Kinase fusion positive intra-osseous spindle cell tumors: A series of eight cases with review of the literature.

Mesenchymal spindle cell tumors with kinase fusions, often presenting in superficial or deep soft tissue locations, may rarely occur in bone. Herein, we describe the clinicopathologic and molecular data of eight bone tumors characterized by various kinase fusions from our files and incorporate the findings with the previously reported seven cases, mainly as single case reports. In the current series all but one of the patients were young children or teenagers, with an age range from newborn to 59 years (mean 19 years). Most tumors (n = 5) presented in the head and neck area (skull base, mastoid, maxilla, and mandible), and remaining three in the tibia, pelvic bone, and chest wall. The fusions included NTRK1 (n = 3), RET (n = 2), NTRK3 (n = 2), and BRAF (n = 1). In the combined series (n = 15), most tumors (73%) occurred in children and young adults (<30 years) and showed a predilection for jaw and skull bones (40%), followed by long and small tubular bones (33%). The fusions spanned a large spectrum of kinase genes, including in descending order NTRK3 (n = 6), NTRK1 (n = 4), RET (n = 2), BRAF (n = 2), and RAF1 (n = 1). All fusions confirmed by targeted RNA sequencing were in-frame and retained the kinase domain within the fusion oncoprotein. Similar to the soft tissue counterparts, most NTRK3-positive bone tumors in this series showed high-grade morphology (5/6), whereas the majority of NTRK1 tumors were low-grade (3/4). Notably, all four tumors presenting in the elderly were high-grade spindle cell sarcomas, with adult fibrosarcoma (FS)-like, malignant peripheral nerve sheath tumor (MPNST)-like and MPNST phenotypes. Overall, 10 tumors had high-grade morphology, ranging from infantile and adult-types FS, MPNST-like, and MPNST, whereas five showed benign/low-grade histology (MPNST-like and myxoma-like). Immunohistochemically (IHC), S100 and CD34 positivity was noted in 57% and 50%, respectively, while co-expression of S100 and CD34 in 43% of cases. One-third of tumors (4 high grade and the myxoma-like) were negative for both S100 and CD34. IHC for Pan-TRK was positive in all eight NTRK-fusion positive tumors tested and negative in two tumors with other kinase fusions. Clinical follow-up was too limited to allow general conclusions.

Role of catecholamine synthases in the maintenance of cancer stem-like cells in malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors that are derived from Schwann cell lineage around peripheral nerves. As in many other cancer types, cancer stem cells (CSCs) have been identified in MPNSTs, and they are considered the cause of treatment resistance, recurrence, and metastasis. As an element defining the cancer stemness of MPNSTs, we previously reported a molecular mechanism by which exogenous adrenaline activates a core cancer stemness factor, YAP/TAZ, through ß2 adrenoceptor (ADRB2). In this study, we found that MPNST cells express catecholamine synthases and that these enzymes are essential for maintaining cancer stemness, such as the ability to self-renew and maintain an undifferentiated state. Through gene knockdown and inhibition of these enzymes, we confirmed that catecholamines are indeed synthesized in MPNST cells. The results confirmed that catecholamine synthase knockdown in MPNST cells reduces the activity of YAP/TAZ. These data suggest that a mechanism of YAP/TAZ activation by de novo synthesized adrenaline, as well as exogenous adrenaline, may exist in the maintenance of cancer stemness of MPNST cells. This mechanism not only helps to understand the pathology of MPNST, but could also contribute to the development of therapeutic strategies for MPNST.

Contemporary surgical management of pediatric non-rhabdomyosarcoma soft tissue sarcoma.

