Brachyury, a crucial regulator of notochordal development, is a novel biomarker for chordomas

Childhood Carcinoma

Carcinoma in children differs from that occurring in adults. It is far rarer and represents only a small fraction of all pediatric cancer diagnoses. Pediatric sarcomas were among the first tumors in which recurrent chromosomal aberrations were discovered. Once defined, these recurrent aberrations, many of them translocations, became incorporated into the pathologist's diagnostic armamentarium. In the past several years, defining chromosomal rearrangements have been identified in pediatric carcinomas as well, and this has become a new frontier in pathologic diagnosis. This article provides an overview of pediatric carcinoma as well as a detailed review of selected types of carcinoma that in particular can present diagnostic difficulty to the practicing pathologist and illustrate new and emerging concepts in pediatric carcinoma.

Revisiting chordoma with brachyury, a "new age" marker: analysis of a validation study on 51 cases

CONTEXT

Chordoma is a rare, notochordal tumor with a characteristic histomorphology and immunohistochemical profile. At times, it presents a diagnostic challenge, especially in small biopsies. Brachyury, a nuclear transcription factor, is a recently described immunohistochemical marker for diagnosing chordomas.

OBJECTIVE

To study the sensitivity and specificity of brachyury in diagnosing chordomas by comparing its expression in axial chordomas with nonchordomatous tumors.

DESIGN

Fifty-one axial chordomas, accessioned during a 10-year period, and 58 nonchordomatous tumors were subjected to brachyury staining by immunohistochemistry.

RESULTS

The 51 chordomas occurred in 36 men and 15 women. Sitewise, 34 cases (66.7%) occurred in the sacrococcyx, 9 (17.6%) in the spine, and 8 (15.7%) in the skull base. Histologically, 34 cases (66.7%) were classical chordomas, 13 cases (25.5%) had a dominant chondroid component, and 2 cases each (3.9%) were chondroid chordomas and dedifferentiated chordomas, respectively. Brachyury staining was positive in 46 of the 51 chordomas (90.2%) and negative in all 58 nonchordomatous tumors. The dedifferentiated area in 2 chordomas was negative for brachyury staining. Fourteen of 15 chordomas with chondroid component showed positive brachyury staining. Immunohistochemical expression of other markers, included cytokeratin (positive in 23 of 23 cases; 100%), epithelial membrane antigen (positive in 22 of 22 cases; 100%) and S100 protein (positive in 18 of 21 cases; 85.7%).

CONCLUSION

Exclusive brachyury expression in more than 90% of chordomas indicates its value as a unique, specific marker with other sensitive markers like cytokeratin, epithelial membrane antigen, and/or S100 protein in substantiating a diagnosis of chordoma, including on small biopsies.

Derivation and characterization of an extra-axial chordoma cell line (EACH-1) from a scapular tumor

BACKGROUND

Extra-axial chordomas are rare low-grade malignant tumors thought to arise from notochordal remnants in the extra-axial skeleton. Few studies have been done on this neoplasm because of its rarity. In addition, there is a lack of a good in vitro model on which to perform more characterization.

METHODS

We describe a twenty-eight-year-old man with a mass in the right scapula. Cytomorphology and immunohistochemistry, including brachyury staining, were used to formulate the final diagnosis. A fragment of the tumor was placed in culture, and cells obtained were injected subcutaneously in an immunocompromised mouse. From the tumor developed in mice, a cell line has been derived and characterized by fluorescence-activated cell-sorting analysis, karyotyping, clonogenicity, and cell and tumor growth curves.

RESULTS

Cytomorphology on the tumor showed nests of round cells with vacuoles and also physaliferous-like cells with uniform nuclei. Immunochemistry revealed a tumor positive for vimentin, moderately positive for S-100 and cytokeratin AE1/AE3, weakly positive for epithelial membrane antigen, and negative for p63 and cytokeratin (CK)-7. Further analysis revealed the tumor was diffusely and strongly positive for brachyury. The cell line derived from the tumor showed rapid doubling-time, a strong expression of mesenchymal cell surface markers, a karyotype of diploid or hypotetraploid clones with numerous chromosomal aberrations, and the ability to form colonies without attachment and to form tumors in immunocompromised mice.

