H3.3 K36M Mutation as a Clinical Diagnosis Method of Suspected Chondroblastoma Cases

Role of epigenetics in paediatric cancer pathogenesis & drug resistance

Paediatric oncogenesis is tightly intertwined with errors in developmental processes involving cell specification and differentiation, which are governed by intricate temporal epigenetic signals. As paediatric cancers are characterised by a low number of somatic mutations, dysregulated chromatin landscapes are believed to be key drivers of oncogenesis. Epigenetic dysregulation is induced by mutations and aberrant expression of histones and epigenetic regulatory genes, to altered DNA methylation patterns and dysregulated noncoding RNA expression. In this review, we discuss epigenetic alterations in paediatric cancer oncogenesis and recurrence, and their potential as diagnostic biomarkers. We also discuss various epigenetic drugs that have entered clinical trials for aggressive paediatric cancers. Targeting paediatric-specific epigenetic vulnerabilities may improve recurrence-free survival in high-risk cancers.

Methionine intervention induces PD-L1 expression to enhance the immune checkpoint therapy response in MTAP-deleted osteosarcoma

Osteosarcoma (OS), a malignant bone tumor with limited treatment options, exhibits low sensitivity to immune checkpoint therapy (ICT). Through genomics and transcriptomics analyses, we identify a subgroup of OS with methylthioadenosine phosphorylase (MTAP) deletion, which contributes to ICT resistance, leading to a "cold" tumor microenvironment. MTAP-deleted OS relies on methionine metabolism and is sensitive to methionine intervention, achieved through either dietary restriction or inhibition of methionine adenosyltransferase 2a (MAT2A), a key enzyme in methionine metabolism. We further demonstrate that methionine intervention triggers programmed death-ligand 1 (PD-L1) transcription factor IKAROS family zinc finger 1 (IKZF1) and enhances PD-L1 expression in MTAP-deleted OS cells. Methionine intervention also activates the immune-related signaling pathways in MTAP-deleted OS cells and attracts CD8+ T cells, thereby enhancing the efficacy of ICT. Combining methionine intervention with ICT provides a significant survival benefit in MTAP-deleted OS murine models, suggesting a rationale for combination regimens in OS ICT.

Disrupting YAP1-mediated glutamine metabolism induces synthetic lethality alongside ODC1 inhibition in osteosarcoma

PURPOSE

Osteosarcoma, a highly malignant primary bone tumor primarily affecting adolescents, frequently develops resistance to initial chemotherapy, leading to metastasis and limited treatment options. Our study aims to uncover novel therapeutic targets for metastatic and recurrent osteosarcoma.

METHODS

In this study, we proved the potential of modulating the YAP1-regulated glutamine metabolic pathway to augment the response of OS to DFMO. We initially employed single-cell transcriptomic data to gauge the activation level of polyamine metabolism in MTAP-deleted OS patients. This was further substantiated by transcriptome sequencing data from recurrent and non-recurrent patient tissues, confirming the activation of polyamine metabolism in progressive OS. Through high-throughput drug screening, we pinpointed CIL56, a YAP1 inhibitor, as a promising candidate for a combined therapeutic strategy with DFMO. In vivo, we utilized PDX and CDX models to validate the therapeutic efficacy of this drug combination. In vitro, we conducted western blot analysis, qPCR analysis, immunofluorescence staining, and PuMA experiments to monitor alterations in molecular expression, distribution, and tumor metastasis capability. We employed CCK-8 and colony formation assays to assess the proliferative capacity of cells in the experimental group. We used flow cytometry and reactive oxygen probes to observe changes in ROS and glutamine metabolism within the cells. Finally, we applied RNA-seq in tandem with metabolomics to identify metabolic alterations in OS cells treated with a DFMO and CIL56 combination. This enabled us to intervene and validate the role of the YAP1-mediated glutamine metabolic pathway in DFMO resistance.

RESULTS

Through single-cell RNA-seq data analysis, we pinpointed a subset of late-stage OS cells with significantly upregulated polyamine metabolism. This upregulation was further substantiated by transcriptomic profiling of recurrent and non-recurrent OS tissues. High-throughput drug screening revealed a promising combination strategy involving DFMO and CIL56. DFMO treatment curbs the phosphorylation of YAP1 protein in OS cells, promoting nuclear entry and initiating the YAP1-mediated glutamine metabolic pathway. This reduces intracellular ROS levels, countering DFMO's anticancer effect. The therapeutic efficacy of DFMO can be amplified both in vivo and in vitro by combining it with the YAP1 inhibitor CIL56 or the glutaminase inhibitor CB-839. This underscores the significant potential of targeting the YAP1-mediated glutamine metabolic pathway to enhance efficacy of DFMO.

CONCLUSION

Our findings elucidate YAP1-mediated glutamine metabolism as a crucial bypass mechanism against DFMO, following the inhibition of polyamine metabolism. Our study provides valuable insights into the potential role of DFMO in an "One-two Punch" therapy of metastatic and recurrent osteosarcoma.

