Matrix metalloproteinase-11/stromelysin-3 exhibits collagenolytic function against collagen VI under normal and malignant conditions

Local adipocyte cancer cell paracrine loop: can "sick fat" be more detrimental?

This review article focuses on the emerging role of tumor resident adipocytes. It provides in vitro and in vivo evidence that they are essential for cancer development/progression. In addition to systemic effects, their tumor-promoting impact is dependent on local functions, notably via a complex adipocyte cancer cell paracrine loop (ACCPL). Indeed, this event leads to dramatic phenotypic and/or functional modifications of both cell types as well as of the extracellular matrix. Adipocytes undergo delipidation leading to adipocytes/cancer-associated adipocytes/cancer-associated fibroblasts de-differentiation processes. In turn, cancer cell aggressiveness is exacerbated through increased proliferation, migration, and invasion properties. This is accompanied by intense tissue remodeling, conducting to the occurrence of the tumor stroma. The molecular pathways involved in ACCPL remain largely unknown. Nevertheless, several clues are starting to emerge. Moreover, obesity is currently a sign of increased risk and poor prognosis in human carcinomas. How adiposopathy might impact tumors and specifically the ACCPL is still under investigation. However, available experimental, epidemiological, and clinical data allow to draw some directions. Interestingly, there are numerous similarities between the ACCPL-induced and obesity-related molecular alterations. It might, therefore, be hypothesized that obesity provides a "constitutively active" local permissive environment for cancer cells. Improving our knowledge about ACCPL in both lean and obese patients remains a challenging task. Indeed, deciphering the cellular and molecular mechanisms behind ACCPL might provide new targets for improving diagnosis/prognosis and the design of innovative therapeutic strategies, and even, in case of obesity, for preventing cancer.

MicroRNA-mRNA interactions in colorectal cancer and their role in tumor progression

MicroRNAs (miRNA/miR) play an important role in gene regulatory networks through targeting mRNAs. They are involved in diverse biological processes such as cell proliferation, differentiation, angiogenesis, and apoptosis. Due to their pivotal effects on multiple genes and pathways, dysregulated miRNAs have been reported to be associated with different diseases, including colorectal cancer (CRC). Recent evidence indicates that aberrant miRNA expression is tightly linked with the initiation and progression of CRC. To elucidate the influence of miRNA regulation in CRC, it is critical to identify dysregulated miRNAs, their target mRNA genes and their involvement in gene regulatory and signaling networks. Various experimental and computational studies have been conducted to decipher the function of miRNAs involved in CRC. Experimental studies that are used for this purpose can be classified into two categories: direct/individual and indirect/high-throughput gene expression studies. Here we review miRNA target identification studies related to CRC with an emphasis on experimental data based on Luciferase reporter assays. Recent advances in determining the function of miRNAs and the signaling pathways they are involved in have also been summarized. The review helps bioinformaticians and biologists to find extensive information about downstream targets of dysregulated miRNAs, and their pro-/anti-CRC effects.

Hematopoietic stem cell-derived adipocytes and fibroblasts in the tumor microenvironment

The tumor microenvironment (TME) is complex and constantly evolving. This is due, in part, to the crosstalk between tumor cells and the multiple cell types that comprise the TME, which results in a heterogeneous population of tumor cells and TME cells. This review will focus on two stromal cell types, the cancer-associated adipocyte (CAA) and the cancer-associated fibroblast (CAF). In the clinic, the presence of CAAs and CAFs in the TME translates to poor prognosis in multiple tumor types. CAAs and CAFs have an activated phenotype and produce growth factors, inflammatory factors, cytokines, chemokines, extracellular matrix components, and proteases in an accelerated and aberrant fashion. Through this activated state, CAAs and CAFs remodel the TME, thereby driving all aspects of tumor progression, including tumor growth and survival, chemoresistance, tumor vascularization, tumor invasion, and tumor cell metastasis. Similarities in the tumor-promoting functions of CAAs and CAFs suggest that a multipronged therapeutic approach may be necessary to achieve maximal impact on disease. While CAAs and CAFs are thought to arise from tissues adjacent to the tumor, multiple alternative origins for CAAs and CAFs have recently been identified. Recent studies from our lab and others suggest that the hematopoietic stem cell, through the myeloid lineage, may serve as a progenitor for CAAs and CAFs. We hypothesize that the multiple origins of CAAs and CAFs may contribute to the heterogeneity seen in the TME. Thus, a better understanding of the origin of CAAs and CAFs, how this origin impacts their functions in the TME, and the temporal participation of uniquely originating TME cells may lead to novel or improved anti-tumor therapeutics.

Functional relationship between matrix metalloproteinase-11 and matrix metalloproteinase-14

