Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma and includes a PAX3- or PAX7-FOXO1 fusion-positive subtype. Amplification of chromosomal region 12q13-q14, which contains the ...CDK4 proto-oncogene, was identified in an aggressive subset of fusion-positive RMS. CDK4/6 inhibitors have antiproliferative activity in CDK4-amplified liposarcoma and neuroblastoma, suggesting CDK4/6 inhibition as a potential therapeutic strategy in fusion-positive RMS.
We examined the biologic consequences of CDK4 knockdown, CDK4 overexpression, and pharmacologic CDK4/6 inhibition by LEE011 in fusion-positive RMS cell lines and xenografts.
Knockdown of CDK4 abrogated proliferation and transformation of 12q13-14-amplified and nonamplified fusion-positive RMS cells via G1-phase cell-cycle arrest. This arrest was mediated by reduced RB phosphorylation and E2F-responsive gene expression. Significant differences in E2F target expression, cell-cycle distribution, proliferation, or transformation were not observed in RMS cells overexpressing CDK4. Treatment with LEE011 phenocopied CDK4 knockdown, decreasing viability, RB phosphorylation, and E2F-responsive gene expression and inducing G1-phase cell-cycle arrest. Although all fusion-positive cell lines showed sensitivity to CDK4/6 inhibition, there was diminished sensitivity associated with CDK4 amplification and overexpression. This variable responsiveness to LEE011 was recapitulated in xenograft models of CDK4-amplified and nonamplified fusion-positive RMS.
Our data demonstrate that CDK4 is necessary but overexpression is not sufficient for RB-E2F-mediated G1-phase cell-cycle progression, proliferation, and transformation in fusion-positive RMS. Our studies indicate that LEE011 is active in the setting of fusion-positive RMS and suggest that low CDK4-expressing fusion-positive tumors may be particularly susceptible to CDK4/6 inhibition.
Primary cutaneous follicle center lymphoma has been distinguished from nodal follicular lymphoma (FL) based on genomic and clinical features. The nature of other extranodal FLs is not well defined. ...We report 15 cases of follicle center lymphoma involving the lower female genital tract. Cases were evaluated using an immunohistochemical panel for B-cell lymphoma, B-cell clonality, fluorescence in situ hybridization for BCL2 gene rearrangement, and next-generation sequencing. All patients had localized disease with no evidence of bone marrow involvement. Most cases (12/15, 80%) had a follicular pattern, at least focally. Large centrocytes were a prominent feature leading to concern for diffuse large B-cell lymphoma by referring pathologists. Neoplastic cells were positive for CD20 and BCL-6, while BCL-2 was positive in 2/15 (13%) cases. Fluorescence in situ hybridization for BCL2 gene rearrangement was negative in 10/11 (91%) cases. Next-generation sequencing performed in 10 cases revealed TNFRSF14 as the most frequently mutated gene in 6/10 (60%) cases. No case had CREBBP or KMT2D mutations as seen in nodal FL. None of the patients had progressive disease with durable complete remission achieved in 10/12 (83%) cases. The median follow-up period was 7.8 years (range: 0.2 to 20.5 y) with a 5-year overall survival of 100%. We conclude that follicle center lymphoma of the lower female genital tract is a novel variant of primary cutaneous follicle center lymphoma. Despite a frequent component of large cells, it is characterized by localized disease and low risk for dissemination. Awareness and recognition are important to distinguish these lesions from aggressive B-cell lymphomas.