Roles of Histone H2B, H3 and H4 Variants in Cancer Development and Prognosis

Histone variants are the paralogs of core histones (H2A, H2B, H3 and H4). They are stably expressed throughout the cell cycle in a replication-independent fashion and are capable of replacing canonical counterparts under different fundamental biological processes. Variants have been shown to take part in multiple processes, including DNA damage repair, transcriptional regulation and X chromosome inactivation, with some of them even specializing in lineage-specific roles like spermatogenesis. Several reports have recently identified some unprecedented variants from different histone families and exploited their prognostic value in distinct types of cancer. Among the four classes of canonical histones, the H2A family has the greatest number of variants known to date, followed by H2B, H3 and H4. In our prior review, we focused on summarizing all 19 mammalian histone H2A variants. Here in this review, we aim to complete the full summary of the roles of mammalian histone variants from the remaining histone H2B, H3, and H4 families, along with an overview of their roles in cancer biology and their prognostic value in a clinical context.

Immunohistochemistry Update in Dermatopathology and Bone and Soft Tissue Pathology

CONTEXT.—

Immunohistochemistry plays an important role in dermatopathology, particularly for melanocytic lesions and poorly differentiated malignancies. In the field of bone and soft tissue pathology, molecular methods remain the gold standard for diagnosis; however, immunohistochemistry targeting underlying molecular alterations represents a valuable screening tool, especially in areas with limited access to molecular testing.

OBJECTIVE.—

To describe the utility and limitations of new and emerging immunohistochemical stains in the diagnosis of skin, soft tissue, and bone tumors.

DATA SOURCES.—

A literature review of recently described immunohistochemical stains in the fields of dermatopathology and bone and soft tissue pathology was performed.

CONCLUSIONS.—

Immunohistochemistry is an important adjunctive tool for select entities in dermatopathology and bone and soft tissue pathology, and it provides pathologists with valuable evidence of their behavior, underlying molecular alterations, and line of differentiation. Furthermore, immunostains targeting molecular abnormalities have the potential to replace current molecular methods. Many of these recently described stains demonstrate higher sensitivity and specificity; however, limitations and pitfalls still exist, and correlation with morphologic and clinical findings remains essential for diagnosis.

Chondroblastoma of Thoracic Vertebrae: a Case Report and Review of the Literature

Chondroblastoma is a rare benign cartilaginous bone tumor typically seen at the epiphysis of long axial bones. In this regard, there are rare findings about spinal chondroblastomas. We report a 29-year-old man with T1 vertebral chondroblastoma misdiagnosed with a traumatic fracture following an accident. The patient was admitted to our clinic with a chief complaint of axial back pain and kyphosis following posterior spinal fixation. We report his clinical and imaging data before his past operation and at this admission. Our patient underwent a two-stage operation. In the first stage, posterior spinal reconstruction and kyphosis correction was performed. In the second stage, mass resection was performed anteriorly in the T1 vertebral body as much as possible. The results confirmed the chondroblastoma diagnosis histologically. Our patient remained symptom-free with no growth in tumor remnant during 6 months follow-up. Although vertebral chondroblastoma is a sporadic tumor, it should be considered in the differential diagnosis when facing a vertebral infiltrative osteolytic mass, even when mimicking a traumatic fracture after the accident. In addition, histological confirmation is necessary under such conditions. We also reviewed the literature's clinical presentations, imaging findings, and treatments of 34 case reports with vertebral chondroblastoma.

Utility of immunohistochemical expression of H3.3K36M and DOG1 in the diagnosis of chondroblastomas: An experience from a tertiary cancer referral center

Despite its characteristic clinicopathological features, chondroblastoma may pose a diagnostic challenge, given its morphological spectrum, potential for subdiagnostic appearances in limited biopsy specimens, and its potential mimicry of other entities. Recently, a characteristic H3F3B mutation underlying most chondroblastomas was described, which led to the identification of H3.3K36M as the corresponding diagnostic immunohistochemical marker. The present study is an evaluation of immunohistochemical features of 26 chondroblastomas, including DOG1 and H3.3K36M immunostaining. H3.3K36M immunostaining was graded as 1+, 2+ and 3+ in terms of staining intensity. There were 17 males and 9 females (M:F = 1.8:1) with ages ranging from 7 to 34 years (average = 16.7, median = 16). The most common location was proximal humerus (8, 30.7 %) followed by proximal tibia (5, 19.2 %), distal femur (3, 11.5 %), proximal femur (3, 11.5 %), pelvis (2,), followed by distal tibia, calcaneum, upper sternum, scapula, and D9 vertebra, in a single case, respectively. Eighteen (69.23 %) tumors displayed all the classic histopathological features. Immunohistochemically, the tumor cells were positive for S-100 P (19/22, 86.3 %), DOG1 (focal to patchy) (21/23 91.3 %), and H3.3K36M (26/26, 100 %). H3.3K36M tested in other tumors, constituting diagnostic mimics of a chondroblastoma, such as giant cell tumor of bone, chondromyxoid fibroma, and tenosynovial giant cell tumors, showed negative staining. Six tumors, initially diagnosed as chondroblastomas were reclassified into other entities with the help of negative H3.3K36M immunostaining. The present study reinforces H3.3K36M as a highly sensitive and specific marker for diagnosing chondroblastoma, including small biopsies, and in uncommon tumor sites with variable histopathological features. DOG1 is also useful in reinforcing a diagnosis of chondroblastoma in a clinicoradiological context, especially in laboratories lacking H3.3K36M immunostain. However, its staining pattern is variable.

