The molecular pathogenesis of dedifferentiated chondrosarcoma

Dedifferentiated Chondrosarcoma from Molecular Pathology to Current Treatment and Clinical Trials

Dedifferentiated chondrosarcoma (DDCS) is a rare subtype of chondrosarcoma, a primary cartilaginous malignant neoplasm. It accounts for up to 1-2% of all chondrosarcomas and is generally associated with one of the poorest prognoses among all chondrosarcomas with the highest risk of metastasis. The 5-year survival rates range from 7% to 24%. DDCS may develop at any age, but the average presentation age is over 50. The most common locations are the femur, pelvis humerus, scapula, rib, and tibia. The standard treatment for localised disease is surgical resection. Most patients are diagnosed in unresectable and advanced stages, and chemotherapy for localised and metastatic dedifferentiated DDCS follows protocols used for osteosarcoma.

Comparative analysis of miRNA expression in dedifferentiated and well-differentiated components of dedifferentiated chondrosarcoma

Dedifferentiated chondrosarcoma (DDCS) is a rare malignant cartilage tumor arising out of a low-grade chondrosarcoma, whereby the well-differentiated and the dedifferentiated components coexist in the same localization. DDCS has a massively increased metastatic potential in comparison to low-grade chondrosarcoma. So far, the underlying mechanisms of DDCS development and the increased malignancy are widely unknown. Targeted DNA sequencing revealed no genetic differences between both tissue components. Besides genetic events, alterations in epigenetic control may play a role in DDCS development. In this preliminary study, we have analyzed the differential miRNA expression in paired samples of both components of four primary DDCS cases and a rare lung metastasis with both components using the nCounter MAX analysis system from NanoString technologies. We identified 21 upregulated and two downregulated miRNAs in the dedifferentiated components of the primary cases. Moreover, three miRNAs were also significantly deregulated in the dedifferentiated component of the lung metastasis, supporting their possible role in DDCS development. Additionally, validated targets of the 23 deregulated miRNAs are involved in signaling pathways, like PI3K/Akt, Wnt/β-catenin, and TGF-β, as well as in cellular processes, like cell cycle regulation, apoptosis, and dedifferentiation. Further investigations are necessary to confirm and understand the role of the identified miRNAs in DDCS development.

Dedifferentiated chondrosarcoma: current standards of care

Dedifferentiated chondrosarcomas are aggressive variants of chondrosarcoma, associated with poor outcomes. Tumor biphasism is the norm. The majority of these tumors are symptomatic at presentation. Radiologically, large soft tissue masses with bony destruction predominate. Treatment protocols of these tumors are not well defined. Surgical resection forms the standard of care for localized disease. (Neo)adjuvant therapies remain controversial as the results from multiple (mainly retrospective) studies remain conflicting. Age at presentation, stage and ability to obtain negative resection margins are important prognostic factors. The overall prognosis is dismal. Newer and novel therapies targeting the complex genetic makeup of these tumors have renewed interest in the adjuvant setting that could hold promise in the near future.

Chondrosarcoma of Mandible: A Rare Case Report

INTRODUCTION

Chondrosarcomas (CS) are malignant mesenchymal tumours with cartilaginous differentiation that rarely affects the maxillofacial region. It accounts for approximately 10-20% of malignant bone tumours. The CS is rare in occurrence with aggressive course with high malignant potential, and poor prognosis.

CASE REPORT

Here we report a rare case of a 37year old female presenting tumoral mass in the lower jaw, for the past 3 years, which was gradually progressive in nature with an area of skin ulceration. The CT revealed a well- defined lesion with soft tissue component measuring 15x12x10 cm in size infiltrating both right and left masseter. Biopsy confirmed the diagnosis of grade IIICS. Considering the size and aggressive nature of the lesion, surgical resection was done. The reconstruction of the mandible was done with vascularised fibula pedicle flap to achieve acceptable cosmesis. The patient was discharged uneventfully. Though few cases of high grade CS have been reported in literature but CS of this enormous size has not been reported yet.

CONCLUSION

In this case report we documented the management of a relatively rare but challenging reconstructive maxillofacial surgery. Since in this case the CS was enormous in size and aggressive surgery was required, the cosmetic and functional outcomes were challenging. In our case report we have found that a vascularised fibula pedicle flap gives a good functional and cosmetic outcome and can be used for reconstruction of complete mandible.

