Significance of tumor-associated stroma in promotion of intratumoral lymphangiogenesis: pivotal role of a hyaluronan-rich tumor microenvironment

Excessive hyaluronan production promotes acquisition of cancer stem cell signatures through the coordinated regulation of Twist and the transforming growth factor β (TGF-β)-Snail signaling axis

The cancer stem cell (CSC) model suggests that a small subpopulation of cancer cells possesses the ability to self-renew and give rise to malignant progeny that drive cancer progression. Recent reports have also proposed the existence of certain extra- or intracellular signals that allow cancer progenitors to dynamically revert to a stem cell state. However, the mechanisms underlying cancer cell plasticity and CSC expansion are not entirely clear. Our previous studies using a hyaluronan synthase 2 (Has2) transgenic mouse model demonstrated that hyaluronan overproduction caused rapid development of aggressive breast carcinoma at a high incidence. Thus, we hypothesize that hyaluronan overproduction may accelerate cancer progression by expanding CSC subpopulations during cancer development. Primary cancer cells were established from mammary tumors developed in the transgenic mice and subjected to the Hoechst 33342 dye exclusion assay to sort side population (SP) from non-side population (non-SP) cells. Flow cytometric analysis demonstrated the enrichment of CD44(high)/CD24(low) CSC-like cells in the SP fraction of hyaluronan-overproducing cancer cells. This subpopulation exhibited several characteristics that were similar to CSCs, including cancer-initiating and mammosphere-forming abilities. Excess hyaluronan production drove the epithelial-to-mesenchymal transition process defined as the loss of epithelial phenotypes, up-regulation of transforming growth factor β (TGF-β), and induction of the epithelial-to-mesenchymal transition-related transcriptional factors Snail and Twist. Inhibition of TGF-β-Snail signaling or silencing of Twist expression abrogated the entrance into a stem cell state. Taken together, our findings suggest that hyaluronan overproduction allows plastic cancer cell populations to revert to stem cell states via Twist and the TGF-β-Snail signaling axis.

Accumulation of extracellular hyaluronan by hyaluronan synthase 3 promotes tumor growth and modulates the pancreatic cancer microenvironment

Extensive accumulation of the glycosaminoglycan hyaluronan is found in pancreatic cancer. The role of hyaluronan synthases 2 and 3 (HAS2, 3) was investigated in pancreatic cancer growth and the tumor microenvironment. Overexpression of HAS3 increased hyaluronan synthesis in BxPC-3 pancreatic cancer cells. In vivo, overexpression of HAS3 led to faster growing xenograft tumors with abundant extracellular hyaluronan accumulation. Treatment with pegylated human recombinant hyaluronidase (PEGPH20) removed extracellular hyaluronan and dramatically decreased the growth rate of BxPC-3 HAS3 tumors compared to parental tumors. PEGPH20 had a weaker effect on HAS2-overexpressing tumors which grew more slowly and contained both extracellular and intracellular hyaluronan. Accumulation of hyaluronan was associated with loss of plasma membrane E-cadherin and accumulation of cytoplasmic β-catenin, suggesting disruption of adherens junctions. PEGPH20 decreased the amount of nuclear hypoxia-related proteins and induced translocation of E-cadherin and β-catenin to the plasma membrane. Translocation of E-cadherin was also seen in tumors from a transgenic mouse model of pancreatic cancer and in a human non-small cell lung cancer sample from a patient treated with PEGPH20. In conclusion, hyaluronan accumulation by HAS3 favors pancreatic cancer growth, at least in part by decreasing epithelial cell adhesion, and PEGPH20 inhibits these changes and suppresses tumor growth.

A case of nonfunctioning pancreatic endocrine tumor with atypical imaging findings due to prominent fibrosis of the tumor stroma

The patient, a 56-year-old woman, was found during routine checkup to have a disorder of hepatic function. Abdominal ultrasonography showed an ill-defined hypoechoic mass in the head and body of the pancreas; however, no blood-flow signal was observed within the tumor on Doppler ultrasonography. Abdominal computed tomography showed a low-density area in the arterial and portal venous phases. The lesion was visualized as an area of low signal intensity on both T1- and T2-weighted magnetic resonance images, whereas fluorodeoxyglucose positron emission tomography showed fluorodeoxyglucose accumulation in the tumor. Although a preoperative diagnosis was difficult to make, a rapid cytologic examination revealed evidence of a pancreatic endocrine tumor, and subtotal stomach-preserving pancreaticoduodenectomy with portal vein resection was performed. Histopathological examination showed tumor cell nests scattered in abundant fibrotic tissue; the tumor cells had proliferated in a cord-like fashion and showed immunostaining for chromogranin A. Staining for fibroblast activation protein α was seen in the fibroblastic cells contained within the fibrous stroma surrounding the tumor cell nests, whereas both the fibroblastic cells in the tumor and those in the stroma showed a high rate of staining for thrombospondin. We presume that tumor-associated fibroblasts were involved in the fibrosis of the tumor stroma.

Accumulation of small hyaluronan oligosaccharides in tumour interstitial fluid correlates with lymphatic invasion and lymph node metastasis

BACKGROUND

Association studies have implicated the glycosaminoglycan hyaluronan (hyaluronic acid, HA) and its degrading enzymes the hyaluronidases in tumour progression and metastasis. Oligosaccharides of degraded HA have been ascribed a number of biological functions that are not exerted by high-molecular-weight HA (HMW-HA). However, whether these small HA oligosaccharides (sHA) have a role in tumour progression currently remains uncertain due to an inability to analyse their concentration in tumours.

METHODS

We report a novel method to determine the concentration of sHA ranging from 6 to 25 disaccharides in tumour interstitial fluid (TIF). Levels of sHA were measured in TIF from experimental rat tumours and human colorectal tumours.

