Two of four alternatively spliced isoforms of RUNX2 control osteocalcin gene expression in human osteoblast cells

Runx2 is a Runt domain transcription factor that transcriptionally regulates osteoblast differentiation and bone formation. In this study, we show that human chondro- and osteosarcoma cell lines, human mesenchymal stem cells (hMSC) and a human primary chondrocytes (HC), osteoblst cells (HOb) express an intact isoform (RUNX2wt) and 3 alternatively spliced isoforms (RUNX2Delta5, Delta7, and Delta5Delta7) that are generated by skipping exon 5 and/or exon 7. Two of the truncated forms of RUNX2 (RUNX2Delta5 and RUNX2Delta5Delta7) did not localize in the nucleus and had lost their DNA binding activity. In cotransfection experiments with an osteocalcin (OC) promoter construct, we confirmed that only RUNX2wt and RUNX2Delta7 could upregulate the OC promoter activity in the osteosarcoma cell line. In addition, the coactivator CBP/p300 enhanced the transcriptional activity of the OC promoter when coexpressed with RUNX2wt or RUNX2Delta7, but not when coexpressed with RUNX2Delta5 or RUNX2Delta5Delta7. In contrast, the corepressor HDAC3 only repressed the activation from the OC promoter when coexpressed with RUNX2wt. These results support the hypothesis that RUNX2 both up- and downregulates its target gene promoters, as exemplified by the OC gene, using various isoforms and context-dependent formation of transcriptional complexes.

Proteomics of chondrocytes with special reference to phosphorylation changes of proteins in stretched human chondrosarcoma cells

For proteomic analysis, cartilage molecular composition is a challenging mixture of highly glycosylated proteoglycans and triple-helical collagens, which constitute the major part of cartilage macromolecules. Selective separation of these molecules from the minor components is generally needed before mass spectrometry-based identification of lower-abundancy proteins is possible. The cell density of cartilage is also very low, therefore, cell cultures offer an easier approach to study cellular responses of chondrocytic cells, e.g., to mechanical stimuli. In this study, we investigated the phosphorylation events in human chondrosarcoma cells during cellular stretching. Human chondrosarcoma cells were stretched to 8% strain at a frequency of 1 Hz. One set of experiments included cellular stretching which lasted 2 hours, and the other one included experiments of 2 hours daily treatment for up to 3 days. Two-dimensional polyacrylamide gel electrophoresis combined with chromatographic phosphoprotein pre-enrichment and electrospray ionization mass spectrometry-based protein identification was used to reveal changes of phosphoproteins in cells exposed to cyclic stretching. We discovered that 2 hours cyclic stretching increased the phosphorylation of moesin, elongation factor eEF1D and leprecan, while the phosphorylation of elongation factor eEF1B decreased after cellular stretching. Western blot analyses with phospho-specific antibodies suggested that stretching induces phosphorylation of ERK of the MAP kinase pathway, but did not induce phosphorylation of phosphatidylinositol 3-kinase. In conclusion, the proteomic approach revealed that cellular stretching induced specific phosphorylation changes in chondrosarcoma cells.

Methylenetetrahydrofolate reductase C677T gene polymorphism in osteosarcoma and chondrosarcoma patients

This study was designed to investigate the association of MTHFR C677T polymorphism and the risk of two common musculoskeletal sarcomas, osteosarcoma and chondrosarcoma. MTHFR genotypes were determined in 56 patients (44 osteosarcoma, 12 chondrosarcoma) and 44 controls using the PCR-RFLP technique. In the gender subgroup analysis, wild-type A allele frequency was higher in male osteosarcoma patients than in male control subjects (P = 0.064). Mutant V allele and mutant VV genotype were similar in the control group compared to the sarcoma groups (P > 0.05). No correlation could be proved between patient tumour site, presence of metastasis, and local tumour relapse and MTHFR polymorphism. The MTHFR C677T polymorphism may not be important in an individual's susceptibility to osteosarcoma and chondrosarcoma in Turkey and may not be a useful marker for identifying patients at high risk of developing sarcomas.

