Angiogenic cytokines in cartilage tumors

Differential expression of angiogenesis markers HSP70, HSP90, VEGF and pERK1/2 in both components of dedifferentiated chondrosarcomas

Dedifferentiated chondrosarcomas (DDCS) are highly malignant bimorphic mesenchymal tumors with poor outcome and limited treatment options. Genes and proteins involved in angiogenesis play an important role in the development of invasion and metastasis. Immunohistochemical stains targeting HSP70, pERK1/2 and VEGFA were applied to a TMA containing 29 DDCS cases representing both tumor components. Higher expression of HSP70 and pERK1/2 was noted in the dedifferentiated component. RNA sequencing performed in 8 paired cases of DDCS comparing well differentiated and dedifferentiated components, showed higher expression of several HSP70 family members and HSP90 in the dedifferentiated component. Furthermore, high mobility group AT-hook 2 (HMAG2) and SET nuclear proto-oncogene demonstrated higher expression in the dedifferentiated component. Thus, the well differentiated and dedifferentiated components of DDCS are different, histologically and transcriptomically. The dedifferentiated component of DDCS shows higher expression of markers that are associated with malignant behavior. Some of these may represent future treatment targets.

Hypoxia-inducible factor 1-alpha and vascular endothelial growth factor in cartilage tumors

Neoangiogenesis has been demonstrated in chondrosarcoma. Anti-angiogenic therapies are being tested in clinical trials for chondrosarcomas. Studies of the underlying mechanisms have been performed almost exclusively in cell lines. We immunostained 20 samples of chondrosarcoma and 20 samples of enchondromas with antibodies against hypoxia-inducible factor 1-alpha (HIF-1-alpha) and vascular endothelial growth factor (VEGF). The immunohistochemical staining of HIF-1-alpha and VEGF were highly correlated. Enchondromas were HIF-1-alpha and VEGF negative, whereas all chondrosarcoma exhibited HIF-1-alpha and VEGF immunostaining. HIF-1-alpha/VEGF double positive cases were almost exclusively chondrosarcomas with a high tumor grade. We suggest that HIF-1-alpha is a marker of malignancy in chondrosarcomas that correlates with tumor neo-angiogenesis. Our findings also suggest that a HIF-1-alpha/VEGF angiogenic pathway may exist in chondrosarcoma in vivo as in other malignant tumors. The inclusion of novel inhibitors to HIF-1-alpha and other factors may optimize anti-angiogenic interventions in chondrosarcoma.

Chondrosarcoma: A Rare Misfortune in Aging Human Cartilage? The Role of Stem and Progenitor Cells in Proliferation, Malignant Degeneration and Therapeutic Resistance

Unlike other malignant bone tumors including osteosarcomas and Ewing sarcomas with a peak incidence in adolescents and young adults, conventional and dedifferentiated chondrosarcomas mainly affect people in the 4th to 7th decade of life. To date, the cell type of chondrosarcoma origin is not clearly defined. However, it seems that mesenchymal stem and progenitor cells (MSPC) in the bone marrow facing a pro-proliferative as well as predominantly chondrogenic differentiation milieu, as is implicated in early stage osteoarthritis (OA) at that age, are the source of chondrosarcoma genesis. But how can MSPC become malignant? Indeed, only one person in 1,000,000 will develop a chondrosarcoma, whereas the incidence of OA is a thousandfold higher. This means a rare coincidence of factors allowing escape from senescence and apoptosis together with induction of angiogenesis and migration is needed to generate a chondrosarcoma. At early stages, chondrosarcomas are still assumed to be an intermediate type of tumor which rarely metastasizes. Unfortunately, advanced stages show a pronounced resistance both against chemo- and radiation-therapy and frequently metastasize. In this review, we elucidate signaling pathways involved in the genesis and therapeutic resistance of chondrosarcomas with a focus on MSPC compared to signaling in articular cartilage (AC).

Ultrasound-triggered PLGA microparticle destruction and degradation for controlled delivery of local cytotoxicity and drug release

In this study, we investigated the low intensity ultrasound (US)-controlled delivery of local cytotoxicity and drug release via induced destruction and degradation of microparticles (MPs) made of poly(lactic-co-glycolic acid) (PLGA). This study was conducted in vitro with potential application towards tumor treatment in conjunction with direct injection. MPs, either loaded with or without doxorubicin (DOX), were prepared using a double-emulsion solvent-evaporation technique. First, the MPs were exposed to US with duty cycle (DC)-modulation. The destruction and degradation of MPs were evaluated using light and scanning electron microscopy. Second, the effects of US-mediated destruction/degradation of MPs on the local cytotoxicity as well as DOX release were evaluated. US-triggered MP destruction/degradation significantly enhanced nearby cell death and DOX release. These affects occurred in proportion to the DC. Our findings indicate that controlled cytotoxicity and DOX release by US could be useful in developing the minimally invasive therapeutic applications for tumor treatment.