RESULTS

While the majority of HA in TIF is HMW-HA, concentrations of sHA up to 6 μg ml(-1) were detected in a subset of tumours, but not in interstitial fluid from healthy tissues. In a cohort of 72 colorectal cancer patients we found that increased sHA concentrations in TIF are associated with lymphatic vessel invasion by tumour cells and the formation of lymph node metastasis.

CONCLUSIONS

These data document for the first time the pathophysiological concentration of sHA in tumours, and provide evidence of a role for sHA in tumour progression.

HAS2 and CD44 in breast tumorigenesis

Metastatic spread of breast cancer cells, facilitated by the epithelial-mesenchymal transition (EMT) process, is responsible for the majority of breast cancer mortality. Increased levels of hyaluronan due to deregulation of hyaluronan-synthesizing enzymes, like HAS2, and expression of CD44, the key receptor for hyaluronan, are correlated to poor outcome of patients with basal-like breast cancer. TGFβ induces HAS2 and CD44, both of which are required in the course of efficient TGFβ-induced EMT processes by mammary epithelial cells. Elucidation of the molecular mechanisms underlying tumor-stroma interactions in breast cancer including the regulation of HAS2 and CD44 expression may contribute to the development of better strategies to treat breast cancer patients.

Vascular endothelial growth factor-C modulates proliferation and chemoresistance in acute myeloid leukemic cells through an endothelin-1-dependent induction of cyclooxygenase-2

High-level expression of vascular endothelial growth factor (VEGF)-C is associated with chemoresistance and adverse prognosis in acute myeloid leukemia (AML). Our previous study has found that VEGF-C induces cyclooxygenase-2 (COX-2) expression in AML cell lines and significant correlation of VEGF-C and COX-2 in bone marrow specimens. COX-2 has been reported to mediate the proliferation and drug resistance in several solid tumors. Herein, we demonstrated that the VEGF-C-induced proliferation of AML cells is effectively abolished by the depletion or inhibition of COX-2. The expression of endothelin-1 (ET-1) rapidly increased following treatment with VEGF-C. We found that ET-1 was also involved in the VEGF-C-mediated proliferation of AML cells, and that recombinant ET-1 induced COX-2 mRNA and protein expressions in AML cells. Treatment with the endothelin receptor A (ETRA) antagonist, BQ 123, or ET-1 shRNAs inhibited VEGF-C-induced COX-2 expression. Flow cytometry and immunoblotting revealed that VEGF-C induces S phase accumulation through the inhibition of p27 and the upregulation of cyclin E and cyclin-dependent kinase-2 expressions. The cell-cycle-related effects of VEGF-C were reversed by the depletion of COX-2 or ET-1. The depletion of COX-2 or ET-1 also suppressed VEGF-C-induced increases in the bcl-2/bax ratio and chemoresistance against etoposide and cytosine arabinoside in AML cells. We also demonstrated VEGF-C/ET-1/COX-2 axis-mediated chemoresistance in an AML xenograft mouse model. Our findings suggest that VEGF-C induces COX-2-mediated resistance to chemotherapy through the induction of ET-1 expression. Acting as a key regulator in the VEGF-C/COX-2 axis, ET-1 represents a potential target for ameliorating resistance to chemotherapy in AML patients.

Deregulation of hyaluronan synthesis, degradation and binding promotes breast cancer

Clinical and experimental data indicate that hyaluronan accumulates in breast cancer compared with normal breast epithelium, which correlates to poor prognosis. In this review, we discuss the expression of genes encoding enzymes that synthesize or degrade hyaluronan, i.e. hyaluronan synthases and hyaluronidases or bind hyaluronan, i.e. CD44 and receptor for hyaluronan-mediated motility (RHAMM, also designated as HMMR or CD168), in relation to breast cancer progression. Hyaluronan and hyaluronan receptors have multi-faceted roles in signalling events in breast cancer. A better understanding of the molecular mechanisms underlying these signalling pathways is highly warranted and may lead to improvement of cancer treatment.

The roles of hyaluronan/RHAMM/CD44 and their respective interactions along the insidious pathways of fibrosarcoma progression

Fibrosarcomas are rare malignant mesenchymal tumors originating from fibroblasts. Importantly, fibrosarcoma cells were shown to have a high content and turnover of extracellular matrix (ECM) components including hyaluronan (HA), proteoglycans, collagens, fibronectin, and laminin. ECMs are complicated structures that surround and support cells within tissues. During cancer progression, significant changes can be observed in the structural and mechanical properties of the ECM components. Importantly, hyaluronan deposition is usually higher in malignant tumors as compared to benign tissues, predicting tumor progression in some tumor types. Furthermore, activated stromal cells are able to produce tissue structure rich in hyaluronan in order to promote tumor growth. Key biological roles of HA result from its interactions with its specific CD44 and RHAMM (receptor for HA-mediated motility) cell-surface receptors. HA-receptor downstream signaling pathways regulate in turn cellular processes implicated in tumorigenesis. Growth factors, including PDGF-BB, TGFβ2, and FGF-2, enhanced hyaluronan deposition to ECM and modulated HA-receptor expression in fibrosarcoma cells. Indeed, FGF-2 through upregulation of specific HAS isoforms and hyaluronan synthesis regulated secretion and net hyaluronan deposition to the fibrosarcoma pericellular matrix modulating these cells' migration capability. In this paper we discuss the involvement of hyaluronan/RHAMM/CD44 mediated signaling in the insidious pathways of fibrosarcoma progression.

