In vivo selective and distant killing of cancer cells using adenovirus-mediated decorin gene transfer

Global impact of proteoglycan science on human diseases

In this comprehensive review, we will dissect the impact of research on proteoglycans focusing on recent developments involved in their synthesis, degradation, and interactions, while critically assessing their usefulness in various biological processes. The emerging roles of proteoglycans in global infections, specifically the SARS-CoV-2 pandemic, and their rising functions in regenerative medicine and biomaterial science have significantly affected our current view of proteoglycans and related compounds. The roles of proteoglycans in cancer biology and their potential use as a next-generation protein-based adjuvant therapy to combat cancer is also emerging as a constructive and potentially beneficial therapeutic strategy. We will discuss the role of proteoglycans in selected and emerging areas of proteoglycan science, such as neurodegenerative diseases, autophagy, angiogenesis, cancer, infections and their impact on mammalian diseases.

Decorin suppresses tumor lymphangiogenesis: A mechanism to curtail cancer progression

The complex interplay between malignant cells and the cellular and molecular components of the tumor stroma is a key aspect of cancer growth and development. These tumor-host interactions are often affected by soluble bioactive molecules such as proteoglycans. Decorin, an archetypical small leucine-rich proteoglycan primarily expressed by stromal cells, affects cancer growth in its soluble form by interacting with several receptor tyrosine kinases (RTK). Overall, decorin leads to a context-dependent and protracted cessation of oncogenic RTK activity by attenuating their ability to drive a pro-survival program and to sustain a pro-angiogenic network. Through an unbiased transcriptomic analysis using deep RNAseq, we discovered that decorin downregulated a cluster of tumor-associated genes involved in lymphatic vessel development when systemically delivered to mice harboring breast carcinoma allografts. We found that Lyve1 and Podoplanin, two established markers of lymphatic vessels, were markedly suppressed at both the mRNA and protein levels and this suppression correlated with a significant reduction in tumor lymphatic vessels. We further discovered that soluble decorin, but not its homologous proteoglycan biglycan, inhibited lymphatic vessel sprouting in an ex vivo 3D model of lymphangiogenesis. Mechanistically, we found that decorin interacted with VEGFR3, the main lymphatic RTK, and its activity was required for the decorin-mediated block of lymphangiogenesis. Finally, we discovered that Lyve1 was in part degraded via decorin-evoked autophagy in a nutrient- and energy-independent manner. These findings implicate decorin as a new biological factor with anti-lymphangiogenic activity and provide a potential therapeutic agent for curtailing breast cancer growth and metastasis.

Small leucine rich proteoglycans: Biology, function and their therapeutic potential in the ocular surface

Small leucine rich proteoglycans (SLRPs) are the largest family of proteoglycans, with 18 members that are subdivided into five classes. SLRPs are small in size and can be present in tissues as glycosylated and non-glycosylated proteins, and the most studied SLRPs include decorin, biglycan, lumican, keratocan and fibromodulin. SLRPs specifically bind to collagen fibrils, regulating collagen fibrillogenesis and the biomechanical properties of tissues, and are expressed at particularly high levels in fibrous tissues, such as the cornea. However, SLRPs are also very active components of the ECM, interacting with numerous growth factors, cytokines and cell surface receptors. Therefore, SLRPs regulate major cellular processes and have a central role in major fundamental biological processes, such as maintaining corneal homeostasis and transparency and regulating corneal wound healing. Over the years, mutations and/or altered expression of SLRPs have been associated with various corneal diseases, such as congenital stromal corneal dystrophy and cornea plana. Recently, there has been great interest in harnessing the various functions of SLRPs for therapeutic purposes. In this comprehensive review, we describe the structural features and the related functions of SLRPs, and how these affect the therapeutic potential of SLRPs, with special emphasis on the use of SLRPs for treating ocular surface pathologies.

Decorin evokes reversible mitochondrial depolarization in carcinoma and vascular endothelial cells

Decorin, a small leucine-rich proteoglycan with multiple biological functions, is known to evoke autophagy and mitophagy in both endothelial and cancer cells. Here, we investigated the effects of soluble decorin on mitochondrial homeostasis using live cell imaging and ex vivo angiogenic assays. We discovered that decorin triggers mitochondrial depolarization in triple-negative breast carcinoma, HeLa, and endothelial cells. This bioactivity was mediated by the protein core in a time- and dose-dependent manner and was specific for decorin insofar as biglycan, the closest homolog, failed to trigger depolarization. Mechanistically, we found that the bioactivity of decorin to promote depolarization required the MET receptor and its tyrosine kinase. Moreover, two mitochondrial interacting proteins, mitostatin and mitofusin 2, were essential for downstream decorin effects. Finally, we found that decorin relied on the canonical mitochondrial permeability transition pore to trigger tumor cell mitochondrial depolarization. Collectively, our study implicates decorin as a soluble outside-in regulator of mitochondrial dynamics.

Decorin inhibits proliferation and metastasis in human bladder cancer cells by upregulating P21

Migration of bladder cancer (BC) cells poses a substantial threat to human health. It is critical to elucidate the mechanism of BC invasion and progression for surgical treatment and the prognosis of patients. Decorin is of interest as an anticancer treatment that can play a vital role in regulating tumorigenesis. The effect of decorin expression on survival in clinical patients was screened and analyzed using bladder urothelial carcinoma data from the Cancer Genome Atlas (TCGA) database. The differential expression of transforming growth factor-β1 (TGF-β1) in tumors was compared against that of normal samples to analyze the correlation between them. MTT, flow cytometry, and Wound/Transwell assays were used to detect cell proliferation, cycle arrest, apoptosis, migration, and invasion. Analysis of TCGA data showed that decorin expression was significantly lower in bladder urothelial carcinoma samples than in normal tissues, while TGF-β1 expression did not change significantly. We found that decorin was correlated with TGF-β1 expression in bladder urothelial cancer. In addition, decorin blocked the G1/S phase by upregulating p21 protein and inhibiting the expression of TGF-β1 and MMP2, promoting the occurrence of apoptosis and inhibiting the proliferation of human BC T24 cells. Moreover, decorin increased the adhesion of tumor cells in vitro, and effectively inhibited cell metastasis. Decorin regulated the expression of TGF-β1 and MMP2 through p21 protein, promoted apoptosis and adhesion, and inhibited the proliferation and metastasis of BC cells.

Benchmark of site- and structure-specific quantitative tissue N-glycoproteomics for discovery of potential N-glycoprotein markers: a case study of pancreatic cancer

Pancreatic cancer is a highly malignant tumor of the digestive tract that is difficult to diagnose and treat. It is more common in developed countries and has become one of the main causes of death in some countries and regions. Currently, pancreatic cancer generally has a poor prognosis, partly due to the lack of symptoms in the early stages of pancreatic cancer. Therefore, most cases are diagnosed at advanced stage. With the continuous in-depth research of glycoproteomics in precision medical diagnosis, there have been some reports on quantitative analysis of cancer-related cells, plasma or tissues to find specific biomarkers for targeted therapy. This research is based on the developed complete N-linked glycopeptide database search engine GPSeeker, combined with liquid-mass spectrometry and stable diethyl isotope labeling, providing a benchmark of site- and structure-specific quantitative tissue N-glycoproteomics for discovery of potential N-glycoprotein markers. With spectrum-level FDR ≤1%, 20,038 intact N-Glycopeptides corresponding to 4518 peptide backbones, 228 N-glycan monosaccharide compositions 1026 N-glycan putative structures, 4460 N-glycosites and 3437 intact N-glycoproteins were identified. With the criteria of ≥1.5-fold change and p value<0.05, 52 differentially expressed intact N-glycopeptides (DEGPs) were found in pancreatic cancer tussues relative to control, where 38 up-regulated and 14 down-regulated, respectively.