Endogenous secretory receptor for advanced glycation endproducts as a novel prognostic marker in chondrosarcoma

BACKGROUND

Chondrosarcoma, the second most frequent primary malignant bone tumor, is classified into 3 grades according to histologic criteria of malignancy. However, a low-grade lesion can be difficult to distinguish from a benign enchondroma, whereas some histologically low-grade lesions may carry a poor prognosis. The receptor for advanced glycation endproducts (RAGE) and its ligand, high-mobility group box-1 (HMGB1), was quantified in enchondromas and chondrosarcomas to determine whether these markers were associated with histological malignancy and prognosis.

METHODS

Enchondromas (n = 20) and typical chondrosarcomas (n = 39) were evaluated for RAGE, endogenous secretory RAGE (esRAGE, a splice variant form), and HMGB1 protein expression by immunohistochemistry including laser confocal microscopy. The content of esRAGE in resected specimens was measured with an enzyme-linked immunosorbent assay. Associations of these molecules with histology and clinical behavior of tumors were analyzed.

RESULTS

Expression of esRAGE and HMGB1 was observed in all specimens. The numbers of cells positive for esRAGE and HMGB1 expression were positively associated with histologic grade. Expression of esRAGE was significantly higher in chondrosarcomas than in enchondromas (P < .001). Tissue esRAGE content was also significantly higher in grade 1 and 2 chondrosarcomas than enchondromas (P = .0255 and P = .008, respectively). High expression of esRAGE in grade 1 chondrosarcoma was associated with subsequent recurrence (P = .0013), lung metastasis (P = .0071), and poor survival (P < .001).

CONCLUSIONS

Assessment of esRAGE expression should aid in diagnostic and prognostic determinations in chondrosarcoma.

Activin A suppresses interleukin-1-induced matrix metalloproteinase 3 secretion in human chondrosarcoma cells

The objective was to investigate the effect of activin A on matrix metalloproteinase 3 (MMP-3) production and to identify the role of activin A in chondroprotection. SW1353 cells, a human chondrosarcoma cell line, were stimulated with interleukin (IL) 1alpha and tumor necrosis factor (TNF) alpha, and the concentrations of activin A, follistatin, and MMP-3 secreted into the culture media were measured by enzyme-linked immunosorbent assay (ELISA). Activin A was added to cell cultures in the presence of IL-1alpha or TNFalpha to determine its effect on the production of MMP-3 and sulfated glycosaminoglycan (sGAG) (measured by Alcian blue assay). To study the mechanism responsible for the chondroprotective effects of activin A, the production of IL-1 receptor antagonist (IL-1ra) and tissue inhibitor for metalloproteinases 1 (TIMP-1) was examined by ELISA. Addition of IL-1alpha did not affect the production of activin A by cultured SW1353 cells. IL-1alpha and activin A inhibited the production of follistatin. Stimulation of SW1353 cells with activin A suppressed IL-1alpha-induced, but not TNFalpha-induced, MMP-3 expression. Activin A had no effect on the production of sGAG, IL-1ra, or TIMP-1, although it suppressed the induction of TIMP-1 and IL-1ra by IL-1alpha. This novel finding of MMP-3 inhibition by activin A suggests a new role of activin A in cartilage remodeling. Activin A may have therapeutic potential for preventing cartilage degradation.

Expression of receptor activator of nuclear factor kappa-B ligand (RANKL) in neoplasms of dogs and cats

BACKGROUND

Receptor activator of nuclear factor kappa-B (RANK), RANK-ligand (RANKL), and the soluble decoy receptor osteoprotegerin (OPG) form a key axis modulating osteoclastogenesis. In health, RANKL-expressing bone stromal cells and osteoblasts activate osteoclasts through RANK ligation, resulting in homeostatic bone resorption. Skeletal tumors of dogs and cats, whether primary or metastatic, may express RANKL and directly induce malignant osteolysis.

HYPOTHESIS

Bone malignancies of dogs and cats may express RANKL, thereby contributing to pathologic bone resorption and pain. Furthermore, relative RANKL expression in bone tumors may correlate with radiographic characteristics of bone pathology.