Mesenchymal CD44 expression contributes to the acquisition of an activated fibroblast phenotype via TWIST activation in the tumor microenvironment

Tumor-stroma interactions play a crucial role in cancer progression by eliciting factors that promote proliferative, angiogenic, and invasive supports to the tumor microenvironment. Mesenchymal stromal/stem cells (MSC) contribute to stroma in part as cancer-associated fibroblasts (CAF), but a complete understanding of how MSC contribute to the tumor stroma is lacking. In this study, we show how CAF phenotypes rely upon MSC expression of the multifunctional cell surface glycoprotein CD44, a putative stem cell marker. Through bone marrow transplantation experiments in a transgenic mouse model of cancer, we determined that CD44 deficiency leads to a relative reduction in the contribution of bone marrow-derived cells to tumor stroma. CD44 attenuation in MSC limited their expression of CAF markers induced by tumor conditioning, and these MSC migrated poorly and provided weak angiogenic support compared with wild-type MSC. These defects were linked to deficiencies in the ability of CD44-attenuated MSC to transcriptionally upregulate Twist expression. Together, our results establish that CD44 expression contributes to critical functions in the tumor stroma.

Biological characteristics and genetic heterogeneity between carcinoma-associated fibroblasts and their paired normal fibroblasts in human breast cancer

Background

The extensional signals in cross-talk between stromal cells and tumor cells generated from extracellular matrix molecules, soluble factor, and cell-cell adhesion complexes cooperate at the extra- and intracellular level in the tumor microenvironment. CAFs are the primary type of stromal cells in the tumor microenvironment and play a pivotal role in tumorigenesis and development. Hitherto, there is hardly any systematic analysis of the intrinsic relationship between CAFs function and its abnormal signaling pathway. The extreme complexity of CAFs’ features and their role in tumor development are needed to be further investigated.

Methodology/Principal Findings

We primary cultured CAFs and NFs from early stages of breast cancer tissue and identified them using their biomarker by immunohistochemistry for Fibronectin, α-SMA and FAP. Microarray was applied to analyze gene expression profiles of human breast CAFs and the paired NFs. The Up-regulated genes classified by Gene Ontology, signal pathways enriched by DAVID pathway analysis. Abnormal signaling pathways in breast cancer CAFs are involved in cell cycle, cell adhesion, signal transduction and protein transport being reported in CAFs derived from other tumors. Significantly, the altered ATM signaling pathway, a set of cell cycle regulated signaling, and immune associated signaling are identified to be changed in CAFs.

Conclusions/Significance

CAFs have the vigorous ability of proliferation and potential of invasion and migration comparing with NFs. CAFs could promote breast cancer cell invasion under co-culture conditions through up-regulated CCL18 and CXCL12. Consistently with its biologic behavior, the gene expression profiling analyzed by microarray shows that some of key signaling pathways, such as cell cycle, cell adhesion, and secreting factors play an important role in CAFs. The altered ATM signaling pathway is abnormally active in the early stage of breast cancer. The set of immune associated signaling may be involved in tumor cell immune evasion.

Correlation between hyaluronic acid,hyaluronic Acid synthase and human renal clear cell carcinoma

OBJECTIVE

To study the correlation between hyaluronic acid (HA), hyaluronic acid synthase (HAS) and human renal clear cell carcinoma (RCCC).

METHODS

The expression of three HAS isoforms' gene and HA in 93 RCCC tissues, 27 nephridial tissues by the side of RCCC from two hospitals were measured with Real-Time RT-PCR、Western Blot and immunohistochemical methods and analyzed.

RESULTS

All RCCC and adjacent normal tissues expressed three HASs' mRNA & protein; at the mRNA level, both RCCC and adjacent normal tissues, expressed more HAS3 than HAS1 or HAS2, their differences were statistically significant (all P values <0.05); but, at the protein level, all HAS isoforms presented the equivalent expression. Compared with the adjacent non-neoplastic kidney tissues, the expression of all HAS isoforms' mRNA in RCCC tissues were increased evidently and their differences were significant (all P values <0.0001); but at the protein level, only the expression of HAS3 increased evidently (P=0.022). In all adjacent normal tissues, more than 80% renal tubular cells strongly expressed HA, however, only the minority RCCC cases (16/93) presented weakly positive HA staining in few cancer nests (5%-30%), the difference were significant (P<0.0001). In RCCC tissues subgrouped according to clinical stage, pathological grade, lymphatic metastasis or not and distant metastasis or not, the HASs' mRNA & protein differential expression all had no statistical significance (all P values >0.05).

CONCLUSION

Different from other malignancy, HA and HASs (except for HAS3) may not play important roles in the biological progress of human RCCC.

Crucial role of hyaluronan in neointimal formation after vascular injury

Background

Hyaluronan (HA) is a primary component of the extracellular matrix of cells, and it is involved in the pathogenesis of atherosclerosis. The purpose of this study was to investigate the role of HA in neointimal formation after vascular injury and determine its tissue-specific role in vascular smooth muscle cells (VSMCs) by using a cre-lox conditional transgenic (cTg) strategy.

Methods and Results

HA was found to be expressed in neointimal lesions in humans with atherosclerosis and after wire-mediated vascular injury in mice. Inhibition of HA synthesis using 4-methylumbelliferone markedly inhibited neointimal formation after injury. In vitro experiments revealed that low-molecular-weight HA (LMW-HA) induced VSMC activation, including migration, proliferation, and production of inflammatory cytokines, and reactive oxygen species (ROS). The migration and proliferation of VSMCs were mediated by the CD44/RhoA and CD44/ERK1/2 pathways, respectively. Because HA synthase 2 (HAS2) is predominantly expressed in injured arteries, we generated cTg mice that overexpress the murine HAS2 gene specifically in VSMCs (cHAS2/CreSM22α mice) and showed that HA overexpression markedly enhanced neointimal formation after cuff-mediated vascular injury. Further, HA-overexpressing VSMCs isolated from cHAS2/CreSM22α mice showed augmented migration, proliferation, and production of inflammatory cytokines and ROS.