Non-rhabdomyosarcoma soft tissue sarcoma (STS) comprises most STS in pediatric patients. It is a diverse set of over 30 histologic subtypes. Treatment is based on risk group determined by tumor size, grade, and the presence of metastases. Surgical resection is a cornerstone of therapy, as tumors are often resistant to chemotherapy or radiation. While patients with isolated tumors less than 5 cm may undergo upfront resection, strong consideration should be given to neoadjuvant chemoradiotherapy to ensure negative margins at surgical resection and optimal outcomes. Sentinel lymph node biopsy is strongly recommended for clear cell and epithelioid sarcomas. The most common metastatic site is the lung, and metastases should be resected at the end of therapy, when feasible. Unfortunately, many high-risk patients progress on therapy, and alternative strategies including earlier metastatic control require investigation.

Association of plexiform and diffuse neurofibromas with malignant peripheral nerve sheath tumor in NF I patients: a whole-body MRI assessment.

OBJECTIVE: The aim of this study is to evaluate neurofibromatosis type 1 (NF1) patients with whole-body MRI (WBMRI) to investigate the frequency of plexiform neurofibromas (pNFs), diffuse neurofibromas (dNFs), and malignant peripheral nerve sheath tumors (MPNSTs). MATERIALS AND METHODS: In this retrospective cross-sectional study, between the years 2015 and 2023, 83 consecutive patients with known NF1 underwent a total of 110 WBMRI screenings for MPNST using a standardized institutional protocol. The lesions are categorized as discrete lesions, pNFs, dNFs, and MPNSTs. Histopathology served as the reference standard for all MPNSTs. RESULTS: Among the 83 patients analyzed, 53 (64%) were women and 30 were men (36%) of ages 36.94±14.43 years (range, 15-66 years). Of the 83 patients, 33 have a positive family history of NF1 and positive genetic studies. Seven of 83 (8%) have only dNF, 20/83 (24%) have pNF, 28/83 (34%) have both dNF and pNF, and 28/83 (34%) have neither. Of the 83 patients, eight (9.6%) were diagnosed with nine total MPNSTs. Age range for patients with MPNSTs at time of diagnosis was 22-51, with an average age of 33.4 years. Only one MPNST (11%) developed from underlying pNF 4 years after WBMRI along the right bronchial tree. Three of eight (37.5%) patients with MPNST died within 5 years of pathologic diagnosis. CONCLUSION: This study suggests the absence of a predisposition for development of MPNST from pNFs and dNFs in the setting of NF1. As such, these lesions may not need special surveillance compared to discrete peripheral nerve sheath tumors.

Coefficient of variation of T2-weighted MRI may predict the prognosis of malignant peripheral nerve sheath tumor.

BACKGROUND: We investigated whether non-enhancement MRI features, including measurement of the heterogeneity of the tumor with MR T2 imaging by calculating coefficient of variation (CV) values, were associated with the prognosis of non-metastatic malignant peripheral nerve sheath tumors (MPNST). METHODS: This retrospective study included 42 patients with MPNST who had undergone surgical resection (mean age, 50 years ± 21; 20 male participants). Non-enhancement MR images were evaluated for signal intensity heterogeneity on T1- and T2-weighted imaging, tumor margin definition on T1- and T2-weighted imaging, peritumoral edema on T2-weight imaging, and CV. We measured the signal intensities of MR T2-weighted images and calculated the corresponding CV values. CV is defined as the ratio of the standard deviation to the mean. The associations between factors and overall survival (OS) were investigated via the Kaplan-Meier method with log-rank tests and the Cox proportional hazards model. RESULTS: The mean CV value of MR T2 images was 0.2299 ± 0.1339 (standard deviation) (range, 0.0381-0.8053). Applying receiver operating characteristics analysis, the optimal cut-off level for CV value was 0.137. This cut-off CV value was used for its stratification into high and low CV values. At multivariate survival analysis, a high CV value (hazard ratio = 3.63; 95% confidence interval = 1.16-16.0; p = 0.047) was identified as an independent predictor of OS. CONCLUSION: The CV value of the signal intensity of heterogenous MPNSTs MR T2-weighted images is an independent predictor of patients' OS.