ANIMALS

Forty-two dogs and 6 cats with spontaneously-occurring tumors involving bones or soft tissues were evaluated.

METHODS

A polyclonal anti-human RANKL antibody was validated for use in canine and feline cells by flow cytometry and immunocytochemistry. Fifty cytologic specimens were collected from bone and soft tissue tumors of 48 tumor-bearing animals and assessed for RANKL expression. In 15 canine osteosarcoma (OSA) samples, relative RANKL expression was correlated with radiographic characteristics of bone pathology.

RESULTS

Expression of RANKL by neoplastic cells was identified in 32/44 canine and 5/6 feline tumor samples. In 15 dogs with OSA, relative RANKL expression did not correlate with either radiographic osteolysis or bone mineral density as assessed by dual energy x-ray absorptiometry.

CONCLUSIONS AND CLINICAL IMPORTANCE

In dogs and cats, tumors classically involving bone and causing pain, often may express RANKL. Confirming RANKL expression in tumors is a necessary step toward the rational institution of novel therapies targeting malignant osteolysis via RANKL antagonism.

Differential expression of Runx2 and Indian hedgehog in cartilaginous tumors

Runx2-Cbfa1, a Runt transcription factor, plays important roles during skeletal development. In its absence, chondrocyte hypertrophy is severely impaired and there is no vascularization of cartilage templates during skeletal development. In addition, Indian hedgehog (Ihh) signaling molecules control the space and timing of chondrocyte differentiation. Our goal was to gain a better understanding of the molecular process underlying the development of chondrosarcoma and to investigate whether there is a biological difference among variable types of chondrosarcomas. To accomplish this we collected a series of 10 enchondromas and 57 chondrosarcomas (conventional, n = 17; mesenchymal, n = 20; clear cell, n = 20), and investigated the expression of Runx2 and Ihh in these cartilaginous tumors by immunohistochemistry. Cellular and matrix-rich areas were evaluated separately. Runx2 was expressed in 100% of conventional, mesenchymal, and clear cell chondrosarcomas, and in 30% of enchondromas. Higher levels of expression of Runx2 were found in cellular areas than in matrixrich areas. Expression levels increased with increasing histological grade in conventional chondrosarcoma, suggesting involvement in tumor progression. Ihh was expressed in 100% of conventional and clear cell chondrosarcomas, especially in matrix-rich areas. Mesenchymal chondrosarcomas revealed only focal expression of Ihh in matrix-rich areas. Small cell areas were negative. Ihh was absent or focally expressed in enchondromas. These findings demonstrate that Runx2 expression is active in variable chondrosarcomas compared to enchondromas, suggesting its importance in growth and differentiation of neoplastic cartilage. Ihh expression is considered a marker of the hypertrophic stage of differentiation in these tumor cells.

Different transcriptional strategies for ccn2/ctgf gene induction between human chondrocytic and breast cancer cell lines

Connective tissue growth factor (CTGF/CCN2) plays a critical role in endochondral bone formation; however, CCN2 also promotes angiogenesis and bone metastasis in breast cancer. Chondrocytic HCS-2/8 cells and breast cancer MDA231 cells produce over 6 times more CCN2 than any other cell type. In this study, we demonstrate that these cell lines employ different transcriptional strategies for ccn2 gene induction. Four tandem copies of the dominant transcriptional enhancer in chondrocytes (4 x TRENDIC) were chimerically connected to an SV40 promoter-luciferase construct and subsequently analyzed. The enhancement of the promoter activity by 4 x TRENDIC was greater in the HCS-2/8 cells (7-fold) than in the other 4 cell lines (3-4 fold). The TRENDIC-binding protein complex was detected at a higher signal in the HCS-2/8 cells than in the other cell lines. In addition, the HCS-2/8 nuclear factors strongly targeted not only TRENDIC, but also the previously reported basal control element and a novel enhancer element in the ccn2 promoter. In contrast, high-level ccn2 gene induction in MDA231 cells was largely dependent on Smad signaling through the Smad-binding element in the ccn2 promoter. Based on these results, we propose a model of differential transcription of the ccn2 gene between the chondrocytic cell line and the breast cancer cell line, and therefore imply that these cells utilize distinct transcriptional strategies to obtain the enhanced CCN2 production that is not observed in other types of cells.