Conclusion

VSMC-derived HA promotes neointimal formation after vascular injury, and HA may be a potential therapeutic target for cardiovascular disease.

Tumor angiogenesis and lymphangiogenesis: tumor/endothelial crosstalk and cellular/microenvironmental signaling mechanisms

Tumor angiogenesis and lymphangiogenesis are key features of tumor progression and metastasis. The role of tumor cells-derived factors in the promotion of associated angiogenesis and lymphangiogenesis is much studied and, no doubt, very important for the understanding of cancer progression. This review aims to present and discuss the work done on the pro-angiogenic and lymphangiogenic cellular interactions within the tumor microenvironment and the signaling pathways that regulate this crosstalk. Such multifactor studies are critical for the development of future therapeutic approaches for cancer because they take into account the complexities of cellular interactions within the tumor microenvironment.

Therapeutic targeting of hyaluronan in the tumor stroma

The tumor stroma, consisting of non-malignant cells and the extracellular matrix, undergoes significant quantitative and qualitative changes throughout malignant transformation and tumor progression. With increasing recognition of the role of the tumor microenvironment in disease progression, stromal components of the tumor have become attractive targets for therapeutic intervention. Stromal accumulation of the glycosaminoglycan hyaluronan occurs in many tumor types and is frequently associated with a negative disease prognosis. Hyaluronan interacts with other extracellular molecules as well as cellular receptors to form a complex interaction network influencing physicochemical properties, signal transduction, and biological behavior of cancer cells. In preclinical animal models, enzymatic removal of hyaluronan is associated with remodeling of the tumor stroma, reduction of tumor interstitial fluid pressure, expansion of tumor blood vessels and facilitated delivery of chemotherapy. This leads to inhibition of tumor growth and increased survival. Current evidence shows that abnormal accumulation of hyaluronan may be an important stromal target for cancer therapy. In this review we highlight the role of hyaluronan and hyaluronan-mediated interactions in cancer, and discuss historical and recent data on hyaluronidase-based therapies and the effect of hyaluronan removal on tumor growth.

The connection between lymphangiogenic signalling and prostaglandin biology: a missing link in the metastatic pathway

Substantial evidence supports important independent roles for lymphangiogenic growth factor signaling and prostaglandins in the metastatic spread of cancer. The significance of the lymphangiogenic growth factors, vascular endothelial growth factor (VEGF)-C and VEGF-D, is well established in animal models of metastasis, and a strong correlation exits between an increase in expression of VEGF-C and VEGF-D, and metastatic spread in various solid human cancers. Similarly, key enzymes that control the production of prostaglandins, cyclooxygenases (COX-1 and COX-2, prototypic targets of Non-steroidal anti-inflammatory drugs (NSAIDs)), are frequently over-expressed or de-regulated in the progression of cancer. Recent data have suggested an intersection of lymphangiogenic growth factor signaling and the prostaglandin pathways in the control of metastatic spread via the lymphatic vasculature. Furthermore, this correlates with current clinical data showing that some NSAIDs enhance the survival of cancer patients through reducing metastasis. Here, we discuss the potential biochemical and cellular basis for such anti-cancer effects of NSAIDs through the prostaglandin and VEGF signaling pathways.

An EMILIN1-negative microenvironment promotes tumor cell proliferation and lymph node invasion

The evidence that EMILIN1 (Elastic Microfibril Interface Located proteIN) deficiency in Emilin1(-/-) mice caused dermal and epidermal hyperproliferation and an abnormal lymphatic phenotype prompted us to hypothesize the involvement of this extracellular matrix component in tumor development and in lymphatic metastasis. Using the 12-dimethylbenz(α)anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA) two-stage model of skin carcinogenesis, we found that Emilin1(-/-) mice presented an accelerated formation, a higher incidence, and the development of a larger number of tumors compared with their wild-type littermates. EMILIN1-negative tumors showed more Ki67-positive proliferating cells and higher levels of pErk1/2. In these tumors, PTEN expression was lower. Emilin1(-/-) mice displayed enhanced lymphangiogenesis both in the tumor and in the sentinel lymph nodes. Accordingly, tumor growth and lymph node metastasis of transplanted syngenic tumors were also increased in Emilin1(-/-) mice. In vitro transmigration assays through lymphatic endothelial cells showed that EMILIN1 deficiency greatly facilitated tumor cell trafficking. Overall, these data established that EMILIN1 exerts a protective role in tumor growth, in tumor lymphatic vessel formation, as well as in metastatic spread to lymph nodes and reinforced the importance of its presence in the microenvironment to determine the tumor phenotype.

Increased hyaluronan content and stromal cell CD44 associate with HER2 positivity and poor prognosis in human breast cancer

Previous in vitro studies have suggested interactions between hyaluronan (HA), CD44 and HER2. We have studied the expression of HA and CD44 in a material of 278 breast cancer cases, half of which were HER2-positive. Intense stromal HA staining was associated with HER2 positivity, large tumor size, lymph node positivity, hormone receptor negativity, poor differentiation, a high body mass index, increased relapse rate and shortened overall survival. Among the 139 HER2-positive cases, the relapse rate was associated with the intensity of stromal HA staining as most of the relapses occurred in the cases with intense stromal HA staining. The presence of HA in the carcinoma cells was related to the frequency of relapses as none of the patients without HA in carcinoma cells experienced a relapse, whereas 33.3% of those with a high percentage of HA-positive carcinoma cells suffered a relapse. CD44 positivity in carcinoma cells was related to poor differentiation, postmenopausal status and triple negative breast carcinoma. CD44 positivity in stromal cells was associated with HER2 positivity, large tumor size, hormone receptor negativity, poor differentiation, increased relapse rate and shortened overall survival. The association between HER2 positivity and intense stromal HA staining indicates that HA could be one of the factors involved in the unfavorable outcome of HER2-positive patients. This study also suggests that HA in breast carcinoma cells and CD44 in stromal cells may have clinical significance.