MMP-11 is a key factor in physiopathological tissue remodeling. As an active form is secreted, its activity must be tightly regulated to avoid detrimental effects. Although TIMP-1 and TIMP-2 reversibly inhibit MMP-11, another more drastic scenario, presumably via hydrolysis, could be hypothesized. In this context, we have investigated the possible implication of MMP-14, since it exhibits a spatiotemporal localization similar to MMP-11. Using native HFL1-produced MMP-11 and HT-1080-produced MMP-14 as well as recombinant proteins, we show that MMP-11 is a MMP-14 substrate. MMP-14 cleaves MMP-11 catalytic domain at the PGG(P1)-I(P1′)LA and V/IQH(P1)-L(P1′)YG scissile bonds, two new cleavage sites. Interestingly, a functional test showed a dramatical reduction in MMP-11 enzymatic activity when incubated with active MMP-14, whereas inactive point-mutated MMP-14 had no effect. This function is conserved between human and mouse. Thus, in addition to the canonical reversible TIMP-dependent inhibitory system, irreversible MMP proteolytic inactivation might occur by cleavage of the catalytic domain in a MMP-dependent manner. Since MMP-14 is produced by HT-1080 cancer cells, whereas MMP-11 is secreted by HFL1 stromal cells, our findings support the emerging importance of tumor-stroma interaction/cross-talk. Moreover, they highlight a Janus-faced MMP-14 function in the MMP cascade, favoring activation of several pro-MMPs, but limiting MMP-11 activity. Finally, both MMPs are active at the cell periphery. Since MMP-14 is present at the cell membrane, whereas MMP-11 is soluble into the cellular microenvironment, this MMP-14 function might represent one critical regulatory mechanism to control the extent of pericellular MMP-11 bioavailability and protect cells from excessive/inappropriate MMP-11 function.

Collagen VI and hyaluronan: the common role in breast cancer

Collagen VI and hyaluronan are widely distributed extracellular matrix macromolecules that play a crucial role in tissue development and are highly expressed in cancers. Both hyaluronan and collagen VI are upregulated in breast cancer, generating a microenvironment that promotes tumour progression and metastasis. A growing number of studies show that these two molecules are involved in inflammation and angiogenesis by recruiting macrophages and endothelial cells, respectively. Additionally, collagen VI induces epithelial-mesenchymal transition that is correlated to increased synthesis of hyaluronan in mammary cells. Hyaluronan has also a specific role in cellular functions that depends mainly on the size of the polymer, whereas the effect of collagen VI in tumour progression may be the result of the intact molecule or the C5 peptide of α3(VI) chain, known as endotrophin. Collectively, these findings strongly support the parallel role of these molecules in tumour progression and suggest that they may be used as prognostic factors for the breast cancer treatment.

Peroxiredoxin-1 protects estrogen receptor α from oxidative stress-induced suppression and is a protein biomarker of favorable prognosis in breast cancer

INTRODUCTION

Peroxiredoxin-1 (PRDX1) is a multifunctional protein, acting as a hydrogen peroxide (H2O2) scavenger, molecular chaperone and immune modulator. Although differential PRDX1 expression has been described in many tumors, the potential role of PRDX1 in breast cancer remains highly ambiguous. Using a comprehensive antibody-based proteomics approach, we interrogated PRDX1 protein as a putative biomarker in estrogen receptor (ER)-positive breast cancer.

METHODS

An anti-PRDX1 antibody was validated in breast cancer cell lines using immunoblotting, immunohistochemistry and reverse phase protein array (RPPA) technology. PRDX1 protein expression was evaluated in two independent breast cancer cohorts, represented on a screening RPPA (n = 712) and a validation tissue microarray (n = 498). In vitro assays were performed exploring the functional contribution of PRDX1, with oxidative stress conditions mimicked via treatment with H2O2, peroxynitrite, or adenanthin, a PRDX1/2 inhibitor.

RESULTS

In ER-positive cases, high PRDX1 protein expression is a biomarker of improved prognosis across both cohorts. In the validation cohort, high PRDX1 expression was an independent predictor of improved relapse-free survival (hazard ratio (HR) = 0.62, 95% confidence interval (CI) = 0.40 to 0.96, P = 0.032), breast cancer-specific survival (HR = 0.44, 95% CI = 0.24 to 0.79, P = 0.006) and overall survival (HR = 0.61, 95% CI = 0.44 to 0.85, P = 0.004). RPPA screening of cancer signaling proteins showed that ERα protein was upregulated in PRDX1 high tumors. Exogenous H2O2 treatment decreased ERα protein levels in ER-positive cells. PRDX1 knockdown further sensitized cells to H2O2- and peroxynitrite-mediated effects, whilst PRDX1 overexpression protected against this response. Inhibition of PRDX1/2 antioxidant activity with adenanthin dramatically reduced ERα levels in breast cancer cells.

CONCLUSIONS

PRDX1 is shown to be an independent predictor of improved outcomes in ER-positive breast cancer. Through its antioxidant function, PRDX1 may prevent oxidative stress-mediated ERα loss, thereby potentially contributing to maintenance of an ER-positive phenotype in mammary tumors. These results for the first time imply a close connection between biological activity of PRDX1 and regulation of estrogen-mediated signaling in breast cancer.

Collagen as a double-edged sword in tumor progression

It has been recognized that cancer is not merely a disease of tumor cells, but a disease of imbalance, in which stromal cells and tumor microenvironment play crucial roles. Extracellular matrix (ECM) as the most abundant component in tumor microenvironment can regulate tumor cell behaviors and tissue tension homeostasis. Collagen constitutes the scaffold of tumor microenvironment and affects tumor microenvironment such that it regulates ECM remodeling by collagen degradation and re-deposition, and promotes tumor infiltration, angiogenesis, invasion and migration. While collagen was traditionally regarded as a passive barrier to resist tumor cells, it is now evident that collagen is also actively involved in promoting tumor progression. Collagen changes in tumor microenvironment release biomechanical signals, which are sensed by both tumor cells and stromal cells, trigger a cascade of biological events. In this work, we discuss how collagen can be a double-edged sword in tumor progression, both inhibiting and promoting tumor progression at different stages of cancer development.