IFI16 inhibits tumorigenicity and cell proliferation of bone and cartilage tumor cells

IFI16 is a member of the interferon-inducible p200-protein family, capable of modulating cell proliferation, and cellular senescence. In this study, these effects of IFI16 were studied in tumor cells derived from bone and cartilage. The level of IFI16 was markedly lower in human osteosarcomas as compared with its level in normal bone. Overexpression of functional IFI16 in human osteosarcoma and chondrosarcoma cell lines markedly inhibited colony formation, and significantly inhibited cell growth, an effect that could be reversed by introduction of gene specific siRNA into tumor cells. These inhibitory effects of IFI16 were associated with upregulation of p21 and inhibition of cyclin E, cyclin D1, c-Myc and Ras. In addition, ectopic expression of IFI16 in tumor cells increased senescence-associated beta-galactosidase and induced a senescence-like phenotype. In view of such effects, IFI16 might be a suitable target for therapeutic intervention in osteosarcoma and chondrosarcoma.

ADAMTS1 is regulated by interleukin-1β, not by hypoxia, in chondrosarcoma

Angiogenesis is characteristic of cartilage tumors, not of normal cartilage tissue. In addition to our previous report on differential expression of proangiogenic vascular endothelial growth factor A (VEGF-A) in cartilage tumors, we analyzed the expression of a disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1), which has been identified as a potent inhibitor of VEGF-A. We further used a chondrosarcoma cell line to study the effect of interleukin (IL)-1beta and hypoxia on the regulation of ADAMTS1 and VEGF-A expression. ADAMTS1 was detected by reverse transcriptase-polymerase chain reaction and immunohistochemistry in all analyzed samples from enchondromas, conventional chondrosacromas, and dedifferentiated chondrosarcomas without exception. In contrast to previous reports on other cancers, we did not detect a consistent decrease in ADAMTS1 expression in chondrosarcomas. Interleukin-1beta stimulation, not hypoxia, transcriptionally downregulated ADAMTS1 in chondrosarcoma cells, whereas VEGF-A expression was upregulated either by hypoxia or IL-1beta. We conclude that ADAMTS1 and VEGF-A in chondrosarcoma cells are regulated independently from each other. We believe that IL-1beta has a stronger impact on vascularization in chondrosarcomas than hypoxia, as both factors, ADAMTS1 and VEGF-A, are regulated in a way that favors angiogenesis.

Osteosarcoma and chondrosarcoma: new signaling pathways as targets for novel therapeutic interventions

Osteosarcomas and chondrosarcomas are the most common primary bone sarcomas. They are often highly aggressive neoplasms that rapidly progress and eventually recur and give distant metastases. Although the prognosis and quality of life have been improved during the last decades, the pathogenesis of these tumours remains elusive. Recent advances in molecular genetics and cytogenetics have brought a wealth of genes and molecular pathways that govern osteoblast and chondroblast differentiation and maturation, providing a better understanding of the biology of osteogenetic and cartilage tumours. In this review we describe the major tumour suppressor and oncogenic pathways, as well as the most important signal transduction cascades implicated in the development and progression of these malignancies. Furthermore, we discuss novel treatment regimens and future, patient-tailored strategies that will add significantly to the current therapeutic armamentarium.

Aggressive clear cell chondrosarcomas: do distinctive characteristics exist?: a report of 4 cases

CONTEXT

Clear cell chondrosarcoma (CCC) is commonly considered to be a low-grade subtype of chondrosarcoma. However, a few cases of CCC behave as high-grade lesions (with early metastases or multiple/synchronous locations).

OBJECTIVE

To investigate morphologic features that can help predict the aggressiveness of these CCCs.

