Genomic Profiling Identifies Association of IDH1/IDH2 Mutation with Longer Relapse-Free and Metastasis-Free Survival in High-Grade Chondrosarcoma

Phase separation of SHP2E76K promotes malignant transformation of mesenchymal stem cells by activating mitochondrial complexes

Mesenchymal stem cells (MSCs), suffering from diverse gene hits, undergo malignant transformation and aberrant osteochondral differentiation. Src homology region 2-containing protein tyrosine phosphatase 2 (SHP2), a nonreceptor protein tyrosine phosphatase, regulates multicellular differentiation, proliferation, and transformation. However, the role of SHP2 in MSC fate determination remains unclear. Here, we showed that MSCs bearing the activating SHP2E76K mutation underwent malignant transformation into sarcoma stem-like cells. We revealed that the SHP2E76K mutation in mouse MSCs led to hyperactive mitochondrial metabolism by activating mitochondrial complexes I and III. Inhibition of complexes I and III prevented hyperactive mitochondrial metabolism and malignant transformation of SHP2E76K MSCs. Mechanistically, we verified that SHP2 underwent liquid-liquid phase separation (LLPS) in SHP2E76K MSCs. SHP2 LLPS led to its dissociation from complexes I and III, causing their hyperactivation. Blockade of SHP2 LLPS by LLPS-defective mutations or allosteric inhibitors suppressed complex I and III hyperactivation as well as malignant transformation of SHP2E76K MSCs. These findings reveal that complex I and III hyperactivation driven by SHP2 LLPS promotes malignant transformation of SHP2E76K MSCs and suggest that inhibition of SHP2 LLPS could be a potential therapeutic target for the treatment of activated SHP2-associated cancers.

A Systematic Review of Adjuvant Chemotherapy in Localized Dedifferentiated Chondrosarcoma

Dedifferentiated chondrosarcoma (DDCS) is a high-grade subtype of chondrosarcoma with the bimorphic histological appearance of a conventional chondrosarcoma component with abrupt transition to a high-grade, non-cartilaginous sarcoma. DDCS can be radiographically divided into central and peripheral types. Wide resection is currently the main therapeutic option for localized DDCS. Moreover, the effectiveness of adjuvant chemotherapy remains controversial. Therefore, we performed a systematic review of available evidence to evaluate the effect of adjuvant chemotherapy on localized DDCS. The purpose was to compare the 5-year survival rate among patients treated with surgery plus adjuvant chemotherapy or surgery alone for localized DDCS. The search was conducted in PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases. Of the 217 studies shortlisted, 11 retrospective non-randomized studies (comprising 556 patients with localized DDCS) were selected. The 5-year survival rates were similar between the two treatment groups (28.2% (51/181) vs. 24.0% (90/375), respectively). The overall pooled odds ratio was 1.25 (95% confidence interval: 0.80-1.94; p = 0.324), and heterogeneity I2 was 2%. However, when limited to peripheral DDCS, adjuvant chemotherapy was associated with prolonged survival (p = 0.03). Due to the paucity of included studies and the absence of prospective comparative studies, no conclusions can be drawn regarding the effectiveness or ineffectiveness of adjuvant chemotherapy for localized DDCS.

Diagnostics of IDH1/2 Mutations in Intracranial Chondroid Tumors: Comparison of Molecular Genetic Methods and Immunohistochemistry

Intracranial chondroid tumors are a heterogeneous group of neoplasms characterized by the presence of a cartilage matrix. These tumors exhibit overlapping clinical and histological features. Mutations in IDH1/2 genes serve as important diagnostic markers of tumor type, particularly chondrosarcoma. To improve the accuracy of IDH1/2 diagnostics, we compared three methods: biochip assay, real-time PCR with DNA melting analysis using TaqMan probes and sequencing (qPCR-DMA-Sanger), and immunohistochemistry (IHC). Tumor samples from 96 patients were investigated. The IDH1 mutations were detected in 34/64 (53%) chondrosarcomas; IHC detected 27/56 (48.2%) mutations, the qPCR-DMA-Sanger method 27/59 (46%) mutations, and the biochip assay revealed 29/60 (48.3%) mutations. The detection of IDH1 mutations in chordoma (2/15) and osteosarcoma (2/7) suggested the need for a revised diagnosis. In benign tumors, IDH1 mutations were present in chondroma (4/6), but absent in chondromyxoid fibroma (0/4). The most frequent IDH1 mutations were R132C (60%), R132L, and R132G (13.5% each), R132H (8%), and R132S (5%). The concordance between the biochip assay and IHC was 90%, between IHC and PCR-DMA-Sanger 83%, and between biochip assay and qPCR-DMA-Sanger was 98%, respectively. No IDH2 mutations were found. The use of independent diagnostic methods may improve the detection of IDH-mutant specimens in chondroid tumors.

Are IDH1 R132 Mutations Associated With Poor Prognosis in Patients With Chondrosarcoma of the Bone?

BACKGROUND

Because chondrosarcomas vary widely in their behavior, and because anticipating their behavior based on histology alone can be challenging, genetic markers represent an appealing area of inquiry that may help us refine our prognostic approaches. Isocitrate dehydrogenase (IDH) mutations are involved in the pathogenesis of a variety of neoplasms, and recently, IDH1/2 mutations have been found in the tissue of benign cartilage tumors as well as in conventional chondrosarcomas and highly aggressive dedifferentiated chondrosarcomas. However, their association with patient survival is still controversial.

QUESTIONS/PURPOSES

(1) What proportion of patients with chondrosarcomas carry IDH mutations, and which IDH mutations can be found? (2) Are any specific IDH mutations associated with poorer overall survival, metastasis-free survival, or local recurrence-free survival?

METHODS

Between April 2017 and December 2022, we treated 74 patients for atypical cartilaginous tumors or chondrosarcomas in a musculoskeletal tumor referral center. Patients were considered potentially eligible for the present study if the histologic diagnosis was confirmed by two expert soft tissue and bone pathologists following the current WHO classification, complete preoperative imaging and follow-up data were available, surgical excision was performed by sarcoma orthopaedic surgeons directed by a team leader, and the minimum follow-up was 2 years after surgical treatment unless the patient died. Data including sex, age, diagnosis, grade, type of operation, local recurrence, metastasis, and oncologic follow-up were recorded. Forty-one patients (55%) were eligible for the study. For each patient, DNA was extracted and quantified from paraffin-embedded sections of tumor tissue, and the mutational status of IDH1 (codons 105 and 132) and IDH2 (codons 140 and 172) genes was assessed. Of those, 56% (23 of 41) of patients had adequate DNA for analysis of IDH mutations: 10 male and 13 female patients, with a median age of 59 years (range 15 to 98 years). There were 22 conventional chondrosarcomas (8 atypical cartilaginous tumors, 11 Grade 2, and 3 Grade 3) and 1 dedifferentiated chondrosarcoma. Stage was IA in 3 patients, IB in 5, IIA in 1, IIB in 13, and III in 1, according to the Musculoskeletal Tumor Society classification. At a median follow-up of 3.5 years (range 4 months to 5.6 years), 14 patients were disease-free, 2 were alive with disease, and 7 died (3 within 2 years from surgery). Eight patients had metastases, and 7 developed local recurrence. We determined the proportion of patients who carried IDH mutations, and compared patients with and without those mutations in terms of overall survival, metastasis-free survival, and local recurrence-free survival using Kaplan-Meier curves.

RESULTS

Six patients showed wild-type IDH genes, and 17 had IDH mutations (12 had IDH1 R132, 3 had IDH1 G105, and 2 had IDH2 R172). Overall survival at 2 years using the Kaplan-Meier estimator was lower in patients with an IDH mutation than in those with the wild-type gene (75% [95% confidence interval 50% to 99%] versus 100% [95% CI 100% to 100%]; p = 0.002). Two-year metastasis-free survival was also lower in patients with an IDH mutation than in those with the wild-type gene (33% [95% CI 7% to 60%] versus 100% [95% CI 100% to 100%]; p = 0.001), as was 2-year local recurrence-free survival (70% [95% CI 42% to 98%] versus 100% [95% CI 100% to 100%]; p = 0.02).

CONCLUSION

We found that IDH1 R132 mutations were negatively associated with the prognosis of patients with bone chondrosarcomas. Nevertheless, more extensive studies (such as multicenter international studies) are needed and advisable to confirm our observations in this preliminary small series. Moreover, evaluating mutational status in fresh samples instead of in paraffin-embedded sections could help to increase the number of patients with adequate DNA for analysis. If our findings will be confirmed, the evaluation of IDH mutational status in biopsy samples or resection specimens could be considered when stratifying patients, highlighting those who may benefit from more aggressive treatment (such as adjuvant chemotherapy) or closer follow-up.

LEVEL OF EVIDENCE

Level III, prognostic study.