Decorin expression is associated with predictive diffusion MR phenotypes of anti-VEGF efficacy in glioblastoma

Previous data suggest that apparent diffusion coefficient (ADC) imaging phenotypes predict survival response to anti-VEGF monotherapy in glioblastoma. However, the mechanism by which imaging may predict clinical response is unknown. We hypothesize that decorin (DCN), a proteoglycan implicated in the modulation of the extracellular microenvironment and sequestration of pro-angiogenic signaling, may connect ADC phenotypes to survival benefit to anti-VEGF therapy. Patients undergoing resection for glioblastoma as well as patients included in The Cancer Genome Atlas (TCGA) and IVY Glioblastoma Atlas Project (IVY GAP) databases had pre-operative imaging analyzed to calculate pre-operative ADC_L values, the average ADC in the lower distribution using a double Gaussian mixed model. ADC_L values were correlated to available RNA expression from these databases as well as from RNA sequencing from patient derived mouse orthotopic xenograft samples. Targeted biopsies were selected based on ADC values and prospectively collected during resection. Surgical specimens were used to evaluate for DCN RNA and protein expression by ADC value. The IVY Glioblastoma Atlas Project Database was used to evaluate DCN localization and relationship with VEGF pathway via in situ hybridization maps and RNA sequencing data. In a cohort of 35 patients with pre-operative ADC imaging and surgical specimens, DCN RNA expression levels were significantly larger in high ADC_L tumors (41.6 vs. 1.5; P = 0.0081). In a cohort of 17 patients with prospectively targeted biopsies there was a positive linear correlation between ADC_L levels and DCN protein expression between tumors (Pearson R² = 0.3977; P = 0.0066) and when evaluating different targets within the same tumor (Pearson R² = 0.3068; P = 0.0139). In situ hybridization data localized DCN expression to areas of microvascular proliferation and immunohistochemical studies localized DCN protein expression to the tunica adventitia of blood vessels within the tumor. DCN expression positively correlated with VEGFR1 & 2 expression and localized to similar areas of tumor. Increased ADC_L on diffusion MR imaging is associated with high DCN expression as well as increased survival with anti-VEGF therapy in glioblastoma. DCN may play an important role linking the imaging features on diffusion MR and anti-VEGF treatment efficacy. DCN may serve as a target for further investigation and modulation of anti-angiogenic therapy in GBM.

The Protective Role of Decorin in Hepatic Metastasis of Colorectal Carcinoma

Decorin, the prototype member of the small leucine-rich proteoglycan gene family of extracellular matrix (ECM) proteins, acts as a powerful tumor suppressor by inducing the p21^Waf1/Cip1 cyclin-dependent kinase inhibitor, as well as through its ability to directly bind and block the action of several tyrosine kinase receptors. Our previous studies suggested that the lack of decorin promotes hepatic carcinogenesis in mice. Based on this, we set out to investigate whether excess decorin may protect against the liver metastases of colon carcinoma. We also analyzed the effect of decorin in tissue microarrays of human colon carcinoma liver metastasis and examined whether the tumor cells can directly influence the decorin production of myofibroblasts. In humans, low levels of decorin in the liver facilitated the development of colon carcinoma metastases in proportion with more aggressive phenotypes, indicating a possible antitumor action of the proteoglycan. In vitro, colon carcinoma cells inhibited decorin expression in LX2 hepatic stellate cells. Moreover, liver-targeted decorin delivery in mice effectively attenuated metastasis formation of colon cancer. Overexpressed decorin reduced the activity of multiple receptor tyrosine kinases (RTKs) including the epidermal growth factor receptor (EGFR), an important player in colorectal cancer (CRC) pathogenesis. Downstream of that, we observed weakened signaling of ERK1/2, PLCγ, Akt/mTOR, STAT and c-Jun pathways, while p38 MAPK/MSK/CREB and AMPK were upregulated culminating in enhanced p53 function. In conclusion, decorin may effectively inhibit metastatic tumor formation in the liver.

MEIS-mediated suppression of human prostate cancer growth and metastasis through HOXB13-dependent regulation of proteoglycans

The molecular roles of HOX transcriptional activity in human prostate epithelial cells remain unclear, impeding the implementation of new treatment strategies for cancer prevention and therapy. MEIS proteins are transcription factors that bind and direct HOX protein activity. MEIS proteins are putative tumor suppressors that are frequently silenced in aggressive forms of prostate cancer. Here we show that MEIS1 expression is sufficient to decrease proliferation and metastasis of prostate cancer cells in vitro and in vivo murine xenograft models. HOXB13 deletion demonstrates that the tumor-suppressive activity of MEIS1 is dependent on HOXB13. Integration of ChIP-seq and RNA-seq data revealed direct and HOXB13-dependent regulation of proteoglycans including decorin (DCN) as a mechanism of MEIS1-driven tumor suppression. These results define and underscore the importance of MEIS1-HOXB13 transcriptional regulation in suppressing prostate cancer progression and provide a mechanistic framework for the investigation of HOXB13 mutants and oncogenic cofactors when MEIS1/2 are silenced.

Protective Role of Decorin in Primary Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) represents one of the most frequent type of primary liver cancers. Decorin, a small leucine-rich proteoglycan of the extracellular matrix, represents a powerful tumor cell growth and migration inhibitor by hindering receptor tyrosine kinases and inducing p21^WAF1/CIP1. In this study, first we tested decorin expression in HCCs utilizing in silico data, as well as formalin fixed paraffin embedded tissue samples of HCC in a tissue microarray (TMA). In silico data revealed that DCN/SMA mRNA ratio is decreased in HCC compared to normal tissues and follows the staging of the disease. Among TMA samples, 52% of HCCs were decorin negative, 33% exhibited low, and 15% high decorin levels corroborating in silico results. In addition, applying conditioned media of hepatoma cells inhibited decorin expression in LX2 stellate cells in vitro. These results raise the possibility that decorin acts as a tumor suppressor in liver cancer and that is why its expression decreased in HCCs. To further test the protective role of decorin, the proteoglycan was overexpressed in a mouse model of hepatocarcinogenesis evoked by thioacetamide (TA). After transfection, the excessive proteoglycan amount was mainly detected in hepatocytes around the central veins. Upon TA-induced hepatocarcinogenesis, the highest tumor count was observed in mice with no decorin production. Decorin gene delivery reduced tumor formation, in parallel with decreased pEGFR, increased pIGF1R levels, and with concomitant induction of pAkt (T308) and phopho-p53, suggesting a novel mechanism of action. Our results suggest the idea that decorin can be utilized as an anti-cancer agent.