CONCLUSIONS

The diagnosis of the extra-axial chordoma is difficult but can be resolved by the detection of a strong brachyury expression. In addition, the derivation of a human extra-axial chordoma cell line could be a useful tool for the basic research of this rare neoplasm.

Novel immunohistochemical markers in the diagnosis of nonglial tumors of nervous system

Immunohistochemistry (IHC) has become an important adjunct tool in diagnostic neuro-oncology practice enabling immunophenotypic characterization of tumor cells. There have been several recent publications regarding new IHC markers that are useful for diagnosis of brain tumors. To introduce the latest advances in IHC in this field, we review the features of novel IHC marker antibodies applicable to selected nonglial tumors in the nervous system, based on recently published reports and our own experiences. We discuss (1) aquaporin-1 and alpha-inhibin for hemangioblastoma, (2) beta-catenin for craniopharyngioma, (3) brachyury for chordoma, and (4) INI-1 for hereditary schwannomas. All the markers presented here are used primarily for supporting or confirming the histologic diagnosis, with the exception of (4), which may be of help in identification of inherited forms in schwannomas. As with other surgical pathology practices, the judicious use of a panel of IHC antibodies selected on the basis of the histologic findings is important for an accurate diagnosis of brain tumors. Of note is that IHC results should be always interpreted in the histopathologic context.

Transcriptional profiling of bovine intervertebral disc cells: implications for identification of normal and degenerate human intervertebral disc cell phenotypes

INTRODUCTION

Nucleus pulposus (NP) cells have a phenotype similar to articular cartilage (AC) cells. However, the matrix of the NP is clearly different to that of AC suggesting that specific cell phenotypes exist. The aim of this study was to identify novel genes that could be used to distinguish bovine NP cells from AC and annulus fibrosus (AF) cells, and to further determine their expression in normal and degenerate human intervertebral disc (IVD) cells.

METHODS

Microarrays were conducted on bovine AC, AF and NP cells, using Affymetrix Genechip(R) Bovine Genome Arrays. Differential expression levels for a number of genes were confirmed by quantitative real time polymerase chain reaction (qRT-PCR) on bovine, AC, AF and NP cells, as well as separated bovine NP and notochordal (NC) cells. Expression of these novel markers were further tested on normal human AC, AF and NP cells, and degenerate AF and NP cells.

RESULTS

Microarray comparisons between NP/AC&AF and NP/AC identified 34 NP-specific and 49 IVD-specific genes respectively that were differentially expressed > or =100 fold. A subset of these were verified by qRT-PCR and shown to be expressed in bovine NC cells. Eleven genes (SNAP25, KRT8, KRT18, KRT19, CDH2, IBSP, VCAN, TNMD, BASP1, FOXF1 & FBLN1) were also differentially expressed in normal human NP cells, although to a lesser degree. Four genes (SNAP25, KRT8, KRT18 and CDH2) were significantly decreased in degenerate human NP cells, while three genes (VCAN, TNMD and BASP1) were significantly increased in degenerate human AF cells. The IVD negative marker FBLN1 was significantly increased in both degenerate human NP and AF cells.

CONCLUSIONS

This study has identified a number of novel genes that characterise the bovine and human NP and IVD transcriptional profiles, and allows for discrimination between AC, AF and NP cells. Furthermore, the similarity in expression profiles of the separated NP and NC cell populations suggests that these two cell types may be derived from a common lineage. Although interspecies variation, together with changes with IVD degeneration were noted, use of this gene expression signature will benefit tissue engineering studies where defining the NP phenotype is paramount.

The surgical management of sacral chordomas

STUDY DESIGN

Retrospective case series.

OBJECTIVE

The purpose of this study was to evaluate factors that contribute to improved local control and survival. In addition, we sought to define the expected morbidity associated with treatment.

SUMMARY OF BACKGROUND DATA

Sacral chordomas are rare tumors presumed to arise from notochordal cells. Local recurrence presents a major problem in the management of these tumors and it has been correlated with survival. Resection of sacral tumors is associated with significant morbidity.