Imaging findings of type I neurofibromatosis with outcome of malignant peripheral nerve sheath tumor in the right lower extremity.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder caused by mutations of the NF1 tumor suppressor gene, characterized by café-au-lait spots, neurofibromas, and Lisch nodules. Malignant peripheral nerve sheath tumor (MPNST) is an extremely rare malignancy with neural differentiation potential. The lifetime risk of developing MPNST in NF-1 patients is 8%-13%.

Malignant triton tumor of uterus: A case report and literature review.

Malignant triton tumor (MTT) is a highly aggressive malignant neoplasm, classified as a variant of malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation. There are few reports that MTT occurred in urogenital system. In the present study, we report the first MTT occurring in the uterus. A 57-year-old woman came to the emergency department due to persistent vaginal bleeding for 2 months. The gynecological palpation found that a club-shaped excrescence existed in the vagina about 7 cm × 3 cm × 3 cm. The mass located in the lower segment of the uterus and the cervix was confirmed by gynecological vaginal ultrasound and magnetic resonance imaging, which was preliminarily diagnosed as cervical carcinoma. After neoplasm punch biopsy, the pathological diagnosis was malignant triton tumor. The patient finally lost follow-up. This is the first report about MTT in the uterus and suggests that pathological biopsy combined with imaging examination is necessary for the diagnosis of rarely MTT.

Dramatic response to entrectinib in a patient with malignant peripheral nerve sheath tumor harboring novel SNRNP70-NTRK3 fusion gene.

Neurotropic tropomyosin receptor kinase (NTRK) gene rearrangements have been reported in limited cases of sarcomas; however, to date, there has been only one report of such rearrangements in malignant peripheral nerve sheath tumors (MPNSTs). Herein, we describe a 51-year-old male patient with a buttock tumor arising from the sciatic nerve, which was diagnosed as MPNST with positive S-100 staining, negative SOX10 staining, and loss of trimethylation at lysine 27 of histone H3 (H3K27me3) confirmed by immunohistochemistry. Soon after the resection of the primary tumor, the patient was found to have pulmonary and lymph node metastases. Chemotherapy with eribulin and trabectedin showed limited effects. However, the patient responded rapidly to pazopanib, but severe side effects caused discontinuation of the treatment. RNA panel testing revealed a novel fusion gene between Small Nuclear Ribonucleoprotein U1 Subunit 70 (SNRNP70) gene and NTRK3 gene. Furthermore, loss of NF1, SUZ12, and CDKN2A genes was confirmed by DNA panel testing, which is compatible with a histological diagnosis of MPNST. SNRNP70 possesses a coiled-coiled domain and seems to induce constitutive activation of NTRK3 through dimerization. In fact, immunohistochemistry revealed diffuse staining of pan-TRK within tumor cells. Treatment with entrectinib, which is an NTRK inhibitor, showed a quick and durable response for 10 months. Although NTRK rearrangements are very rare in MPNST, this case highlights the importance of genetic testing in MPNST, especially using an RNA panel for the detection of rare fusion genes.

Integrating analysis of proteome profile and drug screening identifies therapeutic potential of MET pathway for the treatment of malignant peripheral nerve sheath tumor.

BACKGROUND: Malignant peripheral nerve sheath tumor (MPNST) is an aggressive sarcoma with a poor prognosis that requires novel therapeutic agents. Proteome information is useful for identifying new therapeutic candidates because it directly reflects the biological phenotype. Additionally, in vitro drug screening is an effective tool to identify candidate drugs for common cancers. Hence, we attempted to identify novel therapeutic candidates for MPNST by integrating proteomic analysis and drug screening. METHODS: We performed comprehensive proteomic analysis on 23 MPNST tumor samples using liquid chromatography - tandem mass spectrometry to identify therapeutic targets. We also conducted drug screening of six MPNST cell lines using 214 drugs. RESULTS: Proteomic analysis revealed that the MET and IGF pathways were significantly enriched in the local recurrence/distant metastasis group of MPNST, whereas drug screening revealed that 24 drugs showed remarkable antitumor effects on the MPNST cell lines. By integrating the results of these two approaches, MET inhibitors, crizotinib and foretinib, were identified as novel therapeutic candidates for the treatment of MPNST. CONCLUSIONS: We successfully identified novel therapeutic candidates for the treatment of MPNST, namely crizotinib and foretinib, which target the MET pathway. We hope that these candidate drugs will contribute to the treatment of MPNST.