PRISMA-the 100 most-cited articles on chondrosarcoma recurrence: A bibliometric analysis

BACKGROUND

Chondrosarcoma (CHS) is highly prone to recurrence and has become the most common malignant bone tumor in adults. The authors aim to identify and analyze the top 100 most-cited articles in this field, enabling researchers to quickly grasp the research focus and progress in the area of chondrosarcoma recurrence.

METHODS

A search in the Web of Science database yielded a total of 305 articles related to CHS recurrence between 2013 and 2022. Filtering was done based on the titles and abstracts of the articles in the list, and the top 100 most-cited articles were selected. The following information were analyzed using bibliometric methods: article title, first author, year of publication, journal of publication, total citations, country, institution, and keywords.

RESULTS

Among the selected 100 articles, the most frequently cited one has 224 citations. The most commonly appearing journals, institutions, and countries are as follows: "Clinical Orthopaedics Related Research" (5 times); Fudan University, University of Texas System, and Royal Orthopaedic Hospital (4 times each), with China and the USA cited the most (21 times each). The year 2018 is the most productive year (17 articles). About 97 first authors contributed one article each, and 3 had 2 articles each. Among all 229 keywords, the top 3 in frequency are CHS (20%), recurrence (4%), and surgery (3%). Twenty article topics are related to surgical treatment.

CONCLUSION

Research on CHS recurrence is citation-rich but focuses more on treatments than understanding mechanisms, indicating a need for deeper mechanistic exploration for treatment breakthroughs in the future.

Clinico-Genomic Profiling of Conventional and Dedifferentiated Chondrosarcomas Reveals TP53 Mutation to Be Associated with Worse Outcomes

PURPOSE

Chondrosarcomas are the most common primary bone tumor in adults. Isocitrate dehydrogenase 1 (IDH1) and IDH2 mutations are prevalent. We aimed to assess the clinico-genomic properties of IDH mutant versus IDH wild-type (WT) chondrosarcomas as well as alterations in other genes.

EXPERIMENTAL DESIGN

We included 93 patients with conventional and dedifferentiated chondrosarcoma for which there were available clinical next-generation sequencing data. Clinical and genomic data were extracted and compared between IDH mutant and IDH WT chondrosarcomas and between TP53 mutant and TP53 WT chondrosarcomas.

RESULTS

IDH1 and IDH2 mutations are prevalent in chondrosarcoma (50.5%), more common in chondrosarcomas arising in the extremities, associated with higher age at diagnosis, and more common in dedifferentiated chondrosarcomas compared with grades 1-3 conventional chondrosarcoma. There was no difference in survival based on IDH mutation in univariate and multivariate analyses. TP53 mutation was the next most prevalent (41.9%) and is associated with worse overall survival and metastasis-free survival in both univariate and multivariate analyses. TP53 mutation was also associated with higher risk of recurrence following curative-intent surgery and worse survival among patients that presented with de novo metastatic disease.

CONCLUSIONS

IDH mutations are prevalent in chondrosarcoma though were not associated with survival outcomes in this cohort. TP53 mutations were the next most common alteration and were associated with worse outcomes.

Skull Base Tumors

OBJECTIVE

This article reviews the presenting features, molecular characteristics, diagnosis, and management of selected skull base tumors, including meningiomas, vestibular schwannomas, pituitary neuroendocrine tumors, craniopharyngiomas, chordomas, ecchordosis physaliphora, chondrosarcomas, esthesioneuroblastomas, and paragangliomas.

LATEST DEVELOPMENTS

Skull base tumors pose a management challenge given their complex location and, as a result, the tumors and treatment can result in significant morbidity. In most cases, surgery, radiation therapy, or both yield high rates of disease control, but the use of these therapies may be limited by the surgical accessibility of these tumors and their proximity to critical structures. The World Health Organization classification of pituitary neuroendocrine tumors was updated in 2022. Scientific advances have led to an enhanced understanding of the genetic drivers of many types of skull base tumors and have revealed several potentially targetable genetic alterations. This information is being leveraged in the design of ongoing clinical trials, with the hope of rendering these challenging tumors treatable through less invasive and morbid measures.

ESSENTIAL POINTS

Tumors involving the skull base are heterogeneous and may arise from bony structures, cranial nerves, the meninges, the sinonasal tract, the pituitary gland, or embryonic tissues. Treatment often requires a multidisciplinary approach, with participation from radiation oncologists, medical oncologists, neuro-oncologists, and surgical specialists, including neurosurgeons, otolaryngologists, and head and neck surgeons. Treatment has largely centered around surgical resection, when feasible, and the use of first-line or salvage radiation therapy, with chemotherapy, targeted therapy, or both considered in selected settings. Our growing understanding of the molecular drivers of these diseases may facilitate future expansion of pharmacologic options to treat skull base tumors.

Establishment and characterization of a novel dedifferentiated chondrosarcoma cell line, SMU-DDCS, harboring an IDH1 mutation

Dedifferentiated chondrosarcoma (DDCS) is a high-grade subtype with a bi-morphic histological appearance of a conventional chondrosarcoma component and it can abruptly transition to a high-grade non-cartilaginous sarcoma. To better understand the biological features of DDCSs and to help develop new therapies, a novel DDCS cell line, SMU-DDCS, was established. Tissue from an open biopsy of a tumor resected from a 75-year-old patient was subjected to primary culture. The cell line was established and authenticated by assessing DNA microsatellite short tandem repeats. The cells maintained in monolayer cultures exhibited constant growth, spheroid formation, and high invasive capacity. Out of the four mice inoculated with SMU-DDCS cells, tumors developed in three mice after 2 weeks. R132C mutation was found in the IDH1 but not the IDH2 genomic DNA sequence of SMU-DDCS cells. SMU-DDCS cells exhibited low chemosensitivity to doxorubicin, methotrexate, and cisplatin. This SMU-DDCS cell line harboring an IDH1 mutation will be a useful tool for investigating DDCS development and for evaluating novel therapeutic agents against it.

IDH mutations in G2-3 conventional central bone chondrosarcoma: a mono institutional experience

BACKGROUND

Heterozygous isocitrate dehydrogenase (IDH) mutations occur in about half of conventional central bone chondrosarcomas (CCBC). Aim of this study was to assess the frequency and prognostic impact of IDH mutations in high grade CCBC patients.

METHODS

64 patients with G2 and G3 CCBC were included. DNA extraction, PCR amplification of IDH1/2 exon 4s, and sequencing analysis with Sanger were performed.

RESULTS

IDH mutations were detected in 24/54 patients (44%): IDH1 in 18, IDH2 in 4, and both IDH1/2 in 2 patients. The frequency of mutations was 37% in G2 vs. 69% in G3 (p = 0.039), and 100% in three Ollier disease associated chondrosarcoma. 5-year overall survival (OS) at 124 months (range 1-166) was 51%, with no significant difference based on the IDH mutational status: 61% in IDHmut vs. 44% in IDH wild type (IDHwt). The 5-year relapse free survival (RFS) was 33% (95% CI:10-57) for IDHmut vs. 57% (95%CI: 30-77) for IDHwt. Progression free survival (PFS) was 25% (95%CI:1-65) IDHmut vs. 16% (95%CI: 0.7-52) IDHwt. 55% (5/9) of IDHmut G2 became higher grade at the recurrence, as compared with 25% (3/12) of G2 IDHwt.

CONCLUSIONS

This study shows a higher frequency of IDH mutations in G3 CCBC as compared with G2. No significant differences in OS, RFS, and PFS by mutational status were detected. After relapse, a higher rate of G3 for IDH mutated CCBC was observed.

Identification of co-expressed gene networks promoting CD8+ T cell infiltration and having prognostic value in uveal melanoma

Current immunotherapies are unsatisfactory against uveal melanoma (UM); however, elevated CD8+ T cell infiltration level indicates poor prognosis in UM. Here, we aimed to identify co-expressed gene networks promoting CD8+ T cell infiltration in UM and created a prognostic hazard model based on the identified hub genes. Raw data and clinical information were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Stromal-immune comprehensive score (ESTIMATE) was used to evaluate the immune-infiltration landscape of the tumor microenvironment. Single-Sample Gene Set Enrichment Analysis (ssGSEA) and Weighted Correlation Network Analysis (WGCNA) were used to quantify CD8+ T cell infiltration level and identify hub genes. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to analyze the biological processes. Least absolute shrinkage and selection operator (LASSO) Cox regression were used to establish a prognostic model, which was further validated. Finally, pan-cancer analysis evaluated these genes to be associated with CD8+ T cell infiltration in other tumors. In conclusion, the proposed four-gene (PTPN12, IDH2, P2RX4, and KDELR2) prognostic hazard model had satisfactory prognostic ability. These hub genes may promote CD8+ T cell infiltration in UM through antigen presentation, and CD8+ T cell possibly function as Treg, resulting in poor prognosis. These findings might facilitate the development of novel immunotherapies.