METHODS

Forty-two patients underwent resection for sacral chordoma between 1990 and 2005. Twelve patients had their initial surgery elsewhere. There were 12 female and 30 male patients. The proximal extent of the sacrectomy was at least S2 in 32 patients.

RESULTS

Median survival was 84 months, and 5-year disease-free (DFS) and disease-specific survival (DSF) were 56% and 77%, respectively. Local recurrence (LR) and metastasis occurred in 17 (40%) and 13 (31%) patients, respectively. Local recurrence (P=0.0001), metastasis (P=0.0001), prior resection (P=0.046), and higher grade (P=0.05) were associated with a worse DSF. Prior resections (P=0.0001) and intralesional resections (P=0.01) were associated with a higher rate of LR. Intralesional resections were associated with a lower DSF (P=0.0001). Wide contaminated margins treated with cryosurgery and/or radiation were not associated with a higher LR rate. Rectus abdominus flaps were associated with decreased wound complications (P=0.01). Thirty-one (74%) patients reported that they self catheterize; and 16 (38%) patients required bowel training, while an additional twelve (29%) patients had a colostomy. Twenty-eight (67%) patients reported sexual dysfunction. Two (5%) patients died due to sepsis.

CONCLUSIONS

Intralesional resection should be avoided as it is associated with a higher LR rate and worse survival. Rectus abdominus flaps ought to be considered as they lower the wound complication rate. Sacral resection is associated with significant morbidity.

Chordoma of the mobile spine and sacrum: a retrospective analysis of a series of patients surgically treated at two referral centers

BACKGROUND

Chordoma is a rare tumor, and its natural history is still not well known.

MATERIALS AND METHODS

All patients affected by localized chordoma surgically treated at Istituto Ortopedico Rizzoli, Bologna, and Istituto Nazionale Tumori, Milan, Italy, between 1980 and 2008 were reviewed. Local recurrence, distant metastasis, and overall survival (OS) were analyzed both from time of diagnosis and from time of local recurrence/distant metastasis. A multivariable analysis to identify independent prognostic factors was carried out.

RESULTS

A total of 138 consecutive patients were identified (sacrum 78%, lumbar spine 15%, cervical-dorsal spine 7%). Of these, 130 underwent surgical resection. Median follow-up was 142 months. The 5- and 10-year OS, local relapse-free survival (LRFS), and distant relapse-free survival (DRFS) were, respectively, 78% and 54%, 52% and 33%, and 86% and 72%. Size was an independent prognostic factor for OS (P value < .001), LRFS (P value: .038), and DRFS (P value: .004), while surgical margins independently predicted LRFS (P value: .003) with a trend for OS. The 5- and 10-year OS, LRFS, and DRFS after the first local relapse were 50% and 26%, 47% and 31%, and 64% and 61%. The size of the recurrence and quality of surgical margins did not influence postrelapse OS. The 5-year OS after the second local relapse was 19%. 22% of patients developed distant metastases with a 5-year post-metastases OS of 33%.

CONCLUSIONS

Tumor size and surgical margins affected outcome only on initial presentation. However, wide surgery was feasible in a minority of cases. Most patients died of local-regional disease even when metastases occurred. Indeed, long-term prognosis was such that disease-free survival at 10 years was only 26%.

T (brachyury) gene duplication confers major susceptibility to familial chordoma

Using high-resolution array-CGH, we identified unique duplications of a region on 6q27 in four multiplex families with at least three cases of chordoma, a cancer of presumed notochordal origin. The duplicated region contains only the T (brachyury) gene, which is important in notochord development and is expressed in most sporadic chordomas. Our findings highlight the value of screening for complex genomic rearrangements in searches for cancer-susceptibility genes.