Knockdown of MMP11 inhibits proliferation and invasion of gastric cancer cells

Matrix metalloproteinase 11 (MMP11 or stromelysin-3) has recently been reported to play a crucial role in the development and progression of multiple malignancies. The aim of this study was to investigate the function of MMP11 expression in human gastric adenocarcinoma (GAC). Using immunohistochemistry assay, we studied the expression level of MMP11 in GAC and adjacent non-cancerous tissues (ANCT). The association between MMP11 expression and tumor size and pathological grade, as well as metastatic potential was analyzed. Through small hairpin RNA (shRNA)-mediated MMP11 knockdown in SGC-7901 GAC cells, we observed the changes of the biological behaviors of GAC cells. Our results indicated that the rate of positive expression of MMP11 was higher in GAC tissues than in ANCT (55.0 vs 30.0 percent, P=0.025). MMP11 expression had no association with the factors of age or gender of the GAC patients, or the size, pathological staging and lymph node metastases of the tumors (each P greater than 0.05). Furthermore, MMP11 knockdown inhibited the proliferative activities and invasive potential of SGC-7901 GAC cells with decreased expression of IGF-1, PCNA and VEGF. Taken together, our findings demonstrated that MMP11 expression was increased in GAC tissues, but did not correlate with the clinicopathologic features. Knockdown of MMP11 expression could inhibit the proliferation and invasion of GAC cells probably through down-regulation of the IGF-1 signaling pathway, suggesting that MMP11 might be a potential therapeutic target for the treatment of gastric cancer.

Elastin-derived peptides are new regulators of insulin resistance development in mice

Although it has long been established that the extracellular matrix acts as a mechanical support, its degradation products, which mainly accumulate during aging, have also been demonstrated to play an important role in cell physiology and the development of cardiovascular and metabolic diseases. In the current study, we show that elastin-derived peptides (EDPs) may be involved in the development of insulin resistance (IRES) in mice. In chow-fed mice, acute or chronic intravenous injections of EDPs induced hyperglycemic effects associated with glucose uptake reduction and IRES in skeletal muscle, liver, and adipose tissue. Based on in vivo, in vitro, and in silico approaches, we propose that this IRES is due to interaction between the insulin receptor (IR) and the neuraminidase-1 subunit of the elastin receptor complex triggered by EDPs. This interplay was correlated with decreased sialic acid levels on the β-chain of the IR and reduction of IR signaling. In conclusion, this is the first study to demonstrate that EDPs, which mainly accumulate with aging, may be involved in the insidious development of IRES.

Stromal matrix metalloproteinase-11 is involved in the mammary gland postnatal development

MMP-11 is a bad prognosis paracrine factor in invasive breast cancers. However, its mammary physiological function remains largely unknown. In the present study we have investigated MMP-11 function during postnatal mammary gland development and function using MMP-11-deficient (MMP-11-/-) mice. Histological and immunohistochemical analyses as well as whole-mount mammary gland staining show alteration of the mammary gland in the absence of MMP-11, where ductal tree, alveolar structures and milk production are reduced. Moreover, a series of transplantation experiments allowed us to demonstrate that MMP-11 exerts an essential local paracrine function that favors mammary gland branching and epithelial cell outgrowth and invasion through adjacent connective tissues. Indeed, MMP-11-/- cleared fat pads are not permissive for wild-type epithelium development, whereas MMP-11-/- epithelium transplants grow normally when implanted in wild-type cleared fat pads. In addition, using primary mammary epithelial organoids, we show in vitro that this MMP-11 pro-branching effect is not direct, suggesting that MMP-11 acts via production/release of stroma-associated soluble factor(s). Finally, the lack of MMP-11 leads to decreased periductal collagen content, suggesting that MMP-11 has a role in collagen homeostasis. Thus, local stromal MMP-11 might also regulate mammary epithelial cell behavior mechanically by promoting extracellular matrix stiffness. Collectively, the present data indicate that MMP-11 is a paracrine factor involved during postnatal mammary gland morphogenesis, and support the concept that the stroma strongly impact epithelial cell behavior. Interestingly, stromal MMP-11 has previously been reported to favor malignant epithelial cell survival and promote cancer aggressiveness. Thus, MMP-11 has a paracrine function during mammary gland development that might be harnessed to promote tumor progression, exposing a new link between development and malignancy.

ANTXR1, a stem cell-enriched functional biomarker, connects collagen signaling to cancer stem-like cells and metastasis in breast cancer

Cancer stem-like cells are thought to contribute to tumor recurrence. The anthrax toxin receptor 1 (ANTXR1) has been identified as a functional biomarker of normal stem cells and breast cancer stem-like cells. Primary stem cell-enriched basal cells (CD49f(+)/EpCAM(-)/Lin(-)) expressed higher levels of ANTXR1 compared with mature luminal cells. CD49f(+)/EpCAM(-), CD44(+)/EpCAM(-), CD44(+)/CD24(-), or ALDEFLUOR-positive subpopulations of breast cancer cells were enriched for ANTXR1 expression. CD44(+)/CD24(-)/ANTXR1(+) cells displayed enhanced self-renewal as measured by mammosphere assay compared with CD44(+)/CD24(-)/ANTXR1(-) cells. Activation of ANTXR1 by its natural ligand C5A, a fragment of collagen VI α3, increased stem cell self-renewal in mammosphere assays and Wnt signaling including the expression of the Wnt receptor-lipoprotein receptor-related protein 6 (LRP6), phosphorylation of GSK3α/β, and elevated expression of Wnt target genes. RNAi-mediated silencing of ANTXR1 enhanced the expression of luminal-enriched genes but diminished Wnt signaling including reduced LRP6 and ZEB1 expression, self-renewal, invasion, tumorigenicity, and metastasis. ANTXR1 silencing also reduced the expression of HSPA1A, which is overexpressed in metastatic breast cancer stem cells. Analysis of public databases revealed ANTXR1 amplification in medullary breast carcinoma and overexpression in estrogen receptor-negative breast cancers with the worst outcome. Furthermore, ANTXR1 is among the 10% most overexpressed genes in breast cancer and is coexpressed with collagen VI. Thus, ANTXR1:C5A interactions bridge a network of collagen cleavage and remodeling in the tumor microenvironment, linking it to a stemness signaling network that drives metastatic progression.