IMMUNOHISTOCHEMICAL ANALYSIS BY KI67 AND IDH1 IN PATIENTS WITH CHONDROSARCOMA

Objective

To perform an immunohistochemical evaluation using the IDH1 and Ki67 markers in patients who underwent treatment for chondrosarcoma in a reference service center in Brazil.

Methods

Retrospective analytical observational study using medical records of patients diagnosed with chondrosarcoma. Besides the epidemiological and clinical profile, important variables for prognosis and correlation with immunohistochemical analysis results with Ki67 and IDH1 markers were evaluated.

Results

Histopathological examinations by immunohistochemistry of 56 patients were analyzed, 52% of which were women, with the age group 20-60 years being more prevalent. Grade 1 and 2 histological subtypes corresponded to most chondrosarcomas. The femur, humerus, and tibia were the most frequent anatomical sites. Most tumors (59%) were larger than 8 cm. Ki67 expression was very low (< 10%) in 98% of patients. The analysis of IDH1 was positive in 43% of the cases. The correlation between IDH1 positivity and tumor size was statistically significant, but regarding survival, we observed no significance.

Conclusion

Immunohistochemical analysis using IDH1 and Ki67 markers in patients with conventional chondrosarcoma is not useful for prognostic guidance.Level of Evidence II, Prognostic Assessment, Results of Immunohistochemical Tests and Correlation with Survival.

IDH Mutations in Chondrosarcoma: Case Closed or Not?

Chondrosarcomas are malignant cartilage-producing tumours that frequently harbour isocitrate dehydrogenase 1 and -2 (IDH) gene mutations. Several studies have confirmed that these mutations are key players in the early stages of cartilage tumour development, but their role in later stages remains ambiguous. The prognostic value of IDH mutations remains unclear and preclinical studies have not identified effective treatment modalities (in)directly targeting these mutations. In contrast, the IDH mutation status is a prognostic factor in other cancers, and IDH mutant inhibitors as well as therapeutic strategies targeting the underlying vulnerabilities induced by IDH mutations seem effective in these tumour types. This discrepancy in findings might be ascribed to a difference in tumour type, elevated D-2-hydroxyglutarate levels, and the type of in vitro model (endogenous vs. genetically modified) used in preclinical studies. Moreover, recent studies suggest that the (epi)genetic landscape in which the IDH mutation functions is an important factor to consider when investigating potential therapeutic strategies or patient outcomes. These findings imply that the dichotomy between IDH wildtype and mutant is too simplistic and additional subgroups indeed exist within chondrosarcoma. Future studies should focus on the identification, characterisation, and tailoring of treatments towards these biological subgroups within IDH wildtype and mutant chondrosarcoma.

Conventional Chondrosarcoma of the Rib Cage and Sternum: Clinicopathological and Molecular Analysis of 27 Patients Treated at a Single Institution

Conventional chondrosarcoma of the chest wall is rare, accounting for 15% of cases. Our purpose was to document clinicopathological, imaging and outcome results from a novel set of chest wall chondrosarcomas, and to analyze for <I>IDH</I> mutations and novel molecular alterations. Gross and microscopic pathology, imaging and clinical charts were reviewed. Targeted next-generation sequencing was performed to identify somatic mutations and copy number alterations. The cohort consisted of 27 patients: 16 men and 11 women (mean age 51 years; range 23-76). Palpable mass was the most common presentation. Five were discovered incidentally. Among 20 tumors with complete imaging, 15 arose from a rib and 5 from the sternum. Seven rib tumors were central/intramedullary, 5 were periosteal, 2 were secondary peripheral chondrosarcomas, and one was indeterminate. Among sternal tumors, 4 were central/intramedullary and one was periosteal. Half the periosteal tumors arose from the costochondral junctional cartilage (CCJ). Periosteal chondrosarcomas were sometimes mistaken for extraskeletal masses on initial clinical or radiological examinations. Fifty-nine percent of all tumors were grade 1 and 41% were grade 2. None were dedifferentiated chondrosarcomas. Heterozygous <I>IDH1</I> mutation was detected in one tumor and heterozygous <I>RAD50</I> mutation in another. Local recurrence(s) happened in 41% and metastasis in 41%. Grade had strong association with local recurrence (25% grade 1 vs. 64% grade 2 [p=0.0447]), metastatic recurrence (19% grade 1 vs. 73% grade 2 [p=0.0058]), and survival. Although chest wall chondrosarcomas share morphologic and molecular features with other chondrosarcomas, there is a much higher incidence of periosteal chondrosarcomas. <I>IDH</I> mutant tumors are uncommon. Early diagnosis and margin-negative resection is treatment of choice since chondrosarcomas are chemo- and radioresistant.

Prognostic Significance of Percentage and Size of Dedifferentiation in Dedifferentiated Chondrosarcoma

Dedifferentiated chondrosarcoma is rare, aggressive, and microscopically bimorphic. How pathologic features such as the amounts of dedifferentiation affect prognosis remains unclear. We evaluated the percentages and sizes of dedifferentiation in a consecutive institutional series of dedifferentiated chondrosarcomas from 1999 to 2021. The statistical analysis included cox proportional hazard models and log-rank tests. Of the 67 patients (26 women, 41 men; age, 39 to >89 [median 61] years; 2 with Ollier disease), 58 presented de novo; 9 were identified with conventional chondrosarcomas 0.6-13.2 years (median, 5.5 years) prior. Pathologic fracture and distant metastases were noted in 27 and 7 patients at presentation. The tumors involved the femur (n = 27), pelvis (n = 22), humerus (n = 7), tibia (n = 4), scapula/ribs (n = 4), spine (n = 2), and clivus (n = 1). In the 56 resections, the tumors ranged in size from 3.5 to 46.0 cm (median, 11.5 cm) and contained 1%-99.5% (median, 70%) dedifferentiated components that ranged in size from 0.6 to 24.0 cm (median, 7.3 cm). No correlation was noted between total size and percentage of dedifferentiation. The dedifferentiated components were typically fibrosarcomatous or osteosarcomatous, whereas the associated cartilaginous components were predominantly grade 1-2, rarely enchondromas or grade 3. The entire cohort's median overall survival and progression-free survival were 11.8 and 5.4 months, respectively. In the resected cohort, although the total size was not prognostic, the percentage of dedifferentiation ≥20% and size of dedifferentiation >3.0 cm each predicted worse overall survival (9.9 vs 72.5 months; HR, 3.76; 95% CI, 1.27-11.14; P = .02; 8.7 vs 58.9 months; HR, 3.03; 95% CI, 1.21-7.57; P = .02, respectively) and progression-free survival (5.3 vs 62.1 months; HR, 3.05; 95% CI, 1.13-8.28; P = .03; 5.3 vs 56.6 months; HR, 2.50; 95% CI, 1.06-5.88; P = .04, respectively). In conclusion, both the percentages and sizes of dedifferentiation were better prognostic predictors than total tumor sizes in dedifferentiated chondrosarcomas, highlighting the utility of their pathologic evaluations.

Distinct IDH1/2-associated Methylation Profile and Enrichment of TP53 and TERT Mutations Distinguish Dedifferentiated Chondrosarcoma from Conventional Chondrosarcoma

Dedifferentiated chondrosarcoma (DDCS) is a rare high-grade chondrosarcoma characterized by a well-differentiated chondrosarcoma (WDCS) component that abruptly transitions to a high-grade, noncartilaginous sarcomatous component. To date, the molecular pathogenesis of DDCS and its distinction from conventional chondrosarcoma remain poorly understood. By targeted sequencing, we examined the mutational and copy-number profiles of 18 DDCS, including macrodissected WDCS components, compared with 55 clinically sequenced conventional chondrosarcomas. In conjunction with publicly available external data, we analyzed the methylation and expression profiles of 34 DDCS and 94 conventional chondrosarcomas. Isocitrate dehydrogenase 1/isocitrate dehydrogenase 2 (IDH1/IDH2) mutations were present in 36% conventional chondrosarcomas and 71% DDCS. Compared with conventional chondrosarcomas, DDCS had higher frequencies of TP53 and TERT promoter mutations and CDKN2A/B copy-number losses. Paired analysis of macrodissected WDCS and the high-grade components revealed TERT promoter mutations as early events. Despite phenotypic similarities, the percentage of genome with copy-number alterations in DDCS was significantly lower than that in other high-grade sarcomas. Differential methylation analysis revealed reduction of IDH1/IDH2-associated global hypermethylation characteristically seen in conventional chondrosarcoma and a distinct methylation profile in DDCS. The WDCS and high-grade components in DDCS showed similar methylation profiles. These CpG sites were associated with upregulated expression of genes involved in G2-M checkpoints and E2F targets. Genomic profiling revealed enrichment of TP53, TERT promoter, and CDKN2A/B alterations in DDCS. Integrated methylation and gene expression analysis revealed distinct IDH1/IDH2-associated methylation and transcriptional profiles as early events in DDCS, which may underlie the pathogenesis of dedifferentiation in chondrosarcomas.