Immunohistochemical comparison of chordoma with chondrosarcoma, myxopapillary ependymoma, and chordoid meningioma

Chordoma originates from embryonic notochordal remnants in the midline along the spinal axis and is characterized by cords and lobules of neoplastic cells arranged within myxoid matrix. Because of histologic similarities with myxoid matrix and overlapping immunohistochemical profile, chondrosarcoma, myxopapillary ependymoma, and chordoid meningioma enter in the histologic differential diagnosis at this site. Therefore, the judicious use of a panel of selected immunostains is unquestionably helpful in diagnostically challenging cases. To find useful immunohistochemical markers for assisting in differential diagnosis between chordoma and other tumors with chordoid morphology, an immunohistochemical study using D2-40, epithelial membrane antigen (EMA), pan-cytokeratin (panCK), glial fibrillary acidic protein (GFAP), S-100 protein, galectin-3, neural cell adhesion molecule (NCAM), beta-catenin, E-cadherin, and carcinoembryonic antigen was performed on 14 chordomas, 7 chondrosarcomas, 9 myxopapillary ependymomas, and 4 chordoid meningiomas. Chordoma typically showed positive for EMA and panCK and negative for D2-40 and GFAP; whereas chondrosarcoma revealed positive for D2-40, and negative for EMA, panCK, and GFAP; myxopapillary ependymoma positive for GFAP and negative for EMA; and chordoid meningioma positive for EMA, and negative for panCK and GFAP. On the basis of our immunohistochemical study, a panel of D2-40, EMA, panCK, and GFAP allowed the correct recognition of all tumors examined. Other immunohistochemical markers including S-100 protein, galectin-3, NCAM, beta-catenin, E-cadherin, and carcinoembryonic antigen were of little value in differential diagnosis. In summary, the best immunohistochemical markers useful for the evaluation of tumors with chordoid morphology were D2-40, EMA, cytokeratin, and GFAP. D2-40 was a true chondroid marker to be useful for the differential diagnosis with chordoma.

Analysis of the fibroblastic growth factor receptor-RAS/RAF/MEK/ERK-ETS2/brachyury signalling pathway in chordomas

Chordomas are rare primary malignant bone tumours that derive from notochord precursor cells and express brachyury, a molecule involved in notochord development. Little is known about the genetic events responsible for driving the growth of this tumour, but it is well established that brachyury is regulated through fibroblastic growth factor receptors (FGFRs) through RAS/RAF/MEK/ERK and ETS2 in ascidian, Xenopus and zebrafish, although little is known about its regulation in mammals. The aim of this study was to attempt to identify the molecular genetic events that are responsible for the pathogenesis of chordomas with particular focus on the FGFR signalling pathway on the basis of the evidence in the ascidian and Xenopus models that the expression of brachyury requires the activation of this pathway. Immunohistochemistry showed that 47 of 50 chordomas (94%) expressed at least one of the FGFRs, and western blotting showed phosphorylation of fibroblast growth factor receptor substrate 2 alpha (FRS2alpha), an adaptor signalling protein, that links FGFR to the RAS/RAF/MEK/ERK pathway. Screening for mutations in brachyury (all coding exons and promoter), FGFRs 1-4 (previously reported mutations), KRAS (codons 12, 13, 51, 61) and BRAF (exons 11 and 15) failed to show any genetic alterations in 23 chordomas. Fluorescent in situ hybridisation analysis on FGFR4, ETS2 and brachyury failed to show either amplification of these genes, although there was minor allelic gain in brachyury in three tumours, or translocation for ERG and ETS2 loci. The key genetic events responsible for the initiation and progression of chordomas remain to be discovered.

Markers aiding the diagnosis of chondroid tumors: an immunohistochemical study including osteonectin, bcl-2, cox-2, actin, calponin, D2-40 (podoplanin), mdm-2, CD117 (c-kit), and YKL-40