Decorin Expression in Human Vulva Carcinoma: Oncosuppressive Effect of Decorin cDNA Transduction on Carcinoma Cells

The extracellular matrix proteoglycan decorin is well-known for its oncosuppressive activity. Here, decorin expression was examined in human vulva carcinoma tissue samples and in primary and commercial cell lines representing this malignant disease. Furthermore, the effect of adenovirus-mediated decorin cDNA (Ad-DCN) transduction on the viability, proliferation, and the expression and activity of the epidermal growth factor receptor (ErbB/HER) family members of the cell lines were investigated. Using in situ hybridization and immunohistochemistry for decorin, it was demonstrated that malignant cells in human vulva carcinoma tissues lack decorin expression. This result was true independently on tumor stage, grade or human papillomavirus status. RT-qPCR analyses showed that the human vulva carcinoma cell lines used in this study were also negative for decorin expression. Transduction of the cell lines with Ad-DCN caused a marked reduction in cell viability, while the proliferation of the cells was not affected. Experiments examining potential mechanisms behind the oncosuppressive effect of Ad-DCN transduction revealed that ErbB2/HER2 expression and activity in carcinoma cells were markedly downregulated. In conclusion, the results of this study showed that human vulva carcinoma cells lack decorin expression, and that Ad-DCN transduction of these cells induces oncosuppressive activity in part via downregulation of ErbB2/HER2.

Decorin-mediated oncosuppression - a potential future adjuvant therapy for human epithelial cancers

Currently, the multifaceted role of the extracellular matrix (ECM) in tumourigenesis has been realized. One ECM macromolecule exhibiting potent oncosuppressive actions in tumourigenesis is decorin, the prototype of the small leucine-rich proteoglycan gene family. The actions of decorin include its ability to function as an endogenous pan-receptor tyrosine kinase inhibitor, a regulator of both autophagy and mitophagy, as well as a modulator of the immune system. In this review, we will discuss these topics in more detail. We also provide a summary of preclinical studies exploring the value of decorin-mediated oncosuppression, as a potential future adjuvant therapy for epithelial cancers. LINKED ARTICLES: This article is part of a themed section on Translating the Matrix. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.1/issuetoc.

Decorin is a pivotal effector in the extracellular matrix and tumour microenvironment

Decorin (DCN), an extracellular matrix (ECM) protein, belongs to the small leucine-rich proteoglycan family. As a pluripotent molecule, DCN regulates the bioactivities of cell growth factors and participates in ECM assembly. Accumulating evidence has shown that DCN acts as a ligand of various cytokines and growth factors by directly or indirectly interacting with the corresponding signalling molecules involved in cell growth, differentiation, proliferation, adhesion and metastasis and that DCN especially plays vital roles in cancer cell proliferation, spread, pro-inflammatory processes and anti-fibrillogenesis. The multifunctional nature of DCN thus enables it to be a potential therapeutic agent for a variety of diseases and shows good prospects for clinical and research applications.

DCN, an extracellular matrix (ECM) protein that belongs to the small leucine-rich proteoglycan family, is widely distributed and plays multifunctional roles in the stroma and epithelial cells. Originally, DCN was known as an effective collagen-binding partner for fibrillogenesis [1] and to modulate key biomechanical parameters of tissue integrity in the tendon, skin and cornea [2]; thus, it was named decorin (DCN). Since being initially cloned in 1986, DCN was discovered to be a structural constituent of the ECM [3]. However, the paradigm has been shifted; it has become increasingly evident that in addition to being a matrix structural protein, DCN affects a wide range of biological processes, including cell growth, differentiation, proliferation, adhesion, spread and migration, and regulates inflammation and fibrillogenesis [4–7]. Two main themes for DCN functions have emerged: maintenance of cellular structure and regulation of signal transduction pathways, culminating in anti-tumourigenic effects. Here, we review the interaction network of DCN and emphasize the biological correlations between these interactions, some of which are expected to be therapeutic intervention targets.

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.

Decorin is a devouring proteoglycan: Remodeling of intracellular catabolism via autophagy and mitophagy

Autophagy, a fundamental and evolutionarily-conserved eukaryotic pathway, coordinates a complex balancing act for achieving both nutrient and energetic requirements for proper cellular function and homeostasis. We have discovered that soluble proteoglycans evoke autophagy in endothelial cells and mitophagy in breast carcinoma cells by directly interacting with receptor tyrosine kinases, including VEGF receptor 2 and Met. Under these circumstances, autophagic regulation is considered "non-canonical" and is epitomized by the bioactivity of the small leucine-rich proteoglycan, decorin. Soluble matrix-derived cues being transduced downstream of receptor engagement converge upon a newly-discovered nexus of autophagic machinery consisting of Peg3 for endothelial cell autophagy and mitostatin for tumor cell mitophagy. In this thematic mini-review, we will provide an overview of decorin-mediated autophagy and mitophagy and propose that regulating intracellular catabolism is the underlying molecular basis for the versatility of decorin as a potent oncosuppressive agent.

Molecular insights into the normal operation, regulation, and multisystemic roles of K+-Cl- cotransporter 3 (KCC3)

Long before the molecular identity of the Na+-dependent K+-Cl- cotransporters was uncovered in the mid-nineties, a Na+-independent K+-Cl- cotransport system was also known to exist. It was initially observed in sheep and goat red blood cells where it was shown to be ouabain-insensitive and to increase in the presence of N-ethylmaleimide (NEM). After it was established between the early and mid-nineties, the expressed sequence tag (EST) databank was found to include a sequence that was highly homologous to those of the Na+-dependent K+-Cl- cotransporters. This sequence was eventually found to code for the Na+-independent K+-Cl- cotransport function that was described in red blood cells several years before. It was termed KCC1 and led to the discovery of three isoforms called KCC2, KCC3, and KCC4. Since then, it has become obvious that each one of these isoforms exhibits unique patterns of distribution and fulfills distinct physiological roles. Among them, KCC3 has been the subject of great attention in view of its important role in the nervous system and its association with a rare hereditary sensorimotor neuropathy (called Andermann syndrome) that affects many individuals in Quebec province (Canada). It was also found to play important roles in the cardiovascular system, the organ of Corti, and circulating blood cells. As will be seen in this review, however, there are still a number of uncertainties regarding the transport properties, structural organization, and regulation of KCC3. The same is true regarding the mechanisms by which KCC3 accomplishes its numerous functions in animal cells.

Potent antitumor effect of tumor microenvironment-targeted oncolytic adenovirus against desmoplastic pancreatic cancer

Pancreatic cancer is a leading cause of cancer-related death. Desmoplastic pancreatic tumors exhibit excessive extracellular matrix (ECM) and are thus highly resistant to anticancer therapeutics, since the ECM restricts drug penetration and dispersion. Here, we designed and generated two hypoxia-responsive and cancer-specific hybrid promoters, H(mT)E and H(E)mT. Transgene expression driven by each hybrid promoter was markedly higher under hypoxic conditions than normoxic conditions. Moreover, H(E)mT-driven transgene expression was highly cancer-specific and was superior to that of H(mT)E-driven expression. A decorin-expressing oncolytic adenovirus (Ad; oH(E)mT-DCN) replicating under the control of the H(E)mT promoter induced more potent and highly cancer-specific cell death compared with its cognate control oncolytic Ad, which harbored the endogenous Ad E1A promoter. Moreover, oH(E)mT-DCN exhibited enhanced antitumor efficacy compared with both the clinically approved oncolytic Ad ONYX-015 and its cognate control oncolytic Ad lacking DCN. oH(E)mT-DCN treatment also attenuated the expression of major ECM components, such as collagen I/III, elastin and fibronectin and induced tumor cell apoptosis, leading to extensive viral dispersion within orthotopic pancreatic tumors and pancreatic cancer patient-derived tumor spheroids. Collectively, these findings demonstrate that oH(E)mT-DCN exhibits potent antitumor efficacy by degrading the ECM and inducing apoptosis in a multifunctional process. This process facilitates the dispersion and replication of oncolytic Ad, making it an attractive candidate for the treatment of aggressive and desmoplastic pancreatic cancer.