ERG transcription factor is constitutively expressed in endothelial cells. Because benign and malignant vascular endothelia retain the ERG expression, ERG is considered a useful marker for ...angiosarcomas and related tumors. ERG is also expressed in a subset of prostate carcinomas and Ewing sarcomas due to ERG-involved translocations; therefore, this marker is also of high interest in the study of these malignancies. In this study, we evaluated 109 epithelioid sarcomas for ERG expression, on the basis of an initial observation of an ERG-positive case. We also studied expression of other endothelial antigens in epithelioid sarcoma. ERG was expressed in 38% of epithelioid sarcomas (41/109), usually with a uniform nuclear staining, similar to that seen in angiosarcomas. However, all epithelioid sarcomas were negative for ERG gene rearrangement indicating that ERG expression is not likely related to ERG-involving translocations in epithelioid sarcoma. Other endothelial markers, CD31, claudin 5, and Prox1, were absent in epithelioid sarcomas. The only exception was a pulmonary metastasis of epithelioid sarcoma showing focal CD31 expression, which probably resulted from antigen adsorption onto tumor cell surfaces. However, podoplanin was commonly (7/9) expressed in epithelioid sarcoma; therefore, this marker is not useful in distinguishing epithelioid sarcoma from angiosarcoma. INI1/SMARCB1 gene product was absent in all epithelioid sarcomas (considered here a definitional feature) but was absent from only 1 epithelioid angiosarcoma, indicating its relative specificity for epithelioid sarcoma in this differential diagnostic setting. ERG expression is fairly common in epithelioid sarcoma and should be recognized as a diagnostic pitfall in the differential diagnosis of epithelioid sarcoma and epithelioid angiosarcoma. General lack of endothelial cell–specific markers in epithelioid sarcoma helps in this distinction.
Adverse prognosis in Ewing sarcoma (ES) is associated with the presence of metastases, particularly in bone, tumor hypoxia and chromosomal instability (CIN). Yet, a mechanistic link between these ...factors remains unknown. We demonstrate that in ES, tumor hypoxia selectively exacerbates bone metastasis. This process is triggered by hypoxia-induced stimulation of the neuropeptide Y (NPY)/Y5 receptor (Y5R) pathway, which leads to RhoA over-activation and cytokinesis failure. These mitotic defects result in the formation of polyploid ES cells, the progeny of which exhibit high CIN, an ability to invade and colonize bone, and a resistance to chemotherapy. Blocking Y5R in hypoxic ES tumors prevents polyploidization and bone metastasis. Our findings provide evidence for the role of the hypoxia-inducible NPY/Y5R/RhoA axis in promoting genomic changes and subsequent osseous dissemination in ES, and suggest that targeting this pathway may prevent CIN and disease progression in ES and other cancers rich in NPY and Y5R.
Abstract
Background
Pheochromocytoma and paraganglioma (PPGL) are neuroendocrine tumors with frequent mutations in genes linked to the tricarboxylic acid cycle. However, no pathogenic variant has ...been found to date in succinyl-CoA ligase (SUCL), an enzyme that provides substrate for succinate dehydrogenase (SDH; mitochondrial complex II CII), a known tumor suppressor in PPGL.
Methods
A cohort of 352 patients with apparently sporadic PPGL underwent genetic testing using a panel of 54 genes developed at the National Institutes of Health, including the SUCLG2 subunit of SUCL. Gene deletion, succinate levels, and protein levels were assessed in tumors where possible. To confirm the possible mechanism, we used a progenitor cell line, hPheo1, derived from a human pheochromocytoma, and ablated and re-expressed SUCLG2.
Results
We describe 8 germline variants in the guanosine triphosphate–binding domain of SUCLG2 in 15 patients (15 of 352, 4.3%) with apparently sporadic PPGL. Analysis of SUCLG2-mutated tumors and SUCLG2-deficient hPheo1 cells revealed absence of SUCLG2 protein, decrease in the level of the SDHB subunit of SDH, and faulty assembly of the complex II, resulting in aberrant respiration and elevated succinate accumulation.
Conclusions
Our study suggests SUCLG2 as a novel candidate gene in the genetic landscape of PPGL. Large-scale sequencing may uncover additional cases harboring SUCLG2 variants and provide more detailed information about their prevalence and penetrance.
