Sox9, a master regulator of chondrogenesis, distinguishes mesenchymal chondrosarcoma from other small blue round cell tumors

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.

Cartilaginous features in matrix-producing carcinoma of the breast: four cases report with histochemical and immunohistochemical analysis of matrix molecules

Matrix-producing carcinoma of the breast is a well-established entity in the group of metaplastic carcinoma, which is histologically characterized by myxochondroid matrix formation and is extremely rare. We describe here four additional cases of matrix-producing carcinoma of the breast. All cases of matrix-producing carcinoma show nest-like, sheet-like, and cord-like growth of tumor cells with cellular atypia, in addition to scattered cancer cells within myxoid or myxohyalinous stroma. Three of four cases showed an acellular or oligocellular matrix-rich zone in the center of the tumor. Immunohistochemically, cancer cells of all cases were positive for cytokeratins and epithelial membrane antigens and partially positive for sox9 and p63. Aggrecan and type II collagen, which are cartilage-specific matrix molecules, were deposited in the stroma of all cases. Type I and type IV collagens were also deposited on the stroma of all cases. These findings suggest that, although cancer cells of matrix-producing carcinoma of the breast are epithelial, they transdifferentiate to chondrocyte-like cells and produce cartilage-specific matrix molecules, which are useful markers for diagnosing matrix-producing carcinoma.

Sox10: a pan-schwannian and melanocytic marker

S100 protein is a sensitive marker for melanomas and peripheral nerve sheath tumors. It is, however, expressed by other mesenchymal and epithelial tumors. Despite its low specificity, S100 protein is valuable for the diagnosis of desmoplastic melanomas and peripheral nerve sheath tumors, for which no specific marker is available. Sox10 is a neural crest transcription factor crucial for specification, maturation, and maintenance of Schwann cells and melanocytes. Anti-Sox10 antibody was applied to a variety of neural crest-derived tumors, mesenchymal and epithelial neoplasms, and normal tissues. Sox10 nuclear expression was found in 76 of 78 melanomas (97%) and 38 of 77 malignant peripheral nerve sheath tumors (49%) whereas S100 protein was expressed in 71 melanomas (91%) and 23 malignant peripheral nerve sheath tumors (30%). Sox10 was diffusely expressed in schwannomas and neurofibromas. Sox10 reaction was seen only in sustentacular cells of pheochromocytomas/paragangliomas, and occasionally carcinoid tumors from various organs, but it was not seen in the tumor cells. In normal tissues, Sox10 was expressed in Schwann cells, melanocytes, and myoepithelial cells of salivary, bronchial, and mammary glands. Sox10 reaction was not identified in any other mesenchymal and epithelial tumors except for myoepitheliomas and diffuse astrocytomas. Sox10 was expressed by metastatic melanomas and nodal capsular nevus in sentinel lymph nodes, but not by other lymph node components such as dendritic cells. Our results indicate that Sox10 will serve as a more sensitive and specific marker for the diagnosis of melanocytic and schwannian tumors than S100 protein.

Tissue microarrays analysis in chondrosarcomas: light microscopy, immunohistochemistry and xenograft study

Background

Chondrosarcoma (Chs) is the third most frequent primary malignant tumour of bone and can be primary or secondary, the latter results mainly from the malignant transformation of a benign pre-existing tumour.

Methods

All the cases diagnosed as Chs (primary tumours, recurrences and/or metastasis and xenotransplanted Chs) from the files of our Department were collected. Only cases with paraffin blocks available were selected (Total 32 cases). Six Tissue Microarrays (TMAs) were performed and all the cases and biopsies were distributed into the following groups: a) only paraffin block available from primary and/or metastatic tumours (3 TMAs), b) paraffin block available from primary and/or metastatic tumours as well as from the corresponding Nude mice xenotransplant (2 TMAs), c) only paraffin block available from xenotransplanted Chs (1 TMA). A reclassification of all the cases was performed; in addition, conventional hematoxylin-eosin as well as immunohistochemistry staining (S100, SOX-9, Ki-67, BCL-2, p53, p16, CK, CD99, Survivin and Caveolin) was analyzed in all the TMA.