Chondroid tumors comprise a heterogenous group of benign to overt malignant neoplasms, which may be difficult to differentiate from one another by histological examination. A group of 43 such tumors was stained with nine relevant antibodies in an attempt to find consistent marker profile(s) for the different subgroups. Archival material from three extraskeletal myxoid chondrosarcomas, five chordomas, five chondromyxoid fibromas, five chondroblastomas and 25 chondrosarcomas was stained with antibodies against osteonectin, bcl-2, cox-2, actin, calponin, D2-40 (podoplanin), mdm-2, CD117 (c-kit) and YKL-40. All 25 chondrosarcomas showed a positive staining reaction for D2-40, none for actin and CD117, and a partial reactivity for bcl-2 (36%). Chondroblastomas (5/5) and chondromyxoid fibromas (2/5) were the only tumors with a positive reaction for actin, and all chondroblastomas (n=5) and extraskeletal myxoid chondrosarcomas (n=3) were positive for bcl-2. In contrast to all other tumors, two of three extraskeletal myxoid chondrosarcomas were also positive for CD17 and negative for osteonectin, cox-2, mdm-2 and actin. All five chordomas were negative for D2-40 and positive for mdm-2 and YKL-40. The diagnosis of chondrosarcoma may be aided by its positivity for D2-40 and YKL-40 and its lack of reactivity for actin and CD117. This should be seen in the light of no reaction for D2-40 in chordomas and a corresponding lack of reaction for osteonectin, cox-2, mdm-2 and actin in extraskeletal myxoid chondrosarcomas. A convincing immunoreactivity for calponin and/or actin in chondromyxoid fibromas and chondroblastomas may also be helpful in differentiating these tumors from chondrosarcomas.

Expression of Brachyury in mesenchymal progenitor cells leads to cartilage-like tissue that is resistant to the destructive effect of rheumatoid arthritis synovial fibroblasts

Our objectives were to determine the chondrogenic potential of a murine Brachyury-transformed mesenchymal progenitor cell line in the presence of rheumatoid arthritis-activated synovial fibroblasts (RASFs). Brachyury-transformed mesenchymal progenitor cells were implanted alone or combined with RASFs isolated from diseased human joints in each of six immunodeficient SCID mice. De novo tissue formation was analysed by histology and immunohistochemistry after 60 days. Spheroid nodules resembling cartilage morphologically and by the expression of proteoglycans and collagen II developed in four of six implants in the absence and in five of six implants in the presence of RASFs. No evidence for hypertrophic differentiation could be observed. Mesenchymal progenitor cells transformed with Brachyury are able to produce a cartilage like tissue in vivo over an extended period of time that is resistant to the destructive effect of RASF. This observation may provide opportunities for a cell-based reconstructive treatment in joint disease.

Potential therapeutic targets for chordoma: PI3K/AKT/TSC1/TSC2/mTOR pathway

Chordomas are radio- and chemo-resistant tumours and metastasise in as many as 40% of patients. The aim of this study was to identify potential molecular targets for the treatment of chordoma. In view of the reported association of chordoma and tuberous sclerosis complex syndrome, and the available therapeutic agents against molecules in the PI3K/AKT/TSC1/TSC2/mTOR pathway, a tissue microarray of 50 chordoma cases was analysed for expression of active molecules involved in this signalling pathway by immunohistochemistry and a selected number by western blot analysis. Chordomas were positive for p-AKT (92%), p-TSC2 (96%), p-mTOR (27%), total mTOR (75%), p-p70S6K (62%), p-RPS6 (22%), p-4E-BP1 (96%) and eIF-4E (98%). Phosphatase and tensin homologue deleted on chromosome 10 expression was lost in 16% of cases. Mutations failed to be identified in PI3KCA and RHEB1 in the 23 cases for which genomic DNA was available. Fluorescence in situ hybridisation analysis for mTOR and RPS6 loci showed that 11 of 33 and 21 of 44 tumours had loss of one copy of the respective genes, results which correlated with the loss of the relevant total proteins. Fluorescence in situ hybridisation analysis for loci containing TSC1 and TSC2 revealed that all cases analysed harboured two copies of the respective genes. On the basis of p-mTOR and or p-p70S6K expression there is evidence indicating that 65% of the chordomas studied may be responsive to mTOR inhibitors, rapamycin or its analogues, and that patients may benefit from combined therapy including drugs that inhibit AKT.