Significance

DDCS is a rare, high-grade chondrosarcoma with a dismal prognosis. About 50%-80% of DDCS harbor IDH1/IDH2 mutations. We uncover a significant alteration of IDH-associated methylation profile in DDCS, which we propose is key to the progression to dedifferentiation. In this context, the potential effect of the use of IDH inhibitors is unclear but important to address, as clinical trials of selective IDH1 inhibitors showed worse outcome in DDCS.

Prognostic impact of IDH mutations in chondrosarcoma

BACKGROUND

Mutant isocitrate dehydrogenase (IDH) in chondrosarcoma produces the oncometabolite 2-hydroxyglutarate (2-HG) and contributes to malignant progression, and is therefore a potential therapeutic target for chondrosarcoma. Robust historical control data are important in clinical trials of rare cancers such as chondrosarcoma in order to show a clear benefit of new drugs. However, it remains controversial whether IDH mutation status is associated with the clinical outcome of chondrosarcoma, and this hinders the development of mutant IDH inhibitors in clinical trials.background METHODS: We investigated the relationship between IDH gene status and clinicopathological data in 38 chondrosarcoma patients from whom frozen tumor samples were obtained at the time of biopsy or surgery. Targeted next-generation sequencing was also performed to compare genetic alterations between patients with and without IDH mutations.

METHODS RESULTS

The results revealed 15 cases (40%) of heterozygous IDH1 mutations and five cases (13%) of IDH2 mutations. IDH-mutant chondrosarcoma was associated with worse overall survival than IDH-wild-type chondrosarcoma (IDH1/2 Mut vs. IDH Wt, P = 0.006; IDH1 Mut vs. IDH Wt, P = 0.030; IDH2 Mut vs. IDH Wt, P < 0.0001). IDH mutation was also a significant poor prognostic factor both in univariate (P = 0.026) and multivariate (P = 0.048) analyses. Targeted next-generation sequencing revealed that characteristic mutations in chondrosarcoma, including TP53 and COL2A1, were more common in the IDH-mutant group than in the IDH-wild-type group.results CONCLUSION: This study is the first to report in detail the characteristics and clinical courses of IDH-mutant chondrosarcoma patients in Japan. Our data suggested that IDH-mutant chondrosarcomas might have a worse prognosis than that of IDH-wild-type chondrosarcoma, possibly through the more aggressive characters after metastasis. This information will be useful for designing clinical trials of mutant IDH inhibitors for treatment of advanced chondrosarcoma.

Atypical cartilage in type II germ cell tumors of the mediastinum show significantly different patterns of IDH1/2 mutations from conventional chondrosarcoma

Neoplastic cartilage is a common component of teratomas in type II germ cell tumors. Although IDH1/2 mutations have been well-described in somatic cartilaginous tumors, ranging from benign enchondromas to highly aggressive dedifferentiated chondrosarcomas, the presence of IDH1/2 mutations in cartilaginous neoplasms arising from germ cell tumors has not been previously investigated. To better understand the relationship between these tumors and their bone/soft tissue counterpart, we studied the IDH1/2 mutational status of 20 cases of primary mediastinal mixed germ cell tumors with areas of readily identifiable cartilaginous differentiation. Our study found that cartilaginous lesions arising in germ cell tumors have a different frequency and distribution of IDH1/2 mutations compared to those at somatic sites. We identified IDH1/2 mutations in only 15% (3/20) of cases, compared to a frequency in the literature among differentiated chondroid tumors of bone and soft tissue of 54%, a highly significant decreased frequency (p = 0.0011; chi-square test). Furthermore, they were exclusively IDH2 R172 mutations that occurred at a non-significant, increased frequency in the germ cell tumor group compared to conventional chondrosarcoma (15% vs. 5%, respectively, p > 0.05, chi-square test). The unexpected finding, therefore, was entirely attributable to the absence of IDH1 R132 mutation in chondroid neoplasia of germ cell origin (p < 0.00001, Fisher exact test). Our results suggest that a subset of cartilaginous lesions arising within type II germ cell tumors have a similar oncogenic mechanism to their bone/soft tissue counterpart but that the majority form using different oncogenic mechanisms compared to their somatic counterparts.

A new scoring system for the grading of conventional chondrosarcoma: Its clinicopathological significance

BACKGROUND

Chondrosarcoma is the second most common primary malignant bone tumor, which produces cartilaginous matrix without neoplastic osteoid or bone formation. The histological grade in the WHO Classification of Soft Tissue and Bone (2020 edition) is the most important factor in predicting the clinical outcome of conventional chondrosarcoma, but the lack of clarity in its detailed definition is occasionally problematic. Here, we reviewed conventional chondrosarcoma cases and validated the significance of histological findings. Moreover, we proposed a new scoring system of conventional chondrosarcoma.

MATERIAL AND METHODS

Clinicopathological features of 60 cases of conventional chondrosarcoma and 21 cases of dedifferentiated chondrosarcoma were reviewed.

RESULTS

Moderate to severe nuclear atypia was correlated with distant metastasis. Moderate and severe nuclear atypia, high cellularity, and >1 % myxoid change were correlated with adverse overall survival. On the other hand, cases with mild nuclear atypia showed no tumor-related death and no metastases. Based on the above results, we proposed a new scoring system based on nuclear atypia (mild: 0, moderate: +1, severe: +2), cellularity (no and mildly increased cellularity: 0, moderately and diffusely increased cellularity: +1), necrosis [(-): 0, (+): + 1], and chondromyxoid area [(-): 0, (+): + 1]. Each grade was defined as follows: cases with only mild nuclear atypia as grade 1, cases with total score 1-3 excluding mild nuclear atypia as grade 2, and cases with total score 4 or 5 as grade 3. There were 18 cases (30 %) of grade 1 including 5 cases (28 %) of local recurrence, but no metastasis or tumor-related death; 26 cases (43 %) of grade 2 including 2 cases (8 %) of local recurrence, 3 cases (12 %) of metastasis, and 1 case (4 %) of tumor-related death; and 16 cases (27 %) of grade 3 including 4 cases (25 %) of local recurrence, 6 cases (38 %) of metastasis, and 5 cases (31 %) of tumor-related death. There was no statistically significant association between the histological findings and dedifferentiation.

CONCLUSION

From this study, we propose a new histological scoring system for the grading of conventional chondrosarcoma, based on nuclear atypia, cellularity, necrosis, and myxoid change. Using this system, conventional chondrosarcoma may be clearly classified into three grades: grade 1, non-metastasizing; grade 2, metastasizing but rarely life-threatening; and grade 3, frequently metastasizing and life-threatening.

A genetic model for central chondrosarcoma evolution correlates with patient outcome

BACKGROUND

Central conventional chondrosarcoma (CS) is the most common subtype of primary malignant bone tumour in adults. Treatment options are usually limited to surgery, and prognosis is challenging. These tumours are characterised by the presence and absence of IDH1 and IDH2 mutations, and recently, TERT promoter alterations have been reported in around 20% of cases. The effect of these mutations on clinical outcome remains unclear. The purpose of this study was to determine if prognostic accuracy can be improved by the addition of genomic data, and specifically by examination of IDH1, IDH2, and TERT mutations.

METHODS

In this study, we combined both archival samples and data sourced from the Genomics England 100,000 Genomes Project (n = 356). Mutations in IDH1, IDH2, and TERT were profiled using digital droplet PCR (n = 346), whole genome sequencing (n=68), or both (n = 64). Complex events and other genetic features were also examined, along with methylation array data (n = 84). We correlated clinical features and patient outcomes with our genetic findings.

RESULTS

IDH2-mutant tumours occur in older patients and commonly present with high-grade or dedifferentiated disease. Notably, TERT mutations occur most frequently in IDH2-mutant tumours, although have no effect on survival in this group. In contrast, TERT mutations are rarer in IDH1-mutant tumours, yet they are associated with a less favourable outcome in this group. We also found that methylation profiles distinguish IDH1- from IDH2-mutant tumours. IDH wild-type tumours rarely exhibit TERT mutations and tend to be diagnosed in a younger population than those with tumours harbouring IDH1 and IDH2 mutations. A major genetic feature of this group is haploidisation and subsequent genome doubling. These tumours evolve less frequently to dedifferentiated disease and therefore constitute a lower risk group.

CONCLUSIONS

Tumours with IDH1 or IDH2 mutations or those that are IDHwt have significantly different genetic pathways and outcomes in relation to TERT mutation. Diagnostic testing for IDH1, IDH2, and TERT mutations could therefore help to guide clinical monitoring and prognostication.

Human and machine: Better at pathology together?

Meaningful integration of artificial intelligence (AI) will transform the application of "big data" for patient care, diagnosis, and research. In this issue of Cancer Cell, Chen et al. describe a transparent system to integrate histopathology and molecular data to predict outcomes and identify novel biomarkers in cancer.