Adenovirus-mediated decorin expression induces cancer cell death through activation of p53 and mitochondrial apoptosis

Decorin (DCN) is a small leucine-rich proteoglycan that plays an important role in the regulation of apoptosis, proliferation, intercellular contact, and cell migration. Here we have investigated the detailed mechanism of apoptotic cell death induced by DCN expression. A marked increase in cytotoxicity was observed for both DCN-expressing replication-incompetent (dE1/DCN) and -competent (dB/DCN) adenoviruses (Ads) compared to the corresponding control Ads. FACS and TUNEL assays revealed that the expression of DCN induced apoptotic cell death. Specifically, the expression and stability of p53 were increased by DCN. In addition, western blot data showed that DCN expression activated mitochondrial apoptosis by increasing the expression level of p53. Similarly, DCN-expressing oncolytic Ads induced a greater antitumor effect in a murine xenograft model compared with control Ads. Tissue staining and western blot data from in vivo experiments demonstrated significantly higher levels of apoptosis in tumor tissues from mice treated with DCN-expressing Ads compared to those treated with control Ads. Collectively, these data support that cell killing effect is enhanced with Ad-mediated DCN expression via the induction of p53-mediated mitochondrial apoptosis, which could be a valuable benefit for antitumor efficacy.

Stromal Modulators of TGF-β in Cancer

Transforming growth factor-β (TGF-β) is an intriguing cytokine exhibiting dual activities in malignant disease. It is an important mediator of cancer invasion, metastasis and angiogenesis, on the one hand, while it exhibits anti-tumor functions on the other hand. Elucidating the precise role of TGF-β in malignant development and progression requires a better understanding of the molecular mechanisms involved in its tumor suppressor to tumor promoter switch. One important aspect of TGF-β function is its interaction with proteins within the tumor microenvironment. Several stromal proteins have the natural ability to interact and modulate TGF-β function. Understanding the complex interplay between the TGF-β signaling network and these stromal proteins may provide greater insight into the development of novel therapeutic strategies that target the TGF-β axis. The present review highlights our present understanding of how stroma modulates TGF-β activity in human cancers.

Cetuximab promotes epithelial to mesenchymal transition and cancer associated fibroblasts in patients with head and neck cancer

Purpose

To investigate if cetuximab induces epithelial to mesenchymal transition (EMT) and activation of cancer associated fibroblast (CAF) in the tumors of patients with squamous cell carcinoma of the head and neck (SCCHN).

Methods

Cetuximab was administered for two weeks prior to surgery to 20 treatment-naïve patients. Five untreated patients were included as controls. Tumor biopsies were performed at baseline and before surgery. Gene expression profiles and quantitative real-time PCR (qRT-PCR) analysis of the pre-and post-treatment biopsies were compared. To further investigate EMT and CAF, correlations between previously described EMT and CAF markers and our microarray data set were calculated.

Results

Gene expression profile analyses and qRT-PCR showed that some of the genes modified by cetuximab were related to CAFs and EMT (ZNF521, CXCL12, ASPN, OLFML3, OLFM1, TWIST1, LEF1, ZEB1, FAP). We identified 2 patient clusters with different EMT and CAF characteristics. Whereas one cluster showed clear upregulation of expression of genes implicated in CAF and EMT including markers of embryologic pathways like NOTCH and Wnt, the other did not.

Conclusion

Even if EMT and CAFs are implicated in cetuximab resistance in pre-clinical models, we demonstrate for the first time that these molecular processes may occur clinically early on.

Proteomics of thyroid tumours provides new insights into their molecular composition and changes associated with malignancy

Around 5% of the general population have palpable thyroid nodules. Although most thyroid tumours are benign, thyroid cancer represents the most common malignancy of the endocrine system, comprising mainly follicular and papillary thyroid carcinomas. Previous studies have shed some light on the molecular pathogenesis of thyroid cancer but there have not been any comprehensive mass spectrometry-based proteomic studies of large scale to reveal protein expression differences between thyroid tumours and the molecular alterations associated with tumour malignancy. We applied data-independent acquisition mass spectrometry which enabled quantitative expression analysis of over 1,600 proteins from 32 specimens to compare normal thyroid tissue with the three most common tumours of the thyroid gland: follicular adenoma, follicular carcinoma and papillary carcinoma. In follicular tumours, we found marked reduction of the tumour suppressor and therapeutic target extracellular protein decorin. We made the novel observation that TGFβ-induced protein ig-h3 (TGFBI) was found frequently overexpressed in follicular carcinoma compared with follicular adenoma. Proteomic pathway analysis showed changes in papillary carcinoma were associated with disruption of cell contacts (loss of E-cadherin), actin cytoskeleton dynamics and loss of differentiation markers, all hallmarks of an invasive phenotype.

Antiangiogenic mechanisms and factors in breast cancer treatment

Breast cancer is known to metastasize in its latter stages of existence. The different angiogenic mechanisms and factors that allow for its progression are reviewed in this article. Understanding these mechanisms and factors will allow researchers to design drugs to inhibit angiogenic behaviors and control the rate of tumor growth.

Decorin as a multivalent therapeutic agent against cancer

Decorin is a prototypical small leucine-rich proteoglycan that epitomizes the multifunctional nature of this critical gene family. Soluble decorin engages multiple receptor tyrosine kinases within the target-rich environment of the tumor stroma and tumor parenchyma. Upon receptor binding, decorin initiates signaling pathways within endothelial cells downstream of VEGFR2 that ultimately culminate in a Peg3/Beclin 1/LC3-dependent autophagic program. Concomitant with autophagic induction, decorin blunts capillary morphogenesis and endothelial cell migration, thereby significantly compromising tumor angiogenesis. In parallel within the tumor proper, decorin binds multiple RTKs with high affinity, including Met, for a multitude of oncosuppressive functions including growth inhibition, tumor cell mitophagy, and angiostasis. Decorin is also pro-inflammatory by modulating macrophage function and cytokine secretion. Decorin suppresses tumorigenic growth, angiogenesis, and prevents metastatic lesions in a variety of in vitro and in vivo tumor models. Therefore, decorin would be an ideal therapeutic candidate for combating solid malignancies.

Decorin: A Growth Factor Antagonist for Tumor Growth Inhibition

Decorin (DCN) is the best characterized member of the extracellular small leucine-rich proteoglycan family present in connective tissues, typically in association with or “decorating” collagen fibrils. It has substantial interest to clinical medicine owing to its antifibrotic, anti-inflammatory, and anticancer effects. Studies on DCN knockout mice have established that a lack of DCN is permissive for tumor development and it is regarded as a tumor suppressor gene. A reduced expression or a total disappearance of DCN has been reported to take place in various forms of human cancers during tumor progression. Furthermore, when used as a therapeutic molecule, DCN has been shown to inhibit tumor progression and metastases in experimental cancer models. DCN affects the biology of various types of cancer by targeting a number of crucial signaling molecules involved in cell growth, survival, metastasis, and angiogenesis. The active sites for the neutralization of different growth factors all reside in different parts of the DCN molecule. An emerging concept that multiple proteases, especially those produced by inflammatory cells, are capable of cleaving DCN suggests that native DCN could be inactivated in a number of pathological inflammatory conditions. In this paper, we review the role of DCN in cancer.