Characterizing T-cell dysfunction and exclusion signatures in malignant peripheral nerve sheath tumors reveals susceptibilities to immunotherapy.

PURPOSE: Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors that arise from peripheral nerves and are the leading cause of mortality in Neurofibromatosis Type 1 (NF1). In this study, we characterized whether transcriptomic signatures of T-cell dysfunction (TCD) and exclusion (TCE) that inversely correlate with response to immune checkpoint blockade (ICB) immunotherapy exist in MPNSTs. METHODS: MPNST transcriptomes were pooled from Gene Expression Omnibus (GEO). For each sample, a tumor immune dysfunction and exclusion (TIDE) score, TCD and TCE subscores, and cytotoxic T-cell(CTL) level were calculated. In the TIDE predictive algorithm, tumors are predicted to have an ICB response if they are either immunologically hot (CTL-high) without TCD or immunologically cold (CTL-low) without TCE. TIDE scores greater than zero correspond with ICB nonresponse. RESULTS: 73 MPNST samples met inclusion criteria, including 50 NF1-associated MPNSTs (68.5%). The average TIDE score was + 0.41 (SD = 1.16) with 22 (30.1%) predicted ICB responders. 11 samples were CTL-high (15.1%) with an average TCD score of + 0.99 (SD = 0.63). Among 62 CTL-low tumors, 21 were predicted to have ICB response with an average TCE score of + 0.31(SD = 1.20). Age(p = 0.18), sex(p = 0.41), NF1 diagnosis (p = 0.17), and PRC2 loss(p = 0.29) were not associated with ICB responder status. CONCLUSIONS: Transcriptomic analysis of TCD and TCE signatures in MPNST samples reveals that a select subset of patients with MPNSTs may benefit from ICB immunotherapy.

Management of Central and Peripheral Nervous System Tumors in Patients with Neurofibromatosis.

Neurofibromatosis type I (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis represent a diverse group of genetic tumor predisposition syndromes with a shared feature of tumors affecting the peripheral nerve sheaths. PURPOSE OF REVIEW: Many advancements have been made in understanding the biologic underpinnings of these conditions, and in 2016 the first drug was approved by the FDA to treat pediatric symptomatic unresectable plexiform neurofibromas. RECENT FINDINGS: Mek inhibitors have provided a much-needed therapeutic avenue for NF1 patients with unresectable plexiform neurofibromas (PN), both for reduction of tumor bulk and for improvement in symptoms. Selumetinib is the first FDA approved drug for PN, but is only approved for children. Some research suggests that alternative Mek inhibitors and other mixed tyrosine kinase inhibitors may have better efficacy in adults. Vascular endothelial growth factor (VEGF) inhibitor bevacizumab can prolong hearing and delay the need for surgery in NF2 patients with bilateral vestibular schwannomas. This article provides an update regarding considerations and approaches when treating the tumors associated with the neurofibromatoses (NF), including risk and prognosis metrics, clinical trial results, surgical techniques, and radiation therapy recommendations.

An NTRK-1-associated soft tissue tumor showing distinctive nodules with peripheral accentuation of cellularity.

