesis. By more fully understanding perlecan's functioning in angiogenesis, we may gain invaluable insight that could lead to therapeutic interventions in cancer and other pathologic states.

Proteomic profiling of endorepellin angiostatic activity on human endothelial cells

BACKGROUND

Endorepellin, the C-terminal domain V of the heparan sulfate proteoglycan perlecan, exhibits powerful and targeted anti-angiogenic activity on endothelial cells. To identify proteins involved with endorepellin anti-angiogenic action, we performed an extensive comparative proteomic analysis between vehicle- and endorepellin-treated human endothelial cells.

RESULTS

Proteomic analysis of endorepellin influence on human umbilical vein endothelial cells identified five differentially expressed proteins, three of which (beta-actin, calreticulin, and chaperonin/Hsp60) were down-regulated and two of which (vimentin and the beta subunit of prolyl 4-hydroxylase also known as protein disulfide isomerase) were up-regulated in response to endorepellin treatment-and associated with a fold change (endorepellin/control) /= 2.00, and a statistically significant p-value as determined by Student's t test.

CONCLUSION

The proteins identified represent potential target areas involved with endorepellin anti-angiogenic mechanism of action. Further elucidation as such will ultimately provide useful in utilizing endorepellin as an anti-angiogenic therapy in humans.

Syndecan-1: a dynamic regulator of the myeloma microenvironment

Emerging data in myeloma and other cancers indicates that heparan sulfate proteoglycans promote tumor progression by enhancing their growth and metastasis. By acting as key regulators of cell signaling via their interactions with multiple growth and angiogenic factors, heparan sulfates mediate a shift in the microenvironment that supports the tumor as an 'organ' and promotes an aggressive tumor phenotype. In addition, enzymatic remodeling of heparan sulfate proteoglycans provides a mechanism for rapid, localized and dynamic modulation of proteoglycan function thereby tightly regulating activities within the tumor microenvironment. New data from animal models demonstrates that heparan sulfate or the enzymes that regulate heparan sulfate are viable targets for cancer therapy. This strategy of targeting heparan sulfate may be particularly effective for attacking cancers like myeloma where extensive genetic chaos renders them unlikely to respond well to agents that target a single signaling pathway.

Integrin alpha2beta1 is the required receptor for endorepellin angiostatic activity

Endorepellin, the C-terminal module of perlecan, has angiostatic activity. Here we provide definitive genetic and biochemical evidence that the functional endorepellin receptor is the alpha2beta1 integrin. Notably, the specific endorepellin binding to the receptor was cation-independent and was mediated by the alpha2 I domain. We show that the anti-angiogenic effects of endorepellin cannot occur in the absence of alpha2beta1. Microvascular endothelial cells from alpha2beta1(-/-) mice, but not those isolated from either wild-type or alpha1beta1(-/-) mice, did not respond to endorepellin. Moreover, syngeneic Lewis lung carcinoma xenografts in alpha2beta1(-/-) mice failed to respond to systemic delivery of endorepellin. In contrast, endorepellin inhibited tumor growth and angiogenesis in the wild-type mice expressing integrin alpha2beta1. We conclude that the angiostatic effects of endorepellin in vivo are mediated by a specific interaction of endorepellin with the alpha2beta1 integrin receptor.