Atypical Teratoid Rhabdoid Tumor Research Articles

CSF cytology of common primary CNS neoplasms categorized by CNS WHO 2021.

The detection of neoplastic cells in cerebral spinal fluid (CSF) is pivotal for the management of patients with central nervous system (CNS) tumours. This article delves into the CSF cytological characteristics of common CNS neoplasms, aligning with the 2021 World Health Organization (WHO) classification of CNS tumours. A retrospective review of CSF specimens positive for primary CNS neoplasms was performed at three tertiary medical centres. Only cases that had histopathologic confirmation and/or molecular workup were included. Common primary CNS neoplasms seen in CSF cytology specimens include medulloblastoma, (non-WNT/non-SHH as well as SHH-activated and TP53 mutant), pineoblastoma, atypical teratoid/rhabdoid tumour (AT/RT), IDH-wildtype glioblastoma, and primary diffuse large B-cell lymphoma of the CNS. Ependymomas and germinomas can also have CSF involvement but are less common. Although the typical histologic architecture of these tumours may not be preserved in the CSF, unique cytomorphologic features such as nuclear moulding, nuclear pleomorphism, rhabdoid cells, prominent nucleoli and rosette formation can still be appreciated. Adopting the updated terminology and correlating cytologic observations with molecular findings will streamline the diagnostic process, reducing the complexities and ambiguities pathologists often encounter when analysing CSF specimens for potential primary CNS neoplasms.

Tazemetostat in the therapy of pediatric INI1-negative malignant rhabdoid tumors

Rhabdoid tumors are aggressive tumors that may arise in the kidney, soft tissue, central nervous system, or other organs. They are defined by SMARCB1 (INI1) or SMARCA4 alterations. Often, very young children are affected, and the prognosis is dismal. Four patients with primary atypical teratoid rhabdoid tumor (AT/RT, a rhabdoid tumor in the central nervous system) were treated by resection and high dose chemotherapy. Tazemetostat was introduced after completion of chemotherapy. Three patients have achieved an event free survival of 32, 34, and 30 months respectively. One progressed and died. His overall survival was 20 months. One patient was treated for a relapsed atypical teratoid rhabdoid tumor. The treatment combined metronomic therapy, radiotherapy, tazemetostat and immunotherapy. This patient died of disease progression, with an overall survival of 37 months. One patient was treated for a rhabdoid tumor of the ovary. Tazemetostat was given as maintenance after resection, chemotherapy, and radiotherapy, concomitantly with immunotherapy. Her event free survival is 44 months. Only approximately 40% of patients with rhabdoid tumors achieve long-term survival. Nearly all relapses occur within two years from diagnosis. The event free survival of four of the six patients in our cohort has exceeded this timepoint. Tazemetostat has been mostly tested as a single agent in the relapsed setting. We present promising results when applied as maintenance or add on in the first line treatment.

Abstract C096: Targeting the p53 pathway to treat pediatric Malignant Rhabdoid and Atypical Teratoid Rhabdoid Tumors

Abstract Background: Pediatric rhabdoid tumors, namely Malignant Rhabdoid Tumors (MRTs) and Atypical Teratoid Rhabdoid Tumors (ATRTs) in the central nervous system (CNS), are aggressive pediatric malignancies characterized by the loss of functional INI1 protein due to SMARCB1 gene mutations. Current treatment options for these tumors are limited and ineffective, necessitating the exploration of novel therapeutic strategies. Rhabdoid cells retain an intact p53 pathway, a critical tumor suppressor pathway involved in regulating cell cycle and apoptosis. Previous studies have shown that the MDM2 inhibitor, Idasanutlin, effectively eliminates flanked rhabdoid tumors, suggesting that targeting the p53 pathway holds promise for developing effective therapies against MRTs and ATRTs. Methods: In this study, we employed a combination approach using the MDM2 inhibitor, Idasanutlin, and the XPO1 inhibitor, Selinexor, to activate the p53 pathway. The impact of this combination treatment on tumor cell viability, proliferation, and apoptosis was assessed both in vitro and in vivo using MRT and ATRT models. Additionally, CRISPR screening and proteomic studies were conducted to identify specific dependencies in refractory models and investigate their influence on treatment response. Results: Treatment with the combination of Idasanutlin and Selinexor activated the p53 signaling pathway, leading to increased levels of MDM2 and p21 proteins, two direct targets of p53, and resulting in apoptosis in MRT and ATRT models. In vitro experiments demonstrated a significant reduction in cell viability and proliferation upon treatment. In vivo studies using MRT and ATRT xenograft models showed a remarkable decrease in tumor growth following the combination treatment. However, variable responses were observed among different models, indicating the presence of dependency patterns influencing treatment sensitivity. Proteomic studies and genetic manipulation provided further insights into the potential dependencies Conclusions: Our findings highlight the potential of the combination of Idasanutlin and Selinexor to activate the p53 pathway and induce apoptosis in MRT and ATRT models. Although the treatment strategy effectively activated p53, we identified dependencies that may contribute to incomplete treatment sensitivity. Further investigation into these dependency patterns is necessary to optimize the therapeutic approach. Overall, targeting the p53 pathway using combination therapies shows promise for the development of effective treatments for pediatric MRTs and ATRTs, warranting further preclinical and clinical investigations. Citation Format: Alaa Refaat, Hyekyung Cho, Jennifer Stripay, Charles Roberts, Christopher Tinkle, Anang Shelat, Martine Roussel. Targeting the p53 pathway to treat pediatric Malignant Rhabdoid and Atypical Teratoid Rhabdoid Tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C096.