Lipofibromatosis-like neural tumor is a recently described entity defined by a low-cellularity spindle cell infiltrate in the subcutaneous fat with admixed inflammatory cells. This tumor is histopathologically similar to lipofibromatosis, but unlike lipofibromatosis shows reactivity for S100 and has an NTRK-1 kinase fusion. These lesions are locally aggressive but appear to have a negligible metastatic potential. Subsequently, a more cellular variant has been described with generally low mitotic rate. This variant also displays S100 reactivity and kinase fusions (typically involving NTRK-1), but it has a low risk of metastasis. In this report, we describe a case that aligns with the more cellular variant of NTRK-1 kinase fusion tumors on histopathologic, immunohistochemical, and molecular grounds, but in addition has distinctive nodules with peripheral accentuation of cellularity, reminiscent of those present in epithelioid malignant peripheral nerve sheath tumors. This latter feature is previously undescribed in NTRK kinase fusion soft tissue tumors and offers further support for the presumed neural differentiation of this neoplasm.

Role of perioperative chemotherapy and radiotherapy for localized high-grade malignant peripheral nerve sheath tumor at the extremities and trunk wall: a population-based cohort study.

BACKGROUND: Primary tumor resection is the mainstay of treatment for malignant peripheral nerve sheath tumors. However, the efficacy of perioperative chemotherapy and radiotherapy for malignant peripheral nerve sheath tumors has not been elucidated. METHODS: This retrospective analysis based on a Japanese registry included patients with localized malignant peripheral nerve sheath tumors arising at the extremities and trunk wall. Disease-specific overall survival and local recurrence-free survival were estimated using the Kaplan-Meier method. A Cox regression model was used to identify prognostic factors. Characteristics of groups with or without chemotherapy were adjusted using propensity score matching. RESULTS: In total, 291 patients were included. The 5-year disease-specific overall survival rate was 70.6%. Multivariate analysis of disease-specific overall survival revealed that deep-seated tumors were a poor prognostic factor, but perioperative chemotherapy was not associated with disease-specific overall survival (hazard ratio, 0.81; 95% confidence interval, 0.45-1.43, P = 0.46). Local recurrence was observed in 55 patients (19.0%), and surgical margins (R1 and R2) were significant risk factors. Overall, perioperative chemotherapy did not prolong disease-specific overall survival (5-year disease-specific overall survival: 74.1% vs. 69.3%, P = 0.75) and had limited efficacy in the group with tumor size ≥ 5 cm, although the difference was not statistically significant (5-year disease-specific overall survival: 77.2% vs. 68.6%, respectively, P = 0.13). After adjustment by propensity score matching, perioperative chemotherapy significantly prolonged disease-specific overall survival (5-year disease-specific overall survival: 74.9% vs. 57.1%, P = 0.03), but this effect was not observed in local recurrence-free survival. In all patients, perioperative radiotherapy did not correlate with local recurrence-free survival (hazard ratio, 1.43; 95% confidence interval 0.78-2.62, P = 0.25). CONCLUSIONS: Perioperative chemotherapy had limited efficacy for disease-specific overall survival in patients with localized malignant peripheral nerve sheath tumors.

Malignant Spinal Tumors.

Malignant spinal tumors constitute around 22% of all primary spinal tumors. The most common location of metastases to the spinal region is the extradural compartment. The molecular and genetic characterization of these tumors was the basis for the updated WHO classification of CNS tumors in 2016, where many CNS tumors are now diagnosed according to their genetic profile rather than relying solely on the histopathological appearance. Magnetic resonance imaging (MRI) is the current gold standard for the initial evaluation and subsequent follow-up on intradural spinal cord tumors, and the imaging sequences must include T2-weighted images (WI), short time inversion recovery (STIR), and pre- and post-contrast T1-WI in the axial, sagittal, and coronal planes. The clinical presentation is highly variable and depends on the tumor size, growth rate, type, infiltrative, necrotic and hemorrhagic potential as well as the exact location within the spinal compartment. Surgical intervention remains the mainstay of management of symptomatic and radiographically enlarging spinal tumors, where the goal is to achieve maximal safe resection. Tumor recurrences are managed with repeat surgical resection (preferred whenever possible and safe), radiotherapy, chemotherapy, or any combination of these therapies.

Genetic alterations associated with malignant transformation of sporadic vestibular schwannoma.