The small leucine-rich repeat proteoglycans in tissue repair and atherosclerosis

Proteoglycans consist of a protein core with one or more covalently attached glycosaminoglycan (GAG) side chains and have multiple roles in the initiation and progression of atherosclerosis. Here we discuss the potential and known functions of a group of small leucine-rich repeat proteoglycans (SLRPs) in atherosclerosis. We focus on five SLRPs, decorin, biglycan, lumican, fibromodulin and PRELP, because these have been detected in atherosclerotic plaques or demonstrated to have a role in animal models of atherosclerosis. Decorin and biglycan are modified post-translationally by substitution with chondroitin/dermatan sulphate GAGs, whereas lumican, fibromodulin and PRELP have keratan sulphate side chains, and the core proteins have leucine-rich repeat (LRR) motifs that are characteristic of the LRR superfamily. The chondroitin/dermatan sulphate GAG side chains have been implicated in lipid retention in atherosclerosis. The core proteins are discussed here in the context of (i) interactions with collagens and their implications in tissue integrity, fibrosis and wound repair and (ii) interactions with growth factors, cytokines, pathogen-associated molecular patterns and cell surface receptors that impact normal physiology and disease processes such as inflammation, innate immune responses and wound healing (i.e. processes that are all important in plaque development and progression). Thus, studies of these SLRPs in the context of wound healing are providing clues about their functions in early stages of atherosclerosis to plaque vulnerability and cardiovascular disease at later stages. Understanding of signal transduction pathways regulated by the core protein interactions is leading to novel roles and therapeutic potential for these proteins in wound repair and atherosclerosis.

Insights into the key roles of proteoglycans in breast cancer biology and translational medicine

Proteoglycans control numerous normal and pathological processes, among which are morphogenesis, tissue repair, inflammation, vascularization and cancer metastasis. During tumor development and growth, proteoglycan expression is markedly modified in the tumor microenvironment. Altered expression of proteoglycans on tumor and stromal cell membranes affects cancer cell signaling, growth and survival, cell adhesion, migration and angiogenesis. Despite the high complexity and heterogeneity of breast cancer, the rapid evolution in our knowledge that proteoglycans are among the key players in the breast tumor microenvironment suggests their potential as pharmacological targets in this type of cancer. It has been recently suggested that pharmacological treatment may target proteoglycan metabolism, their utilization as targets for immunotherapy or their direct use as therapeutic agents. The diversity inherent in the proteoglycans that will be presented herein provides the potential for multiple layers of regulation of breast tumor behavior. This review summarizes recent developments concerning the biology of selected proteoglycans in breast cancer, and presents potential targeted therapeutic approaches based on their novel key roles in breast cancer.

Proteoglycan form and function: A comprehensive nomenclature of proteoglycans

We provide a comprehensive classification of the proteoglycan gene families and respective protein cores. This updated nomenclature is based on three criteria: Cellular and subcellular location, overall gene/protein homology, and the utilization of specific protein modules within their respective protein cores. These three signatures were utilized to design four major classes of proteoglycans with distinct forms and functions: the intracellular, cell-surface, pericellular and extracellular proteoglycans. The proposed nomenclature encompasses forty-three distinct proteoglycan-encoding genes and many alternatively-spliced variants. The biological functions of these four proteoglycan families are critically assessed in development, cancer and angiogenesis, and in various acquired and genetic diseases where their expression is aberrant.

Cell-matrix interactions: focus on proteoglycan-proteinase interplay and pharmacological targeting in cancer

Proteoglycans are major constituents of extracellular matrices, as well as cell surfaces and basement membranes. They play key roles in supporting the dynamic extracellular matrix by generating complex structural networks with other macromolecules and by regulating cellular phenotypes and signaling. It is becoming evident, however, that proteolytic enzymes are required partners for matrix remodeling and for modulating cell signaling via matrix constituents. Proteinases contribute to all stages of diseases, particularly cancer development and progression, and contextually participate in either the removal of damaged products or in the processing of matrix molecules and signaling receptors. The dynamic interplay between proteoglycans and proteolytic enzymes is a crucial biological step that contributes to the pathophysiology of cancer and inflammation. Moreover, proteoglycans are implicated in the expression and secretion of proteolytic enzymes and often modulate their activities. In this review, we describe the emerging biological roles of proteoglycans and proteinases, with a special emphasis on their complex interplay. We critically evaluate this important proteoglycan-proteinase interactome and discuss future challenges with respect to targeting this axis in the treatment of cancer.

Extracellular matrix macromolecules: potential tools and targets in cancer gene therapy

Tumour cells create their own microenvironment where they closely interact with a variety of soluble and non-soluble molecules, different cells and numerous other components within the extracellular matrix (ECM). Interaction between tumour cells and the ECM is bidirectional leading to either progression or inhibition of tumourigenesis. Therefore, development of novel therapies targeted primarily to tumour microenvironment (TME) is highly rational. Here, we give a short overview of different macromolecules of the ECM and introduce mechanisms whereby they contribute to tumourigenesis within the TME. Furthermore, we present examples of individual ECM macromolecules as regulators of cell behaviour during tumourigenesis. Finally, we focus on novel strategies of using ECM macromolecules as tools or targets in cancer gene therapy in the future.

Extracellular matrix macromolecules: potential tools and targets in cancer gene therapy

Tumour cells create their own microenvironment where they closely interact with a variety of soluble and non-soluble molecules, different cells and numerous other components within the extracellular matrix (ECM). Interaction between tumour cells and the ECM is bidirectional leading to either progression or inhibition of tumourigenesis. Therefore, development of novel therapies targeted primarily to tumour microenvironment (TME) is highly rational. Here, we give a short overview of different macromolecules of the ECM and introduce mechanisms whereby they contribute to tumourigenesis within the TME. Furthermore, we present examples of individual ECM macromolecules as regulators of cell behaviour during tumourigenesis. Finally, we focus on novel strategies of using ECM macromolecules as tools or targets in cancer gene therapy in the future.

Decorin induces mitophagy in breast carcinoma cells via peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and mitostatin

Tumor cell mitochondria are key biosynthetic hubs that provide macromolecules for cancer progression and angiogenesis. Soluble decorin protein core, hereafter referred to as decorin, potently attenuated mitochondrial respiratory complexes and mitochondrial DNA (mtDNA) in MDA-MB-231 breast carcinoma cells. We found a rapid and dynamic interplay between peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and the decorin-induced tumor suppressor gene, mitostatin. This interaction stabilized mitostatin mRNA with concurrent accumulation of mitostatin protein. In contrast, siRNA-mediated abrogation of PGC-1α-blocked decorin-evoked stabilization of mitostatin. Mechanistically, PGC-1α bound MITOSTATIN mRNA to achieve rapid stabilization. These processes were orchestrated by the decorin/Met axis, as blocking the Met-tyrosine kinase or knockdown of Met abrogated these responses. Furthermore, depletion of mitostatin blocked decorin- or rapamycin-evoked mitophagy, increased vascular endothelial growth factor A (VEGFA) production, and compromised decorin-evoked VEGFA suppression. Collectively, our findings underscore the complexity of PGC-1α-mediated mitochondrial homeostasis and establish mitostatin as a key regulator of tumor cell mitophagy and angiostasis.