Distinguishing chordoid meningiomas from their histologic mimics: an immunohistochemical evaluation

Chordoid meningioma, World Health Organization grade II, is an uncommon variant of meningioma with a propensity for aggressive behavior and increased likelihood of recurrence. As such, recognition of this entity is important in cases that show similar morphologic overlap with other chondroid/myxoid neoplasms that can arise within or near the central nervous system. A formal comparison of the immunohistochemical features of chordoid meningioma versus tumors with significant histologic overlap has not been previously reported. In this study, immunohistochemical staining was performed with antibodies against D2-40, S100, pankeratin, epithelial membrane antigen (EMA), brachyury, and glial fibrillary acidic protein (GFAP) in 4 cases of chordoid glioma, 6 skeletal myxoid chondrosarcomas, 10 chordoid meningiomas, 16 extraskeletal myxoid chondrosarcoma, 18 chordomas, 22 low-grade chondrosarcomas, and 27 enchondromas. Staining extent and intensity were evaluated semiquantitatively and mean values for each parameter were calculated. Immunostaining with D2-40 showed positivity in 100% of skeletal myxoid chondrosarcomas, 96% of enchondromas, 95% of low-grade chondrosarcomas, 80% of chordoid meningiomas, and 75% of chordoid gliomas. Staining with S100 demonstrated diffuse, strong positivity in all (100%) chordoid gliomas, skeletal myxoid chondrosarcomas, low-grade chondrosarcomas, and enchondromas, 94% of chordomas, and 81% of extraskeletal myxoid chondrosarcomas, with focal, moderate staining in 40% of chordoid meningiomas. Pankeratin highlighted 100% of chordoid gliomas and chordomas, 38% of extraskeletal myxoid chondrosarcomas, and 20% of chordoid meningiomas. EMA staining was positive in 100% of chordoid gliomas, 94% of chordomas, 90% of chordoid meningiomas, and 25% of extraskeletal myxoid chondrosarcomas. Brachyury was positive only in the chordomas (100%), whereas GFAP was positive only in the chordoid gliomas (100%). EMA was the most effective antibody for differentiating chordoid meningioma from skeletal myxoid chondrosarcoma, low-grade chondrosarcoma, and enchondroma, whereas D2-40 was the most effective antibody for differentiating chordoid meningioma from extraskeletal myxoid chondrosarcoma and chordoma. Our findings demonstrate that in conjunction with clinical and radiographic findings, immunohistochemical evaluation with a panel of D2-40, EMA, brachyury, and GFAP is most useful in distinguishing chordoid meningioma from chordoid glioma, skeletal myxoid chondrosarcoma, extraskeletal myxoid chondrosarcoma, chordoma, low-grade chondrosarcoma, and enchondroma. A lack of strong, diffuse S100 reactivity may also be useful in excluding chordoid meningioma. Among the neoplasms evaluated, brachyury and GFAP proved to be both sensitive and specific markers for chordoma and chordoid glioma, respectively. Of note, this study is the first to characterize the D2-40 immunoprofile in extraskeletal myxoid chondrosarcoma, results that could be of utility in differential diagnostic assessment.

Identification of nucleus pulposus precursor cells and notochordal remnants in the mouse: implications for disk degeneration and chordoma formation

A classically identified "notochordal" cell population in the nucleus pulposus is thought to regulate disk homeostasis. However, the embryonic origin of these cells has been under dispute for >60 years. Here we provide the first direct evidence that all cell types in the adult mouse nucleus pulposus are derived from the embryonic notochord. Additionally, rare isolated embryonic notochord cells remained in the vertebral column and resembled "notochordal remnants," which in humans have been proposed to give rise to a rare type of late-onset cancer called chordoma. Previously, this cell type had not been identified in the mouse model system. The development and characterization of a mouse model that can be used to fate map nucleus pulposus precursor cells in any mutant background will be useful for uncovering the cellular and molecular mechanisms of disk degeneration. In addition, the identification of notochordal remnants in mice is the first step towards generating an in vivo model of chordoma.