INTRODUCTION: Malignant peripheral nerve sheath tumor of the vestibulocochlear nerve (VN-MPNST) is exceedingly rare and carries a poor prognosis. Little is known about its underlying genetics and in particular the process of malignant transformation. There is an ongoing debate on whether the transformation is initiated by ionizing radiation. We present here the analysis and comparison of two post-radiation VN-MPNST and one undergoing spontaneous transformation. METHODS: Four tumors from three patients (radiation-naïve vestibular schwannoma before (VS) and after (VN-MPNST) malignant transformation in addition to two post-radiation VN-MPNST) were subjected to DNA whole-genome microarray and whole-exome sequencing and tumor-specific mutations were called. Mutational signatures were characterized using MuSiCa. RESULTS: The tumor genomes were characterized predominantly by copy-number aberrations with 36-81% of the genome affected. Even the VS genome was grossly aberrated. The spontaneous malignant transformation was characterized by a near-total whole-genome doubling, disappearance of NF2 mutation and new mutations in three cancer-related genes (GNAQ, FOXO4 and PDGFRB). All tumors had homozygous loss of the tumor suppressor CDKN2A. Neither mutational signature nor copy number profile was associated with ionizing radiation. CONCLUSION: The VN-MPNST genome in our cases is characterized by large copy-number aberrations and homozygous deletion of CDKN2A. Our study demonstrates a VS with genetic alterations similar to its malignant counterpart, suggesting the existence of premalignant VS. No consistent mutational signature was associated with ionizing radiation.

VEGF and VEGFR family members are expressed by neoplastic cells of NF1-associated tumors and may play an oncogenic role in malignant peripheral nerve sheath tumor growth through an autocrine loop.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder. The role of angiogenesis and VEGF pathway in the pathogenesis of neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs) remains poorly understood. We assessed the expression of VEGF and VEGFR family members in cohorts of plexiform neurofibromas (pNF), MPNSTs and MPNST cell lines at transcript [pNF, n = 49; MPNST, n = 34] and protein levels [pNF, n = 21; MPNST, n = 9]. VEGF and VEGFR members were variably expressed in cell lines. VEGFA (p = 3.10-5), VEGFR1 (p = 0.08), and VEGFR2 (p = 2.10-4) mRNAs were overexpressed in MPNSTs in comparison with pNFs. Both VEGFA and VEGFR1 proteins were expressed by spindle tumor cells of pNFs and MPNSTs. VEGFA was expressed more in MPNSTs than in pNFs (p = 9.10-6) and a trend for VEGFR1 overexpression was observed (p = 0.06). VEGFR2 was not found at the protein level. The microvascular density was significantly reduced in MPNSTs as compared to pNFs (p = 0.0025), with no differences regarding the expression of the activated phosphorylated forms of ERK (P-ERK [p = 0.63]) and AKT (P-AKT [p = 0.41]) in endothelial cells, suggesting that VEGF-dependant angiogenesis may not be critical for MPNST oncogenesis. Altogether, these results indicate that the VEGF-VEGFR pathway may play a role in the development of pNFs and MPNSTs, independently of angiogenesis. Whether or not it drives an oncogenic autocrine/paracrine loop in neoplastic cells, participating in an increased activation of signaling pathways downstream of tyrosine kinase receptors, including VEGFRs, is a tempting hypothesis. Nevertheless, the specific targeting of angiogenesis in MPNSTs may not be sufficient to slow down tumor growth.

Loss of dimethylated H3K27 (H3K27me2) expression is not a specific marker of malignant peripheral nerve sheath tumor (MPNST): An immunohistochemical study of 137 cases, with emphasis on MPNST and melanocytic tumors.