miR-181a Targets RGS16 to Promote Chondrosarcoma Growth, Angiogenesis, and Metastasis

Chondrosarcoma is the most common primary malignant bone tumor in adults, has no effective systemic treatment, and patients with this disease have poor survival. Altered expression of microRNA (miR) is involved in tumorigenesis; however, its role in chondrosarcoma is undetermined. miR-181a is overexpressed in high-grade chondrosarcoma, is upregulated by hypoxia, and increases VEGF expression. Here, the purpose was to determine the mechanism of miR-181a regulation of VEGF, determine whether miR-181a overexpression promotes tumor progression, and to evaluate an antagomir-based approach for chondrosarcoma treatment. Therapeutic inhibition of miR-181a decreased expression of VEGF and MMP1 in vitro, and angiogenesis, MMP1 activity, tumor growth, and lung metastasis, all by more than 50%, in a xenograft mouse model. A target of miR-181a is a regulator of G-protein signaling 16 (RGS16), a negative regulator of CXC chemokine receptor 4 (CXCR4) signaling. CXCR4 signaling is increased in chondrosarcoma, its expression is also increased by hypoxia, and is associated with angiogenesis and metastasis; however, receptor blockade is only partially effective. RGS16 expression is restored after miR-181a inhibition and partially accounts for the antiangiogenic and antimetastatic effects of miR-181a inhibition. These data establish miR-181a as an oncomiR that promotes chondrosarcoma progression through a new mechanism involving enhancement of CXCR4 signaling by inhibition of RGS16.

IMPLICATIONS

Targeting miR-181a can inhibit tumor angiogenesis, growth, and metastasis, thus suggesting the possibility of antagomir-based therapy in chondrosarcoma.

MicroRNA regulates vascular endothelial growth factor expression in chondrosarcoma cells

BACKGROUND

Systemic treatments to prevent or treat chondrosarcoma metastasis are lacking and targeted therapy has yet to be developed. Hypoxia develops in tumors as they grow and hypoxia-related alterations in gene expression underlie some of the traits of cancer. One critical trait is the ability to induce sustained angiogenesis, which is usually related to expression of vascular endothelial growth factor (VEGF). A potential hypoxia-related mechanism resulting in altered gene expression involves microRNA. Little is known about microRNA expression in chondrosarcoma and its potential role in regulation of VEGF expression.

QUESTIONS/PURPOSES

Our purposes were (1) to determine if there is hypoxia-regulated microRNA overexpressed in chondrosarcoma; (2) if that contributes to increased VEGF expression; and (3) can VEGF expression be inhibited with a specific antagomir?

METHODS

MicroRNA expression was analyzed in two primary human chondrosarcomas and articular cartilage using array analysis and a cutoff of a fourfold difference in expression between tumor and normal tissue. The effects of hypoxia and hypoxia-inducible factor-1α (HIF-1α) transfection and silencing with siRNA on expression of candidate microRNAs were analyzed in chondrosarcoma cell line JJ. VEGF expression was measured with quantitative polymerase chain reaction and enzyme-linked immunosorbent assay after specific microRNA transfection and knockdown.

RESULTS

miR-181a was identified by array analysis and confirmed with quantitative reverse transcription-polymerase chain reaction, which showed that miR-181a was overexpressed in both human chondrosarcomas (33- and 55-fold) and the JJ cell line (sixfold) compared with cartilage and chondrocytes, respectively. In vitro, hypoxia and HIF-1α transfection each further increased miR-181a expression twofold in JJ cells. miR-181a transfection of JJ cells doubled expression of VEGF mRNA and increased secreted VEGF protein by 46% in normoxia, an effect that could be either direct or indirect. Similar enhancement of VEGF expression by miR-181a was found during hypoxia. Transfection with the antagomir anti-miR-181a decreased VEGF protein by 27% in normoxia and 23% in hypoxia.

CONCLUSIONS

miR-181a is a hypoxia-regulated microRNA that is overexpressed in chondrosarcoma and enhances VEGF expression, an effect that could be inhibited by anti-miR-181a.

CLINICAL RELEVANCE

Systemic treatment options for chondrosarcoma are limited. Antiangiogenic strategies could potentially be effective in limiting tumor progression. One method of inhibiting VEGF expression and associated angiogenesis could be an antagomir-based therapy targeted at miR-181a or other oncogenic microRNAs, although methods of systemic delivery are still under development. The effectiveness of antagomirs also needs to be compared with other antiangiogenic modalities in preclinical models.

Anti-angiogenic therapy, a new player in the field of sarcoma treatment

Sarcomas encompass a heterogeneous family of mesenchymal malignancies. In metastatic disease improvement in outcome has been limited and there is a clear need for the development of new therapies. One potential target is angiogenesis, already an accepted target for treatment of more prevalent cancers. Multiple (pre)clinical studies focused on the role of angiogenesis and anti-angiogenic treatment in sarcomas. However, getting significant results is complicated due to the relatively small number of patients and the broad range of sarcoma subtypes. Recently, pazopanib has been approved for the treatment of advanced soft tissue sarcoma patients, which is an important step forward and paves the way for the introduction of anti-angiogenic treatment in sarcomas. However, more studies are needed to understand the biological mechanisms by which patients respond to angiogenic inhibitors and to detect markers of response. This review covers the knowledge that has been gained on the role of angiogenesis and anti-angiogenic therapy in sarcomas.

