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Andrew Futreal and colleagues identify the major cartilage collagen gene COL2A1 as a frequent target of somatic mutation in chondrosarcoma. The mutation patterns are consistent with selection for variants likely to impair normal collagen biosynthesis. Chondrosarcoma is a heterogeneous collection of malignant bone tumors and is the second most common primary malignancy of bone after osteosarcoma. Recent work has identified frequent, recurrent mutations in IDH1 or IDH2 in nearly half of central chondrosarcomas. However, there has been little systematic genomic analysis of this tumor type, and, thus, the contribution of other genes is unclear. Here we report comprehensive genomic analyses of 49 individuals with chondrosarcoma (cases). We identified hypermutability of the major cartilage collagen gene COL2A1 , with insertions, deletions and rearrangements identified in 37% of cases. The patterns of mutation were consistent with selection for variants likely to impair normal collagen biosynthesis. In addition, we identified mutations in IDH1 or IDH2 (59%), TP53 (20%), the RB1 pathway (33%) and Hedgehog signaling (18%).

Chondrosarcomas are primary cancers of cartilaginous tissue with highly contrasting prognoses. These tumors are defined by recurrent mutations in the IDH genes and other genetic alterations including inactivation of CDKN2A and COL2A1 ; however, these have no clinical value. Here we use multi-omics molecular profiles from a series of cartilage tumors and find an mRNA classification that identifies two subtypes of chondrosarcomas defined by a balance in tumor differentiation and cell cycle activation. The microRNA classification reveals the importance of the loss of expression of the 14q32 locus in defining the level of malignancy. Finally, DNA methylation is associated with IDH mutations. We can use the multi-omics classifications to predict outcome. We propose an mRNA-only classifier to reproduce the integrated multi-omics classification, and its application to relapsed tumor samples shows the progressive nature of the classification. Thus, it may be possible to use mRNA-based signatures to detect patients with high-risk chondrosarcomas. Chondrosarcomas are heterogenous tumours of the bone cartilage and have highly variable prognoses. Here, the authors perform a multi-omics analysis, revealing molecular features that can stratify clinical outcomes.

Extraskeletal myxoid chondrosarcoma is a rare subtype of sarcoma that affects the soft tissue and bones in middle-aged and elderly adults. Its diagnosis can be challenging, with the differential diagnoses including a wide variety of mesenchymal tumors. The line of differentiation of extraskeletal myxoid chondrosarcoma has been controversial, but recent evidence suggests a neuroendocrine phenotype. INSM1 is a zinc-finger transcription factor that plays a pivotal role in neuroendocrine differentiation, and has been proposed as a promising immunohistochemical marker of neuroendocrine carcinoma. The aim of this study was to determine the prevalence of INSM1 expression in extraskeletal myxoid chondrosarcoma and to understand its significance in sarcoma diagnosis. We immunostained the representative sections of 31 NR4A3-rearranged extraskeletal myxoid chondrosarcomas and 187 histological mimics. Nuclear staining of moderate or higher intensity in at least 5% of tumor cells was considered positive. Twenty-eight of the 31 extraskeletal myxoid chondrosarcomas (90%) were positive for INSM1, providing strong evidence for neuroendocrine differentiation. The staining was diffuse (>50%) in 17 cases, with most immunopositive tumors showing at least focal strong expression. The INSM1 staining extent was not correlated with cytomorphology, synaptophysin expression, or fusion types (EWSR1 vs non-EWSR1). In contrast, INSM1 expression was negative in 94% of the 187 other mesenchymal tumors. INSM1-positive mimics comprised a small subset of chordoma (1 of 10), soft tissue myoepithelioma (1 of 20), ossifying fibromyxoid tumor (3 of 10), and Ewing sarcoma (3 of 10), among other tumor types. The majority of these cases showed labeling in <25% of the tumor cells. Although not entirely sensitive or specific, INSM1 could be a potential marker for the diagnosis of extraskeletal myxoid chondrosarcoma when molecular genetic access is limited.

Driver mutations in IDH1 and IDH2 are initiating events in the evolution of chondrosarcoma and several other cancer types. Here, we present evidence that mutant IDH1 is recurrently lost in metastatic central chondrosarcoma. This may reflect either relaxed positive selection for the mutant IDH1 locus, or negative selection for the hypermethylation phenotype later in tumor evolution. This finding highlights the challenge for therapeutic intervention by mutant IDH1 inhibitors in chondrosarcoma.