Results

The distribution of the cases according to the histopathological pattern and the location of tumours were as follows: fourteen Grade I Chs (all primaries), two primary Grade II Chs, ten Grade III Chs (all primaries), five dedifferentiated Chs (four primaries and one primary with metastasis), and two Chs from cell cultures (Ch grade III). One recurrent extraskeletal myxoid Chs was included as a control in the TMA. Although there was heterogeneity in immunohistochemistry results of the different material analyzed, S100, SOX-9, Caveolin and Survivin were more expressed. The number of passages in xenotransplants fluctuated between 1 and 13. Curiously, in Grade I Chs, these implanted tumours hardly grew, and the number of passages did not exceed one.

Conclusion

The study of Chs by means of TMA techniques is very important because it will improve the assessment of different antibodies applied in the immunohistochemical assays. Xenotransplanted tumours in TMA improve knowledge concerning the variability in the morphological pattern shown by these tumours during the evolution in nudes.

Congenital intracranial mesenchymal chondrosarcoma: case report and review of the literature in pediatric patients

In this paper we report the 1st case of a congenital intracranial mesenchymal chondrosarcoma in a 2-month-old infant, apparently present at birth. A magnetic resonance image showed a large left parietal solid mass, while microscopy revealed a mixture of undifferentiated small cells and mature hyaline cartilage islands, positive for vimentin, S-100, and CD99. A surgical excision was performed but the patient died after a few weeks as a result of a rapid relapse of the tumor. We also review the pediatric cases (in patients less than 20 years old) of extraskeletal (intracranial) mesenchymal chondrosarcomas of the literature, with a focus on the most recent cytogenetic and immunohistochemical studies.

SOX9 expression is a general marker of basal cell carcinoma and adnexal-related neoplasms

BACKGROUND

SOX9 is a transcription factor that fulfills multiple functions during development. In the hair follicle SOX9 is expressed in the outer layer of the epithelial sheath, and the hair stem cell compartment. Recent data suggest that Sox9 acts as a downstream target of the Sonic hedgehog (Shh) pathway. Activation of the Shh pathway is a major cause of cutaneous basal cell carcinoma (BCC). Here we test whether activation of SOX9 is a general feature of BCC, or whether it could be used as a biomarker to better define subtypes of these skin tumors. In addition we investigated SOX9 expression in other skin epidermal tumors.

METHODS

Tumors sections were stained with hematoxylin & eosin (H&E). SOX9 activation was determined by immunofluorescence.

RESULTS

SOX9 activation was observed in all subtypes of BCC tested. Staining was heterogeneous and could be detected among the basaloid cells of the palisading cell layer as well as in the tumour nest. SOX9 expression was detected in all adnexal tumors analyzed and absent in Bowen's disease and Merkel tumor.

CONCLUSIONS

SOX9 expression is a general feature of BCC and adnexal skin neoplasms, suggesting a contribution of SOX9 to the pathogenesis of these tumors.

Identification of DNA hypermethylation of SOX9 in association with bladder cancer progression using CpG microarrays

CpG island arrays represent a high-throughput epigenomic discovery platform to identify global disease-specific promoter hypermethylation candidates along bladder cancer progression. DNA obtained from 10 pairs of invasive bladder tumours were profiled vs their respective normal urothelium using differential methylation hybridisation on custom-made CpG arrays (n=12 288 clones). Promoter hypermethylation of 84 clones was simultaneously shown in at least 70% of the tumours. SOX9 was selected for further validation by bisulphite genomic sequencing and methylation-specific polymerase chain reaction in bladder cancer cells (n=11) and primary bladder tumours (n=101). Hypermethylation was observed in bladder cancer cells and associated with lack of gene expression, being restored in vitro by a demethylating agent. In primary bladder tumours, SOX9 hypermethylation was present in 56.4% of the cases. Moreover, SOX9 hypermethylation was significantly associated with tumour grade and overall survival. Thus, this high-throughput epigenomic strategy has served to identify novel hypermethylated candidates in bladder cancer. In vitro analyses supported the role of methylation in silencing SOX9 gene. The association of SOX9 hypermethylation with tumour progression and clinical outcome suggests its relevant clinical implications at stratifying patients affected with bladder cancer.

Primary orbital mesenchymal chondrosarcoma: a case report and literature review

BACKGROUND

Mesenchymal chondrosarcoma (MC) is a subtype of chondrosarcoma, with an incidence varying from 1 to 8% of all chondrosarcomas. It is an aggressive neoplasm with a high tendency for late recurrence and occasional delayed distant metastasis. Orbital MC is very rare, and only approximately 30 cases have been described in the literature. We describe here one case of primary orbital MC.