Chondrosarcoma of bone

Chondrosarcoma is a cartilage forming neoplasm, which is the second most common primary malignancy of bone. Clinicians who treat chondrosarcoma patients must determine the grade of the tumor, and must ascertain the likelihood of metastasis. Acral lesions are unlikely to metastasize, regardless of grade, whereas axial, or more proximal lesions are much more likely to metastasize than tumors found in the distal extremities with equivalent histology. Chondrosarcoma is resistant to both chemotherapy and radiation, making wide local excision the only treatment. Local recurrence is frequently seen after intralesional excision, thus wide local excision is sometimes employed despite significant morbidity, even in low-grade lesions. Chondrosarcoma is difficult to treat. The surgeon must balance the risk of significant morbidity with the ability to minimize the chance of local recurrence and maximize the likelihood of long-term survival.

CXCR4-targeted therapy inhibits VEGF expression and chondrosarcoma angiogenesis and metastasis

Chondrosarcoma is notable for its lack of response to conventional cytotoxic chemotherapy, propensity for developing lung metastases, and poor survival. Therefore, a better understanding of angiogenic and metastatic pathways is needed. Multiple pathways regulate angiogenesis and metastasis, including chemokines and their receptors. In this study, we investigated chemokine (C-X-C motif) receptor 4 (CXCR4) signaling in chondrosarcoma and tested the hypotheses that CXCR4 inhibition suppresses tumor angiogenesis and metastasis. CXCR4 expression, analyzed by real-time PCR and Western blot, was increased in human chondrosarcoma cell line JJ compared with normal chondrocytes and was further increased in JJ by hypoxia (2% O2), vascular endothelial growth factor A (VEGFA; 10 ng/mL), and in xenograft tumors in nude mice. The CXCR4 ligand CXCL12 (10 ng/mL) doubled secreted VEGFA, measured with ELISA, under hypoxic conditions and this conditioned media increased human umbilical vein endothelial cell tube formation. These effects were inhibited by CXCR4 siRNA or AMD3100 (5 μg/mL). In a xenograft mouse model, four weeks of AMD3100 treatment (1.25 mg/kg, intraperitoneally twice daily) inhibited tumor angiogenesis, tumor growth, and metastasis. VEGFA content in tumor extracts was decreased (7.19 ± 0.52 ng/mL control vs. 3.96 ± 0.66 treatment) and bioimaging of angiogenesis was decreased by 56%. Tumor volumes averaged 4.44 ± 0.68 cm(3) in control compared with 2.48 ± 0.61 cm(3) in the treatment group. The number of lung metastatic nodules was 23 ± 9 in control compared with 10 ± 6 in the treatment group (N = 8/group). Therefore, CXCR4-targeted therapy may be a treatment strategy for chondrosarcoma.

Mutations in the isocitrate dehydrogenase genes IDH1 and IDH2 in tumors

Heterozygous hotspot mutations in isocitrate dehydrogenases (IDH) IDH1 or IDH2 are frequently observed in specific types of cartilaginous tumors, gliomas, and leukemias. Mutant IDH enzyme loses its normal activity to convert isocitrate into α-ketoglutarate (αKG) and instead acquires the ability to reduce αKG to D-2-hydroxyglutarate. Through direct competition with αKG, accumulation of the oncometabolite D-2-hydroxyglutarate in IDH mutated tumors results in inhibition of αKG-dependent dioxygenases involved in DNA and histone demethylation. Apart from epigenetic alterations, perturbations in the tricarboxylic acid cycle (depletion of intermediates) and activation of the intricately linked hypoxia signaling pathway are apparent in IDH mutated cells. As molecular details are being unraveled, the emerging concept is that IDH mutations result in tumor formation by epigenetic alterations that affect gene expression and result in inhibition of cellular differentiation. Activation of hypoxic stress signaling reprograms cellular energy metabolism and promotes anabolic processes and angiogenesis, thus, providing an advantage to promote neoplastic growth.