Macrophages are important mediators of either tumor- or inflammation-induced lymphangiogenesis

The lymphatic system provides important functions for tissue fluid homeostasis and immune response. Lymphangiogenesis, the formation of new lymphatics, comprises a series of complex cellular events in vitro or in vivo, e.g., proliferation, differentiation, and sprouting. Recent evidence has implied that macrophages act as a direct structural contributor to lymphatic endothelial walls or secret VEGF-C/-D and VEGF-A to initiate lymphangiogenesis in inflamed or tumor tissues. Bone marrow-derived macrophages are versatile cells that express different functional programs in response to exposure to microenvironmental signals, and can be identified by specific expression of a number of proteins, F4/80, CD11b, and CD68. Several causative factors, e.g., NF-κB, IL-1β, TNF-α, SDF-1, M-CSF, especially TonEBP/VEGF-C signaling, may be actively involved in macrophage-induced lymphangiogenesis. Alteration of macrophage phenotype and function has a profound effect on the development and progression of inflammation and malignancy, and macrophage depletion for controlling lymphangiogenesis may provide a novel approach for prevention and treatment of lymphatic-associated diseases.

Hyaluronan synthase 2 (HAS2) promotes breast cancer cell invasion by suppression of tissue metalloproteinase inhibitor 1 (TIMP-1)

Invasion and metastasis are the primary causes of breast cancer mortality, and increased knowledge about the molecular mechanisms involved in these processes is highly desirable. High levels of hyaluronan in breast tumors have been correlated with poor patient survival. The involvement of hyaluronan in the early invasive phase of a clone of breast cancer cell line MDA-MB-231 that forms bone metastases was studied using an in vivo-like basement membrane model. The metastatic to bone tumor cells exhibited a 7-fold higher hyaluronan-synthesizing capacity compared with MDA-MB-231 cells predominately due to an increased expression of hyaluronan synthase 2 (HAS2). We found that knockdown of HAS2 completely suppressed the invasive capability of these cells by the induction of tissue metalloproteinase inhibitor 1 (TIMP-1) and dephosphorylation of focal adhesion kinase. HAS2 knockdown-mediated inhibition of basement membrane remodeling was rescued by HAS2 overexpression, transfection with TIMP-1 siRNA, or addition of TIMP-1-blocking antibodies. Moreover, knockdown of HAS2 suppressed the EGF-mediated induction of the focal adhesion kinase/PI3K/Akt signaling pathway. Thus, this study provides new insights into a possible mechanism whereby HAS2 enhances breast cancer invasion.

The ADAMTS1 protease gene is required for mammary tumor growth and metastasis

A disintegrin and metalloprotease with thrombospondin motifs protein 1 (ADAMTS1) is a protease commonly up-regulated in metastatic carcinoma. Its overexpression in cancer cells promotes experimental metastasis, but whether ADAMTS1 is essential for metastatic progression is unknown. To address this question, we investigated mammary cancer progression and spontaneous metastasis in the MMTV-PyMT mouse mammary tumor model in Adamts1 knockout mice. Adamts1(-/-)/PyMT mice displayed significantly reduced mammary tumor and lung metastatic tumor burden and increased survival, compared with their wild-type and heterozygous littermates. Histological examination revealed an increased proportion of tumors with ductal carcinoma in situ and a lower proportion of high-grade invasive tumors in Adamts1(-/-)/PyMT mice, compared with Adamts1(+/+)/PyMT mice. Increased apoptosis with unaltered proliferation and vascular density in the Adamts1(-/-)/PyMT tumors suggested that reduced cell survival accounts for the lower tumor burden in ADAMTS1-deficient mice. Furthermore, Adamts1(-/-) tumor stroma had significantly lesser amounts of proteolytically cleaved versican and increased numbers of CD45(+) leukocytes. Characterization of immune cell gene expression indicated that cytotoxic cell activation was increased in Adamts1(-/-) tumors, compared with Adamts1(+/+) tumors. This finding is supported by significantly elevated IL-12(+) cell numbers in Adamts1(-/-) tumors. Thus, in vivo ADAMTS1 may promote mammary tumor growth and progression to metastasis in the PyMT model and is a potential therapeutic target to prevent metastatic breast cancer.

Role of the lymphatics in cancer metastasis and chemotherapy applications

The lymphatic system was first described centuries ago. The recent discovery of various molecular markers has allowed for more in-depth research of the lymphatic system and its role in health and disease. The lymphatic system has recently been elucidated as playing an active role in cancer metastasis. The knowledge of the active processes involved in lymphatic metastasis provides novel treatment targets for various malignancies.

Prostate cancer increases hyaluronan in surrounding nonmalignant stroma, and this response is associated with tumor growth and an unfavorable outcome

Our objective was to investigate whether the presence of a tumor increases hyaluronan (HA) levels in surrounding prostate tissues and whether this extratumoral HA influences tumor growth and outcome. From a series of 287 men diagnosed with prostate cancer at transurethral resection and followed up with watchful waiting, tissue microarrays were constructed, stained, and scored for HA. A high HA staining score in the tumor stroma or in nonmalignant prostate tissue stroma were both associated positively with higher Gleason score and larger tumor volume, and was associated with a poor outcome. HA staining score was not an independent marker for outcome (multivariate Cox, with Gleason score, tumor volume, stage, and HA variables). In an orthotopic rat prostate cancer model, hyaluronic acid synthase-1 mRNA levels and HA staining were increased in normal prostate tissue surrounding prostate cancer. Orthotopic prostate cancer growth was increased by intraprostatic injection of HA. In conclusion, cancer in the prostate apparently stimulates HA synthesis both in tumor stroma and in the surrounding normal tissue. This promoted tumor growth and was associated with an unfavorable outcome.