IDH2: A novel biomarker for environmental exposure in blood circulatory system disorders (Review)

As the risk of harmful environmental exposure is increasing, it is important to find suitable targets for the diagnosis and treatment of the diseases caused. Isocitrate dehydrogenase 2 (IDH2) is an enzyme located in the mitochondria; it plays an important role in numerous cell processes, including maintaining redox homeostasis, participating in the tricarboxylic acid cycle and indirectly taking part in the transmission of the oxidative respiratory chain. IDH2 mutations promote progression in acute myeloid leukemia, glioma and other diseases. The present review mainly summarizes the role and mechanism of IDH2 with regard to the biological effects, such as the mitophagy and apoptosis of animal or human cells, caused by environmental pollution such as radiation, heavy metals and other environmental exposure factors. The possible mechanisms of these biological effects are described in terms of IDH2 expression, reduced nicotine adenine dinucleotide phosphate content and reactive oxygen species level, among other variables. The impact of environmental pollution on human health is increasingly attracting attention. IDH2 may therefore become useful as a potential diagnostic and therapeutic target for environmental exposure-induced diseases.

The Molecular Mechanisms of Resistance to IDH Inhibitors in Acute Myeloid Leukemia

Gain-of-function mutations of isocitrate dehydrogenases 1/2 (IDH1/2) play crucial roles in the development and progression of acute myeloid leukemia (AML), which provide promising therapeutic targets. Two small molecular inhibitors, ivosidenib and enasidenib have been approved for the treatment of IDH1- and IDH2-mutant AML, respectively. Although these inhibitors benefit patients with AML clinically, drug resistance still occurs and have become a major problem for targeted therapies of IDH-mutant AML. A number of up-to-date studies have demonstrated molecular mechanisms of resistance, providing rationales of novel therapeutic strategies targeting mutant IDH1/2. In this review, we discuss mechanisms of resistance to ivosidenib and enasidenib in patients with AML.

IDH mutation and cancer stem cell

Cancer stem cells (CSCs) are a small population of cells in human malignancies that resemble the biology of human pluripotent stem cells. CSCs are closely related to the critical hallmarks in human cancers, ranging from oncogenesis to disease progression, therapeutic resistance, and overall outcome. Mutations in isocitrate dehydrogenase (IDH) were recently identified as founder mutations for human cancers. An increasing amount of evidence indicates that IDH mutations are closely related to the establishment and maintenance of CSCs. Biosynthesis of oncometabolite, metabolic reprogramming, and epigenetic shifts establish distinctive molecular signatures in IDH-mutated CSCs. Additionally, IDH mutation and IDH-related pathways could be valuable molecular targets to impact the CSC components in human cancers and to improve the disease outcome.

Clinical usefulness of 2-hydroxyglutarate as a biomarker in IDH-mutant chondrosarcoma

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2-HG is expected to be a useful biomarker for diagnosing and treating IDH-mutant tumors.

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Both intratumoral and serum levels of 2-HG were significantly higher in IDH-mutant tumors.

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Serum 2-HG levels were correlated with tumor volume and tumor progression.

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MR spectroscopy (MRS) detected 2-HG peaks in a xenograft model of IDH-mutant chondrosarcoma.

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In vivo MRS can be a useful tool for determining the therapeutic effect of mutant IDH inhibitors.

Background

Chondrosarcoma is a common form of malignant bone tumor with limited treatment options. Approximately half of chondrosarcomas harbor gain-of-function mutations in isocitrate dehydrogenase (IDH), and mutant IDH produces 2-hydroxyglutarate (2-HG), which is an oncometabolite that contributes to malignant transformation. Therefore, inhibiting 2-HG production is a novel and promising treatment for advanced chondrosarcoma. 2-HG is also expected to be a useful biomarker for the diagnosis and treatment of IDH-mutant tumors. However, few studies have confirmed this using chondrosarcoma clinical specimens. Non-invasive monitoring of 2-HG levels is useful to infer that mutant IDH inhibitors reach therapeutic targets and to confirm their therapeutic efficacy in clinical practice.

Methods

To evaluate the clinical utility of 2-HG as a surrogate biomarker for diagnosis and therapeutic efficacy, we measured intra-tumor and serum levels of 2-HG using frozen tissues and peripheral blood from patients with chondrosarcoma. We also developed a non-invasive method to detect intra-tumor 2-HG signals in vivo using magnetic resonance spectroscopy (MRS)

Results

Both intratumoral and serum 2-HG levels were significantly elevated in IDH-mutant tumors, and these levels correlated with decreased survival. Furthermore, we detected intratumoral 2-HG peaks using MR spectroscopy in a xenograft model of IDH-mutant chondrosarcoma, and observed that 2-HG peak signals disappeared after administering an inhibitor of mutant IDH1.

Conclusions

Our findings suggest that both intratumoral and serum 2-HG levels represent potentially useful biomarkers for IDH-mutant tumors and that the 2-HG signal in MR spectra has potential value as a non-invasive biomarker. Taken together, these findings may positively impact the clinical development of mutant IDH inhibitors for the treatment of advanced chondrosarcoma.

Noncanonical roles of p53 in cancer stemness and their implications in sarcomas

Impairment of the prominent tumor suppressor p53, well known for its canonical role as the "guardian of the genome", is found in almost half of human cancers. More recently, p53 has been suggested to be a crucial regulator of stemness, orchestrating the differentiation of embryonal and adult stem cells, suppressing reprogramming into induced pluripotent stem cells, or inhibiting cancer stemness (i.e., cancer stem cells, CSCs), which underlies the development of therapy-resistant tumors. This review addresses these noncanonical roles of p53 and their implications in sarcoma initiation and progression. Indeed, dysregulation of p53 family proteins is a common event in sarcomas and is associated with poor survival. Additionally, emerging studies have demonstrated that loss of wild-type p53 activity hinders the terminal differentiation of mesenchymal stem cells and leads to the development of aggressive sarcomas. This review summarizes recent findings on the roles of aberrant p53 in sarcoma development and stemness and further describes therapeutic approaches to restore normal p53 activity as a promising anti-CSC strategy to treat refractory sarcomas.

Clinical development of IDH1 inhibitors for cancer therapy

Isocitrate dehydrogenase 1 (IDH1) has been investigated as a promising therapeutic target in select cancers with a mutated version of the enzyme (mtIDH1). With only one phase III trial published to date and two indications approved for routine clinical use by the FDA, we reviewed the entire clinical trial portfolio to broadly understand mtIDH1 inhibitor activity in patients. We queried PubMed.gov and ClinicalTrials.gov to identify published and ongoing clinical trials related to IDH1 and cancer. Progression-free survival (PFS), overall survival (OS), 2-hydroxyglutarate levels, and adverse events were summarized. To date, ten clinical trials investigating mtIDH1 inhibitors among patients with diverse malignancies (cholangiocarcinoma, acute myeloid leukemia, chondrosarcoma, glioma) have been published. Almost every trial (80%) has investigated ivosidenib. In multiple phase I trials, ivosidenib treatment resulted in promising radiographic and biochemical responses with improved survival outcomes (relative to historic data) among patients with both solid and hematologic mtIDH1 malignancies. Among patients enrolled in a phase III trial with advanced cholangiocarcinoma, ivosidenib resulted in a PFS rate of 32% at 6 months, as compared to 0% with placebo. There was a 5.2 month increase in OS with ivosidenib relative to placebo, after considering crossover. The treatment-specific grade ≥3 adverse event rate of ivosidenib was 2%-26% among all patients, and was just 3.6% among 284 patients who had a solid tumor across four trials. Although <1% of malignancies harbor IDH1 mutations, small molecule mtIDH1 inhibitors, namely ivosidenib, appear to be biologically active and well tolerated in patients with solid and hematologic mtIDH1 malignancies.

Metabolic adaptations in cancers expressing isocitrate dehydrogenase mutations

The most frequently mutated metabolic genes in human cancer are those encoding the enzymes isocitrate dehydrogenase 1 (IDH1) and IDH2; these mutations have so far been identified in more than 20 tumor types. Since IDH mutations were first reported in glioma over a decade ago, extensive research has revealed their association with altered cellular processes. Mutations in IDH lead to a change in enzyme function, enabling efficient conversion of 2-oxoglutarate to R-2-hydroxyglutarate (R-2-HG). It is proposed that elevated cellular R-2-HG inhibits enzymes that regulate transcription and metabolism, subsequently affecting nuclear, cytoplasmic, and mitochondrial biochemistry. The significance of these biochemical changes for tumorigenesis and potential for therapeutic exploitation remains unclear. Here we comprehensively review reported direct and indirect metabolic changes linked to IDH mutations and discuss their clinical significance. We also review the metabolic effects of first-generation mutant IDH inhibitors and highlight the potential for combination treatment strategies and new metabolic targets.