Diversity of angiogenesis among malignant bone tumors

Several studies have demonstrated that angiogenesis assessed by microvessel density (MVD) correlates with patient prognosis in various types of cancer, whereas data regarding the relevance of angiogenesis and prognosis in malignant bone tumors are scarce and controversial. The aim of this study was to examine MVD in representative malignant bone tumors, such as osteosarcoma, chondrosarcoma and Ewing's sarcoma, in order to clarify the role of angiogenesis in prognosis. A total of 69 patients with malignant bone tumors, including 44 osteosarcomas, 20 chondrosarcomas and 5 Ewing's sarcomas, were reviewed retrospectively and treated at our hospital between 1980 and 2007. Biopsy or pre-chemotherapy surgical specimens were immunohistochemically stained with anti-CD34 antibody. The MVD values of osteosarcomas and Ewing's sarcomas were significantly higher compared to chondrosarcoma. In osteosarcomas with high MVD, American Joint Committee on Cancer stage IIA, good histological response to chemotherapy was significantly correlated with better disease-free survival, while MVD was closely associated with age and chemotherapy response. In chondrosarcomas, the surgical margin (marginal and intralesional), MVD (high), tumor size (≥8) and histological grade (grades 2 and 3) significantly correlated with a shorter disease-free survival, while MVD was closely associated with age and histological grade. These findings showed that osteosarcomas and Ewing's sarcomas were hypervascular, compared to chondrosarcomas. In osteosarcomas, hypervascularity induced good chemotherapy response, leading to better prognosis, while in chondrosarcomas, high MVD was associated with histological grade and predicted poor prognosis.

Angiogenesis in hand chondroma: an immunohistochemical study

Hand chondroma is a particular cartilagineous tumour, being clinically benign, but morphologically malignant. This study investigates the expression of VEGF together with other growth factors and proliferation markers such as TGFβ2, Ki-67, TNF, FGF1, P53 in 8 cases of hand chondroma treated with courettage, in order to define the ethiopathogenesis of this tumour and the clinical significance of the resulting immunohistochemical profile, with particular respect to angiogenesis. VEGF was expressed in all cases; 5 cases were positive for TFGβ2 and 3 for PDGF. None of the other factors was expressed. On the basis of histologic results a specific model of tumour progression based on the indicators of angiogenesis could be related to hand tumours, in which VEGF expression should be the first stadium of the tumour aggressiveness, and the following PDGF, TGF 2 expression should be accompanied with a morphological outline worsening. Nevertheless the non constant expression of these indicators and the absent expression of proliferated indicators can explain the scant tendency to the relapse in presence of accurate curettage. It is important to remember that the cellular polymorphism typical of the cartilaginous tumours does not allow the application of an only oncogenesis model.

CXCR4 and axillary lymph nodes: review of a potential biomarker for breast cancer metastasis

CXCR4 is a 7-transmembrane G-protein chemokine receptor that allows for migration of hematopoietic cells from the bone marrow to the peripheral lymph nodes. Research has shown CXCR4 to be implicated in the invasion and metastasis of several cancers, including carcinoma of the breast. CXCL12 is the ligand for CXCR4 and is highly expressed in areas common for breast cancer metastasis, including the axillary lymph nodes. Axillary lymph nodes positive for breast carcinoma have been an important component of breast cancer diagnosis, treatment, and subsequent research. The goal of this paper is to analyze the literature that has explained the pathways from CXCR4 expression to breast cancer metastasis of the lymph nodes and the prognostic and/or predictive implications of lymph node metastases in the presence of elevated CXCR4.

The Bone Niche of Chondrosarcoma: A Sanctuary for Drug Resistance, Tumour Growth and also a Source of New Therapeutic Targets

Chondrosarcomas are malignant cartilage-forming tumours representing around 20% of malignant primary tumours of bone and affect mainly adults in the third to sixth decade of life. Unfortunately, the molecular pathways controlling the genesis and the growth of chondrosarcoma cells are still not fully defined. It is well admitted that the invasion of bone by tumour cells affects the balance between early bone resorption and formation and induces an “inflammatory-like” environment which establishes a dialogue between tumour cells and their environment. The bone tumour microenvironment is then described as a sanctuary that contributes to the drug resistance patterns and may control at least in part the tumour growth. The concept of “niche” defined as a specialized microenvironment that can promote the emergence of tumour stem cells and provide all the required factors for their development recently emerges in the literature. The present paper aims to summarize the main evidence sustaining the existence of a specific bone niche in the pathogenesis of chondrosarcomas.

Analysis of angiogenic factors and cyclooxygenase-2 expression in cartilaginous tumors- clinical and histological correlation

OBJECTIVES

To study the role of angiogenesis and cyclooxygenase-2 expression in cartilaginous tumors and correlate these factors with prognosis.

INTRODUCTION

For chondrosarcoma, the histological grade is the current standard for predicting tumor outcome. However, a low-grade chondrosarcoma can follow an aggressive course-as monitored by sequential imaging techniques-even when it is histologically indistinguishable from an enchondroma. Therefore, additional tools are needed to help identify the biological potential of these tumors. The degree of angiogenesis that is induced by the tumor could assist in this task. Angiogenesis can be quantified by measuring the expression of vascular endothelial growth factor and CD34, and cyclooxygenase-2 can induce angiogenesis by stimulating the production of proangiogenic factors.

METHODS

In total, 21 enchondromas and 58 conventional chondrosarcomas were studied by examining the clinical and histopathological findings in conjunction with the immunostaining markers of angiogenesis and cyclooxygenase- 2 expression.