Hyaluronan-CD44 interactions as potential targets for cancer therapy

It is becoming increasingly clear that signals generated in tumor microenvironments are crucial to tumor cell behavior, such as survival, progression and metastasis. The establishment of these malignant behaviors requires that tumor cells acquire novel adhesion and migration properties to detach from their original sites and to localize to distant organs. CD44, an adhesion/homing molecule, is a major receptor for the glycosaminoglycan hyaluronan, which is one of the major components of the tumor extracellular matrix. CD44, a multistructural and multifunctional molecule, detects changes in extracellular matrix components, and thus is well positioned to provide appropriate responses to changes in the microenvironment, i.e. engagement in cell-cell and cell-extracellular matrix interactions, cell trafficking, lymph node homing and the presentation of growth factors/cytokines/chemokines to co-ordinate signaling events that enable the cell responses that change in the tissue environment. The potential involvement of CD44 variants (CD44v), especially CD44v4-v7 and CD44v6-v9, in tumor progression has been confirmed for many tumor types in numerous clinical studies. The downregulation of the standard CD44 isoform (CD44s) in colon cancer is postulated to result in increased tumorigenicity. CD44v-specific functions could be caused by their higher binding affinity than CD44s for hyaluronan. Alternatively, CD44v-specific functions could be caused by differences in associating molecules, which may bind selectively to the CD44v exon. This minireview summarizes how the interaction between hyaluronan and CD44v can serve as a potential target for cancer therapy, in particular how silencing CD44v can target multiple metastatic tumors.

Lymphangiogenesis in post-natal tissue remodeling: lymphatic endothelial cell connection with its environment

The main physiological function of the lymphatic vasculature is to maintain tissue fluid homeostasis. Lymphangiogenesis or de novo lymphatic formation is closely associated with tissue inflammation in adults (i.e. wound healing, allograft rejection, tumor metastasis). Until recently, research on lymphangiogenesis focused mainly on growth factor/growth factor-receptor pathways governing this process. One of the lymphatic vessel features is the incomplete or absence of basement membrane. This close association of endothelial cells with the underlying interstitial matrix suggests that cell-matrix interactions play an important role in lymphangiogenesis and lymphatic functions. However, the exploration of interaction between extracellular matrix (ECM) components and lymphatic endothelial cells is in its infancy. Herein, we describe ECM-cell and cell-cell interactions on lymphatic system function and their modification occurring in pathologies including cancer metastasis.

Inhibition of oesophageal squamous cell carcinoma progression by in vivo targeting of hyaluronan synthesis

Background

Oesophageal cancer is a highly aggressive tumour entity with at present poor prognosis. Therefore, novel treatment options are urgently needed. Hyaluronan (HA) is a polysaccharide present in the matrix of human oesophageal squamous cell carcinoma (ESCC). Importantly, in vitro ESCC cells critically depend on HA synthesis to maintain the proliferative phenotype. The aim of the present study is (1) to study HA-synthase (HAS) expression and regulation in human ESCC, and (2) to translate the in vitro results into a mouse xenograft model of human ESCC to study the effects of systemic versus tumour targeted HAS inhibition on proliferation and distribution of tumour-bound and stromal hyaluronan.

Methods

mRNA expression was investigated in human ESCC biopsies by semiquantitative real-time RT PCR. Furthermore, human ESCC were xenografted into NMRI nu/nu mice. The effects on tumour progression and morphology of 4-methylumbelliferone (4-MU), an inhibitor of HA-synthesis, and of lentiviral knock down of HA-synthase 3 (HAS3), the main HAS isoform in the human ESCC tissues and the human ESCC cell line used in this study, were determined. Tumour progression was monitored by calliper measurements and by flat-panel detector volume computed tomography (fpVCT). HA content, cellular composition and proliferation (Ki67) were determined histologically.

Results

mRNA of HAS isoform 3 (HAS3) was upregulated in human ESCC biopsies and HAS3 mRNA was positively correlated to expression of the epidermal growth factor (EGF) receptor. EGF was also proven to be a strong inductor of HAS3 mRNA expression in vitro. During the course of seven weeks, 4-MU inhibited progression of xenograft tumours. Interestingly, remodelling of the tumour into a more differentiated phenotype and inhibition of cell proliferation were observed. Lentiviral knockdown of HAS3 in human ESCC cells prior to xenografting mimicked all effects of 4-MU treatment suggesting that hyaluronan produced by ESCC is accountable for major changes in tumour environment in vivo.

Conclusions

Systemic inhibition of HA-synthesis and knockdown of tumour cell HAS3 cause decreased ESCC progression accompanied by tumour stroma remodelling and may therefore be used in novel approaches to ESCC therapy.

Hyaluronan metabolism in remodeling extracellular matrix: probes for imaging and therapy of breast cancer

Clinical and experimental evidence increasingly support the concept of cancer as a disease that emulates a component of wound healing, in particular abnormal stromal extracellular matrix remodeling. Here we review the biology and function of one remodeling process, hyaluronan (HA) metabolism, which is essential for wound resolution but closely linked to breast cancer (BCA) progression. Components of the HA metabolic cycle (HAS2, SPAM1 and HA receptors CD44, RHAMM/HMMR and TLR2) are discussed in terms of their known functions in wound healing and in breast cancer progression. Finally, we discuss recent advances in the use of HA-based platforms for developing nanoprobes to image areas of active HA metabolism and for therapeutics in breast cancer.