Dedifferentiated Central Chondrosarcoma: A Clinical, Histopathological, and Immunohistochemical Analysis of 57 Cases

Dedifferentiated central chondrosarcoma (DCCS) is a rare cartilage tumor with invasive biological behavior and a poor prognosis. To better understand the morphological characteristics of this type of tumor and its internal mechanism of dedifferentiation, we retrospectively analyzed 57 cases of DCCS. A total of 29 female and 28 male patients were included, ranging in age from 20 to 76 years, with a median age of 54 years. Fifty-seven cases of DCCS occurred in the pelvis (n = 29), femur (n = 17), scapula (n = 4), tibia (n = 2), humerus (n = 2), metatarsals (n = 1), fibula (n = 1), and radius (n = 1). Radiologically, DCCS had two different appearances on imaging, with an area showing calcifications of the cartilage forming the tumor juxtaposed to a lytic area with a highly aggressive, non-cartilaginous component. Histopathologically, the distinctive morphological features consisted of two kinds of defined components: a well-differentiated cartilaginous tumor and non-cartilaginous sarcoma. The cartilaginous components included grade 1 (n = 38; 66.7%) and grade 2 (n = 19; 33.3%) cartilage. The sarcoma components included those of osteosarcoma (n = 29; 50.9%), undifferentiated pleomorphic sarcoma (n = 20; 35.1%), rhabdomyosarcoma (n = 3; 5.2%), fibrosarcoma (n = 2; 3.5%), spindle cell sarcoma (n = 2; 3.5%) and angiosarcoma (n = 1; 1.8%). Immunohistochemistry showed that the expression of p53 and RB in the sarcoma components was significantly higher than that in the cartilaginous components, suggesting that these factors play roles in the dedifferentiation process of chondrosarcoma. DCCS is a highly malignant tumor with a poor prognosis. Except for the patients who were lost to follow-up, most of our patients died.

Biological Heterogeneity of Chondrosarcoma: From (Epi) Genetics through Stemness and Deregulated Signaling to Immunophenotype

Chondrosarcoma (ChS) is a primary malignant bone tumor. Due to its heterogeneity in clinical outcomes and resistance to chemo- and radiotherapies, there is a need to develop new potential therapies and molecular targets of drugs. Many genes and pathways are involved in in ChS progression. The most frequently mutated genes are isocitrate dehydrogenase ½ (IDH1/2), collagen type II alpha 1 chain (COL2A1), and TP53. Besides the point mutations in ChS, chromosomal aberrations, such as 12q13 (MDM2) amplification, the loss of 9p21 (CDKN21/p16/INK4A and INK4A-p14ARF), and several gene fusions, commonly occurring in sarcomas, have been found. ChS involves the hypermethylation of histone H3 and the decreased methylation of some transcription factors. In ChS progression, changes in the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K-AKT-mTOR) and hedgehog pathways are known to play a role in tumor growth and chondrocyte proliferation. Due to recent discoveries regarding the potential of immunotherapy in many cancers, in this review we summarize the current state of knowledge concerning cellular markers of ChS and tumor-associated immune cells. This review compares the latest discoveries in ChS biology from gene alterations to specific cellular markers, including advanced molecular pathways and tumor microenvironment, which can help in discovering new potential checkpoints in inhibitory therapy.

Clonality analysis and IDH1 and IDH2 mutation detection in both components of dedifferentiated chondrosarcoma, implicated its monoclonal origin

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Dedifferentiated chondrosarcoma is composed of highly differentiated chondrosarcoma and highly malignant non-cartilaginous sarcomas with abruptly-defined.

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The question of whether the two components originated from the same archaeocyte has not yet been clarified.

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Clonality analysis showed that the two components were same X chromosome inactivation.

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The mutation states of IDH1 and IDH2 gene were consistent in the two components of a DDCS.

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We conclude that the two components of a DDCS originate from the same primitive cell.