RESULTS

The significant variables that were associated with poor outcome were 1) higher-grade chondrosarcomas, 2) tumors that developed in flat bones, and 3) over-expression of CD34 (with a median count that was higher than 5.9 vessels in 5 high power fields). Moreover, CD34 expression (measured using the Chalkley method) revealed significantly higher microvessel density in flat bone chondrosarcomas.

DISCUSSION

Previous studies have shown a positive correlation between Chalkley microvessel density and histological grade; however, in our sample, we found that the former is predictive of the outcome. Chondrosarcomas in flat bones have been shown to correlate with a poor prognosis. We also found that CD34 microvessel density values were significantly higher in flat-bone chondrosarcomas. This could explain-at least in part-the more aggressive biological course that is taken by these tumors.

CONCLUSIONS

These results provide evidence that CD34 microvessel density in chondrosarcomas can be helpful in predicting patient outcome and may add to our understanding of chondrosarcoma pathogenesis.

Increased levels of hypoxia-inducible factor-1α are associated with Bcl-xL expression, tumor apoptosis, and clinical outcome in chondrosarcoma

Hypoxia-inducible factor (HIF)-1α is a key nuclear transcription factor that regulates the cellular response to hypoxia, and is important for solid tumor growth and survival. However, the underlying role of HIF-1α in human chondrosarcoma has not been well characterized. This study aims to investigate the expression patterns of HIF-1α in chondrosarcoma, and its association with clinicopathologic features, Bcl-xL expression, apoptosis index (AI), and overall survival of patients with chondrosarcoma. Our results shown that the protein levels of HIF-1α were increased, and the mRNA and protein levels of Bcl-xL were also increased in SW1353 cells under hypoxic conditions. In eight patients with chondrosarcoma, increased expression of HIF-1α and Bcl-xL was detected in chondrosarcoma tissues compared with the paired adjacent normal tissues. Of 34 archival specimens of chondrosarcomas, 20 (58.8%) showed high HIF-1α protein expression as compared to benign cartilage tumors. Increased HIF-1α expression was correlated with a higher pathological grade and MSTS stage of chondrosarcoma. Moreover, HIF-1α expression was significantly associated with Bcl-xL expression and AI. More significantly, the survival rate of patients with HIF-1α high tumors was significantly lower than that of patients with HIF-1α low tumors. These findings suggest that increased HIF-1α levels mediated up-regulation of Bcl-xL play a prominent role in evasion of apoptosis and tumor progression, and can be predictive for the prognosis in human chondrosarcoma.

Correlation of hypoxic signalling to histological grade and outcome in cartilage tumours

AIMS

The molecular mechanisms underlying the progression of central chondrosarcoma are so far poorly understood. The aim of this study was to identify genes involved in the progression of these tumours by comparison of gene expression and correlation of expression profiles to histological grade and clinical outcome.

METHODS AND RESULTS

Array-based gene expression profiling of 19 chondrosarcoma samples was performed. Beside differences in the expression of cartilage matrix molecules, high-grade chondrosarcoma showed enhanced expression of the matrix metalloproteinase MMP-2 and of the hypoxia-inducible molecule galectin 1. Immunohistochemical analysis of galectin 1 and of further hypoxia-associated proteins was performed on 68 central and peripheral tumour samples. Hypoxia-inducible factor 1alpha (HIF-1alpha) activation was significantly elevated in high-grade central chondrosarcoma. A negative correlation of carbonic anhydrase IX expression to metastasis-free survival was independent of histological grade.

CONCLUSIONS

The expression patterns identified in this study point towards a substantial role for angiogenic and hypoxic signalling in chondrosarcoma progression. The constitutive activation of the transcription factor HIF-1alpha in high-grade chondrosarcoma could play a central role in the regulation of cell metabolism and vascularization in these tumours and may, for this reason, represent a potential target for chondrosarcoma therapy.

Cartilage tumours and bone development: molecular pathology and possible therapeutic targets

As a group, cartilage tumours are the most common primary bone lesions. They range from benign lesions, such as enchondromas and osteochondromas, to malignant chondrosarcoma. The benign lesions result from the deregulation of the hedgehog signalling pathway, which is involved in normal bone development. These lesions can be the precursors of malignant chondrosarcomas, which are notoriously resistant to conventional chemotherapy and radiotherapy. Cytogenetic studies and mouse models are beginning to identify genes and signalling pathways that have roles in tumour progression, such as hedgehog, p53, insulin-like growth factor, cyclin-dependent kinase 4, hypoxia-inducible factor, matrix metalloproteinases, SRC and AKT, suggesting potential new therapeutic approaches.

CXCR4/SDF1 mediate hypoxia induced chondrosarcoma cell invasion through ERK signaling and increased MMP1 expression

Background

Chondrosarcoma is a disease that does not respond to conventional cytotoxic chemotherapy and expression of MMP1 is a marker for a poor prognosis. The mechanism of increased MMP1 expression in chondrosarcoma is not completely known. Our goal is to identify molecular pathways that could serve as therapeutic targets. Chondrosarcoma become hypoxic as they grow, are capable of eliciting an angiogenic response, and typically metastasize to the lungs. The present study determined the effect of hypoxia and specifically HIF-1a on expression of CXCR4 and MMP1 and their role in chondrosarcoma cell invasion.