Distinct and atypical intrinsic and extrinsic cell death pathways between photoreceptor cell types upon specific ablation of Ranbp2 in cone photoreceptors

Non-autonomous cell-death is a cardinal feature of the disintegration of neural networks in neurodegenerative diseases, but the molecular bases of this process are poorly understood. The neural retina comprises a mosaic of rod and cone photoreceptors. Cone and rod photoreceptors degenerate upon rod-specific expression of heterogeneous mutations in functionally distinct genes, whereas cone-specific mutations are thought to cause only cone demise. Here we show that conditional ablation in cone photoreceptors of Ran-binding protein-2 (Ranbp2), a cell context-dependent pleiotropic protein linked to neuroprotection, familial necrotic encephalopathies, acute transverse myelitis and tumor-suppression, promotes early electrophysiological deficits, subcellular erosive destruction and non-apoptotic death of cones, whereas rod photoreceptors undergo cone-dependent non-autonomous apoptosis. Cone-specific Ranbp2 ablation causes the temporal activation of a cone-intrinsic molecular cascade highlighted by the early activation of metalloproteinase 11/stromelysin-3 and up-regulation of Crx and CoREST, followed by the down-modulation of cone-specific phototransduction genes, transient up-regulation of regulatory/survival genes and activation of caspase-7 without apoptosis. Conversely, PARP1⁺-apoptotic rods develop upon sequential activation of caspase-9 and caspase-3 and loss of membrane permeability. Rod photoreceptor demise ceases upon cone degeneration. These findings reveal novel roles of Ranbp2 in the modulation of intrinsic and extrinsic cell death mechanisms and pathways. They also unveil a novel spatiotemporal paradigm of progression of neurodegeneration upon cell-specific genetic damage whereby a cone to rod non-autonomous death pathway with intrinsically distinct cell-type death manifestations is triggered by cell-specific loss of Ranbp2. Finally, this study casts new light onto cell-death mechanisms that may be shared by human dystrophies with distinct retinal spatial signatures as well as with other etiologically distinct neurodegenerative disorders.

The secondary demise of healthy neurons upon the degeneration of neurons harboring primary genetic defect(s) is hallmark to neurodegenerative diseases. However, the factors and mechanisms driving these cell-death processes are not understood, a severe limitation which has hampered the therapeutic development of neuroprotective approaches. The neuroretina is comprised of two main types of photoreceptor neurons, rods and cones. These undergo degeneration upon heterogeneous mutations or environmental stressors and the underlying diseases present conspicuous spatiotemporal pathological signatures whose molecular bases are not understood. We employed the multifunctional protein, Ran-binding protein-2 (Ranbp2), which is implicated in cell-type and stress-dependent clinical manifestations, to examine its role(s) in primary and secondary photoreceptor death mechanisms upon its specific loss in cones. Contrary to prior findings, we found that dying cones can trigger the loss of healthy rods. This process arises by the immediate activation of novel Ranbp2-responsive factors and downstream cascade events in cones that promote extrinsically the demise of rods. The mechanisms of rod and cone demise are molecularly distinct. Collectively, the data uncover distinct Ranbp2 roles in intrinsic and extrinsic cell-death and will likely contribute to our understanding of the spatiotemporal onset and progression of diseases affecting photoreceptor mosaics and other neural networks.

Collagen VI in cancer and its biological mechanisms

Collagen VI is a widely distributed extracellular matrix protein highly expressed in a variety of cancers that favors tumor growth and progression. A growing number of studies indicate that collagen VI directly affects malignant cells by acting on the Akt-GSK-3β-β-catenin-TCF/LEF axis, enhancing the production of protumorigenic factors and inducing epithelial-mesenchymal transition. Moreover, it affects the tumor microenvironment by increasing the recruitment of macrophages and endothelial cells, thus promoting tumor inflammation and angiogenesis. Furthermore, collagen VI promotes chemotherapy resistance and can be regarded as a potential biomarker for cancer diagnosis. Collectively, these findings strongly support a role for collagen VI as an important regulator in tumors and provide new targets for cancer therapies.

Adipocytes: impact on tumor growth and potential sites for therapeutic intervention

The prevalence of obesity has increased dramatically in recent decades, reaching epidemic proportions. It is becoming clear that obesity is associated not only with type 2 diabetes mellitus and cardiovascular disease, but also with multiple types of cancer. Obesity is characterized by impaired adipose tissue function, leading to adipocyte hypertrophy, inflammation, hypoxia and induced angiogenesis, extracellular matrix remodeling and fibrosis as well as additional stress responses. While epidemiological data indicate that obesity is a well-established risk factor for certain malignancies, the molecular mechanisms underlying the link between obesity and cancer are still poorly understood. Recent data implicates systemic and paracrine factors secreted from adipose tissue during the obese state, promoting cancer development and progression. Here, we focus on the obesity-associated adipose tissue remodeling that may not only lead to metabolic complications, but also to a permissive pro-tumorigenic environment. Particular attention is given to the local pro-tumorigenic effects derived from adipocytes that present an important part of the tumor microenvironment of at least some cancers, in an attempt to describe the nature of the major players of the adipocyte-cancer cell crosstalk that dictates to a large extent tumor progression.