Decorin deficiency promotes hepatic carcinogenesis

Hepatocellular carcinoma represents one of the most-rapidly spreading cancers in the world. In the majority of cases, an inflammation-driven fibrosis or cirrhosis precedes the development of the tumor. During malignant transformation, the tumor microenvironment undergoes qualitative and quantitative changes that modulate the behavior of the malignant cells. A key constituent for the hepatic microenvironment is the small leucine-rich proteoglycan decorin, known to interfere with cellular events of tumorigenesis mainly by blocking various receptor tyrosine kinases (RTK) such as EGFR, Met, IGF-IR, PDGFR and VEGFR2. In this study, we characterized cell signaling events evoked by decorin deficiency in two experimental models of hepatocarcinogenesis using thioacetamide or diethyl nitrosamine as carcinogens. Genetic ablation of decorin led to enhanced tumor occurrence as compared to wild-type animals. These findings correlated with decreased levels of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) and a concurrent elevation in retinoblastoma protein phosphorylation via cyclin dependent kinase 4. Decreased steady state p21(Waf1/Cip1) levels correlated with enhanced expression of transcription factor AP4, a known transcriptional repressor of p21(Waf1/Cip1), and enhanced c-Myc protein levels. In addition, translocation of β-catenin was a typical event in diethyl nitrosamine-evoked tumors. In parallel, decreased phosphorylation of both c-Myc and β-catenin was observed in Dcn(-/-) livers likely due to the hindered GSK3β-mediated targeting of these proteins to proteasomal degradation. We discovered that in a genetic background lacking decorin, four RTKs were constitutively activated (phosphorylated), including three known targets of decorin such as PDGFRα, EGFR, IGF-IR, and a novel RTK MSPR/RON. Our findings provide powerful genetic evidence for a crucial in vivo role of decorin during hepatocarcinogenesis as lack of decorin in the liver and hepatic stroma facilitates experimental carcinogenesis by providing an environment devoid of this potent pan-RTK inhibitor. Thus, our results support future utilization of decorin as an antitumor agent in liver cancer.

Lumican binds ALK5 to promote epithelium wound healing

Lumican (Lum), a small leucine-rich proteoglycan (SLRP) family member, has multiple matricellular functions both as an extracellular matrix component and as a matrikine regulating cell proliferation, gene expression and wound healing. To date, no cell surface receptor has been identified to mediate the matrikine functions of Lum. This study aimed to identify a perspective receptor that mediates Lum effects on promoting wound healing. Transforming growth factor-β receptor 1 (ALK5) was identified as a potential Lum-interacting protein through in silico molecular docking and molecular dynamics. This finding was verified by biochemical pull-down assays. Moreover, the Lum function on wound healing was abrogated by an ALK5-specific chemical inhibitor as well as by ALK5 shRNAi. Finally, we demonstrated that eukaryote-specific post-translational modifications are not required for the wound healing activity of Lum, as recombinant GST-Lum fusion proteins purified from E. coli and a chemically synthesized LumC₁₃ peptide (the last C-terminal 13 amino acids of Lum) have similar effects on wound healing in vitro and in vivo.

Decorin causes autophagy in endothelial cells via Peg3

Soluble decorin affects the biology of several receptor tyrosine kinases by triggering receptor internalization and degradation. We found that decorin induced paternally expressed gene 3 (Peg3), an imprinted tumor suppressor gene, and that Peg3 relocated into autophagosomes labeled by Beclin 1 and microtubule-associated light chain 3. Decorin evoked Peg3-dependent autophagy in both microvascular and macrovascular endothelial cells leading to suppression of angiogenesis. Peg3 coimmunoprecipitated with Beclin 1 and LC3 and was required for maintaining basal levels of Beclin 1. Decorin, via Peg3, induced transcription of Beclin 1 and microtubule-associated protein 1 light chain 3 alpha genes, thereby leading to a protracted autophagic program. Mechanistically, decorin interacted with VEGF receptor 2 (VEGFR2) in a region overlapping with its natural ligand VEGFA, and VEGFR2 was required for decorin-evoked Beclin 1 and microtubule-associated protein 1 light chain 3 alpha expression as well as for Peg3 induction in endothelial cells. Moreover, decorin induced VEGFR2-dependent mitochondrial fragmentation and loss of mitochondrial membrane potential. Thus, we have unveiled a mechanism for a secreted proteoglycan in inducing Peg3, a master regulator of macroautophagy in endothelial cells.

Monitoring the initial delivery of an oncolytic measles virus encoding the human sodium iodide symporter to solid tumors using contrast-enhanced computed tomography

BACKGROUND

We aimed to determine the feasibility of monitoring viral delivery and initial distribution to solid tumors using iodinated contrast agent and micro-computed tomography (CT).

METHODS

Human BxPC-3 pancreatic tumor xenografts were established in nude mice. An oncolytic measles virus with an additional transcriptional unit encoding the sodium iodide symporter (NIS), as a reporter for viral infection, was mixed with a 1:10 dilution of Omnipaque 300 (GE Healthcare, Milwaukee, WI, USA) contrast agent and injected directly into tumors. Mice were imaged with micro-CT immediately before and after injection to determine the location of contrast agent/virus mixture. Mice were imaged again on day 3 after injection with micro-single-photon emission CT/CT to determine the location of NIS-mediated (99m) TcO(4) transport.

RESULTS

A 1:10 dilution of Omnipaque had no effect on viral infectivity or cell viability in vitro and was more than adequate for CT imaging of the intratumoral injectate distribution. The volume of tumor coverage with initial CT contrast agent and the 3-day postinfection measurement of virally infected tumor volume were significantly correlated. Additionally, regions of the tumor that did not receive contrast agent from the initial injection were largely devoid of viral infection at early time points.

CONCLUSIONS

Contrast-enhanced viral delivery enables a rapid and accurate prediction of the initial viral distribution within a solid tumor. This technique should enable real-time monitoring of viral propagation from initially infected tumor regions to adjacent tumor regions.

Biological functions of decorin in cancer

Decorin is a member of the extracellular matrix small leucine-rich proteoglycans family that exists and functions in stromal and epithelial cells. Accumulating evidence suggests that decorin affects the biology of various types of cancer by directly or indirectly targeting the signaling molecules involved in cell growth, survival, metastasis, and angiogenesis. More recent studies show that decorin plays important roles during tumor development and progression and is a potential cancer therapeutic agent. In this article, we summarize recent studies of decorin in cancer and discuss decorin's therapeutic and prognostic value.

Decorin interferes with platelet-derived growth factor receptor signaling in experimental hepatocarcinogenesis

Decorin, a secreted small leucine-rich proteoglycan, acts as a tumor repressor in a variety of cancers, mainly by blocking the action of several receptor tyrosine kinases such as the receptors for hepatocyte, epidermal and insulin-like growth factors. In the present study we investigated the effects of decorin in an experimental model of thioacetamide-induced hepatocarcinogenesis and its potential role in modulating the signaling of platelet-derived growth factor receptor-α (PDGFRα). Genetic ablation of decorin in mice led to enhanced tumor prevalence and a higher tumor count compared with wild-type mice. These findings correlated with decreased levels of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1) and concurrent activation (phosphorylation) of PDGFRα in the hepatocellular carcinomas generated in the decorin-null vis-à-vis wild-type mice. Notably, in normal liver PDGFRα localized primarily to the membrane of nonparenchymal cells, whereas in the malignant counterpart PDGFRα was expressed by the malignant cells at their cell surfaces. This process was facilitated by a genetic background lacking endogenous decorin. Double immunostaining of the proteoglycan and the receptor revealed only minor colocalization, leading to the hypothesis that decorin would bind to the natural ligand PDGF rather than to the receptor itself. Indeed, we found, using purified proteins and immune-blot assays, that decorin binds to PDGF. Collectively, our findings support the idea that decorin acts as a secreted tumor repressor during hepatocarcinogenesis by hindering the action of another receptor tyrosine kinase, such as the PDGFRα, and could be a novel therapeutic agent in the battle against liver cancer.