Results

CXCR4 and its ligand, SDF1, are upregulated in primary chondrosarcoma tumors compared to normal articular cartilage, and CXCR4 was upregulated in chondrosarcoma cell line JJ compared to normal chondrocytes. Hypoxia and specifically HIF-1a increased CXCR4 and MMP1 expression in JJ cell line and chondrosarcoma invasion in vitro. The hypoxia mediated increase in MMP1 expression and chondrosarcoma invasion could be inhibited by siRNA directed at HIF-1a or CXCR4, the CXCR4 inhibitor AMD3100, as well as with ERK inhibitor U0126 and ERK siRNA.

Conclusions

Chondrosarcoma cell invasion is increased by hypoxia induced expression of CXCR4 and MMP1 and is mediated by HIF-1a and ERK. Both invasion and MMP1 can be inhibited with CXCR4 blockade, suggesting that CXCR4/SDF1 signaling may be a therapeutic target for chondrosarcoma.

HDAC4 represses vascular endothelial growth factor expression in chondrosarcoma by modulating RUNX2 activity

Chondrosarcoma is a primary bone tumor with a dismal prognosis; most patients with this disease develop fatal pulmonary metastases, suggesting the need for a better systemic treatment. Anti-angiogenesis treatment may be useful, because angiogenesis is critical for both tumor growth and metastasis. Vascular endothelial growth factor (VEGF) is the most potent pro-angiogenic factor and is regulated by pathways related to the normal physiologic response to hypoxia and genetic alterations related to the malignant phenotype. Our prior work has shown that VEGF is overexpressed in high grade chondrosarcoma and chondrosarcoma cell lines. Working on the premise that developmental pathways giving a selective growth advantage are often recapitulated in tumors, we investigated the regulation of VEGF by HDAC4 and Runx2 in chondrosarcoma. We tested the hypothesis that there is dysregulation of HDAC4/Runx2/VEGF gene expression and that decreased HDAC4 expression accounts for at least some of the increased VEGF expression seen in chondrosarcoma. We show that reduced expression of HDAC4 in chondrosarcoma cells increases expression of Runx2 leading to increased expression of VEGF and in vitro angiogenesis. Thus, both hypoxia and dysregulated expression of a developmental pathway are causes of increased VEGF expression in chondrosarcoma.

PTEN deficiency causes dyschondroplasia in mice by enhanced hypoxia-inducible factor 1α signaling and endoplasmic reticulum stress

Chondrocytes within the growth plates acclimatize themselves to a variety of stresses that might otherwise disturb cell fate. The tumor suppressor PTEN(phosphatase and tensin homolog deleted from chromosome 10) has been implicated in the maintenance of cell homeostasis. However, the functions of PTEN in regulating chondrocytic adaptation to stresses remain largely unknown. In this study, we have created chondrocyte-specific Pten knockout mice (Ptenco/co;Col2a1-Cre) using the Cre-loxP system. Following AKT activation, Pten mutant mice exhibited dyschondroplasia resembling human enchondroma. Cartilaginous nodules originated from Pten mutant resting chondrocytes that suffered from impaired proliferation and differentiation, and this was coupled with enhanced endoplasmic reticulum (ER) stress. We further found that ER stress in Pten mutant chondrocytes only occurred under hypoxic stress,characterized by an upregulation of unfolded protein response-related genes as well as an engorged and fragmented ER in which collagens were trapped. An upregulation of hypoxia-inducible factor 1α (HIF1α) and downstream targets followed by ER stress induction was also observed in Ptenmutant growth plates and in cultured chondrocytes, suggesting that PI3K/AKT signaling modulates chondrocytic adaptation to hypoxic stress via regulation of the HIF1α pathway. These data demonstrate that PTEN function in chondrocytes is essential for their adaptation to stresses and for the inhibition of dyschondroplasia.

Expression of hypoxia-inducible factor-1alpha and its relationship to tumour angiogenesis and cell proliferation in cartilage tumours

We investigated the use of hypoxia-inducible factor (HIF) proteins as prognostic markers in chondrosarcoma and the relationship of HIF to the biological characteristics of cartilage tumours. The expression of HIF-1alpha, HIF-2alpha, proliferating cell nuclear antigen (PCNA) and microvessel density (MVD) were measured immunohistochemically in 29 specimens of cartilage tumour. There was no HIF-1alpha and HIF-2alpha staining in any of the nine benign cartilage tumours. In 20 specimens of chondrosarcoma, the rate of HIF-1alpha and HIF-2alpha expression was 40% and 25%, respectively. The tumour size (> or = 8 cm), histological grade (grade 2 and grade 3) surgical margin (marginal and intralesional) and HIF-1alpha expression (positive) correlated significantly with a shorter disease-free survival. There was a significant association between HIF-1alpha and the MVD and a strong trend towards a correlation between HIF-1alpha and the PCNA index or histological grade. Our findings suggest that HIF-1alpha protein may be a useful objective marker in the assessment of the prognosis in chondrosarcoma, since it plays an important role in tumour angiogenesis and cell proliferation.