CASE REPORT

A 14-year-old boy without a past medical history presented with a 1-month history of progressive proptosis on the right eye. Computed tomography (CT) scans of the orbit revealed a right intraconic lesion, with areas of calcification. The lesion was excised. Histopathological analysis revealed that the tumor had a biphasic pattern, showing a combination of small cell malignancy and well-differentiated cartilage. Immunohistochemistry examination revealed a diffuse membrane expression of CD99 on the small cell malignancy; S-100 was positive only within the cartilage component. The patient received chemotherapy, and no metastatic disease was found at the 2-month follow-up.

CONCLUSION

Although rare, MC should be considered in the differential diagnosis of a well-circumscribed orbital lesion in young adults, especially when CT scans reveal areas of calcification within the tumor.

Expression and biological role of the prostaglandin D synthase/SOX9 pathway in human ovarian cancer cells

New therapeutic strategies for ovarian cancer include the identification of involved signaling pathways that could potentially serve as a source of biomarkers for early stages of the disease. In this study, we show that the embryonic male prostaglandin D synthase (Pgds)/SOX9 pathway is expressed at both the RNA and protein levels in different types of human ovarian tumors, pointing to Pgds and SOX9 as possible diagnostic markers for ovarian carcinomas. Using ovarian cancer cell lines, we found, first, that components of the Pgds/SOX9 pathway are expressed in these cells, and second, that treatment of these cells with prostaglandin D2 (PGD2) can inhibit their growth via its DP1 receptor and induce apoptosis. Finally, using siRNA and overexpression strategies, we demonstrate that SOX9 expression is induced by PDG2 and is responsible for PDG2-mediated growth inhibition. Accordingly, as stimulating the PGD2/DP1 signal transduction pathway upregulates SOX9 expression, either activators of this pathway or DP1 agonists may be useful as new therapeutic agents.

Transcriptional regulation of scar gene expression in primary astrocytes

The failure of the adult injured spinal cord to support axonal regeneration is in part attributed to the glial scar. Reactive astrocytes constitute a major cellular component of the glial scar and are heterogeneous with respect to the extracellular matrix proteins that they secrete. Astrocytes may produce antiregenerative molecules such as chondroitin sulphate proteoglycans (CSPGs) or proregenerative molecules such as laminin and fibronectin. While many different CSPGs are expressed after spinal cord injury (SCI) they all rely on the same enzymes, xylosyltransferase-I and -II (XT-I, XT-II) and chondroitin 4-sulfotransferase (C4ST) to add the repulsive chondroitin sulfate side chains to their core proteins. We show that XT-I, XT-II, and C4ST are part of a CSPG biosynthetic gene (CBG) battery. Using primary astrocyte cultures and quantitative PCR we demonstrate that TGFbeta2, PDGF, and IL-6 induce the expression of CBGs, laminin and fibronectin by several-fold. We further show that over-expression of the transcription factor SOX9 also strongly induces the expression of CBGs but does not increase the expression of laminin or fibronectin. Correspondingly, SOX9 knock-down in primary astrocytes causes a decrease in CBG and an increase in laminin and fibronectin mRNA levels. Finally, we show that the in vivo expression profiles of TGFbeta2, PDGF, IL-6, and SOX9 are consistent with their potential roles in differentially regulating CBGs, laminin and fibronectin gene expression in the injured spinal cord. This work suggests that SOX9 levels may be pivotal in determining the balance of pro- and anti-regenerative extracellular matrix molecules produced by astrocytes.

Adult human sarcomas. I. Basic science

When connective tissue undergoes malignant transformation, glioblastomas and sarcomas arise. However, the ancient biochemical mechanisms, which are now operational in sarcomas distorted by mutations and gene fusions in misaligned chromosomes, were originally acquired by those cells that emerged during the Cambrian explosion. Preserved throughout evolution up to the genus Homo, these mechanisms dictate the apoptosis- and senescence-resistant immortality of malignant cells. A 'retroviral paradox' distinguishes human sarcomas from those of the animal world. In contrast to the retrovirally induced sarcomatous transformation of animal (avian, murine, feline and simian) cells, human sarcomas have so far failed to yield a causative retroviral isolate. However, the proto-oncogenes/oncogenes transduced from their host cells by retroviruses of animals are the same that are active in human sarcomas. Since the encoded oncoproteins arise after birth, they are recognized frequently by the immune system of the host. Immune lymphocytes that kill autologous sarcoma cells in vitro commonly fail to do so in vivo. Sarcoma vaccines generate immune T- and natural killer cell reactions; even when vaccinated patients do not show a clinical response, their tumors become more sensitive to chemotherapy. The aim of this review is to lay a solid molecular biological foundation for the conclusion that targeting the sarcoma oncogenes will result in regression of the disease.