Dichotomy of decorin activity on the insulin-like growth factor-I system

The stromal-specific proteoglycan decorin has emerged in recent years as a critical regulator of tumor initiation and progression. Decorin regulates the biology of various types of cancer by modulating the activity of several receptor tyrosine kinases coordinating growth, survival, migration, and angiogenesis. Decorin binds to surface receptors for epidermal growth factor and hepatocyte growth factor with high affinity, and negatively regulates their activity and signaling via robust internalization and eventual degradation. The insulin-like growth factor (IGF)-I system plays a critical role in the regulation of cell growth both in vivo and in vitro. The IGF-I receptor (IGF-IR) is also essential for cellular transformation, owing to its ability to enhance cell proliferation and protect cancer cells from apoptosis. Recent data have pointed to a role of decorin in regulating the IGF-I system in both nontransformed and transformed cells. Significantly, there is a surprising dichotomy in the mechanism of decorin action on IGF-IR signaling, which differs considerably between physiological and pathological cellular models. In this review, we summarize the current knowledge on decorin regulation of the IGF-I system in normal and transformed cells, and discuss possible decorin-based therapeutic approaches to target IGF-IR-driven tumors.

Physiology of SLC12 transporters: lessons from inherited human genetic mutations and genetically engineered mouse knockouts

Among the over 300 members of the solute carrier (SLC) group of integral plasma membrane transport proteins are the nine electroneutral cation-chloride cotransporters belonging to the SLC12 gene family. Seven of these transporters have been functionally described as coupling the electrically silent movement of chloride with sodium and/or potassium. Although in silico analysis has identified two additional SLC12 family members, no physiological role has been ascribed to the proteins encoded by either the SLC12A8 or the SLC12A9 genes. Evolutionary conservation of this gene family from protists to humans confirms their importance. A wealth of physiological, immunohistochemical, and biochemical studies have revealed a great deal of information regarding the importance of this gene family to human health and disease. The sequencing of the human genome has provided investigators with the capability to link several human diseases with mutations in the genes encoding these plasma membrane proteins. The availability of bacterial artificial chromosomes, recombination engineering techniques, and the mouse genome sequence has simplified the creation of targeting constructs to manipulate the expression/function of these cation-chloride cotransporters in the mouse in an attempt to recapitulate some of these human pathologies. This review will summarize the three human disorders that have been linked to the mutation/dysfunction of the Na-Cl, Na-K-2Cl, and K-Cl cotransporters (i.e., Bartter's, Gitleman's, and Andermann's syndromes), examine some additional pathologies arising from genetically modified mouse models of these cotransporters including deafness, blood pressure, hyperexcitability, and epithelial transport deficit phenotypes.

Localization of decorin gene expression in normal human breast tissue and in benign and malignant tumors of the human breast

The small extracellular matrix proteoglycan decorin which possesses a potent antitumor activity has been shown to be present in various amounts in the stroma of several tumors including those of the breast. Regarding decorin in breast malignancies the published data are conflicting, i.e., whether breast cancer cells express it or not. Here, we first compared decorin gene expression levels between healthy human breast tissue and selected types of human breast cancer using GeneSapiens databank. Next, we localized decorin mRNA in tissue specimen of normal human breast, intraductal breast papillomas and various histologic types of human breast cancer using in situ hybridization (ISH) with digoxigenin-labeled RNA probes for decorin. We also examined the effect of decorin transduction on the behavior of cultured human breast cancer MCF7 cells. Analysis of GeneSapiens databank revealed that in various human breast cancers decorin expression is significant. However, ISH results clearly demonstrated that human breast cancer cells independently of the type of the cancer do not express decorin mRNA. This was also true for papilloma-forming cells of the human breast. Indeed, decorin gene expression in healthy human breast tissue as well as in benign and malignant tumors of human breast was shown to take place solely in cells of the original stroma. Decorin transduction using decorin adenoviral vector in decorin-negative MCF7 cells resulted in a significant decrease in the proliferation of these cells and changed cell cohesion. Decorin-transduced MCF7 cells also exhibited increased apoptosis. In conclusion, our study shows that in human breast tissue only cells of the original stroma are capable of decorin gene expression. Our study also shows that transduction of decorin in decorin-negative human breast cancer cells markedly modulates the growth pattern of these cells.

Decorin protein core affects the global gene expression profile of the tumor microenvironment in a triple-negative orthotopic breast carcinoma xenograft model

Decorin, a member of the small leucine-rich proteoglycan gene family, exists and functions wholly within the tumor microenvironment to suppress tumorigenesis by directly targeting and antagonizing multiple receptor tyrosine kinases, such as the EGFR and Met. This leads to potent and sustained signal attenuation, growth arrest, and angiostasis. We thus sought to evaluate the tumoricidal benefits of systemic decorin on a triple-negative orthotopic breast carcinoma xenograft model. To this end, we employed a novel high-density mixed expression array capable of differentiating and simultaneously measuring gene signatures of both Mus musculus (stromal) and Homo sapiens (epithelial) tissue origins. We found that decorin protein core modulated the differential expression of 374 genes within the stromal compartment of the tumor xenograft. Further, our top gene ontology classes strongly suggests an unexpected and preferential role for decorin protein core to inhibit genes necessary for immunomodulatory responses while simultaneously inducing expression of those possessing cellular adhesion and tumor suppressive gene properties. Rigorous verification of the top scoring candidates led to the discovery of three genes heretofore unlinked to malignant breast cancer that were reproducibly found to be induced in several models of tumor stroma. Collectively, our data provide highly novel and unexpected stromal gene signatures as a direct function of systemic administration of decorin protein core and reveals a fundamental basis of action for decorin to modulate the tumor stroma as a biological mechanism for the ascribed anti-tumorigenic properties.

Recombinant human decorin suppresses liver HepG2 carcinoma cells by p21 upregulation

Background

Decorin is a multifunctional molecule of the extracellular matrix and impedes different kinds of tumor cell growth, but the role and molecular mechanism by which decorin inhibits HepG2 cells is not fully understood. Our objective was to construct recombinant human decorin (pcDNA3.1-DCN) and to explore the mechanism by which it inhibits HepG2 cells.

Methods

This experiment was divided into three groups, ie, a control group, an empty vector group, and a pcDNA3.1-DCN group. pcDNA3.1-DCN was constructed using recombinant DNA technology, and the vector for pcDNA3.1-DCN and pcDNA3.1 was then transfected into HepG2 cells using Lipofectamine 2000.

Results

Compared with cells in the control group and in the empty vector group, growth of cells in the pcDNA3.1-DCN group was significantly suppressed, the ratios of cells in the G0/G1 phases and proportion of early apoptotic cells were significantly increased, and the level of p21^WAF1/CIP1 (p21) protein was markedly upregulated (P < 0.05). However, there was no significant difference among the three groups in p53 protein expression (P > 0.05).

Conclusion

The pcDNA3.1-DCN vector was successfully constructed and transfected into HepG2 cells, and decorin overexpression suppressed the growth of HepG2 cells by upregulation of p21 via a p53-independent pathway.