Isocitrate dehydrogenase gene variants in cancer and their clinical significance

Human isocitrate dehydrogenase (IDH) genes encode for the IDH1, 2 & 3 isoenzymes which catalyse the formation of 2-oxoglutarate from isocitrate and are essential for normal mammalian metabolism. Although mutations in these genes in cancer were long thought to lead to a 'loss of function', combined genomic and metabolomic studies led to the discovery that a common IDH 1 mutation, present in low-grade glioma and acute myeloid leukaemia (AML), yields a variant (R132H) with a striking change of function leading to the production of (2R)-hydroxyglutarate (2HG) which consequently accumulates in large quantities both within and outside cells. Elevated 2HG is proposed to promote tumorigenesis, although the precise mechanism by which it does this remains uncertain. Inhibitors of R132H IDH1, and other subsequently identified cancer-linked 2HG producing IDH variants, are approved for clinical use in the treatment of chemotherapy-resistant AML, though resistance enabled by additional substitutions has emerged. In this review, we provide a current overview of cancer linked IDH mutations focussing on their distribution in different cancer types, the effects of substitution mutations on enzyme activity, the mode of action of recently developed inhibitors, and their relationship with emerging resistance-mediating double mutations.

Metabolic Pathways and Targets in Chondrosarcoma

Chondrosarcomas are the second most common primary bone malignancy. Chondrosarcomas are characterized by the production of cartilaginous matrix and are generally resistant to radiation and chemotherapy and the outcomes are overall poor. Hence, there is strong interest in determining mechanisms of cancer aggressiveness and therapeutic resistance in chondrosarcomas. There are metabolic alterations in chondrosarcoma that are linked to the epigenetic state and tumor microenvironment that drive treatment resistance. This review focuses on metabolic changes in chondrosarcoma, and the relationship between signaling via isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2), hedgehog, PI3K-mTOR-AKT, and SRC, as well as histone acetylation and angiogenesis. Also, potential treatment strategies targeting metabolism will be discussed including potential synergy with immunotherapies.

Circulating tumour DNA is a promising biomarker for risk stratification of central chondrosarcoma with IDH1/2 and GNAS mutations

Chondrosarcoma (CS) is a rare tumour type and the most common primary malignant bone cancer in adults. The prognosis, currently based on tumour grade, imaging and anatomical location, is not reliable, and more objective biomarkers are required. We aimed to determine whether the level of circulating tumour DNA (ctDNA) in the blood of CS patients could be used to predict outcome. In this multi-institutional study, we recruited 145 patients with cartilaginous tumours, of which 41 were excluded. ctDNA levels were assessed in 83 of the remaining 104 patients, whose tumours harboured a hotspot mutation in IDH1/2 or GNAS. ctDNA was detected pre-operatively in 31/83 (37%) and in 12/31 (39%) patients postoperatively. We found that detection of ctDNA was more accurate than pathology for identification of high-grade tumours and was associated with a poor prognosis; ctDNA was never associated with CS grade 1/atypical cartilaginous tumours (ACT) in the long bones, in neoplasms sited in the small bones of the hands and feet or in tumours measuring less than 80 mm. Although the results are promising, they are based on a small number of patients, and therefore, introduction of this blood test into clinical practice as a complementary assay to current standard-of-care protocols would allow the assay to be assessed more stringently and developed for a more personalised approach for the treatment of patients with CS.

Chondrosarcoma of the spine: a narrative review

Chondrosarcoma is an uncommon primary bone tumor with an estimated incidence of 0.5 per 100,000 patient-years. Primary chondrosarcoma of the mobile spine and sacrum cumulatively account for less than 20% of all cases, most .commonly causing patients to present with focal pain with or without radiculopathy, or myelopathy secondary to neural element compression. Because of the rarity, patients benefit from multidisciplinary care at academic tertiary-care centers. Current standard-of-care consists of en bloc surgical resection with negative margins; for high grade lesions adjuvant focused radiation with ≥60 gray equivalents is taking an increased role in improving local control. Prognosis is dictated by lesion grade at the time of resection. Several groups have put forth survival calculators and epidemiological evidence suggests prognosis is quite good for lesions receiving R0 resection. Future efforts will be focused on identifying potential chemotherapeutic adjuvants and refining radiation treatments as a means of improving local control.

Malignant Cartilage-Forming Tumors

Chondrosarcomas are heterogeneous matrix-producing cartilaginous neoplasms with variable clinical behavior. Subtypes include conventional (75%), dedifferentiated (10%), clear cell (2%), mesenchymal (2%), and periosteal chondrosarcoma (<1%). Tumor location and primary vs secondary also play a role. In conventional chondrosarcoma, histologic grading (I, II, and III) remains the gold standard for predicting recurrence and metastases. Due to the locally aggressive but overall nonmetastatic behavior, grade I chondrosarcomas (primary and secondary) of long and short tubular bones have been reclassified as atypical cartilaginous tumor. In this review, the pathologic features of malignant cartilage tumors are discussed with updates on recent genetic findings.

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.

IDH1 R132C and ERC2 L309I Mutations Contribute to the Development of Maffucci's Syndrome

Background

Maffucci's syndrome is characterized by the coexistence of multiple enchondromas and soft-tissue hemangiomas. It has been clear that somatic mosaic isocitrate dehydrogenase type 1 (IDH1) or isocitrate dehydrogenase type 2 (IDH2) mutations are associated with Maffucci's syndrome and Ollier disease, but the mechanisms underlying hemangiomas of the Maffucci's syndrome is still obscure. This study aimed to determine the mechanism of hemangiomas in Maffucci's syndrome.

Methods

We received a 26-year-old female patient with typical Maffucci's syndrome, and exome sequencing was conducted using DNA from her peripheral blood and enchondroma tissues. Somatic mutations were characterized by a comparative analysis of exome sequences and further confirmed by the sequencing of PCR products derived from original blood and tissue samples. The mutations of an additional 69 patients with Ollier disease were further tested. The functional impacts of these somatic mutations on Maffucci's syndrome, especially the development of hemangiomas, were evaluated.

Results

We reported a typical case of Maffucci's syndrome, which was confirmed by both imaging findings and pathology. Through exome sequencing of this patient's DNA samples, we identified an R132C mutation in the isocitrate dehydrogenase type 1 (IDH1) gene and an L309I mutation in the ELKS/RAB6-interacting/CAST family member 2 (ERC2) gene in this patient. Approximately 33.3% of the clones were positive for the IDH1 R132C mutation, and 19.0% of the clones were positive for the ECR2 L309I mutation. The IDH1 R132C mutation was detected in most of the patients with Ollier disease (51/69 patients), and the mean frequency of this mutation was 63.3% in total sequence readouts, but the ECR2 L309I mutation was absent in all of the patients with Ollier disease. In vitro experiments confirmed that the IDH1 R132C mutation promotes chondrocyte proliferation, and the ERC2 L309I mutation enhances angiogenesis.

Conclusions

Our results suggest that while IDH1 is a known pathogenic gene in enchondromatosis, ERC2 is a novel gene identified in Maffucci's syndrome. The somatic L309I mutation of ERC2 contributes to the pathogenesis of hypervascularization to facilitate the development of hemangiomas in Maffucci's syndrome. The combination of the IDH1 R132C and ERC2 L309I mutations contributes to the development of Maffucci's syndrome, and these results may enable further research on the pathogenesis of Maffucci's syndrome.

Somatic IDH1 variant (p.R132C) in an adult male with Maffucci syndrome

Maffucci syndrome is a rare, highly variable somatic mosaic condition, and well-known cancer-related gain-of-function variants in either the IDH1 or IDH2 genes have been found in the affected tissues of most reported individuals. Features include benign enchondroma and spindle-cell hemangioma, with a recognized increased risk of various malignancies. Fewer than 200 affected individuals have been reported; therefore, accurate estimates of malignancy risk are difficult to quantify and recommended surveillance guidelines are not available. The same gain-of-function IDH1 and IDH2 variants are also implicated in a variety of other benign and malignant tumors. An adult male presented with several soft palpable lesions on the right upper limb. Imaging and histopathology raised the possibility of Maffucci syndrome. DNA was extracted from peripheral blood lymphocytes and tissue surgically resected from a spindle-cell hemangioma. Sanger sequencing and droplet digital polymerase chain reaction (PCR) analysis of the IDH1 gene were performed. We identified a somatic mosaic c.394C > T (p.R132C) variant in exon 5 of IDH1, in DNA derived from hemangioma tissue at ∼17% variant allele fraction. This variant was absent in DNA derived from blood. This variant has been identified in the affected tissue of most reported individuals with Maffucci syndrome. Although this individual has a potentially targetable variant, and there is a recognized risk of malignant transformation in this condition, a decision was made not to intervene with an IDH1 inhibitor. The reasons and prospects for therapy in this condition are discussed.