Targeting the tumor microenvironment for cancer therapy

BACKGROUND

With the emergence of the tumor microenvironment as an essential ingredient of cancer malignancy, therapies targeting the host compartment of tumors have begun to be designed and applied in the clinic.

CONTENT

The malignant features of cancer cells cannot be manifested without an important interplay between cancer cells and their local environment. The tumor infiltrate composed of immune cells, angiogenic vascular cells, lymphatic endothelial cells, and cancer-associated fibroblastic cells contributes actively to cancer progression. The ability to change these surroundings is an important property by which tumor cells are able to acquire some of the hallmark functions necessary for tumor growth and metastatic dissemination. Thus in the clinical setting the targeting of the tumor microenvironment to encapsulate or destroy cancer cells in their local environment has become mandatory. The variety of stromal cells, the complexity of the molecular components of the tumor stroma, and the similarity with normal tissue present huge challenges for therapies targeting the tumor microenvironment. These issues and their interplay are addressed in this review. After a decade of intensive clinical trials targeting cellular components of the tumor microenvironment, more recent investigations have shed light on the important role in cancer progression played by the noncellular stromal compartment composed of the extracellular matrix.

SUMMARY

A better understanding of how the tumor environment affects cancer progression should provide new targets for the isolation and destruction of cancer cells via interference with the complex crosstalk established between cancer cells, host cells, and their surrounding extracellular matrix.

Adipocyte-derived endotrophin promotes malignant tumor progression

Adipocytes represent a major cell type in the mammary tumor microenvironment and are important for tumor growth. Collagen VI (COL6) is highly expressed in adipose tissue, upregulated in the obese state, and enriched in breast cancer lesions and is a stimulator of mammary tumor growth. Here, we have described a cleavage product of the COL6α3 chain, endotrophin (ETP), which serves as the major mediator of the COL6-mediated tumor effects. ETP augmented fibrosis, angiogenesis, and inflammation through recruitment of macrophages and endothelial cells. Moreover, ETP expression was associated with aggressive mammary tumor growth and high metastatic growth. These effects were partially mediated through enhanced TGF-β signaling, which contributes to tissue fibrosis and epithelial-mesenchymal transition (EMT) of tumor cells. Our results highlight the crucial role of ETP as an obesity-associated factor that promotes tumor growth in the context of adipocyte interactions with tumor and stromal cells.

A new paradigm for mechanobiological mechanisms in tumor metastasis

Tumor metastases and epithelial to mesenchymal transition (EMT) involve tumor cell invasion and migration through the dense collagen-rich extracellular matrix surrounding the tumor. Little is neither known about the mechanobiological mechanisms involved in this process, nor the role of the mechanical forces generated by the cells in their effort to invade and migrate through the stroma. In this paper we propose a new fundamental mechanobiological mechanism involved in cancer growth and metastasis, which can be both protective or destructive depending on the magnitude of the forces generated by the cells. This new mechanobiological mechanism directly challenges current paradigms that are focused mainly on biological and biochemical mechanisms associated with tumor metastasis. Our new mechanobiological mechanism describes how tumor expansion generates mechanical forces within the stroma to not only resist tumor expansion but also inhibit or enhance tumor invasion by, respectively, inhibiting or enhancing matrix metalloproteinase (MMP) degradation of the tensed interstitial collagen. While this mechanobiological mechanism has not been previously applied to the study of tumor metastasis and EMT, it may have the potential to broaden our understanding of the tumor invasive process and assist in developing new strategies for preventing or treating cancer metastasis.

In vivo evidence that TRAF4 is required for central nervous system myelin homeostasis

Tumor Necrosis Factor Receptor-Associated Factors (TRAFs) are major signal transducers for the TNF and interleukin-1/Toll-like receptor superfamilies. However, TRAF4 does not fit the paradigm of TRAF function in immune and inflammatory responses. Its physiological and molecular functions remain poorly understood. Behavorial analyses show that TRAF4-deficient mice (TRAF4-KO) exhibit altered locomotion coordination typical of ataxia. TRAF4-KO central nervous system (CNS) ultrastructure shows strong myelin perturbation including disorganized layers and disturbances in paranode organization. TRAF4 was previously reported to be expressed by CNS neurons. Using primary cell culture, we now show that TRAF4 is also expressed by oligodendrocytes, at all stages of their differentiation. Moreover, histology and electron microscopy show degeneration of a high number of Purkinje cells in TRAF4-KO mice, that was confirmed by increased expression of the Bax pro-apoptotic marker (immunofluorescence), TUNEL analysis, and caspase-3 activation and PARP1 cleavage (western blotting). Consistent with this phenotype, MAG and NogoA, two myelin-induced neurite outgrowth inhibitors, and their neuron partners, NgR and p75NTR were overexpressed (Q-RT-PCR and western blotting). The strong increased phosphorylation of Rock2, a RhoA downstream target, indicated that the NgR/p75NTR/RhoA signaling pathway, known to induce actin cytoskeleton rearrangement that favors axon regeneration inhibition and neuron apoptosis, is activated in the absence of TRAF4 (western blotting). Altogether, these results provide conclusive evidence for the pivotal contribution of TRAF4 to myelination and to cerebellar homeostasis, and link the loss of TRAF4 function to demyelinating or neurodegenerative diseases.