Decorin: a guardian from the matrix

Decorin, an archetypal member of the small leucine-rich proteoglycan gene family, has a broad binding repertoire that encompasses matrix structural components, such as collagens, and growth factors, particularly those that belong to the transforming growth factor-β ligand superfamily. Within the tumor microenvironment, stromal decorin has an inherent proclivity to directly bind and down-regulate several receptor tyrosine kinases, which are often overexpressed in cancer cells. The decorin interactome commands a powerful antitumorigenic signal by potently repressing and attenuating tumor cell proliferation, survival, migration, and angiogenesis. This collection of interacting molecules also regulates key downstream signaling processes indirectly via the sequestration of growth factors or directly via the antagonism of receptor tyrosine kinases. We propose that decorin can be considered a "guardian from the matrix" because of its innate ability to oppose pro-tumorigenic cues.

Differential effects of extracellular matrix and mechanical strain on airway smooth muscle cells from ovalbumin- vs. saline-challenged Brown Norway rats

The asthmatic airway is characterized by alterations in decorin and biglycan and increased airway smooth muscle (ASM). Further, the asthmatic airway may be subjected to abnormal mechanical strain. We hypothesized that ASM cells obtained from ovalbumin (OVA)--and saline (SAL)--challenged rats would respond differently to matrix and mechanical strain. ASMC were seeded on plastic, decorin or biglycan. Additional cells were grown on decorin, biglycan or collagen type 1, and then subjected to mechanical strain (Flexercell). The number of OVA ASMC was significantly greater than SAL ASM when seeded on plastic. A significant decrease was observed for both OVA and SAL ASMC seeded on decorin compared to plastic; the reduction in ASMC number was more modest for OVA. Biglycan decreased SAL ASMC number only. Strain reduced cell number for SAL and OVA ASMC grown on all matrices. Strain affected expression of β1-integrin differently in OVA vs. SAL ASMC. These data suggest that matrix and mechanical strain modulate ASMC number; these effects are differentially observed in OVA ASMC.

Decorin antagonizes the angiogenic network: concurrent inhibition of Met, hypoxia inducible factor 1α, vascular endothelial growth factor A, and induction of thrombospondin-1 and TIMP3

Decorin, a small leucine-rich proteoglycan, inhibits tumor growth by antagonizing multiple receptor tyrosine kinases including EGFR and Met. Here, we investigated decorin during normoxic angiogenic signaling. An angiogenic PCR array revealed a profound decorin-evoked transcriptional inhibition of pro-angiogenic genes, such as HIF1A. Decorin evoked a reduction of hypoxia inducible factor (HIF)-1α and vascular endothelial growth factor A (VEGFA) in MDA-231 breast carcinoma cells expressing constitutively-active HIF-1α. Suppression of Met with decorin or siRNA evoked a similar reduction of VEGFA by attenuating downstream β-catenin signaling. These data establish a noncanonical role for β-catenin in regulating VEGFA expression. We found that exogenous decorin induced expression of thrombospondin-1 and TIMP3, two powerful angiostatic agents. In contrast, decorin suppressed both the expression and enzymatic activity of matrix metalloprotease (MMP)-9 and MMP-2, two pro-angiogenic proteases. Our data establish a novel duality for decorin as a suppressor of tumor angiogenesis under normoxia by simultaneously down-regulating potent pro-angiogenic factors and inducing endogenous anti-angiogenic agents.

Signaling by the matrix proteoglycan decorin controls inflammation and cancer through PDCD4 and MicroRNA-21

The mechanisms linking immune responses and inflammation with tumor development are not well understood. Here, we show that the soluble form of the extracellular matrix proteoglycan decorin controls inflammation and tumor growth through PDCD4 (programmed cell death 4) and miR-21 (microRNA-21) by two mechanisms. First, decorin acted as an endogenous ligand of Toll-like receptors 2 and 4 and stimulated production of proinflammatory molecules, including PDCD4, in macrophages. Second, decorin prevented translational repression of PDCD4 by decreasing the activity of transforming growth factor-β1 and the abundance of oncogenic miR-21, a translational inhibitor of PDCD4. Moreover, increased PDCD4 abundance led to decreased release of the anti-inflammatory cytokine interleukin-10, thereby making the cytokine profile more proinflammatory. This pathway operates in both pathogen-mediated and sterile inflammation, as shown here for sepsis and growth retardation of established tumor xenografts, respectively. Decorin was an early response gene evoked by septic inflammation, and protein concentrations of decorin were increased in the plasma of septic patients and mice. In cancer, decorin reduced the abundance of anti-inflammatory molecules and increased that of proinflammatory molecules, thereby shifting the immune response to a proinflammatory state associated with reduced tumor growth. Thus, by stimulating proinflammatory PDCD4 and decreasing the abundance of miR-21, decorin signaling boosts inflammatory activity in sepsis and suppresses tumor growth.

Decreased expression of decorin and p57(KIP2) correlates with poor survival and lymphatic metastasis in lung cancer patients

PURPOSE

Decorin, p57(KIP2), and TGF-beta 1 have been investigated as prognostic factors because they appear to be associated with tumorigenesis; however, the effect of decorin and p57(KIP2) in lung cancer remains poorly understood. The purpose of this study was to examine the expression of decorin, p57(KIP2), and TGF-beta 1 in 64 lung cancer specimens and 36 normal lung specimens, and to analyze the relationships with respect to clinicopathological features and patient survival in lung cancer.

METHODS

The expression levels of decorin, p57(KIP2), and TGF-beta 1 were examined by in situ hybridization and immunohistochemistry.

RESULTS

Normal tissues exhibited a higher expression level of decorin than tumor tissues (p<0.05) and tumor tissues exhibited a higher expression level of TGF-beta 1 than normal tissues (p<0.05). The expression levels of p57(KIP2) and TGF-beta 1 were significantly associated with histological types of lung cancer (p<0.05), and the expression levels of decorin and p57(KIP2) were significantly associated with lymphatic invasion (p<0.05). Moreover, increased expression of decorin and p57(KIP2) correlated with increased survival (decorin, p=0.018; p57(KIP2), p=0.012).

CONCLUSION

Decreased expression levels of decorin and p57(KIP2) were associated with poor postsurgical survival time and lymphatic metastasis in lung cancer patients; moreover, low expression was an adverse prognostic factor.

Pathophysiological mechanisms of autosomal dominant congenital stromal corneal dystrophy: C-terminal-truncated decorin results in abnormal matrix assembly and altered expression of small leucine-rich proteoglycans

Autosomal-dominant congenital stromal corneal dystrophy (CSCD) is a human genetic disease characterized by corneal opacities beginning shortly after birth. It is linked to a frameshift mutation in decorin, resulting in a C-terminal truncation lacking 33 amino acids that includes the "ear" repeat, a feature specific for small leucine-rich proteoglycans. Our goals are to elucidate the roles of the mutant decorin in CSCD pathophysiology and to decipher the mechanism whereby mutant decorin affects matrix assembly. A novel animal model that recapitulates human CSCD was generated. This transgenic mouse model targets expression of truncated decorin to keratocytes, thereby mimicking the human frameshift mutation. Mutant mice expressed both wild-type and mutant decorin. Corneal opacities were found throughout, with increased severity toward the posterior stroma. The architecture of the lamellae was disrupted with relatively normal lamellae separated by regions of abnormal fibril organization. Within abnormal zones, the interfibrillar spacing and the fibril diameters were increased. Truncated decorin negatively affected the expression of endogenous decorin, biglycan, lumican, and keratocan and positively affected fibromodulin. Our results provide a mechanistic explanation for the generation of corneal opacities in CSCD. Thus, truncated decorin acts in a dominant-negative manner to interfere dually with matrix assembly and binding to receptor tyrosine kinases, thereby causing abnormal expression of endogenous small leucine-rich proteoglycans leading to structural abnormalities within the cornea and vision loss.