Chondroblastoma is a rare primary bone tumor of young people that typically arises in the ends of the long bones. Radiologic investigations show a small, circumscribed, lytic lesion. The tumor is characterized histologically by the proliferation of chondroblasts along with areas of mature cartilage, giant cells, and occasionally, secondary aneurysmal bone cyst formation. Chondroblastoma, however, may also present with atypical features, such as prominent hemosiderin deposition, numerous giant cells, or the presence of a large aneurysmal bone cyst component. Malignant entities such as clear cell chondrosarcoma and chondroblastic osteosarcoma must also be considered. Recently, immunohistochemical stains such as DOG1 and SOX9 have been described in chondroblastoma, and K36M mutations in either the H3F3A or H3F3B genes have also been identified. While generally regarded as a benign entity, chondroblastoma manifests an intermediate type of behavior, given its ability to recur locally, and rarely, metastasize.

Chondrosarcomas are rare cartilaginous neoplasms with limited treatment options. Isocitrate dehydrogenase 1/2 (m IDH1/2 ) mutations occur in 65% of chondrosarcomas. Here we report safety and efficacy of olutasidenib, an mIDH1 inhibitor, evaluated in patients with locally advanced or metastatic m IDH1 chondrosarcoma (Clinicaltrials.gov identifier: NCT03684811). The primary endpoint was objective response rate by tumor evaluation; secondary endpoints included adverse events, progression-free and overall survival. Patients received olutasidenib 150 mg twice daily. Twenty-three patients were enrolled; 16 were diagnosed with conventional chondrosarcoma (cCS). Median age was 57 (range, 30-71) years. In 21 response-evaluable patients, 11 (52%) had stable disease, 8 (38%) had progressive disease, and 2 (10%) were not evaluable. Median progression-free survival (mPFS) was 2.0 months (95% confidence interval [95%CI]: 1.7, 4.7); median overall survival was 16.0 months (95%CI: 7.7, not reached). Among patients with cCS, 10 (63%) had stable disease; 6 (38%) had progressive disease; mPFS was 3.5 months (95%CI: 1.7, 5.1). Median overall survival in cCS patients was 19.0 months (95% CI: 7.7, not reached). No dose-limiting toxicities were reported during the study. Olutasidenib was well tolerated and conferred disease control in cCS. Study limitations include open-label design and low patient sample due to rarity of cCS. Chondrosarcomas are rare cartilaginous neoplasms with limited treatment options. Here this trial evaluates the safety and efficacy of olutasidenib (mIDH1 inhibitor) on 23 patients with locally advanced or metastatic mIDH1 chondrosarcoma.

Chondrosarcoma (CS), the second most common malignant bone tumor after osteosarcoma, accounts for 20–30% of all malignant bone tumors. It mainly affects adults, middle-aged, and elderly people. The CS family includes various entities displaying peculiar biological, genetic, and epigenetic characteristics and clinical behaviors. Conventional CS is the most common subtype. High-grade, dedifferentiated, and mesenchymal CS, as well as unresectable and metastatic CS, exhibit poor prognoses due to their intrinsic resistance to radiotherapy and chemotherapy, underscoring the urgent need for novel therapeutic strategies. CS research is dealing with several challenges. Experimental studies can rely on animal and patient-derived models, but the paucity of representative near-patient preclinical models has hampered predictive drug screening research. This review describes the main clinical and molecular features of CS subtypes, discussing recent data on the genetic alterations and molecular mechanisms involved in CS pathogenesis and progression. The review provides an overview of the current in vitro and in vivo CS models, discusses their advantages and limitations, and highlights the recent efforts in the development of new targeted therapies against CS dependencies, including IDH1/2 mutations, NAD+ dependency, and SIRT1-HIF-2α axis, or exploring DR5 targeting, antiangiogenic therapies, epigenetic drugs, and immunological approaches. All such strategies, in combination with advanced preclinical modeling and personalized multi-omic profiling, hold promise for improving the survival of patients with advanced CS.