Effect of Micro-/Nanoparticle Hybrid Hydrogel Platform on the Treatment of Articular Cartilage-Related Diseases

Joint diseases that mainly lead to articular cartilage injury with prolonged severe pain as well as dysfunction have remained unexplained for many years. One of the main reasons is that damaged articular cartilage is unable to repair and regenerate by itself. Furthermore, current therapy, including drug therapy and operative treatment, cannot solve the problem. Fortunately, the micro-/nanoparticle hybrid hydrogel platform provides a new strategy for the treatment of articular cartilage-related diseases, owing to its outstanding biocompatibility, high loading capability, and controlled release effect. The hybrid platform is effective for controlling symptoms of pain, inflammation and dysfunction, and cartilage repair and regeneration. In this review, we attempt to summarize recent studies on the latest development of micro-/nanoparticle hybrid hydrogel for the treatment of articular cartilage-related diseases. Furthermore, some prospects are proposed, aiming to improve the properties of the micro-/nanoparticle hybrid hydrogel platform so as to offer useful new ideas for the effective and accurate treatment of articular cartilage-related diseases.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

The implications of IDH mutations for cancer development and therapy

Mutations in the genes encoding the cytoplasmic and mitochondrial forms of isocitrate dehydrogenase (IDH1 and IDH2, respectively; collectively referred to as IDH) are frequently detected in cancers of various origins, including but not limited to acute myeloid leukaemia (20%), cholangiocarcinoma (20%), chondrosarcoma (80%) and glioma (80%). In all cases, neomorphic activity of the mutated enzyme leads to production of the oncometabolite D-2-hydroxyglutarate, which has profound cell-autonomous and non-cell-autonomous effects. The broad effects of IDH mutations on epigenetic, differentiation and metabolic programmes, together with their high prevalence across a variety of cancer types, early presence in tumorigenesis and uniform expression in tumour cells, make mutant IDH an ideal therapeutic target. Herein, we describe the current biological understanding of IDH mutations and the roles of mutant IDH in the various associated cancers. We also present the available preclinical and clinical data on various methods of targeting IDH-mutant cancers and discuss, based on the underlying pathogenesis of different IDH-mutated cancer types, whether the treatment approaches will converge or be context dependent.

Prognostic importance of IDH mutations in chondrosarcoma: An individual patient data meta-analysis

Introduction

IDH1/2 mutations are prevalent in cartilaginous tumors including chondrosarcoma. This meta‐analysis using individual patient data (IPD) aimed to investigate the clinical and prognostic association of these mutations in chondrosarcoma patients.

Methods

Two electronic databases including PubMed and Web of Science were searched for relevant data. We included studies providing IPD of chondrosarcoma with available IDH1/2 mutational status for meta‐analysis. Chi‐square and t‐test were performed to compare the groups with and without IDH1/2 mutations. For survival analysis, log‐rank test, and Cox proportional hazards model were used to investigate the association of IDH mutations with patient outcomes.

Results

Fourteen studies with 488 patients were analyzed. IDH1 and IDH2 mutations were detected in 38.7% and 12.1% of cases, respectively. IDH1/2 mutations were significantly associated with an older age (p = 0.003), tumor origins (p < 0.001), tumor grades (p < 0.001), larger diameter (p = 0.003), relapse (p = 0.014), and patient mortality (p = 0.04). Multivariate Cox regression analysis adjusted for age, gender, tumor grade, and tumor sites confirmed the negative impact of IDH1/2 mutations on patient overall survival (HR = 1.90; 95% CI = 1.06–3.42; p = 0.03).

Conclusion

Our meta‐analysis demonstrated the distinct characteristics of IDH1/2‐mutated chondrosarcomas in comparison to those without mutations. These mutations could serve as an independent prognostic biomarker to better prognosticate patient outcomes and design appropriate treatment plans.

Biological Roles and Therapeutic Applications of IDH2 Mutations in Human Cancer

Isocitrate dehydrogenase (IDH) is a key metabolic enzyme catalyzing the interconversion of isocitrate to α-ketoglutarate (α-KG). Mutations in IDH lead to loss of normal enzymatic activity and gain of neomorphic activity that irreversibly converts α-KG to 2-hydroxyglutarate (2-HG), which can competitively inhibit a-KG-dependent enzymes, subsequently induces cell metabolic reprograming, inhibits cell differentiation, and initiates cell tumorigenesis. Encouragingly, this phenomenon can be reversed by specific small molecule inhibitors of IDH mutation. At present, small molecular inhibitors of IDH1 and IDH2 mutant have been developed, and promising progress has been made in preclinical and clinical development, showing encouraging results in patients with IDH2 mutant cancers. This review will focus on the biological roles of IDH2 mutation in tumorigenesis, and provide a proof-of-principle for the development and application of IDH2 mutant inhibitors for human cancer treatment.

Wild-type IDH1 inhibits the tumor growth through degrading HIF-α in renal cell carcinoma

The purpose of our study was to explore the effect and intrinsic mechanism of wild-type IDH1 and its substrate α-KG on renal cell carcinoma (RCC). IDH1 was observed lower expression in RCC cell lines. Phenotype experiment was carried out in the wild-type IDH1 and mutant IDH1R132H plasmid treated cell line. The results showed that the wild-type IDH1 could significantly inhibit the proliferation, migration and promote the apoptosis of RCC cell lines, which were consistent with the IDH1's substrate α-KG. The mutant IDH1R132H was found to lose this biological function of IDH1. Moreover, we verified the proliferation inhibition of IDH1 in vivo. In addition, we verified the correlation between IDH1 and hypoxia signal-related proteins in vitro and in vivo, specifically, IDH1 overexpression could significantly reduce the expression of HIF-1α and HIF-2α proteins and its downstream proteins (VEGF, TGF-α). Furthermore, we preliminarily verified the possibility of α-KG in the RCC's treatment by injecting α-KG into the xenograft model. α-KG significantly reduced tumor size and weight in tumor-bearing mice. This study provided a new therapeutic target and small molecule for the study of the treatment and mechanism of RCC.

Mutant IDH and non-mutant chondrosarcomas display distinct cellular metabolomes

BACKGROUND

Majority of chondrosarcomas are associated with a number of genetic alterations, including somatic mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 genes, but the downstream effects of these mutated enzymes on cellular metabolism and tumor energetics are unknown. As IDH mutations are likely to be involved in malignant transformation of chondrosarcomas, we aimed to exploit metabolomic changes in IDH mutant and non-mutant chondrosarcomas.

METHODS

Here, we profiled over 69 metabolites in 17 patient-derived xenografts by targeted mass spectrometry to determine if metabolomic differences exist in mutant IDH1, mutant IDH2, and non-mutant chondrosarcomas. UMAP (Uniform Manifold Approximation and Projection) analysis was performed on our dataset to examine potential similarities that may exist between each chondrosarcoma based on genotype.

RESULTS

UMAP revealed that mutant IDH chondrosarcomas possess a distinct metabolic profile compared with non-mutant chondrosarcomas. More specifically, our targeted metabolomics study revealed large-scale differences in organic acid intermediates of the tricarboxylic acid (TCA) cycle, amino acids, and specific acylcarnitines in chondrosarcomas. Lactate and late TCA cycle intermediates were elevated in mutant IDH chondrosarcomas, suggestive of increased glycolytic metabolism and possible anaplerotic influx to the TCA cycle. A broad elevation of amino acids was found in mutant IDH chondrosarcomas. A few acylcarnitines of varying carbon chain lengths were also elevated in mutant IDH chondrosarcomas, but with minimal clustering in accordance with tumor genotype. Analysis of previously published gene expression profiling revealed increased expression of several metabolism genes in mutant IDH chondrosarcomas, which also correlated to patient survival.

CONCLUSIONS

Overall, our findings suggest that IDH mutations induce global metabolic changes in chondrosarcomas and shed light on deranged metabolic pathways.

Clinical Efficacy of Olaparib in IDH1/IDH2-Mutant Mesenchymal Sarcomas

PURPOSE

Tumors with neomorphic mutations in IDH1/2 have defective homologous recombination repair, resulting in sensitivity to poly (ADP-ribose) polymerase (PARP) inhibition. The Olaparib Combination trial is a phase II, open-label study in which patients with solid tumors harboring IDH1/2 mutations were treated with olaparib as monotherapy, with objective response and clinical benefit rates as the primary end points.

METHODS

Ten patients with IDH1/2-mutant tumors by next-generation sequencing were treated with olaparib 300 mg twice daily.

RESULTS

Three of five patients with chondrosarcomas had clinical benefit, including one patient with a partial response and two with stable disease lasting > 7 months. A patient with pulmonary epithelioid hemangioendothelioma had stable disease lasting 11 months. In contrast, clinical benefit was not observed among four patients with cholangiocarcinoma.

CONCLUSION

These results indicate preliminary activity of PARP inhibition in patients with IDH1/2-mutant chondrosarcoma and pulmonary epithelioid hemangioendothelioma. Further studies of PARP inhibitors alone and in combination in this patient population are warranted.