Outpatient Chemotherapy plus Radiotherapy in Sarcomas: Improving Cancer Control with Radiosensitizing Agents

Background

Cancer control by radiotherapy (RT) can be improved with concurrent chemotherapy. Outpatient strategies for sarcomas that combine chemotherapy and RT are possible since supportive care and RT techniques have improved.

Methods

The current status of non-anthracycline chemotherapy in combination with radiation for high-risk sarcoma is reviewed.

Results

Ifosfamide with mesna and newer activated ifosfamide agents (ZIO-201 and glufosfamide) have high potential to improve sarcoma cancer control. In Ewing's sarcoma and osteosarcoma, high-dose ifosfamide with mesna (2.8 g/m2/day of each x 5 days; mesna day 6) can be safely given to outpatients using continuous infusion. Reducing ifosfamide nephrotoxicity and central nervous system side effects are discussed. Other outpatient radiosensitization regimens include gemcitabine (600–1000 mg/m2/dose IV over 1 hour weekly x 2–3 doses), temozolomide (75 mg/m2/daily x 3–6 weeks), or temozolomide (100 mg/m2/dose daily x 5) + irinotecan (10 mg/m2/dose daily x 5 x 2 weeks). In osteosarcoma with osteoblastic metastases on bone scan, samarium (1 mCi/kg; day 3 of RT) and gemcitabine (600 mg/m2 IV over 1 hour day 9 of RT) is a radiosensitization strategy. Future drugs for radiosensitization include beta-D-glucose targeted activated ifosfamide (glufosfamide) and sapacitabine, an oral nucleoside with in vitro activity against solid tumors including sarcomas.

Conclusions

The potential to treat major causes of sarcoma treatment failure (local recurrence and distant metastases) with concurrent chemotherapy during radiation should be considered in high-grade sarcomas.

Lysis of human chondrosarcoma cells by cytolytic T lymphocytes recognizing a MAGE-A3 antigen presented by HLA-A1 molecules

Treatment of chondrosarcomas is limited to resection because these tumors are unresponsive to standard adjuvant treatments, such as chemotherapy and radiation. We have previously shown that high-grade chondrosarcomas express unspecified members of the Melanoma Antigen (MAGE) gene family. We show here that FS human chondrosarcoma (FS) cells express MAGE-A3 gene and HLA-A1 molecules. In vitro assays show that a cytolytic T-lymphocyte clone (CTL) specific for a MAGE-A3 peptide presented by HLA-A1 specifically lysed FS chondrosarcoma cells. Addition of antigenic peptide did not increase the susceptibility of FS cells to CTL mediated lysis, suggesting that HLA-A1 expression by the chondrosarcoma cells limited their susceptibility to lysis by the anti-MAGE-A3 CTL clone. Incubation of FS cells with 50 U/mL interferon-gamma increased surface expression of HLA class-I molecules, increased their susceptibility to lysis, and had no effect on MAGE-A3 gene expression. These results suggest that immunotherapy targeted against chondrosarcoma cells is possible.

VEGF and BMP expression in mouse osteosarcoma cells

Osteosarcoma is the most common primary bone malignancy. Despite improvements in therapy, approximately 30% of patients experience pulmonary metastasis. Expression of several growth factors, including VEGF and BMPs, has been implicated in tumor progression and metastatic potential. We hypothesized increased metastatic potential of mouse osteosarcoma cells positively correlates with the expression of VEGF and BMPs. We studied the expression patterns of these growth factors in two murine osteosarcoma cell lines with varying degrees of metastatic potential: K7M2 (highly metastatic) and K12 (minimally metastatic). Expression of VEGF and BMP2 were higher in the metastatic K7M2 cell line. We also investigated the effects of the BMP antagonist noggin on osteosarcoma growth characteristics in vitro. We noted decreased motility, altered morphology, and increased cell death in the highly metastatic K7M2 cell line. Less metastatic K12 cells showed substantial cell death without clear alteration of motility or morphology. These data suggest BMP2 expression may be an important factor in osteosarcoma metastasis and noggin administration theoretically could block its actions. Inhibition of BMPs and VEGF should be investigated further as a possible strategy for decreasing the incidence of pulmonary metastases in osteosarcoma.