DESIGN

To investigate possible hallmarks of this aggressiveness, we are presenting the clinicopathologic features of 6 cases of CCC, 4 of which presented aggressive features and 2 low-grade behavior. The patients were 5 men and 1 woman; their ages ranged from 22 to 47 years. Histologic appearance, ultrastructure, and immunohistochemical expression of metalloproteinase 1 and 2 and their inhibitors were evaluated in all 6 cases.

RESULTS

Pain was the most common symptom; the lesions were located in the femur (4), humerus (2), and vertebral body (1), with 1 patient presenting a double/synchronous lesion. Although no major differences were detected using conventional light microscopy, an ultrastructural analysis--at variance with usual cases--showed a lack of superficial microvilli in more than 50% of neoplastic cells in the aggressive cases, therefore suggesting a less differentiated phenotype. In addition, metalloproteinase 2 was more diffusely expressed in the aggressive tumors than in the conventional CCCs, whereas p53 labeling was always negative.

CONCLUSIONS

The aggressive behavior of some CCCs may be, at least in part, correlated to a lesser degree of cell differentiation and to the expression of tumor cell proteins, such as metalloproteinase 2, which are able to favor neoplastic spreading.

Relative quantification of glycosaminoglycan-induced upregulation of TFPI-mRNA expression in vitro

OBJECTIVE

Tissue factor pathway inhibitor (TFPI) is a multivalent Kunitz-type serine proteinase inhibitor that plays a central role in the extrinsic pathway of blood coagulation and is mainly expressed by endothelial cells. In this study we examined the in vitro effects of heparin and other glycosaminoglycans on TFPI mRNA-expression in cultivated human endothelial (Ea.hy 926) and in chondrosarcoma (SW 1353) cells.

METHODS

We used a LightCycler-based method for relative quantification of the TFPI-mRNA expression before and after stimulation. The cells were stimulated with different concentrations of heparin (with and without addition of protamin), heparan sulfate (HS) and chondroitin-6-sulfate (CS). Cells were harvested after incubation times of 4, 8 and 24h, total RNA was isolated, and cDNA was synthesized and quantified relatively to a constantly expressed housekeeping gene.

RESULTS

Stimulation of Ea.hy 926 cells with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) caused a time- and dose-dependent upregulation of TFPI-mRNA expression with LMWH showing the stronger effect. In contrast to this, HS led to a strongly and CS to a slightly decreased TFPI-mRNA expression. SW 1353 cells which were stimulated with LMWH/UFH and HS/CS did not show a significant up- or downregulative effect.

CONCLUSION

Our results show that we have developed a versatile method for the relative quantification of TFPI-mRNA expression. As a conclusion, the determined heparin-induced upregulation of TFPI-mRNA expression can be considered a major component of the modulation of the anticoagulant properties of the endothelium.

Intrinsic radiation resistance in human chondrosarcoma cells

Human chondrosarcomas rarely respond to radiation treatment, limiting the options for eradication of these tumors. The basis of radiation resistance in chondrosarcomas remains obscure. In normal cells radiation induces DNA damage that leads to growth arrest or death. However, cells that lack cell cycle control mechanisms needed for these responses show intrinsic radiation resistance. In previous work, we identified immortalized human chondrosarcoma cell lines that lacked p16(ink4a), one of the major tumor suppressor proteins that regulate the cell cycle. We hypothesized that the absence of p16(ink4a) contributes to the intrinsic radiation resistance of chondrosarcomas and that restoring p16(ink4a) expression would increase their radiation sensitivity. To test this we determined the effects of ectopic p16(ink4a) expression on chondrosarcoma cell resistance to low-dose gamma-irradiation (1-5 Gy). p16(ink4a) expression significantly increased radiation sensitivity in clonogenic assays. Apoptosis did not increase significantly with radiation and was unaffected by p16(ink4a) transduction of chondrosarcoma cells, indicating that mitotic catastrophe, rather than programmed cell death, was the predominant radiation effect. These results support the hypothesis that p16(ink4a) plays a role in the radiation resistance of chondrosarcoma cell lines and suggests that restoring p16 expression will improve the radiation sensitivity of human chondrosarcomas.