Histone deacetylase inhibitors upregulate MMP11 gene expression through Sp1/Smad complexes in human colon adenocarcinoma cells

MMP-11 (stromelysin-3) is a matrix metalloproteinase associated with tumor progression and poor prognosis. Its expression was initially described exclusively in stromal cells surrounding tumors, but more recently it has also been detected in macrophages and hepatocarcinoma cells. Here we show MMP-11 expression in human epithelial colon adenocarcinoma cell lines (Caco-2, HT-29 and BCS-TC2). Treatment of BCS-TC2 cells with butyrate and trichostatin A (TSA) (histone deacetylase inhibitors) increases MMP11 promoter activity and protein expression. Using electrophoretic mobility shift assay (EMSA) and supershift assays, we demonstrate for the first time that Sp1 is able to bind to the GC-boxes within the MMP11 proximal promoter region; this binding has been confirmed by chromatin immunoprecipitation. Sp1 is involved in MMP11 basal expression and it is essential for the upregulation of transcription by histone deacetylase inhibitors as deduced from mutant constructs lacking the Sp1 sites and by inhibition of its binding to the promoter with mithramycin. This regulation requires the formation of Sp1/Smad2 heterocomplexes, which is stimulated by an increase in the acetylation status of Smad after butyrate or TSA treatments. We have also found that ERK1/2-mitogen-activated protein kinase (MAPK), but not p38-MAPK or JNK, is involved in the upregulation of MMP11 by HDAC inhibitors.

Let-7c functions as a metastasis suppressor by targeting MMP11 and PBX3 in colorectal cancer

Accumulating evidence shows that microRNAs, functioning as either oncogenes or tumour suppressors by negatively regulating downstream target genes that are actively involved in tumour initiation and progression, may be promising biomarkers and therapy targets. Data mining through a microRNA chip database indicated that let-7c may be associated with tumour metastasis. Here, we confirmed that down-regulation of let-7c in primary cancer tissues was significantly associated with metastases, advanced TNM stages and poor survival of colorectal cancer patients. Moreover, ectopic expression of let-7c in a highly metastatic Lovo cell line remarkably suppressed cell migration and invasion in vitro by the down-regulation of K-RAS, MMP11 and PBX3, as well as tumour growth and metastases in vivo, whereas inhibition of let-7c in low-metastatic HT29 cells increased cell motility and invasion by the enhanced gene expression of K-RAS, MMP11 and PBX3. Interestingly, the luciferase reporters' activities with the 3'-UTRs of K-RAS, MMP11 and PBX3 were inhibited significantly by let-7c. Importantly, rescue experiments involving the over-expression of these genes without their 3'-UTRs completely reversed the effects of let-7c on tumour metastasis, both in vitro and in vivo. Finally, the levels of let-7c were inversely correlated with those of MMP11 and PBX3, but not with those of K-RAS. Taken together, these results demonstrate that let-7c, apart from its tumour growth suppression role, also functions as a tumour metastasis suppressor in colorectal cancer by directly destabilizing the mRNAs of MMP11 and PBX3 at least.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Matrix metalloproteinase-11 overexpressed in lobular carcinoma cells of the breast promotes anoikis resistance

The purpose of the present study was to examine the pathobiological properties of a matrix metalloproteinase, MMP-11 (also known as stromelysin-3), in the carcinogenesis of lobular carcinoma of the breast. Immunohistochemical staining demonstrated immunoreactivity with specific antibody to MMP-11 in 16 of 30 lobular carcinoma cells, but not in the non-cancerous terminal duct lobular unit. In positive cases, both noninvasive and invasive cancer cells exhibited immunoreactivity with anti-MMP-11 antibody; however, the staining patterns in noninvasive and invasive foci were distinct. In the noninvasive foci, immunoreactivity was observed in the cytoplasm beneath the plasma membrane, whereas immunoreactivity was found in all of the cytoplasm of infiltrating lobular carcinoma cells. Enforced expression of MMP-11 in the cultured lobular carcinoma MDA-MB-330 cells did not affect cell growth or Matrigel invasion activity. By contrast, overexpression of MMP-11 significantly increased resistance to anoikis, a programmed cell death triggered by a lack of proper cell matrix interaction, as evidenced by decrease in annexin V-positive cells and apoptotic DNA ladders. The present findings indicate that MMP-11 is overexpressed in many lobular carcinoma cells and that it may play a role in lobular carcinogenesis through increasing resistance to anoikis.

Gli1 enhances migration and invasion via up-regulation of MMP-11 and promotes metastasis in ERα negative breast cancer cell lines

Gli1 is an established oncogene and its expression in Estrogen Receptor (ER) α negative and triple negative breast cancers is predictive of a poor prognosis; however, the biological functions regulated by Gli1 in breast cancer have not been extensively evaluated. Herein, Gli1 was over-expressed or down-regulated (by RNA interference and by expression of the repressor form of Gli3) in the ERα negative, human breast cancer cell lines MDA-MB-231 and SUM1315. Reduced expression of Gli1 in these two cell lines resulted in a decrease in migration and invasion. Gli1 over-expression increased the migration and invasion of MDA-MB-231 cells with a corresponding increase in expression of MMP-11. Silencing MMP-11 in MDA-MB-231 cells that over-expressed Gli1 abrogated the Gli1-induced enhancement of migration and invasion. Sustained suppression of Gli1 expression decreased growth of MDA-MB-231 in vitro by increasing apoptosis and decreasing proliferation. In addition, silencing of Gli1 reduced the numbers and sizes of pulmonary metastases of MDA-MB-231 in an in vivo experimental metastasis assay. In summary, Gli1 promotes the growth, survival, migration, invasion and metastasis of ERα negative breast cancer. Additionally, MMP-11 is up-regulated by Gli1 and mediates the migration and invasion induced by Gli1 in MDA-MB-231.