INTRODUCTION: Loss-of-function mutations in EED and SUZ12, core components of the polycomb repressive complex 2 (PRC2), occur in >90% of sporadic and radiation-associated malignant peripheral nerve sheath tumors (MPNST) and in roughly 70% of NF1-related tumors. PRC2 inactivation results in loss of H3K27me3 expression and aberrant downstream transcription. H3K27me3 expression is lost in 40-90% of spindle cell MPNST but is not specific. A single study has suggested that dimethylated H3K27 (H3K27me2) is a more specific marker of MPNST. METHODS: We compared the expression of H3K27me3 and H3K27me2 by immunohistochemistry in a series of MPNST (n = 26), neurofibroma (n = 11), conventional dermatofibrosarcoma protuberans (n = 8), fibrosarcomatous dermatofibrosarcoma protuberans (n = 7), spindle cell rhabdomyosarcoma (n = 6), high-risk solitary fibrous tumor (n = 9), dedifferentiated chondrosarcoma (n = 7), synovial sarcoma (n = 9), diffuse midline glioma, H3K27-altered (n = 13), conventional diffuse astrocytoma (n = 2), conventional cutaneous melanoma (n = 8), uveal melanoma (n = 8), cellular blue nevus (n = 17) and melanoma arising in blue nevus (n = 6). RESULTS: H3K27me3 and H3K27me2 expression patterns were concordant in 115/137 (84%) with 85 cases (62%) expressing both markers and 30 cases (22%) showing loss of both. Discordant results were seen in 22 cases (H3K27me3 loss with retained H3K27me2, 10 cases (7%); H3K27me3 expression with H3K27me2 loss, 12 cases (9%)). H3K27me2 loss was not specific for MPNST and was also seen in certain other tumors, in particular those in the "blue nevus family". CONCLUSION: We conclude that H3K27me2 loss is not specific for MPNST, and like H3K27me3, should be used in the appropriate clinicopathologic, immunohistochemical and molecular genetic context. Loss of H3K27me2 with retained H3K27me3 is a common feature of "blue nevus family" melanocytic tumors known to harbor GNAQ/GNA11 mutations.

Malignant peripheral nerve sheath tumor of the orbit: a case report and review of the literature.

Malignant peripheral nerve sheath tumor is a rare tumor which infrequently involves the orbit. They occur most often in the setting of neurofibromatosis 1 (NF1), and therefore the involvement of the orbit without a history of NF1 is even less common. Management of this tumor is fraught with a high rate of recurrences and metastases, with a high mortality rate. Primary surgical excision with tumor-free margins remains the primary treatment, while adjuvant modalities such as radiation and chemotherapy play a more minor role.

Enhancer reprogramming in PRC2-deficient malignant peripheral nerve sheath tumors induces a targetable de-differentiated state.

Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that frequently harbor genetic alterations in polycomb repressor complex 2 (PRC2) components-SUZ12 and EED. Here, we show that PRC2 loss confers a dedifferentiated early neural-crest phenotype which is exclusive to PRC2-mutant MPNSTs and not a feature of neurofibromas. Neural crest phenotype in PRC2 mutant MPNSTs was validated via cross-species comparative analysis using spontaneous and transgenic MPNST models. Systematic chromatin state profiling of the MPNST cells showed extensive epigenomic reprogramming or chromatin states associated with PRC2 loss and identified gains of active enhancer states/super-enhancers on early neural crest regulators in PRC2-mutant conditions around genomic loci that harbored repressed/poised states in PRC2-WT MPNST cells. Consistently, inverse correlation between H3K27me3 loss and H3K27Ac gain was noted in MPNSTs. Epigenetic editing experiments established functional roles for enhancer gains on DLX5-a key regulator of neural crest phenotype. Consistently, blockade of enhancer activity by bromodomain inhibitors specifically suppressed this neural crest phenotype and tumor burden in PRC2-mutant PDXs. Together, these findings reveal accumulation of dedifferentiated neural crest like state in PRC2-mutant MPNSTs that can be targeted by enhancer blockade.

R-Ras subfamily proteins elicit distinct physiologic effects and phosphoproteome alterations in neurofibromin-null MPNST cells.