Interaction between the extracellular matrix and lymphatics: consequences for lymphangiogenesis and lymphatic function

The lymphatic system is important for body fluid balance as well as immunological surveillance. Due to the identification of new molecular markers during the last decade, there has been a recent dramatic increase in our knowledge on the molecular mechanisms involved in lymphatic vessel growth (lymphangiogenesis) and lymphatic function. Here we review data showing that although it is often overlooked, the extracellular matrix plays an important role in the generation of new lymphatic vessels as a response to physiological and pathological stimuli. Extracellular matrix-lymphatic interactions as well as biophysical characteristics of the stroma have consequences for tumor formation, growth and metastasis. During the recent years, anti-lymphangiogenesis has emerged as an additional therapeutic modality to the clinically applied anti-angiogenesis strategy. Oppositely, enhancement of lymphangiogenesis in situations of lymph accumulation is seen as a promising strategy to a set of conditions where few therapeutic avenues are available. Knowledge on the interaction between the extracellular matrix and the lymphatics may enhance our understanding of the underlying mechanisms and may ultimately lead to better therapies for conditions where reduced or increased lymphatic function is the therapeutic target.

Hyaluronan deficiency in tumor stroma impairs macrophage trafficking and tumor neovascularization

Despite the importance of stromal cells in tumor progression, our overall understanding of the molecular signals that regulate the complex cellular interactions within tumor stroma is limited. Here, we provide multiple lines of evidence that tumor-associated macrophages (TAM) preferentially traffic to stromal areas formed within tumors in a manner dependent on a hyaluronan (HA)-rich tumor microenvironment. To address the role of stroma-derived HA in macrophage recruitment, we disrupted the HA synthase 2 (Has2) gene in stromal fibroblasts using conditional gene targeting. The Has2 null fibroblasts showed severe impairment in recruiting macrophages when inoculated with tumor cells into nude mice, which shows the contribution of stroma-derived HA in intratumoral macrophage mobilization. Furthermore, a deficiency in stromal HA attenuated tumor angiogenesis and lymphangiogenesis concomitantly with impaired macrophage recruitment. Taken together, our results suggest that stromal HA serves as a microenvironmental signal for the recruitment of TAMs, which are key regulatory cells involved in tumor neovascularization.

Lymphangiogenesis: Molecular mechanisms and future promise

The growth of lymphatic vessels (lymphangiogenesis) is actively involved in a number of pathological processes including tissue inflammation and tumor dissemination but is insufficient in patients suffering from lymphedema, a debilitating condition characterized by chronic tissue edema and impaired immunity. The recent explosion of knowledge on the molecular mechanisms governing lymphangiogenesis provides new possibilities to treat these diseases.

The road to integrative cancer therapies: emergence of a tumor-associated fibroblast protease as a potential therapeutic target in cancer

Great inroads have been made in defining the oncogenic pathways intrinsic to neoplastic cells and the mechanisms by which they are activated in tumors. Knowledge of these pathways provides numerous opportunities that are actively being pursued to develop targeted therapies for cancer. Complementary studies, focused on the non-transformed components of the tumor microenvironment (TME), have revealed that the extrinsic cues provided by the TME are also essential for tumor cells to manifest a fully transformed phenotype, angiogenesis and metastasis. Delineation of these cues and their underlying cellular and molecular pathways will thus lead to a new era of integrative cancer therapy based on combinatorial drug regimens that act synergistically to destroy the neoplastic cells by targeting both the intrinsic and extrinsic pro-oncogenic pathways. Tumor-associated fibroblasts (TAFs) and proteases are two of the key regulators of epithelial-derived tumors that represent potential targets of such integrative therapies. Herein, we consider the potential therapeutic benefit of inhibiting the function of fibroblast activation protein (FAP), a cell surface serine protease with dipeptidyl peptidase and endopeptidase activity that is expressed on TAFs and pericytes, in an integrative approach to treating cancer.

Role of carcinoma-associated fibroblasts and hypoxia in tumor progression

In recent years, a variety of experimental evidence has convincingly shown that progression of malignant tumors does not depend exclusively on cell-autonomous properties of the cancer cells, but can also be influenced by the tumor stroma. The concept that cancer cells are subjected to microenvironmental control has thus emerged as an important chapter in cancer biology. Recent findings have suggested an important role, in particular, for macrophages, endothelial cells, and cancer-associated fibroblasts (CAFs) in tumor growth and progression. Numerous lines of evidence indicate that the bone marrow is the source, at least in part, of these cells. This chapter summarizes our current knowledge of how bone marrow contributes to the tumor stroma, with particular emphasis on CAFs. The potential role of hypoxia in modulating the differentiation and activity of CAFs, and the therapeutical implications of targeting CAFs for anticancer therapy are discussed.

Mesenchymal stem cell transition to tumor-associated fibroblasts contributes to fibrovascular network expansion and tumor progression

Background

Tumor associated fibroblasts (TAF), are essential for tumor progression providing both a functional and structural supportive environment. TAF, known as activated fibroblasts, have an established biological impact on tumorigenesis as matrix synthesizing or matrix degrading cells, contractile cells, and even blood vessel associated cells. The production of growth factors, cytokines, chemokines, matrix-degrading enzymes, and immunomodulatory mechanisms by these cells augment tumor progression by providing a suitable environment. There are several suggested origins of the TAF including tissue-resident, circulating, and epithelial-to-mesenchymal-transitioned cells.