Brachyury, SOX-9, and podoplanin, new markers in the skull base chordoma vs chondrosarcoma differential: a tissue microarray-based comparative analysis

The distinction between chondrosarcoma and chordoma of the skull base/head and neck is prognostically important; however, both have sufficient morphologic overlap to make delineation difficult. As a result of gene expression studies, additional candidate markers have been proposed to help in separating those entities. We sought to evaluate the performance of new markers: brachyury, SOX-9, and podoplanin alongside the more traditional markers glial fibrillary acid protein, carcinoembryonic antigen, CD24, and epithelial membrane antigen. Paraffin blocks from 103 skull base/head and neck chondroid tumors from 70 patients were retrieved (1969-2007). Diagnoses were made based on morphology and/or whole-section immunohistochemistry for cytokeratin and S100 protein yielding 79 chordomas (comprising 45 chondroid chordomas and 34 conventional chordomas), and 24 chondrosarcomas. A tissue microarray containing 0.6 mm cores of each tumor in triplicate was constructed using a manual array (MTA-1; Beecher Instruments). For visualization of staining, the ImmPRESS detection system (Vector Laboratories) with 2-diaminobenzidine substrate was used. Sensitivities and specificities were calculated for each marker. Core loss from the microarray ranged from 25 to 29% yielding 66-78 viable cases per stain. The classic marker, cytokeratin, still has the best performance characteristics. When combined with brachyury, accuracy improves slightly (sensitivity and specificity for detection of chordoma 98 and 100%, respectively). Positivity for both epithelial membrane antigen and AE1/AE3 had a sensitivity of 90% and a specificity of 100% for detecting chordoma in this study. SOX-9 is apparently common to both notochordal and cartilaginous differentiation, and is not useful in the chordoma-chondrosarcoma differential diagnosis. Glial fibrillary acid protein, carcinoembryonic antigen, CD24, and epithelial membrane antigen did not outperform other markers, and are less useful in the diagnosis of chordoma vs chondrosarcoma. Podoplanin still remains the only positive marker for chondrosarcoma, though its accuracy is less than previously reported.

Chordoma and chondrosarcoma gene profile: implications for immunotherapy

Chordoma and chondrosarcoma are malignant bone tumors characterized by the abundant production of extracellular matrix. The resistance of these tumors to conventional therapeutic modalities has prompted us to delineate the gene expression profile of these two tumor types, with the expectation to identify potential molecular therapeutic targets. Furthermore the transcriptional profile of chordomas and chrondrosarcomas was compared to a wide variety of sarcomas as well as to that of normal tissues of similar lineage, to determine whether they express unique gene signatures among other tumors of mesenchymal origin, and to identify changes associated with malignant transformation. A HG-U133A Affymetrix Chip platform was used to determine the gene expression signature in 6 chordoma and 14 chondrosarcoma lesions. Validation of selected genes was performed by qPCR and immunohistochemistry (IHC) on an extended subset of tumors. By unsupervised clustering, chordoma and chondrosarcoma tumors grouped together in a genomic cluster distinct from that of other sarcoma types. They shared overexpression of many extracellular matrix genes including aggrecan, type II & X collagen, fibronectin, matrillin 3, high molecular weight-melanoma associated antigen (HMW-MAA), matrix metalloproteinase MMP-9, and MMP-19. In contrast, T Brachyury and CD24 were selectively expressed in chordomas, as were Keratin 8,13,15,18 and 19. Chondrosarcomas are distinguished by high expression of type IX and XI collagen. Because of its potential usefulness as a target for immunotherapy, the expression of HMW-MAA was analyzed by IHC and was detected in 62% of chordomas and 48% of chondrosarcomas, respectively. Furthermore, western blotting analysis showed that HMW-MAA synthesized by chordoma cell lines has a structure similar to that of the antigen synthesized by melanoma cells. In conclusion, chordomas and chondrosarcomas share a similar gene expression profile of up-regulated extracellular matrix genes. HMW-MAA represents a potential useful target to apply immunotherapy to these tumors.