Well-differentiated chondrosarcoma of the humerus with prominent granular cell component: a hitherto unreported occurrence

We report the case of a well-differentiated chondrosarcoma of the proximal humerus in a 60-year-old man that featured a prominent component of granular cells, the granules being shown by electron microscopy to be lysosomal. Although secondary granular cell changes have been described in a large variety of tumor types, this is, to the best of our knowledge, the first documentation of this phenomenon in a skeletal chondrosarcoma.

Interleukin-10 does not affect IL-1-induced interleukin-6 and metalloproteinase production in human chondrosarcoma cells, SW1353

Cartilage repair by transplantation of autologous chondrocytes is an option when restoring functional joints. Control of chondrocyte function is thus required. Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine affecting the expression of a wide range of immune mediators in hematopoietic and non-hematopoietic cells. Previous studies indicated that IL-10 has therapeutic potential in the treatment of chronic inflammatory joint disorders such as rheumatoid arthritis and osteoarthritis. IL-10 has been found to be chondroprotective by down-regulating metalloproteinase expression and by inhibiting the synthesis of pro-inflammatory cytokines, such as IL-6, in immune cells. In contrast, the effects of IL-10 on chondrocytes are poorly understood and have to be identified with regard to their future clinical use. In this study, we investigated the effects of IL-10 on the expression of cartilage-degrading mediators in the human chondrosarcoma cell line, SW1353, after exposure to IL-1, a key mediator in cartilage and bone destruction. We found a strong induction of the pro-inflammatory cytokine, IL-6, in IL-1-exposed SW1353 cells. Surprisingly, IL-10 had no effect on IL-1-induced IL-6, pro-MMP1, and pro-MMP13 secretion. Although RT-PCR analyses demonstrated the expression of both receptor chains of the IL-10 receptor complex (IL-10R1 and IL-10R2), exposure of SW1353 to IL-10 did not lead to phosphorylation of STAT3, the major transcription factor induced by IL-10. This was not due to a defect in STAT3, because stimulation with IL-6 resulted in its phosphorylation. Failure of SW1353 cells to respond to IL-10 was consistent with a deficient surface expression of IL-10R1. From these results we conclude that IL-10 does not exert its chondroprotective character on chondrocytes directly. Furthermore, the unresponsiveness of chondrocytes towards IL-10 might explain the vulnerability of joint cartilage to inflammation.

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.

PDGFRα, PDGFRβ and KIT expression/activation in conventional chondrosarcoma

Chondrosarcomas represent 20% of all primary bone sarcomas, and many studies have attempted to unravel molecular targets for future development of new therapies. The aim of this study was to investigate the expression/activation of PDGFRalpha, PDGFRbeta and KIT receptor tyrosine kinases (RTKs) as potential therapeutic targets in conventional central primary chondrosarcomas (CCS). The expression of PDGFRalpha, PDGFRbeta and KIT RTKs was detected in 16 CCSs using immunohistochemistry (IHC), and their level of expression and activation status were analysed by immunoprecipitation and western blot experiments. PDGFRalpha, PDGFRbeta and KIT cDNAs were screened to verify the presence of activating mutations and the presence of the cognate ligands was analysed by means of RT-PCR. RTK gene amplification was further studied by means of fluorescence in situ hybridization (FISH) analysis. The immunophenotyping and biochemical analyses showed that the CCSs co-expressed PDGFRalpha and PDGFRbeta, with the latter showing definitively greater protein expression and phosphorylation levels. PDGFRbeta was expressed but not activated in control healthy joint cartilage, in line with no PDGFB detection. Conversely, the KIT gene product did not seem to play a relevant role. These findings, in the absence of activating mutations or an abnormal genomic profile and the presence of PDGFA and PDGFB expression, are consistent with an autocrine/paracrine loop activation of the corresponding receptors. The CCS gene profile described here offers a rationale for the use of RTK inhibitors alone or in combination with chemotherapy, and supports further investigation of RTKs and their downstream signals.