Small Round Cell Tumors of Bone

Context.—Primary small round cell tumors of the bone are a heterogeneous group of malignant neoplasms presenting predominantly in children and adolescents. They include Ewing sarcoma/peripheral neuroectodermal tumor or Ewing family tumors, lymphoma, mesenchymal chondrosarcoma, and small cell osteosarcoma. Even though they share many morphological similarities, their unique biological and genetic characteristics have provided substantial insights into the pathology of these diverse neoplasms.

Objective.—To provide an overview of the clinical, radiologic, pathologic, and genetic characteristics of these tumors along with a pertinent review of the literature.

Data Sources.—A literature search using PubMed and Ovid MEDLINE was performed, and data were obtained from various articles pertaining to clinicopathologic, biological, and genetic findings in these tumors. Additionally, findings from rare cases have been included from author's subspecialty experience.

Conclusion.—The diagnosis of small round cell tumors can be made accurately by applying clinicopathologic criteria, as well as a panel of immunohistochemical and genetic studies in appropriate cases. Molecular genetic studies may provide further insight into the biology, histogenesis, and prognosis of these tumors.

Immunohistochemical Analysis of Sox9 in Ovarian Sertoli Cell Tumors and Other Tumors in the Differential Diagnosis

The distinction of ovarian Sertoli cell tumor from other tumors in the histological differential diagnosis, particularly endometrioid carcinoma and carcinoid tumor, may be difficult. Many immunohistochemical markers have been studied for this differential diagnosis, but currently available markers are neither 100% sensitive nor specific. Sox9 is a transcription factor involved in Sertoli cell differentiation in the testis. The role that this molecule plays in the pathogenesis of ovarian Sertoli cell tumors and the potential use as an immunohistochemical marker for differential diagnosis have not been investigated. Immunohistochemical staining for Sox9 was performed in 152 ovarian tumors: pure Sertoli cell tumor (n = 36), endometrioid borderline tumor (n = 38), well-differentiated endometrioid carcinoma (n = 26), sertoliform endometrioid carcinoma (n = 13), and carcinoid tumor (n = 39). Nuclear expression was considered positive. Extent and intensity of staining were semiquantitatively scored. In addition, immunohistochemical composite scores in positive cases (ranging from 1 to 12) were calculated based on the extent score multiplied by the intensity score. Sox9 was expressed in 44% of Sertoli cell tumors, 55% of endometrioid borderline tumors, 65% of well-differentiated endometrioid carcinomas, 39% of sertoliform endometrioid carcinomas, and 10% of carcinoid tumors. The mean Sox9 immunohistochemical composite scores in positive cases were 6.3 for Sertoli cell tumor, 5.3 for endometrioid borderline tumor, 8.0 for well-differentiated endometrioid carcinoma, 2.8 for sertoliform endometrioid carcinoma, and 6.8 for carcinoid tumor. The differences in the mean Sox9 composite scores between Sertoli cell tumor and the other tumor categories were not statistically significant (p values ranged from 0.092 to 0.523). We conclude that Sox9 is variably expressed in ovarian Sertoli cell tumor and other tumors that are in the differential diagnosis and, thus, is not helpful for immunohistochemical distinction. Understanding the role of Sox9 in the pathogenesis of ovarian Sertoli cell tumor requires further study.

Molecular pathology of chondroid neoplasms: part 2, malignant lesions

This is the second part of a two-part review presenting an overview of the molecular findings associated with both benign and malignant chondroid neoplasms. The first part presented a brief review of modern methods in molecular pathology, along with a review of the cytogenetic and molecular genetic findings in benign chondroid neoplasms. This second part reviews the cytogenetic and molecular genetic findings in malignant chondroid neoplasms. Clinical aspects of the various lesions are briefly discussed, and each tumor is illustrated with representative radiographic and pathologic images.