Frequent deletion of the CDKN2A locus in chordoma: analysis of chromosomal imbalances using array comparative genomic hybridisation

The initiating somatic genetic events in chordoma development have not yet been identified. Most cytogenetically investigated chordomas have displayed near-diploid or moderately hypodiploid karyotypes, with several numerical and structural rearrangements. However, no consistent structural chromosome aberration has been reported. This is the first array-based study characterising DNA copy number changes in chordoma. Array comparative genomic hybridisation (aCGH) identified copy number alterations in all samples and imbalances affecting 5 or more out of the 21 investigated tumours were seen on all chromosomes. In general, deletions were more common than gains and no high-level amplification was found, supporting previous findings of primarily losses of large chromosomal regions as an important mechanism in chordoma development. Although small imbalances were commonly found, the vast majority of these were detected in single cases; no small deletion affecting all tumours could be discerned. However, the CDKN2A and CDKN2B loci in 9p21 were homo- or heterozygously lost in 70% of the tumours, a finding corroborated by fluorescence in situ hybridisation, suggesting that inactivation of these genes constitute an important step in chordoma development.

The human T-box mesodermal transcription factor Brachyury is a candidate target for T-cell-mediated cancer immunotherapy

PURPOSE

Identification of tumor antigens is essential in advancing immune-based therapeutic interventions in cancer. Particularly attractive targets are those molecules that are selectively expressed by malignant cells and that are also essential for tumor progression.

EXPERIMENTAL DESIGN AND RESULTS

We have used a computer-based differential display analysis tool for mining of expressed sequence tag clusters in the human Unigene database and identified Brachyury as a novel tumor antigen. Brachyury, a member of the T-box transcription factor family, is a key player in mesoderm specification during embryonic development. Moreover, transcription factors that control mesoderm have been implicated in the epithelial-mesenchymal transition (EMT), which has been postulated to be a key step during tumor progression to metastasis. Reverse transcription-PCR analysis validated the in silico predictions and showed Brachyury expression in tumors of the small intestine, stomach, kidney, bladder, uterus, ovary, and testis, as well as in cell lines derived from lung, colon, and prostate carcinomas, but not in the vast majority of the normal tissues tested. An HLA-A0201 epitope of human Brachyury was identified that was able to expand T lymphocytes from blood of cancer patients and normal donors with the ability to lyse Brachyury-expressing tumor cells.

CONCLUSIONS

To our knowledge, this is the first demonstration that (a) a T-box transcription factor and (b) a molecule implicated in mesodermal development, i.e., EMT, can be a potential target for human T-cell-mediated cancer immunotherapy.

Parachordoma of the gastric serosa: report of a myxoid mimicry in an unusual location

The authors report a case of an incidentally discovered myxoid stromal tumor occurring in the outer wall of the stomach of a 65-year-old woman. The tumor was phenotypically consistent with parachordoma (or myoepithelioma), showing a chordoid microscopic appearance of tumor cells loosely arranged within a myxoid or hyaline background. Immunoreactivity for high-molecular-weight keratins, S100 protein, and vimentin was detected. In this report, the authors address the differential diagnosis of parachordoma and the unusual location of this neoplasm.

Diagnosing an extra-axial chordoma of the proximal tibia with the help of brachyury, a molecule required for notochordal differentiation

Chordomas are rare malignant bone tumours considered to arise from notochordal remnants that persist in the axial skeleton. Although their morphology can resemble that of a carcinoma, chondrosarcoma or malignant melanoma, the axial location and their well-defined immunophenotype, including expression of cytokeratins (CK7/20/8/18/19) and S100, generally allow the diagnosis to be made with confidence once the possibility is considered. In contrast, making a robust diagnosis of an extra-axial chordoma has been difficult in the absence of specific markers for chordomas. We have recently shown in gene expression microarray and immunohistochemistry studies that brachyury, a transcription factor crucial for notochordal development, is a specific and sensitive maker for chordomas. We now present a case of an intracortical tibial tumour, with detailed report of the imaging, and morphological features consistent with a chordoma, where notochordal differentiation was demonstrated with an antibody to brachyury. The tumour cells were also positive for cytokeratins, including CK19, and S100, CEA, EMA and HMBE1, findings which support the diagnosis of chordoma. Brachyury can be employed as a marker of notochordal differentiation and help identify confidently, for the first time, extra-axial bone and soft tissue chordomas, and tumours which may show focal notochordal differentiation.