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SMARCB1 deletion in atypical teratoid rhabdoid tumors results in human endogenous retrovirus K (HML-2) expression.

ABSTRACT: Atypical Teratoid Rhabdoid Tumor (AT/RT) is a rare pediatric central nervous system cancer often characterized by deletion or mutation of SMARCB1, a tumor suppressor gene. In this study, we found that SMARCB1 regulates Human Endogenous Retrovirus K (HERV-K, subtype HML-2) expression. HML-2 is a repetitive element scattered throughout the human genome, encoding several intact viral proteins that have been associated with stem cell maintenance and tumorigenesis. We found HML-2 env expression in both the intracellular and extracellular compartments in all AT/RT cell lines (n = 4) and in 95% of AT/RT patient tissues (n = 37) evaluated. SMARCB1 knock-down in neural stem cells (NSCs) led to an upregulation of HML-2 transcription. We found that SMARCB1 binds adjacent to the HML-2 promoter, repressing its transcription via chromatin immunoprecipitation; restoration of SMARCB1 expression in AT/RT cell lines significantly downregulated HML-2 expression. Further, targeted downregulation of HML-2 transcription via CRISPR-dCas9 coupled with suppressor proteins led to cellular dispersion, decreased proliferation, and cell death in vitro. HML-2 knock-down with shRNA, siRNA, and CRISPR-dCas9 significantly decreased Ras expression as measured by qRT-PCR, suggesting that HML-2 modulates MAPK/ERK signaling in AT/RT cells. Overexpression of NRAS was sufficient to restore cellular proliferation, and MYC, a transcription factor downstream of NRAS, was bound to the HERV-K LTR significantly more in the absence of SMARCB1 expression in AT/RT cells. We show a mechanism by which these undifferentiated tumors remain pluripotent, and we demonstrate that their formation is aided by aberrant HML-2 activation, which is dependent on SMARCB1 and its interaction with MYC.

SUBMITTER: Doucet-O'Hare TT

PROVIDER: S-EPMC8213802 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature

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SMARCB1 deletion in atypical teratoid rhabdoid tumors results in human endogenous retrovirus K (HML-2) expression.

Doucet-O'Hare Tara T TT DiSanza Brianna L BL DeMarino Catherine C Atkinson Abigail L AL Rosenblum Jared S JS Henderson Lisa J LJ Johnson Kory R KR Kowalak Jeffrey J Garcia-Montojo Marta M Allen Sariah J SJ Orr Brent A BA Santi Mariarita M Wang Tongguang T Fathi Saeed S Lee Myoung Hwa MH Sampson Kevon K Li Wenxue W Zhuang Zhengping Z Nath Avindra A

Scientific reports 20210618 1

Atypical Teratoid Rhabdoid Tumor (AT/RT) is a rare pediatric central nervous system cancer often characterized by deletion or mutation of SMARCB1, a tumor suppressor gene. In this study, we found that SMARCB1 regulates Human Endogenous Retrovirus K (HERV-K, subtype HML-2) expression. HML-2 is a repetitive element scattered throughout the human genome, encoding several intact viral proteins that have been associated with stem cell maintenance and tumorigenesis. We found HML-2 env expression in bo ...[more]