BACKGROUND: Loss of the Ras GTPase-activating protein neurofibromin promotes nervous system tumor pathogenesis in patients with neurofibromatosis type 1 (NF1). Neurofibromin loss potentially hyperactivates classic Ras (H-Ras, N-Ras, K-Ras), M-Ras, and R-Ras (R-Ras, R-Ras2/TC21) subfamily proteins. We have shown that classic Ras proteins promote proliferation and survival, but not migration, in malignant peripheral nerve sheath tumor (MPNST) cells. However, it is unclear whether R-Ras, R-Ras2 and M-Ras are expressed and hyperactivated in MPNSTs and, if so, whether they contribute to MPNST pathogenesis. We assessed the expression and activation of these proteins in MPNST cells and inhibited them to determine the effect this had on proliferation, migration, invasion, survival and the phosphoproteome. METHODS: NF1-associated (ST88-14, 90-8, NMS2, NMS-PC, S462, T265-2c) and sporadic (STS-26T, YST-1) MPNST lines were used. Cells were transfected with doxycycline-inducible vectors expressing either a pan-inhibitor of the R-Ras subfamily [dominant negative (DN) R-Ras] or enhanced green fluorescent protein (eGFP). Methodologies used included immunoblotting, immunocytochemistry, PCR, Transwell migration, 3H-thymidine incorporation, calcein cleavage assays and shRNA knockdowns. Proteins in cells with or without DN R-Ras expression were differentially labeled with SILAC and mass spectrometry was used to identify phosphoproteins and determine their relative quantities in the presence and absence of DN R-Ras. Validation of R-Ras and R-Ras2 action and R-Ras regulated networks was performed using genetic and/or pharmacologic approaches. RESULTS: R-Ras2 was uniformly expressed in MPNST cells, with R-Ras present in a major subset. Both proteins were activated in neurofibromin-null MPNST cells. Consistent with classical Ras inhibition, DN R-Ras and R-Ras2 knockdown inhibited proliferation. However, DN R-Ras inhibition impaired migration and invasion but not survival. Mass spectrometry-based phosphoproteomics identified thirteen protein networks distinctly regulated by DN R-Ras, including multiple networks regulating cellular movement and morphology. ROCK1 was a prominent mediator in these networks. DN R-Ras expression and RRAS and RRAS2 knockdown inhibited migration and ROCK1 phosphorylation; ROCK1 inhibition similarly impaired migration and invasion, altered cellular morphology and triggered the accumulation of large intracellular vesicles. CONCLUSIONS: R-Ras proteins function distinctly from classic Ras proteins by regulating distinct signaling pathways that promote MPNST tumorigenesis by mediating migration and invasion. Mutations of the NF1 gene potentially results in the activation of multiple Ras proteins, which are key regulators of many biologic effects. The protein encoded by the NF1 gene, neurofibromin, acts as an inhibitor of both classic Ras and R-Ras proteins; loss of neurofibromin could cause these Ras proteins to become persistently active, leading to the development of cancer. We have previously shown that three related Ras proteins (the classic Ras proteins) are highly activated in malignant peripheral nerve sheath tumor (MPNST) cells with neurofibromin loss and that they drive cancer cell proliferation and survival by activating multiple cellular signaling pathways. Here, we examined the expression, activation and action of R-Ras proteins in MPNST cells that have lost neurofibromin. Both R-Ras and R-Ras2 are expressed in MPNST cells and activated. Inhibition of R-Ras action inhibited proliferation, migration and invasion but not survival. We examined the activation of cytoplasmic signaling pathways in the presence and absence of R-Ras signaling and found that R-Ras proteins regulated 13 signaling pathways distinct from those regulated by classic Ras proteins. Closer study of an R-Ras regulated pathway containing the signaling protein ROCK1 showed that inhibition of either R-Ras, R-Ras2 or ROCK1 similarly impaired cellular migration and invasion and altered cellular morphology. Inhibition of R-Ras/R-Ras2 and ROCK1 signaling also triggered the accumulation of abnormal intracellular vesicles, indicating that these signaling molecules regulate the movement of proteins and other molecules in the cellular interior. Video Abstract.