Chondroblastoma of foot bones; a clinicopathological study of 29 cases confirming the diagnostic utility of H3K36M and H3G34W antibodies at an uncommon site

OBJECTIVE

Chondroblastoma (CB) is a benign cartilaginous bone neoplasm which commonly occurs in long bones of adolescents. CB can uncommonly involve foot. Its mimics include both benign and malignant lesions. H3K36M immunohistochemical (IHC) stain is a helpful tool for establishing the diagnosis of CB in such challenging situations. In addition, H3G34W IHC stain helps to rule out giant cell tumor which is the closest differential of CB. Our objective was to describe the clinicopathological features and frequencies of H3K36M, H3G34W and SATB2 IHC stains in CB of foot.

MATERIALS AND METHODS

We reviewed H&E slides and blocks of 29 cases diagnosed as "chondroblastoma" of foot at our institutions.

RESULTS

Patient's age ranged from 6 to 69 (mean: 23.3 and median: 23) years. Males were almost 5 times more commonly affected than females. Talus and calcaneum were involved in 13 (44.8 %) cases each. Microscopically, tumors were composed of polygonal mononuclear cells and multinucleated giant cells and chondroid matrix. Other histological features included aneurysmal bone cyst-like (ABC-like) change (44.8 %), osteoid matrix (31 %), chicken-wire calcification (20.7 %), and necrosis (10.3 %). H3K36M was expressed in 100 % and SATB2 in 91.7 % cases. H3G34W was negative in all cases, where performed. One out of 11 patients with follow up information developed local recurrence after 48 months.

CONCLUSION

CB in foot occur at an elder age and show more frequent ABC-like changes as compared to long bones. Males are affected ~5:1 as compared to 2:1 in long bones. H3K36M are H3G34W are extremely useful diagnostic markers for CB, especially elderly (aged or higher) patients and we report the largest series of foot CB cases confirmed by immunohistochemistry.

Metaphyseal chondroblastoma in a pediatric patient

Chondroblastoma is a rare, benign neoplasm usually located in the epiphyses and apophyses of the long bones in the immature skeleton. Radiologically, these tumors have a classic appearance of a lytic lesion with chondroid matrix surrounded by a thin sclerotic rim. Here, we describe the case of a 5-year-old male who presented with a chondroblastoma unusually located exclusively in the metaphyseal region, which led to an elusive diagnosis. The presence of tumors outlying the traditional location or epidemiological spectrum, along with the potential for histopathological misdiagnosis, can pose a diagnostic and therapeutic challenge for the treating team.

Anti-histone H3.3K36M Antibody is a Highly Sensitive and Specific Immunohistochemistry Marker for the Diagnosis of Chondroblastoma. A Validation Based on Study 136 Cases Comprising Chondroblastoma and its Mimics from Single a Centre in India

Introduction: Chondroblastoma has a wide range of differential diagnosis encompassing various benign and malignant entities. The closest differential diagnosis is giant cell tumor of the bone due to overlapping radiological and histomorphological features. Extensive aneurysmal bone cyst like changes and lack of adequately sampled chondroid matrix often masquerades the primary bone lesion and amplifies the diagnostic difficulty in small biopsies with limited tissue. Immunohistochemistry is helpful in such instances to resolve the diagnostic dilemma. Objectives: To analyze the immunohistochemical expression of anti-histone H3F3K36M antibody inchondroblastoma and validate its utility in differentiating chondroblastomafrom its histological mimics. Material and methods: Immunohistochemistry was performed using anti-histone antibody H3.3K36M in 44 histologically diagnosed chondroblastoma and 92 other histological mimickers. All chondroblastoma and giant cell tumor of the bone included in the study were also tested for anti-histone H3.3 G34W antibody. Of the 33 giant cell tumors of bone with classic morphology and imaging findings, 24 H3.3 G34W positive and 9 negative tumors were included intentionally to rule out the possibility of chondroblastoma. The sensitivity, specificity, positive and negative predictive value of marker with regard to chondroblastoma was calculated. Results: Immunohistochemistry revealed unequivocal nuclear positivity for H3.3K36M in the mononuclear cells in all the 44 Chondroblastoma tested, denoting a sensitivity of 100% cases. Allthesetumors tested simultaneously for anti-histone H3.3G34W were negative. None of the histological mimickers were positive H3.3K36M indicating a specificity of 100%. The positive and negative predictive value was 100%. Conclusion: H3.3K36M mutant antibody is highly sensitive and specific IHC marker and can be used as a valuable adjunct to distinguish chondroblastomafrom its histological mimics especially on small biopsies.