Dedifferentiated chondrosarcoma (DDCS) is a highly malignant tumor that belongs to an uncommon subtype of chondrosarcoma with a poor prognosis. Microscopically, it is composed of highly differentiated chondrosarcoma and highly malignant noncartilaginous sarcomas with an abrupt interface. The question of whether the two components originated from the same archaeocyte has not yet been clarified. To further investigate this issue, DNA was separately extracted from the two components of the same patient. In total, 18 DDCS patients were analyzed. A portion of DNA samples from 9 female patients was used for clonality analysis. Another portion of DNA from 9 female and DNA from 9 male patients was used for isocitrate dehydrogenase 1(IDH1) and IDH2 gene mutation detection. The results of clonality analysis showed that the same X chromosome inactivation and consistent mutation states of the IDH1 and IDH2 genes in the two DDCS components. We conclude that the two DDCS components originate from the same primitive cell and that DDCS is monoclonal in origin.

TP53 in bone and soft tissue sarcomas

Genomic and functional study of existing and emerging sarcoma targets, such as fusion proteins, chromosomal aberrations, reduced tumor suppressor activity, and oncogenic drivers, is broadening our understanding of sarcomagenesis. Among these mechanisms, the tumor suppressor p53 (TP53) plays significant roles in the suppression of bone and soft tissue sarcoma progression. Although mutations in TP53 were thought to be relatively low in sarcomas, modern techniques including whole-genome sequencing have recently illuminated unappreciated alterations in TP53 in osteosarcoma. In addition, oncogenic gain-of-function activities of missense mutant p53 (mutp53) have been reported in sarcomas. Moreover, new targeting strategies for TP53 have been discovered: restoration of wild-type p53 (wtp53) activity through inhibition of TP53 negative regulators, reactivation of the wtp53 activity from mutp53, depletion of mutp53, and targeting of vulnerabilities in cells with TP53 deletions or mutations. These discoveries enable development of novel therapeutic strategies for therapy-resistant sarcomas. We have outlined nine bone and soft tissue sarcomas for which TP53 plays a crucial tumor suppressive role. These include osteosarcoma, Ewing sarcoma, chondrosarcoma, rhabdomyosarcoma (RMS), leiomyosarcoma (LMS), synovial sarcoma, liposarcoma (LPS), angiosarcoma, and undifferentiated pleomorphic sarcoma (UPS).

TCF-1 participates in the occurrence of dedifferentiated chondrosarcoma

The present study demonstrated that T cell factor 1 (TCF-1) protein, a component of the canonical Wnt/β-catenin signaling pathway, can regulate the expression of runt-related transcription factor 2 (runx2) gene and Sry-related HMG box 9 (sox9) gene, which may participate in the differentiation of chondrosarcoma. Dedifferentiated chondrosarcoma (DDCS) is a special variant of conventional chondrosarcoma (CCS), associated with poor survival and high metastasis rate. However, little is known about the mechanism of its occurrence; thus, no effective treatment is available except surgery. Earlier, high expression of runx2 and low expression of sox9 were found in DDCS compared with CCS. Using Western blot to detect clinical tissue samples (including 8 CCS samples and 8 DDCS samples) and immunohistochemistry to detect 85 different-grade chondrosarcoma specimens, a high expression of TCF-1 in DDCS tissues was found compared with CCS tissues. This difference in expression was related to patients' prognosis. Results of luciferase, chromatin immunoprecipitation, and gel electrophoresis mobility shift assays demonstrated that TCF-1 protein could bind to the promoter of runx2 gene directly and sox9 gene indirectly. Hence, it could regulate expression of runx2 gene positively and sox9 gene negatively. Furthermore, in vitro and in vivo experiments showed that TCF-1 protein was closely related to the phenotype and aggressiveness of chondrosarcoma. In conclusion, this study proved that TCF-1 participates in the dedifferentiation of DDCS, which may be mediated by runx2 gene and sox9 gene. Also, TCF-1 can be of important prognostic value and a promising therapeutic target for DDCS patients.

BMPR2-pSMAD1/5 signaling pathway regulates RUNX2 expression and impacts the progression of dedifferentiated chondrosarcoma