We report a novel group of clinically aggressive spinal cord ependymomas characterized by Grade III histology, MYCN amplification, an absence of NF2 alterations or other recurrent pathogenic ...mutations, and a unique methylation classifier profile. Seven cases were found to have MYCN amplification in the course of routine mutational profiling of 552 patients with central nervous system tumors between December 2016 and July of 2019 and an eighth patient was identified from an unrelated set of cases. Methylation array analysis revealed that none of the 8 cases clustered with any of the nine previously described ependymoma methylation subgroups, and 7 of 8 formed their own tight unique cluster. Histologically all cases showed grade III features, and all demonstrated aggressive clinical behavior. These findings are presented in the context of data from three other studies describing similar cases. Therefore, a combined total of 27 MYCN amplified spinal cord ependymoma cases have now been reported in the literature, warranting their consideration as a distinctive subtype of spinal cord ependymoma (SP-EPN-MYCN) with their unique molecular characteristics and aggressive clinical behavior. Keywords: Spinal cord ependymoma, MYCN amplification, Next generation sequencing, Methylation classifier
Summary
Peripheral T‐cell lymphomas (PTCL) are morphologically and biologically heterogeneous and a subset expresses CD30, including anaplastic large cell lymphomas (ALCL) and a minority of PTCL, not ...otherwise specified (PTCL, NOS). ALCL with ALK translocations (ALCL, ALK+) are readily identified by routine diagnostic methods, but differentiating ALCL without ALK translocation (ALCL, ALK−) and PTCL, NOS expressing CD30 (PTCL CD30+) can be challenging. Furthermore, rare PTCL co‐express CD30 and CD15 (PTCL CD30+CD15+); some resemble ALCL, ALK− while others resemble classic Hodgkin lymphoma. To explore the relationship between PTCL CD30+CD15+ and ALCL, ALK−, we analysed 19 cases of PTCL with CD30 expression, previously diagnosed as ALCL, ALK− (nine cases) and PTCL CD30+CD15+ (10 cases) for DUSP22/IRF4 rearrangements, coding RNA expression and selected transcriptome analysis using the NanoString nCounter gene expression analysis platform. Unsupervised clustering showed no clear segregation between ALCL, ALK− and PTCL CD30+CD15+. Three cases previously classified as PTCL CD30+CD15+ showed DUSP22/IRF4 rearrangements, favouring a diagnosis of ALCL, ALK−. Our results suggest that cases previously designated PTCL CD30+CD15+, likely fall within the spectrum of ALCL, ALK−; additionally, a subset of ALCL, ALK− with DUSP22/IRF4 rearrangement expresses CD15, consistent with previous reports and expands the immunophenotypic spectrum of this lymphoma subgroup.
Peripheral T‐cell lymphomas expressing diffuse CD30 and variable CD15 share genomic features with anaplastic large cell lymphoma, ALK−. A subset of these cases shows DUSP22 rearrangements. Cases initially described as PTCL with CD30 and CD15 expression are best classified as anaplastic large cell lymphoma, ALK−.
Epstein-Barr virus (EBV)-positive plasmacytoma is a rare plasma cell neoplasm. It remains unclear whether EBV-positive plasmacytoma represents a distinct entity or a variant of plasmacytoma. It ...shares morphologic features with plasmablastic lymphoma (PBL) and may cause diagnostic uncertainty. To better understand EBV-positive plasmacytoma and explore diagnostic criteria, this study describes 19 cases of EBV-positive plasmacytoma, compared with 27 cases of EBV-negative plasmacytoma and 48 cases of EBV-positive PBL. We reviewed the clinicopathologic findings and performed immunohistochemistry, in situ hybridization for EBV, fluorescence in situ hybridization for MYC , and next-generation sequencing. We found that 63.2% of patients with EBV-positive plasmacytoma were immunocompromised. Anaplastic features were observed in 7/19 cases. MYC rearrangement was found in 25.0% of them, and extra copies of MYC in 81.3%. EBV-positive and EBV-negative plasmacytomas possessed similar clinicopathologic features, except more frequent cytologic atypia, bone involvement and MYC aberrations in the former group. The survival rate of patients with EBV-positive plasmacytoma was comparable to that of patients with EBV-negative plasmacytoma. In comparison to PBL, EBV-positive plasmacytoma is less commonly associated with a "starry-sky" appearance, necrosis, absence of light chain expression, and a high Ki67 index (>75%). The most recurrently mutated genes/signaling pathways in EBV-positive plasmacytoma are epigenetic regulators, MAPK pathway, and DNA damage response, while the most frequently reported mutations in PBL are not observed. Collectively, EBV-positive plasmacytoma should be regarded as a biological variant of plasmacytoma. Thorough morphologic examination remains the cornerstone for distinguishing EBV-positive plasmacytoma and PBL, and molecular studies can be a valuable complementary tool.
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