Constitutive hedgehog signaling in chondrosarcoma up-regulates tumor cell proliferation

Chondrosarcoma is a malignant cartilage tumor that may arise from benign precursor lesions, such as enchondromas. Some cases of multiple enchondromas are caused by a mutation that results in constitutive activation of Hedgehog-mediated signaling. We found that chondrosarcomas expressed high levels of the Hedgehog target genes PTCH1 and GLI1. Treatment with parathyroid hormone-related protein down-regulated Indian Hedgehog (IHH) expression in normal growth plates but not in chondrosarcoma or enchondroma organ cultures. Treatment of the chondrosarcoma organ cultures with Hedgehog protein increased cell proliferation rate, whereas addition of chemical inhibitors of Hedgehog signaling decreased the proliferation rate. Chondrosarcoma xenografts from 12 different human tumors were established in NOD-SCID mice. Treatment with triparanol, an inhibitor of Hedgehog signaling, resulted in a 60% decrease in tumor volume, a 30% decrease in cellularity, and a 20% reduction in proliferation rate. These results show that Hedgehog signaling is active in chondrosarcoma and benign cartilage tumors and regulates tumor cell proliferation. Our data raise the intriguing possibility that Hedgehog blockade could serve as an effective treatment for chondrosarcoma, a tumor for which there are currently no universally effective nonsurgical management options.

Association between a variation inLRCH1 and knee osteoarthritis: A genome-wide single-nucleotide polymorphism association study using DNA pooling

OBJECTIVE

To perform a large-scale association analysis of single-nucleotide polymorphisms (SNPs) in patients with radiographically defined osteoarthritis (OA) of the knee.

METHODS

We examined >25,000 SNPs located within approximately 14,000 genes for associations with radiographically defined knee OA, using polymerase chain reaction and MassExtend amplification techniques. Allele frequencies were estimated initially in DNA pools from 335 female patients with knee OA and 335 asymptomatic and radiographically negative female control subjects. All were of northern European ancestry. Significant allele frequency differences were validated by genotyping of individual DNA samples. Confirmed significant findings were verified in 2 additional case-control samples from the UK (443 cases and 303 controls) and Newfoundland (346 cases and 264 controls). Chondrosarcoma cell lines were used to test for potential differences in gene expression.

RESULTS

The marker most strongly associated with the risk of knee OA was rs912428, a C/T polymorphism in intron 1 of LRCH1, a gene on chromosome 13q14 that encodes a novel protein of as-yet-unknown function. The frequency of the T allele compared with controls was consistently increased by 40% across all 3 case-control groups. Additional subanalyses in case-control samples with hip OA and hand OA suggested similar trends, but did not reach statistical significance. Association fine-mapping using 10 additional SNPs in LRCH1 confirmed intron 1 as the region of highest association but failed to reveal variations with significance stronger than the marker SNP, as did the haplotype analysis. LRCH1 was not up-regulated or overexpressed in chondrosarcoma cell lines exposed to inflammatory stimuli, suggesting a possible structural role.

CONCLUSION

A genetic variant in LRCH1 was consistently associated with knee OA in 3 samples from 2 populations. Our results also suggest that the same association with OA may exist at other sites. Additional genetic and experimental work is needed to elucidate the precise mechanism by which the LRCH1 gene influences OA risk.

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.

CD24 is expressed specifically in the nucleus pulposus of intervertebral discs

Intervertebral disc (IVD) consists of a soft gelatinous material in its center, the nucleus pulposus (NP), bounded peripherally by fibrocartilage, annulus fibrosus (AF). Despite the number of patients with IVD degeneration, gene expression analysis has not been undertaken in NP and therefore little is known about the molecular markers expressed in NP. Here, we undertook a microarray screen in NP with the other nine tissues to identify the specific cell surface markers for NP. Five membrane associating molecules out of 10,490 genes were identified as highly expressing genes in NP compared with the other tissues. Among them, we identified CD24, a glycosylphosphatidylinositol (GPI) anchor protein as a cell surface marker for NP. CD24 expression was also detected in the herniated NP and chordoma, a malignant primary tumor derived from notochordal cells, while it was absent in chondrosarcoma. Therefore, CD24 is a molecular marker for NP as well as the diseases of IVD.