Diagnostic Relevance of the Immunohistochemical Detection of Growth Factors in Benign and Malignant Cartilaginous Tumors

The goal of this study was to evaluate the diagnostic relevance of the expression of growth factors in cartilaginous tumors and to investigate on the possible correlation with grade, local recurrence, metastatic potential, and survival. Expression of VEGF, PDGF, FGF1, TFGbeta2, TNFalpha, Ki-67, and p53 was analyzed in 21 cases of benign and malignant cartilaginous tumors using immunohistochemistry. Immunohistochemical staining was performed on sections from paraffin-embedded tissue. The correlation of these markers' expression and grading or clinical outcome was also evaluated. Immunohistochemistry revealed a high correlation between grading and VEGF-positive staining (P=0.001). In addition, a correlation with local recurrence was found in cases with a positive expression of Ki-67 (P=0.035), TGFbeta (P=0.007), PDGF (P=0.007), and p53 (P=0.0455), with a time-related association. These data suggest a progressive modification in the biologic behavior of malignant cartilaginous tumors. VEGF could be used as a marker in the preoperative surgical assessment of chondrosarcoma. New therapeutic strategies could be considered for VEGF-positive cases. Positive expression of TGFbeta and PDGF seems to be a predictor of clinical outcome.

The MAPK-AP-1/-Runx2 signalling axes are implicated in chondrosarcoma pathobiology either independently or via up-regulation of VEGF

AIMS

To investigate whether and how the JNK/ERK-AP-1/-Runx2 signalling pathways and vascular endothelial growth factor (VEGF) are engaged in the pathogenesis of cartilaginous tumours. Chondrosarcoma is the third most common primary skeletal malignancy. Nevertheless, the molecular events underlying its pathogenesis remain elusive. JNK/ERK MAPKs and their downstream effectors, c-Jun and c-Fos (AP-1), are involved in chondroblastic differention/proliferation. These proteins interact with the Runx2 transcription factor, which is also implicated in chondroblast biology. VEGF, a key angiogenic factor, is up-regulated in human chondrosarcomas.

METHODS AND RESULTS

Normal cartilage and neoplastic cells from 45 chondrosarcomas and 21 enchondromas were investigated immunohistochemically. We evaluated the cellular levels of JNK2, p-JNK2 (phosphorylated/activated JNK2), its main substrate, c-Jun, pc-Jun (phosphorylated/activated c-Jun) and c-Fos. Moreover, the levels of p-ERK (phosphorylated/activated ERK), Runx2 and VEGF were assessed. Positive immunostaining for all proteins was observed in the majority of the examined chondrosarcomas and in a small fraction of enchondromas. The expression levels of all proteins were positively and significantly correlated with each other. These levels were substantially augmented in high-grade compared with low-grade chondrosarcomas and in low-grade tumours compared with benign enchondromas, implying a potential use as molecular markers for prediction of high-grade neoplasms.

CONCLUSIONS

The JNK/ERK-AP-1/-Runx2 signal transduction 'network' is associated with chondroblastic malignant transformation and chondrosarcoma development, either separately or through coordinated induction of VEGF.

Recent advances in the basic science of chondrosarcoma

Chondrosarcoma are a heterogeneous group of tumors whose treatment is limited to surgical removal. Molecular genetic analysis of these tumors has revealed some of the abnormalities responsible for the traits of the malignant phenotype.

Differential expression of VEGF-A and angiopoietins in cartilage tumors and regulation by interleukin-1β

BACKGROUND

Vascular endothelial growth factor (VEGF)-A and angiopoietin (Ang)-1 and Ang-2 are key factors in angiogenic signaling. In this study the expression of these factors was identified in cartilage tumors. As interleukin (IL)-1beta has been found to be an indispensable factor in angiogenic signaling, we further analyzed the effect of IL-1beta on the expression of VEGF-A, Ang-1, and Ang-2 using a previously established cell culture model.

METHODS

Surgical specimens of enchondromas, conventional chondrosarcomas, and dedifferentiated chondrosarcomas were obtained from 72 patients. VEGF-A, Ang-1, and Ang-2 mRNA expression was detected by conventional and quantitative reverse transcription polymerase chain reaction (PCR). VEGF-A expression was also detected by immunohistochemistry or Western blot.

RESULTS

Differential expression of VEGF-A, Ang-1, and Ang-2 was clearly demonstrated in cartilage tumors. VEGF-A expression was positively correlated with the tumor type. Higher VEGF-A expression levels were detected in conventional chondrosarcomas Grades II and III (using a 3-tier grading system) than in dedifferentiated chondrosarcomas (P < .05). A typical pattern of VEGF-A isoforms was identified, including VEGF(121), VEGF(145), VEGF(165), and VEGF(189). Ang-1 presented as a low-level transcript with slightly elevated levels in chondrosarcomas (P < .05). Highly variable Ang-2 expression levels were detected in solitary cases of conventional chondrosarcomas. IL-1beta regulated VEGF-A and Ang-1 expressions in a dose-dependent manner. Whereas low IL-1beta concentrations increased VEGF-A and Ang-1 transcription, high IL-1beta concentrations had the opposite effect. IL-1beta did not activate Ang-2 expression.

CONCLUSIONS

Angiogenic signaling in cartilage tumors is variable and at least partly regulable by IL-1beta. The findings are of therapeutic relevance, either as a desired effect or a side effect in medical treatment.