Bone morphogenetic protein receptors (BMPRs) are multifunctional proteins; they have indispensible roles in the process of BMP signaling. However, their function in dedifferentiated chondrosarcoma is uncertain. It has been reported that BMPR2 is associated with chondrosarcoma. Moreover, the detection of BMPR2 is more frequent in dedifferentiated chondrosarcomas (DDCS) than in conventional chondrosarcomas (CCS). BMPR2, phospho-SMAD1/5 (pSMAD1/5), and runt-related transcription factor 2 (RUNX2) expressions were found to be associated with the pathological grades of chondrosarcoma and could be a promising target of treatment outcome. Moreover, BMPR2 was found to induce the RUNX2 expression via pSmad1/5. Knockdown of BMPR2 and pSmad1/5 results in the downregulation of RUNX2 expression in DDCS cells, while the upregulation of BMPR2 and Smad1/5 in CCS cells leads to increased RUNX2 expression. The luciferase reporter gene assay suggested that BMPR2 can induce the RUNX2 expression at the transcriptional level. By chromatin immunoprecipitation (ChIP) and electrophoresis mobility shift assay (EMSA), it was found that pSmad1/5 combined directly to RUNX2. The in vivo tumorigenicity assay in mice showed that the inhibition of BMPR2 or Smad1/5 in DDCS cell line reduced tumor growth, while the upregulation of BMPR2 or Smad1/5 in CCS cell line increased tumor growth. Furthermore, a BMPR signaling inhibitor, LDN-193189, was introduced to investigate its role as a potential drug to treat DDCS. Taken together, the present-study results suggest that BMPR2-pSmad1/5 signaling pathway has an important role in regulating not only the RUNX2 expression but also the tumorigenesis of DDCS.

Solitary fibrous tumors: loss of chimeric protein expression and genomic instability mark dedifferentiation

Solitary fibrous tumors, which are characterized by their broad morphological spectrum and unpredictable behavior, are rare mesenchymal neoplasias that are currently divided into three main variants that have the NAB2-STAT6 gene fusion as their unifying molecular lesion: usual, malignant and dedifferentiated solitary fibrous tumors. The aims of this study were to validate molecular and immunohistochemical/biochemical approaches to diagnose the range of solitary fibrous tumors by focusing on the dedifferentiated variant, and to reveal the genetic events associated with dedifferentiation by integrating the findings of array comparative genomic hybridization. We studied 29 usual, malignant and dedifferentiated solitary fibrous tumors from 24 patients (including paired samples from five patients whose tumors progressed to the dedifferentiated form) by means of STAT6 immunohistochemistry and (when frozen material was available) reverse-transcriptase polymerase chain reaction and biochemistry. In addition, the array comparative genomic hybridization findings were used to profile 12 tumors from nine patients. The NAB2/STAT6 fusion was detected in all of the tumors, but immunohistochemistry and western blotting indicated that chimeric protein expression was atypical or absent in 9 out of 11 dedifferentiated tumors. The comparative genomic hybridization results revealed that the usual and malignant solitary fibrous tumors had a simple profile, whereas the genome of the dedifferentiated tumors was complex and unstable, and suggested that 13q and 17p deletions and TP53 mutations may be present in malignant lesions before the full expression of a dedifferentiated phenotype. Solitary fibrous tumor dedifferentiation is associated with the loss of chimeric oncoprotein expression, genomic instability, and cell decommitment and reprogramming. The assessment of dedifferentiated solitary fibrous tumors is based on the presence of the fusion transcripts and, in principle, negative STAT6 immunohistochemistry should not rule out a diagnosis of solitary fibrous tumor.

Wnt/β-catenin pathway in bone cancers

The Wnt signaling pathway regulates some of the crucial aspects of cellular processes. The beta-catenin dependent Wnt signaling (Wnt/β-catenin) pathway controls the expression of key developmental genes, and acts as an intracellular signal transducer. The association of Wnt/β-catenin pathway is often reported with different cancers. In this study, we have reviewed the association of Wnt/β-catenin pathway with bone cancers, focusing on carcinogenesis and therapeutic aspects. Wnt/β-catenin pathway is a highly complex and unique signaling pathway, which has ability to regulate gene expression, cell invasion, migration, proliferation, and differentiation for the initiation and progression of bone cancers, especially osteosarcoma. Association of Wnt/β-catenin pathway with chondrosarcoma, Ewing's sarcoma and chondroma is also documented. Recently, targeting Wnt/β-catenin pathway has gained significant interests as a potential therapeutic application for the treatment of bone cancers. Small RNA technology to knockdown aberrant Wnt/β-catenin or inhibition of β-catenin expression by natural component has shown promising effects against bone cancers. Advances in understanding the mechanisms of Wnt signaling and new technologies have facilitated the discovery of agents that can target and regulate Wnt/β-catenin signaling pathway, and these may provide a basement for the innovative therapeutic approaches in the treatment of bone cancers.