Influence of stromal-epithelial interactions on breast cancer in vitro and in vivo

Stromal cell-secreted chemokines including CCL2 have been implicated in the primary tumor microenvironment, as mediators of tumor cell migration, proliferation, and angiogenesis. Expression of CCL2 and its principal receptor CCR2 was analyzed by RQ-PCR in primary tumor cells and breast cancer cell lines. Breast cancer cell lines (MDA-MB-231, T47D) were co-cultured directly on a monolayer of primary breast tumor and normal stromal cells, retrieved using EpCAM+ magnetic beads, and changes in expression of CCL2, CCR2, MMP11, ELK1, VIL2, and Ki67 detected by RQ-PCR. Epithelial cell migration and proliferation in response to stromal cell-secreted factors was also analyzed. In vivo, tumor xenografts were formed by co-injecting T47D cells with primary tumor stromal cells. Following establishment, tumors were harvested and digested, epithelial cells retrieved and analyzed by RQ-PCR. Whole tumor tissue was also analyzed by immunohistochemistry for CD31 and the VIL2 encoded protein Ezrin. Tumor stromal cells expressed significantly higher levels of CCL2 than normal cells, with no CCR2 expression detected. Primary epithelial cells and breast cancer cell lines expressed elevated CCL2, with relative expression of CCR2 found to be higher than the ligand. Interaction of breast cancer epithelial cells with primary tumor, but not normal stromal cells, stimulated increased expression of CCL2 (8-fold), ELK1 (6-fold), VIL2 (6-fold), and MMP11 (17-fold). Factors secreted by stromal cells, including CCL2, stimulated a significant increase in epithelial cell migration, with no effect on cell proliferation in vitro observed. In vivo, the presence of stromal cells resulted in tumors of increased volume, mediated at least in part through neoangiogenesis demonstrated by immunohistochemistry (CD31). Admixed tumor xenografts exhibited increased expression of Ki67, MMP11, VIL2, and ELK1. Elevated Ezrin protein was also detected, with increased cytoplasmic localization. The results presented highlight mechanisms through which breast cancer epithelial cells can harness stromal cell biology to support tumor progression.

Markers of vascular differentiation, proliferation and tissue remodeling in juvenile nasopharyngeal angiofibromas

Juvenile nasopharingeal angiofibroma (JNA) is a histologically benign locally aggressive tumor characterized by irregular vessels embedded in a fibrous stroma. Excessive vascularity results in bleeding complications, and the inhibition of angiogenesis is a promising strategy for managing extensive JNA tumors. To better characterize the endothelial components of JNA, we aimed to evaluate markers of vascular differentiation and proliferation, such as friend leukemia integration-1 (FLI-1) and endoglin, lymphatic markers, including podoplanin and vascular endothelial growth factor receptor 3 (VEGFR3) and its cognate ligand VEGFC, GLUT-1, a diagnostic marker that discriminates between hemangiomas and vascular malformations, and two markers of tissue remodeling, stromelysin 3 (ST3) and secreted acid protein rich in cysteine (SPARC). Antigens were assessed immunohistochemically in vessels and stromal cells of JNA archival cases (n=22). JNA endothelial cells were positive for endoglin, VEGFC and FLI-1, whereas podoplanin and VEGFR3 were negative in all cases. Both endothelial cells and fibroblasts stained for ST3 and SPARC. GLUT-1 was investigated in JNA cases, in infantile hemangiomas (n=123) and in vascular malformations (n=135) as controls. JNAs and vascular malformations were GLUT-1-negative, while hemangiomas showed positive staining. The presence of markers of endothelial differentiation and proliferation highlighted the hyper-proliferative state of JNA vessels. The absence of podoplanin and VEGFR3 underscores their blood endothelial cell characteristic. The absence of GLUT-1 discriminates JNAs from hemangiomas. ST3 and SPARC up-regulation in endothelial cells and fibroblasts may contribute to a compensatory signaling for controlling angiogenesis. Some of these markers may eventually serve as therapeutic targets. Our results may aid in the understanding of JNA pathophysiology.

Matrix metalloproteinase 11/stromelysin-3 exerts both activator and repressor functions during the hematogenous metastatic process in mice

MMP11 expression is a poor prognosis factor in human carcinomas. Although it has been shown to favor primary tumor development, its role in metastatic processes remains unclear. We studied the hematogenous metastatic activity of C26 mouse colon cancer cells injected into the tail vain of wild-type or MMP11-deficient mice during 2 months. Using X-ray computed tomography to image metastasis development in recipient living mice, lung metastases were found to occur earlier and to grow faster in wild-type mice. Histological analyses of the lung, liver, kidney, adrenal gland, mammary gland, ovary and salivary gland, performed at the end of experiment, also showed lower numbers of metastases in wild-type mice, regardless of organ. Lung metastases showed similar Factor VIII-positive vascular networks regardless of the mouse MMP11 status. However, those found in MMP11-deficient mice also exhibited vessel-like structures that did not express Factor VIII, Lyve-1 and vimentin, and were not stained with PAS. Consequently, they did not correspond to vascular or lymphatic vessels or to vascular mimicry channels. Collectively, these results revealed significant spatio-temporal variability that is dependent on host MMP11 status. Furthermore, they point-out the paradoxical role of MMP11 in favoring the onset and growth of lung metastases but limiting lung foci number, and inhibiting the cancer cell dissemination to other organs. These data highlight the complexity of the metastatic process in which the same factor can play activator or repressor functions depending on the metastatic step.