Femoral mesenchymal chondrosarcoma with secondary aneurysmal bone cysts mimicking a small-cell osteosarcoma

Mesenchymal chondrosarcoma is a rare but aggressive, high-grade malignancy of primitive cartilage-forming mesenchyme that arises most commonly from skeletal sites. Although there are radiological findings suggestive of the diagnosis, imaging features often overlap with those of other skeletal sarcomas. The definitive diagnosis relies on the histological finding of a typical bimorphic appearance, consisting of nests of small, round, poorly differentiated cells and more mature cartilaginous tissue. To highlight this, we present the case of a 21-year-old man who was referred to our institution with a history of right knee pain. Initial imaging and histological evaluation of a core biopsy of the lesion suggested osteosarcoma of the distal right femur; after review, however, the correct diagnosis of mesenchymal chondrosarcoma was made. Adequate tissue sampling and thorough histological evaluation of biopsy specimens is vital for the accurate diagnosis of primary bone malignancies, especially those of chondroid origin.

Meningeal tumors of childhood and infancy. An update and literature review

Meningeal derived tumors of the first 2 decades of life are often diagnostically challenging due to the wide morphologic spectrum encountered and the rarity of most individual entities. The 2 most common patterns include the dural/leptomeningeal-based mass and neoplastic meningitis. Both primary and secondary meningeal presentations may occur, either early or late in the course of various meningothelial, mesenchymal, embryonal, glial, hematopoietic, histiocytic, melanocytic, and inflammatory tumors. As in other areas of pediatric pathology, there are significant differences between this patient cohort and adults, differences which will be emphasized in this review.

Identification of differently expressed genes in human colorectal adenocarcinoma

AIM: To investigate the differently expressed genes in human colorectal adenocarcinoma.

METHODS: The integrated approach for gene expression profiling that couples suppression subtractive hybridization, high-throughput cDNA array, sequencing, bioinformatics analysis, and reverse transcriptase real-time quantitative polymerase chain reaction (PCR) was carried out. A set of cDNA clones including 1260 SSH inserts amplified by PCR was arrayed using robotic printing. The cDNA arrays were hybridized with florescent-labeled probes prepared from RNA of human colorectal adenocarcinoma (HCRAC) and normal colorectal tissues.

RESULTS: A total of 86 genes were identified, 16 unknown genes and 70 known genes. The transcription factor Sox9 influencing cell differentiation was downregulated. At the same time, Heat shock protein 10 KDis downregulated and Calmoulin is up-regulated.

CONCLUSION: Downregulation of heat shock protein 10 KD lost its inhibition of Ras, and then attenuated the Ras GTPase signaling pathway, increased cell proliferation and inhibited cell apoptosis. Down-regulated transcription factor So x 9 influences cell differentiation and cell-specific gene expression. Down-regulated So x 9 also decreases its binding to calmodulin, accumulates calmodulin as receptor-activated kinase and phosphorylase kinase due to the activation of PhK.

Type II collagen as specific marker for mesenchymal chondrosarcomas compared to other small cell sarcomas of the skeleton

Mesenchymal chondrosarcoma is a rare, usually highly malignant chondrogenic neoplasm. The diagnosis of mesenchymal chondrosarcoma can be challenging, it nonetheless has important therapeutic and diagnostic implications. Thus, biopsies of mesenchymal chondrosarcomas without conspicuous cartilaginous differentiation cannot be safely distinguished from other small cell mesenchymal neoplasms such as Ewing's sarcoma and peripheral neuroendrocrine tumors, synovial sarcomas and hemangiopericytomas, because all of these neoplasms might show overlapping histological features, and so far, there have been no safe immunohistochemical markers available in order to differentiate these neoplasms. In our study on a large series of mesenchymal chondrosarcomas (n=30) and other small cell sarcomas (Ewing's sarcomas (n=12), synovial sarcomas (n=6), hemangiopericytomas (n=5), small cell osteosarcomas (n=3), and desmoplastic small round cell tumors (n=1)), we could establish the presence of type II collagen in the extracellular tumor matrix of the small cell areas of mesenchymal chondrosarcomas as a specific and sensitive marker to identify mesenchymal chondrosarcomas and to exclude other small cell neoplasms (except chondroblastic areas in small cell osteosarcomas). In contrast, the S-100 protein was less sensitive and vimentin and total collagen content unspecific for discriminating these neoplasms. Thus, the presence of type II collagen in the extracellular tumor matrix significantly facilitates the diagnosis of mesenchymal chondrosarcomas in the absence of histologically visible chondroid matrix formation.