Methodology/Principal Findings

We provide evidence that TAF are derived from mesenchymal stem cells (MSC) that acquire a TAF phenotype following exposure to or systemic recruitment into adenocarcinoma xenograft models including breast, pancreatic, and ovarian. We define the MSC derived TAF in a xenograft ovarian carcinoma model by the immunohistochemical presence of 1) fibroblast specific protein and fibroblast activated protein; 2) markers phenotypically associated with aggressiveness, including tenascin-c, thrombospondin-1, and stromelysin-1; 3) production of pro-tumorigenic growth factors including hepatocyte growth factor, epidermal growth factor, and interleukin-6; and 4) factors indicative of vascularization, including alpha-smooth muscle actin, desmin, and vascular endothelial growth factor. We demonstrate that under long-term tumor conditioning in vitro, MSC express TAF–like proteins. Additionally, human MSC but not murine MSC stimulated tumor growth primarily through the paracrine production of secreted IL6.

Conclusions/Significance

Our results suggest the dependence of in vitro Skov-3 tumor cell proliferation is due to the presence of tumor-stimulated MSC secreted IL6. The subsequent TAF phenotype arises from the MSC which ultimately promotes tumor growth through the contribution of microvascularization, stromal networks, and the production of tumor-stimulating paracrine factors.

Identification of molecular distinctions between normal breast-associated fibroblasts and breast cancer-associated fibroblasts

Stromal fibroblasts influence the behavior of breast epithelial cells. Fibroblasts derived from normal breast (NAF) inhibit epithelial growth, whereas fibroblasts from breast carcinomas (CAF) have less growth inhibitory capacity and can promote epithelial growth. We sought to identify molecules that are differentially expressed in NAF versus CAF and potentially responsible for their different growth regulatory abilities. To determine the contribution of soluble molecules to fibroblast–epithelial interactions, NAF were grown in 3D, transwell or direct contact co-cultures with MCF10AT epithelial cells. NAF suppressed proliferation of MCF10AT in both direct contact and transwell co-cultures, but this suppression was significantly greater in direct co-cultures, indicating involvement of both soluble and contact factors. Gene expression profiling of early passage fibroblast cultures identified 420 genes that were differentially expressed in NAF versus CAF. Of the eight genes selected for validation by real-time PCR, FIBULIN 1, was overexpressed in NAF, and DICKKOPF 1, NEUREGULIN 1, PLASMINOGEN ACTIVATOR INHIBITOR 2, and TISSUE PLASMINOGEN ACTIVATOR were overexpressed in CAF. A higher expression of FIBULIN 1 in normal- than cancer-associated fibroblastic stroma was confirmed by immunohistochemistry of breast tissues. Among breast cancers, stromal expression of Fibulin 1 protein was higher in estrogen receptor α-positive cancers and low stromal expression of Fibulin 1 correlated with a higher proliferation of cancer epithelial cells. In conclusion, expression profiling of NAF and CAF cultures identified many genes with potential relevance to fibroblast–epithelial interactions in breast cancer. Furthermore, these early passage fibroblast cultures can be representative of gene expression in stromal fibroblasts in vivo.

Developmental and pathological lymphangiogenesis: from models to human disease

The lymphatic vascular system, the body's second vascular system present in vertebrates, has emerged in recent years as a crucial player in normal and pathological processes. It participates in the maintenance of normal tissue fluid balance, the immune functions of cellular and antigen trafficking and absorption of fatty acids and lipid-soluble vitamins in the gut. Recent scientific discoveries have highlighted the role of lymphatic system in a number of pathologic conditions, including lymphedema, inflammatory diseases, and tumor metastasis. Development of genetically modified animal models, identification of lymphatic endothelial specific markers and regulators coupled with technological advances such as high-resolution imaging and genome-wide approaches have been instrumental in understanding the major steps controlling growth and remodeling of lymphatic vessels. This review highlights the recent insights and developments in the field of lymphatic vascular biology.

Stromal myofibroblasts are drivers of invasive cancer growth

Tissue integrity is maintained by the stroma in physiology. In cancer, however, tissue invasion is driven by the stroma. Myofibroblasts and cancer-associated fibroblasts are important components of the tumor stroma. The origin of myofibroblasts remains controversial, although fibroblasts and bone marrow-derived precursors are considered to be the main progenitor cells. Myofibroblast reactions also occur in fibrosis. Therefore, we wonder whether nontumorous myofibroblasts have different characteristics and different origins as compared to tumor-associated myofibroblasts. The mutual interaction between cancer cells and myofibroblasts is dependent on multiple invasive growth-promoting factors, through direct cell-cell contacts and paracrine signals. Since fibrosis is a major side effect of radiotherapy, we address the question how the main methods of cancer management, including chemotherapy, hormonotherapy and surgery affect myofibroblasts and by inference the surrogate endpoints invasion and metastasis.

Impact of the hyaluronan-rich tumor microenvironment on cancer initiation and progression

Hyaluronan acts as a microenvironmental stimulus that can influence the malignant phenotype of cancer cells. During cancer progression, hyaluronan assembles an extracellular matrix that is favorable for both the motility and proliferation of cancer cells and the recruitment of inflammatory and bone marrow-derived progenitor cells. The varied roles of this polysaccharide are regulated via multiple mechanisms involving biosynthesis, degradation, binding with other extracellular molecules, and activation of signaling pathways. Recent animal studies have provided evidence that aberrant biosynthesis of hyaluronan accelerates tumor growth through a diverse repertoire of host-tumor interactions, such as stromal cell recruitment, angiogenesis, lymphangiogenesis, and inflammation. Hyaluronan in the tumor microenvironment thus significantly impacts cancer initiation and progression via stroma-cancer cell interactions.