Targeted Next-Generation Sequencing Identifies Molecular and Genetic Events in Dedifferentiated Chondrosarcoma

CONTEXT.—

Dedifferentiated chondrosarcoma is a rare adult bone tumor with a dismal prognosis and is composed of a conventional chondrosarcoma juxtaposed to high-grade nonchondrogenic sarcoma. Dedifferentiated chondrosarcomas may represent tumor progression from a differentiated to a primitive histotype.

OBJECTIVE.—

To determine the genetic and molecular events that drive progression from a conventional chondrosarcoma to high grade nonchondrogenic sarcoma.

DESIGN.—

We analyzed the genomic landscape of paired conventional and dedifferentiated components of 11 dedifferentiated chondrosarcoma using targeted next-generation DNA sequencing with immunohistochemical validation. Clinical, radiographic, and pathologic features of tumors were reviewed. Capture-based DNA sequencing targeting the coding regions of 479 cancer genes and select introns was performed.

RESULTS.—

The tumors arose in the femur (n = 4; 36%), scapula (n = 3; 27%), pelvis (n = 3; 27%), and humerus (n = 1; 9%) of 7 men (64%) and 4 women (36%; median age, 61 years). DNA was adequate for sequencing from all 11 dedifferentiated components (100%) and 9 paired conventional chondrosarcoma components (82%). All tumors (100%) harbored either IDH1 p.R132 or IDH2 p.R172S hotspot mutations. Seven tumors (64%) displayed COL2A1 alterations. TERT promoter mutations were present in 5 of 9 pairs (56%) and 2 (22%) additional unpaired dedifferentiated components. IDH1/2, COL2A1, and TERT mutations were identical in both components of the paired samples. Pathogenic missense or truncating mutations in TP53 and large-scale copy number alterations were more common in dedifferentiated components than in those of matched conventional components.

CONCLUSIONS.—

The results support IDH1/2, COL2A1, and TERT promoter mutations being common in dedifferentiated chondrosarcoma and as likely early events in progression, whereas inactivating mutation of TP53 and high-level copy number alterations may be later events in the dedifferentiated phenotype.

Molecular epidemiology of IDH2 hotspot mutations in cancer and immunohistochemical detection of R172K, R172G, and R172M variants

IDH1/2 hotspot mutations occur in glioma, cholangiocarcinoma, chondrosarcoma, sinonasal carcinoma, and T-cell lymphoma and have diagnostic, prognostic, and/or therapeutic value. Availability of immunohistochemistry (IHC) protocols for specific IDH2 mutation detection is limited. A targeted exome sequencing assay MSK-IMPACT cohort comprising >38,000 cancer cases was explored for the presence of IDH1/2 mutations in solid malignancies and select T-cell lymphomas. Seventy-four formalin-fixed paraffin-embedded IDH1/2-mutated (n = 62) and wild-type (n = 12) samples were used for testing and optimization of anti-IDH2 monoclonal antibodies (mAbs) 14H7, 3C11, and MMab1 targeting R172K, R172G, and R172M mutant proteins, respectively. IDH1/2 mutations were common in glioma (26.8% and 1.6%), intrahepatic cholangiocarcinoma (23.1% and 5.7%), chondrosarcoma (19.4% and 10.7%), sinonasal undifferentiated/large-cell neuroendocrine carcinoma (0% and 84.2%), angioimmunoblastic T-cell lymphoma (0% and 22%), and peripheral T-cell lymphoma (0 and 5.1%). In other cancers, IDH2 mutations were rare. IDH2 R172 variants included R172K (39%), R172S (29%), R172W (12%), R172G (10%), R172M (5%), and R172T (4%). 14H7, 3C11, and MMab1 detected all IDH2 R172K, R172G, and R172M, respectively, and produced a crisp, granular cytoplasmic staining pattern. 3C11 was also positive in 5 of 6 IDH1 R132G mutants showing a homogeneous, smooth cytoplasmic staining. All 3 mAbs were negative in other IDH1/2 mutant or wild-type cases. IHC using mAbs 14H7, 3C11, and MMab1 can facilitate molecular diagnosis as a reliable, fast, and inexpensive alternative for specific IDH2 variant detection. Given the distinct distribution of IDH2 R172 mutations in cancers, these mAbs could also serve as useful pathologic diagnostic markers.

The epigenomics of sarcoma

Epigenetic regulation is critical to physiological control of development, cell fate, cell proliferation, genomic integrity and, fundamentally, transcriptional regulation. This epigenetic control occurs at multiple levels including through DNA methylation, histone modification, nucleosome remodelling and modulation of the 3D chromatin structure. Alterations in genes that encode chromatin regulators are common among mesenchymal neoplasms, a collection of more than 160 tumour types including over 60 malignant variants (sarcomas) that have unique and varied genetic, biological and clinical characteristics. Herein, we review those sarcomas in which chromatin pathway alterations drive disease biology. Specifically, we emphasize examples of dysregulation of each level of epigenetic control though mechanisms that include alterations in metabolic enzymes that regulate DNA methylation and histone post-translational modifications, mutations in histone genes, subunit loss or fusions in chromatin remodelling and modifying complexes, and disruption of higher-order chromatin structure. Epigenetic mechanisms of tumorigenesis have been implicated in mesenchymal tumours ranging from chondroblastoma and giant cell tumour of bone to chondrosarcoma, malignant peripheral nerve sheath tumour, synovial sarcoma, epithelioid sarcoma and Ewing sarcoma - all diseases that present in a younger patient population than most cancers. Finally, we review current and potential future approaches for the development of sarcoma therapies based on this emerging understanding of chromatin dysregulation.

Association of Clinicopathological Features With Outcome in Chondrosarcomas of the Head and Neck

OBJECTIVE

The aim of this study is to assess the association between clinical and radiological features as well as of isocitrate dehydrogenase 1 and 2 (IDH 1,2) mutations with outcome in head and neck chondrosarcomas.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

METHODS

Clinical, histological, and molecular data of patients with head and neck chondrosarcomas treated by surgery were collected.

RESULTS

Forty-six patients were included. The mean age at diagnosis was 56 years (range, 17-78). The tumor originated from the skull base (52.2%), facial bones (28.2%), or laryngotracheal area (19.6%). At last follow-up (median 52.5 months), 38 patients were alive, 30 of which were disease free, whereas 8 had died, 4 of disease progression and 4 of other causes. Fourteen (30.4%) had local recurrence and 2 (4.3%) had lung metastasis. All cases were negative for cytokeratin AE1/AE3, brachyury, and IDH1 at immunohistochemistry, while Sanger sequencing identified IDH1/2 point mutations, typically IDH1 R132C, in 9 (37.5%) tumors arising from the skull base. Margin infiltration on the surgical specimen negatively affected the outcome, whereas no correlation was identified with IDH mutation status.

CONCLUSIONS

An adequate margin positively affects survival. IDH mutation status does not affect patient outcome.

Phase I Study of the Mutant IDH1 Inhibitor Ivosidenib: Safety and Clinical Activity in Patients With Advanced Chondrosarcoma

PURPOSE

Surgery is the primary therapy for localized chondrosarcoma; for locally advanced and/or metastatic disease, no known effective systemic therapy exists. Mutations in the isocitrate dehydrogenase 1/2 (IDH1/2) enzymes occur in up to 65% of chondrosarcomas, resulting in accumulation of the oncometabolite D-2-hydroxyglutarate (2-HG). Ivosidenib (AG-120) is a selective inhibitor of mutant IDH1 approved in the United States for specific cases of acute myeloid leukemia. We report outcomes of patients with advanced chondrosarcoma in an ongoing study exploring ivosidenib treatment.

PATIENTS AND METHODS

This phase I multicenter open-label dose-escalation and expansion study of ivosidenib monotherapy enrolled patients with mutant IDH1 advanced solid tumors, including chondrosarcoma. Ivosidenib was administered orally (100 mg twice daily to 1,200 mg once daily) in continuous 28-day cycles. Responses were assessed every other cycle using RECIST (version 1.1).

RESULTS

Twenty-one patients (escalation, n = 12; expansion, n = 9) with advanced chondrosarcoma received ivosidenib (women, n = 8; median age, 55 years; range, 30-88 years; 11 had received prior systemic therapy). Treatment-emergent adverse events (AEs) were mostly grade 1 or 2. Twelve patients experienced grade ≥ 3 AEs; only one event was judged treatment related (hypophosphatemia, n = 1). Plasma 2-HG levels decreased substantially in all patients (range, 14%-94.2%), to levels seen in healthy individuals. Median progression-free survival (PFS) was 5.6 months (95% CI, 1.9 to 7.4 months); the PFS rate at 6 months was 39.5%. Eleven (52%) of 21 patients experienced stable disease.

CONCLUSION

In patients with chondrosarcoma, ivosidenib showed minimal toxicity, substantial 2-HG reduction, and durable disease control. Future studies of ivosidenib monotherapy or rational combination approaches should be considered in patients with advanced mutant IDH1 chondrosarcoma.