Chondrosarcoma is the second most common malignant bone tumor, characterized by the production of cartilaginous matrix and a high degree of resistance to conventional therapies such as chemotherapy and radiotherapy. Effective treatment options remain limited, highlighting the urgent need for preclinical models to explore novel therapeutic approaches. This study aimed to establish patient-derived organoid (PDO) models of chondrosarcoma and to investigate their utility in elucidating molecular mechanisms and drug responses. Chondrosarcoma specimens were collected from patients and cultured using a modified air–liquid interface (ALI) organoid method. The resulting PDO were serially expanded in vitro and transplanted into NOD-SCID IL2Rgnull mice for in vivo validation. Histological and genetic analyses were performed to compare organoids with the corresponding primary tumors. Whole-exome profiling was used to identify genetic alterations. Organoid-based drug sensitivity testing was conducted using vismodegib, a Sonic Hedgehog (SHH) pathway inhibitor. Two PDO lines were successfully established. Organoid-derived xenografts preserved the histological and genetic features of the parental tumors. Genomic profiling revealed loss-of-function mutations in PTCH1 and BCOR , suggesting activation of the Sonic Hedgehog signaling pathway. Consistently, vismodegib exhibited strong in vitro antitumor activity, indicating functional pathway dependence. We established the first PDO models of chondrosarcoma that faithfully recapitulate key tumor features. These models provide a valuable preclinical platform for dissecting molecular pathogenesis and for advancing the development of targeted therapeutic strategies in this intractable malignancy.

Background Changes in gut microbiota metabolism might play an important role in the development of some cancers. However, the causal relationships of gut microbiome-related metabolic pathways in chondrosarcomas and the specific pathways affected remain largely unknown. Methods We used two-sample bidirectional and multivariate Mendelian randomization (MR) to reveal a causal relationship between the gut microbiota metabolic pathway (GMMP) and chondrosarcoma associated gene 1(CSAG1) via the largest available genome-wide association study (GWAS). Results Univariate MR analysis revealed that tetrapyrrole biosynthesis from glutamate, menaquinol 6 biosynthesis, glycogen degradation II, 8-amino-7-oxononanoate biosynthesis, taxadiene biosynthesis, glycolysis and tRNA charging had a significant causal relationship with CSAG1.Multivariate MR analysis suggested that tetrapyrrole biosynthesis, menaquinol 6 biosynthesis, glycogen degradation II, glycolysis and tRNA charging still had a significant causal effect on CSAG1. According to the results of reverse MR analysis, no significant causal effect of CSAG1 on the GMMP was found. Conclusions This study offers further insights into the gut microbiota-mediated mechanism of chondrosarcoma development.

This review provides an overview of histopathology, clinical presentation, molecular pathways, and potential new systemic treatments of high-grade chondrosarcomas (CS), including grade 2–3 conventional, dedifferentiated, and mesenchymal CS. The diagnosis of CS combines radiological and histological data in conjunction with patient clinical presentations. Conventional CS is the most frequent subtype of CS (85%) and represents about 25% of primary bone tumors in adults; they can be categorized according to their bone location into central, peripheral, and periosteal chondrosarcomas. Central and peripheral CS differ at the molecular level with either IDH1/2 mutations or EXT1/2 mutations, respectively. CDKN2A/B deletions are also frequent in conventional CS, as well as COL2A1 mutations. Dedifferentiated CS develops when low-grade conventional CS transforms into a high-grade sarcoma and most frequently exhibits features of osteosarcoma, fibrosarcoma, or undifferentiated pleomorphic sarcoma. Their molecular characteristics are similar to conventional CS. Mesenchymal CS is a totally different pathological entity exhibiting recurrent translocations. Their clinical presentation and management are different too. The standard treatment of CSs is wide en-bloc resection. CS are relatively radiotherapy resistant; therefore, doses >60 Gy are needed in an attempt to achieve local control in unresectable tumors. Chemotherapy is possibly effective in mesenchymal chondrosarcoma and is of uncertain value in dedifferentiated chondrosarcoma. Due to resistance to standard anticancer agents, the prognosis is poor in patients with metastatic or unresectable chondrosarcomas. Recently, the refined characterization of the molecular profile, as well as the development of new treatments, allow new therapeutic options for these rare tumors. The efficiency of IDH1 inhibitors in other malignancies suggests that these inhibitors will be part of IDH1/2 mutated conventional CS management soon. Other treatment approaches, such as PIK3-AKT-mTOR inhibitors, cell cycle inhibitors, and epigenetic or immune modulators based on improving our understanding of CS molecular biology, are emerging.