Physiology and pathophysiology of matrix metalloproteases

Matrix metalloproteases (MMPs) comprise a family of enzymes that cleave protein substrates based on a conserved mechanism involving activation of an active site-bound water molecule by a Zn(2+) ion. Although the catalytic domain of MMPs is structurally highly similar, there are many differences with respect to substrate specificity, cellular and tissue localization, membrane binding and regulation that make this a very versatile family of enzymes with a multitude of physiological functions, many of which are still not fully understood. Essentially, all members of the MMP family have been linked to disease development, notably to cancer metastasis, chronic inflammation and the ensuing tissue damage as well as to neurological disorders. This has stimulated a flurry of studies into MMP inhibitors as therapeutic agents, as well as into measuring MMP levels as diagnostic or prognostic markers. As with most protein families, deciphering the function(s) of MMPs is difficult, as they can modify many proteins. Which of these reactions are physiologically or pathophysiologically relevant is often not clear, although studies on knockout animals, human genetic and epigenetic, as well as biochemical studies using natural or synthetic inhibitors have provided insight to a great extent. In this review, we will give an overview of 23 members of the human MMP family and describe functions, linkages to disease and structural and mechanistic features. MMPs can be grouped into soluble (including matrilysins) and membrane-anchored species. We adhere to the 'MMP nomenclature' and provide the reader with reference to the many, often diverse, names for this enzyme family in the introduction.

Adipocyte extracellular matrix composition, dynamics and role in obesity

The central role of the adipose tissue in lipid metabolism places specific demands on the cell structure of adipocytes. The protein composition and dynamics of the extracellular matrix (ECM) is of crucial importance for the functioning of those cells. Adipogenesis is a bi-phasic process in which the ECM develops from a fibrillar to a laminar structure as cells move from the commitment phase to the growth phase characterized by storage of vast amounts of triglycerides. Mature adipocytes appear to spend a lot of energy on the maintenance of the ECM. ECM remodeling is mediated by a balanced complement of constructive and destructive enzymes together with their enhancers and inhibitors. ECM remodeling is an energy costing process regulated by insulin, by the energy metabolism, and by mechanical forces. In the obese, overgrowth of adipocytes may lead to instability of the ECM, possibly mediated by hypoxia.

Overexpression of matrix metalloproteinase 11 in human gastric carcinoma and its clinicopathologic significance

Matrix metalloproteinase 11 (stromelysin-3) has recently been reported to play a key role in human tumor progression and poor clinical outcome. The aim of this study was to investigate the significance of matrix metalloproteinase 11 expression in gastric cancer. Using real-time quantitative reverse-transcription polymerase chain reaction analysis and immunohistochemistry, we studied matrix metalloproteinase 11 expression levels in non-malignant gastric tissues and in gastric cancer tissues. The association between matrix metalloproteinase 11 expression levels and tumor stage and grade, as well as metastatic potential, was analyzed. Our results show that matrix metalloproteinase 11 expression was significantly higher in gastric cancer specimens compared with nonmalignant tissues at both transcriptional and protein levels, indicating its positive role in the development of gastric cancer. In addition, increased matrix metalloproteinase 11 expression levels were associated with advanced-stage and high-grade tumors, suggesting its involvement in the progression of gastric cancer. More importantly, increased matrix metalloproteinase 11 expression in gastric cancer specimens was correlated with increased expression of IGF-1, a molecule known to stimulate the proliferation, enhanced survival, and migration of cancer cells. Our results demonstrate that matrix metalloproteinase 11 is a novel factor in the development and progression of gastric cancer and suggest that matrix metalloproteinase 11 is a marker for advanced gastric cancer.

Gene expression profiling of the tumor microenvironment during breast cancer progression

INTRODUCTION

The importance of the tumor microenvironment in breast cancer has been increasingly recognized. Critical molecular changes in the tumor stroma accompanying cancer progression, however, remain largely unknown. We conducted a comparative analysis of global gene expression changes in the stromal and epithelial compartments during breast cancer progression from normal to preinvasive to invasive ductal carcinoma.

METHODS

We combined laser capture microdissection and gene expression microarrays to analyze 14 patient-matched normal epithelium, normal stroma, tumor epithelium and tumor-associated stroma specimens. Differential gene expression and gene ontology analyses were performed.

RESULTS

Tumor-associated stroma undergoes extensive gene expression changes during cancer progression, to a similar extent as that seen in the malignant epithelium. Highly upregulated genes in the tumor-associated stroma include constituents of the extracellular matrix and matrix metalloproteases, and cell-cycle-related genes. Decreased expression of cytoplasmic ribosomal proteins and increased expression of mitochondrial ribosomal proteins were observed in both the tumor epithelium and the stroma. The transition from preinvasive to invasive growth was accompanied by increased expression of several matrix metalloproteases (MMP2, MMP11 and MMP14). Furthermore, as observed in malignant epithelium, a gene expression signature of histological tumor grade also exists in the stroma, with high-grade tumors associated with increased expression of genes involved in immune response.

CONCLUSIONS

Our results suggest that the tumor microenvironment participates in tumorigenesis even before tumor cells invade into stroma, and that it may play important roles in the transition from preinvasive to invasive growth. The immune cells in the tumor stroma may be exploited by the malignant epithelial cells in high-grade tumors for aggressive invasive growth.