PMID: 34145313

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Project description:BACKGROUND: To describe therapeutic approaches in children with atypical Teratoid Rhabdoid Tumours (ATRT) in France. METHODS: Observational study including all children less than 18 years old diagnosed with ATRT in France between 2009 and 2011. RESULTS: Forty seven children were included in this retrospective study. Six patients received no curative treatment while forty-one patients had a curative project. Median age was 1.5 years (range 0-16). The disease was disseminated in 10 patients. Surgical resection was complete in 21 cases. Chemotherapy was administered in 41 children. Twenty-six patients received upfront Vincristine-Methotrexate (5g/m2 x 3) with intra-thecal Methotrexate, which was stopped in eleven patients: in four cases the disease progressed and in seven cases the toxicities were manageable. Fifteen children received different chemotherapy courses and in four of them the diseases progressed. Eight patients underwent second-look surgery. Radiotherapy was administered in 17 patients at a median time of 19 weeks (13-44) after diagnosis. High-dose chemotherapy (HDCT) was given in 9 children and maintenance therapy in 5 children, starting at respectively 35 and 42 weeks after diagnosis. Median follow-up was 26 months (0.6-47). Median time for progression was 5 months. Two-years overall survival was 32% + /-8%. Median survival was 8 months. DISCUSSION: The survival rate of children with ATRT remains poor, the addition of VM is easily manageable but its benefit remains uncertain. The disease progressed mostly before radiotherapy. Future trials should focus on the delay of radiotherapy and the benefit of HDCT. Because ATRT is a rare disease of infancy carrying grim prognosis, focus on long term outcome, especially neurocognitive remain very limited. With the new era of multimodality therapy, some patients are now long term survivors. We reviewed the neuropsychological (NP) status of the survivors from the Canadian ATRT registry. Among patients diagnosed between 1995-2012, 16/72 were survivors (22%). Formal NP assessments were available in 7 patients. Four patients could not be tested (3 too young, 1 blind significantly impaired, 1 lost to follow up). Additionally 1 patient was in special education class (grade 12), one received educational assistance (grade 8), one meet academic expectation (grade 4). Data on last survivor is pending. For the 7 patients with comprehensive NP, the median age at diagnosis was 28.2 months (11.2-60.7). Four tumors were infratentorial and 3 were metastatic. Four patients underwent complete resection. All patients received post operative sequential high dose chemotherapy (Carpoplatin/Thiotepa). Five patients received intrathecal chemotherapy. Two patients underwent radiation (1focal, 1CSI). Median age at time of NP was 7.3 years (3.9-9.28). Full Scale Intellectual Quotient (FSIQ) ranged from 60 to 119 (median = 71). Simple expressive and receptive language appeared relatively preserved (low average to superior). Three most recently diagnosed patients assessed at a median time of 2.6 years (2.6-4.7) from diagnosis had average to high average scores for FSIQ, academic and visual spatial skills, visual and verbal memory. Four other diagnosed earlier tested at a median time of 5.1 years (3.3-8.3) post-diagnosis had a FSIQ ranging from 60 to 71 (median = 68). Approximately 50% of their scores were in the impaired range. Whether these findings suggest further decline overtime or reflect improvement in overall management of these recently diagnosed patients remain unclear. Nevertheless this cohort of infants appears significantly impaired at school age despite the absence of systematic radiotherapy. Larger series focusing on neurocognition are definitely needed before embracing adjuvant radiotherapy as standard of care.

Project description:Loss of function in SMARCB1/INI1 has been observed in a group of malignancies collectively defined as SMARCB1/INI1-deficient neoplasms. Primary intracranial SMARCB1/INI1-deficient tumors in adults are extremely rare. We collected eight primary adult sellar SMARCB1/INI1-deficient tumors to study their clinicopathological and (epi)genetic characteristics. We performed a comprehensive assessment of the clinical, radiological, morphological and immunohistochemical features. FISH analysis for the SMARCB1 locus and target exome sequencing for 425 cancer relevant genes were performed. Furthermore, six bona fide proximal epithelioid sarcoma (PES), fourteen atypical teratoid/rhabdoid tumors (ATRT) in brain and five pediatric poorly differentiated chordomas (PDC) in the clivus were collected for comparative analysis of differential diagnostic maker expression and DNA methylation profile. The median age was 47.1 years, ranging from 26 to 73 years. On morphology, tumors were characterized by sheets of monomorphic larger epithelioid-like cells, in two cases with rhabdoid cells. "Stag-horn" vasculatures were observed in five cases. The loss of INI1 protein expression, co-expression of epithelial makers and mesenchymal markers were observed in all cases. CD34 expression was observed in six cases. Heterozygous deletion of SMARCB1/INI1 was confirmed using FISH in six cases. The results of target exome sequencing showed three patients harbored heterozygous point mutations in SMARCB1. The epigenetic features of the primary adult sellar SMARCB1/INI1-deficient tumors resembled the ATRT-MYC subgroup, but clustered apart from PES and PDC. Based on epigenetic characteristics, primary adult sellar SMARCB1/INI1-deficient tumors represent a subtype of ATRT with similar epigenetic characteristics of ATRT-MYC subgroup. Our findings suggest that DNA methylation profiling should be utilized for differential diagnosis for the majority of epithelioid sarcoma and (sellar) rhabdoid tumor.

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SMARCB1 deletion in atypical teratoid rhabdoid tumors results in human endogenous retrovirus K (HML-2) expression.

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SMARCB1 deletion in atypical teratoid rhabdoid tumors results in human endogenous retrovirus K (HML-2) expression.

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