Sox genes and cancer

Sox genes encode transcription factors belonging to the HMG (High Mobility Group) superfamily. They are conserved across species and involved in a number of developmental processes. In vitro studies have shown at least one Sox gene to be capable of inducing oncogenic transformation of fibroblast cells. In addition, overexpression and/or amplification of Sox genes are associated with a large number of tumour types in vivo. We review here the available evidence linking Sox gene expression and cancer, and show that this link is supported by extensive EST database analysis. This work provides a basis for further studies aimed at investigating the possible role of Sox genes in the oncogenic process.

A slug, a fox, a pair of sox: transcriptional responses to neural crest inducing signals

The neural crest, a cell type found only in vertebrate embryos, gives rise to the structures of the skull and face and most of the peripheral nervous system, as well as other cell types characteristic of vertebrates. These cells are of great clinical significance and a wide variety of congenital defects are due to aberrant neural crest development. Increasing numbers of studies are contributing to our understanding of how this group of cells form and differentiate during normal development. Wnt, FGF, BMP, and Notch-mediated signals all have essential roles in this process, and several of these signals appear to play multiple temporally distinct roles. Changes in the response of neural crest cells to the same signal over time may be mediated, in part, by an ever-changing cocktail of transcription factors expressed within these cells. Neural crest development is thus a complex multistep process, and elucidating the molecular mechanisms that mediate distinct aspects of this process will require that we determine the role of each of these factors alone and in combination. Here, we review some recent advances in our understanding of the signals and downstream transcription factors involved in neural crest cell formation.

Genetics of chondrosarcoma and related tumors

PURPOSE OF REVIEW

The burgeoning body of information on the genetic changes present in and underlying the development and biology of human cancers has carried implications regarding the possible genetic events that are responsible for not only the genesis of these cancers but also the hope of the cure for these cancers. Chondrosarcomas are a group of tumors that fall into this category. The purpose of this review is to summarize the genetic findings in these tumors.

RECENT FINDINGS

The histopathologic variability of chondrosarcomas is reflected in the complexity and lack of specificity of their cytogenetic and molecular genetic findings, except for extraskeletal myxoid chondrosarcomas. These are characterized in the preponderant number of cases by a translocation, t(9;22)(q22;q12), and in a small number of cases by variant translocations t(9;17)(q22;q11) and t(9;15)(q22;q21). These translocations lead to the formation of abnormal fusion genes and gene products (proteins). In each of these translocations, the CHN gene is involved, resulting in the chimeric fusion genes EWS/CHN, RBP56/CHN, and TCF12/CHN, respectively. The specific translocations and their associated molecular genetic changes are diagnostic of extraskeletal myxoid chondrosarcomas. The abnormal proteins resulting from these fusion genes aberrantly affect gene transcription and cellular signaling pathways thought to be responsible for initiating sarcoma formation. In skeletal (central) chondrosarcomas of varying histopathologic types, the cytogenetic and molecular genetic findings are variable, complex, and apparently lacking in specificity. These changes may reflect a stepwise process (or processes) of oncogenesis involving an array of genes.

SUMMARY

Although some cartilaginous tumors are characterized by specific or recurrent chromosome alterations and molecular genetic changes, much is yet to be learned about the nature and sequence of these genetics events and about their unique role in the stepwise process involved in the development and biology of each tumor type, both malignant and nonmalignant. Until such time, some of the genetic changes, particularly the presence of specific translocations, can be of definite diagnostic value.

Mesenchymal chondrosarcoma of the thyroid - a rare tumour at an unusual site

We describe the light microscopic, immunohistochemical and ultrastructural features of the first case in the literature of a primary mesenchymal chondrosarcoma (MC) of the thyroid and discuss its differential diagnosis at unusual extraskeletal sites. A nodular lesion of the thyroid with no evidence of extrathyroid disease showed the bimorphic pattern and haemangiopericytoma-like areas typical of MC. In the undifferentiated areas, the cells were CD99 positive/CD117 negative, while the stroma showed focal positivity for alpha-inhibin. In spite of its rarity, it is important to diagnose primary mesenchymal chondrosarcoma in a parenchymatous organ such as the thyroid because its biological behaviour may be different from that of tumours of similar morphology and complete resection is the treatment of choice. The patient is free of disease nearly 66 months after its first presentation. Cytogenetic and immunohistological markers may play important roles in diagnosis of this lesion in future, especially with limited tissue samplings; however, for the present a thorough sampling of the tumour remains the best diagnostic strategy.

Immunophenotypic analysis of human articular chondrocytes: Changes in surface markers associated with cell expansion in monolayer culture

Cartilage tissue engineering relies on in vitro expansion of primary chondrocytes. Monolayer is the chosen culture model for chondrocyte expansion because in this system the proliferative capacity of chondrocytes is substantially higher compared to non-adherent systems. However, human articular chondrocytes (HACs) cultured as monolayers undergo changes in phenotype and gene expression known as "dedifferentiation." To gain a better understanding of the cellular mechanisms involved in the dedifferentiation process, our research focused on the characterization of the surface molecule phenotype of HACs in monolayer culture. Adult HACs were isolated by enzymatic digestion of cartilage samples obtained post-mortem. HACs cultured in monolayer for different time periods were analyzed by flow cytometry for the expression of cell surface markers with a panel of 52 antibodies. Our results show that HACs express surface molecules belonging to different categories: integrins and other adhesion molecules (CD49a, CD49b, CD49c, CD49e, CD49f, CD51/61, CD54, CD106, CD166, CD58, CD44), tetraspanins (CD9, CD63, CD81, CD82, CD151), receptors (CD105, CD119, CD130, CD140a, CD221, CD95, CD120a, CD71, CD14), ectoenzymes (CD10, CD26), and other surface molecules (CD90, CD99). Moreover, differential expression of certain markers in monolayer culture was identified. Up-regulation of markers on HACs regarded as distinctive for mesenchymal stem cells (CD10, CD90, CD105, CD166) during monolayer culture suggested that dedifferentiation leads to reversion to a primitive phenotype. This study contributes to the definition of HAC phenotype, and provides new potential markers to characterize chondrocyte differentiation stage in the context of tissue engineering applications.

Chondrosarcoma cell differentiation

A mixed population of lymphocytes from a healthy donor co-existed with an established culture of allogeneic chondrosarcoma cells, during which time the tumor cells changed from malignantly transformed to benign fibroblast-like morphology; from multilayered to a monolayered growth pattern; lost their potency to grow in colonies in soft agar; and showed signs of senescence. A discussion of possible molecular mechanisms for this event is offered. If there are as yet undiscovered lymphokines that can induce reversal of the malignant geno/phenotype, the cognate gene(s) should be cloned for genetic engineering and for the mass production of the corresponding molecular mediators for clinical trials.

The genetic and molecular basis of congenital eye defects

The mature eye is a complex organ that develops through a highly organized process during embryogenesis. Alterations in its genetic programming can lead to severe disorders that become apparent at birth or shortly afterwards; for example, one-half of the cases of blindness in children have a genetic cause. This review outlines the genetic basis of eye development, as determined by mutation analysis in patients and in model organisms. A better understanding of how this intricate organ develops at the genetic and cellular level is central to our understanding of the pathologies that afflict it.

SOX2 functions to maintain neural progenitor identity

Neural progenitors of the vertebrate CNS are defined by generic cellular characteristics, including their pseudoepithelial morphology and their ability to divide and differentiate. SOXB1 transcription factors, including the three closely related genes Sox1, Sox2, and Sox3, universally mark neural progenitor and stem cells throughout the vertebrate CNS. We show here that constitutive expression of SOX2 inhibits neuronal differentiation and results in the maintenance of progenitor characteristics. Conversely, inhibition of SOX2 signaling results in the delamination of neural progenitor cells from the ventricular zone and exit from cell cycle, which is associated with a loss of progenitor markers and the onset of early neuronal differentiation markers. The phenotype elicited by inhibition of SOX2 signaling can be rescued by coexpression of SOX1, providing evidence for redundant SOXB1 function in CNS progenitors. Taken together, these data indicate that SOXB1 signaling is both necessary and sufficient to maintain panneural properties of neural progenitor cells.