Atypical Teratoid Rhabdoid Tumor: 28-years institutional experience

Abstract Introduction/Objective Atypical teratoid/rhabdoid tumor (ATRT) is a malignant central nervous system tumor affecting young children, characterized by biallelic mutations of SMARCB1 (hSNF5/INI1), consisting of a varying mixture of rhabdoid cells, small round blue cell (SRBC) and epithelial/mesenchymal components. Combination of surgical resection, chemoradiotherapy and autologous stem cell transplantation (SCT) has led to significant improvement in survival. Methods/Case Report Cases of ATRT in the past 28 years have been re-examined, including H&E stains, immunohistochemistry, available molecular studies and clinical charts. Results (if a Case Study enter NA) A total of 23 cases of ATRT were recruited to include 20 pediatric (age 3-36 months, median 13.5 months) and 3 adult cases (27, 38 and 46 years). 73.9% were male. Two pediatric cases presented in patients with Pierre-Robin sequence and Phelan-McDermid syndrome and one adult had history of Choriocarcinoma. 72.7% of cases initially presented in the posterior fossa, with 3 cases presenting in temporal lobe, 1 in frontal lobe, 1 in 3rd ventricle and 1 in pituitary gland. Mean size at presentation was 4.7 cm (range 2-10 cm). Median survival was 12.5 weeks with 8 patients surviving 5-13 years. 10/22 cases developed recurrences and/or spinal drop metastasis. Median time to first recurrence/ drop metastasis was 3.5 months (range 0-66 months). Cases showed varying proportions of rhabdoid, SRBC, epithelioid and mesenchymal components. By immunohistochemistry, INI1 was lost in 19/19 cases. Keratins, GFAP and Synaptophysin were positive in 13/17, 14/20 and 17/21 cases, respectively. Interestingly, GAB-1 and YAP1 were positive in 5/6 and 4/4 cases, respectively. Five cases had SMARCB1 mutation on NGS, one had NF2 truncation and another showed variation of unknown significance involving mainly NOTCH1 gene. 21/22 patients underwent surgical resection, of which 17 additionally received a combination of chemoradiotherapy and SCT and 1/22 underwent palliation. Conclusion Our data highlights the spectrum of presentation and survival of cases of ATRT and the importance of INI1 immunohistochemistry in the diagnosis, especially for the occasional cases co-expressing GAB1 and YAP, a potential diagnostic pitfall with medulloblastoma.

Deep topographic proteomics of a human brain tumour

The spatial organisation of cellular protein expression profiles within tissue determines cellular function and is key to understanding disease pathology. To define molecular phenotypes in the spatial context of tissue, there is a need for unbiased, quantitative technology capable of mapping proteomes within tissue structures. Here, we present a workflow for spatially-resolved, quantitative proteomics of tissue that generates maps of protein abundance across tissue slices derived from a human atypical teratoid-rhabdoid tumour at three spatial resolutions, the highest being 40 µm, to reveal distinct abundance patterns of thousands of proteins. We employ spatially-aware algorithms that do not require prior knowledge of the fine tissue structure to detect proteins and pathways with spatial abundance patterns and correlate proteins in the context of tissue heterogeneity and cellular features such as extracellular matrix or proximity to blood vessels. We identify PYGL, ASPH and CD45 as spatial markers for tumour boundary and reveal immune response-driven, spatially-organised protein networks of the extracellular tumour matrix. Overall, we demonstrate spatially-aware deep proteo-phenotyping of tissue heterogeneity, to re-define understanding tissue biology and pathology at the molecular level.

EPCO-44. RHABDOID TUMOR PREDISPOSITION SYNDROME DUE TO A GERMLINE SMARCB1 MUTATION IN TWO INFANT SIBLINGS

Abstract INTRODUCTION Rhabdoid tumors (RTs) are highly aggressive malignancies caused by a loss–of–function mutation in the SMARCB1 tumor suppressor gene on chromosome 22 that makes up the SW1/SNF chromatin remodeling complex involved in gene transcription. In rhabdoid tumor predisposition syndrome (RTPS), a biallelic germline SMARCB1 mutation markedly increases the risk of affected individuals developing early, aggressive, and rapidly progressing RTs, most commonly in the CNS, referred to as atypical teratoid rhabdoid tumors (AT/RT), and the kidneys, but oftentimes presents with synchronous lesions. In this case series, we present a family affected by RTPS with a recurrence of AT/RT in two infant siblings with the same germline SMARCB1 mutation. CASE SERIES DESCRIPTION An 8-month-old female was brought to the emergency department for 3 months of vomiting, developmental regression, and CN VI palsy. Brain imaging revealed a posterior fossa mass, acquired obstructive hydrocephalus, and spinal metastasis. Four years later, her 3-month-old sister was also brought in for evaluation for 2 months of vomiting, irritability, increasing head circumference, and vertical gaze palsy. Her brain imaging similarly showed a posterior fossa mass and acquired obstructive hydrocephalus, but no metastasis. Both siblings underwent subtotal tumor resections and ventriculoperitoneal shunt placement followed by chemotherapy. While on active treatment, they experienced rapid disease progression and ultimately succumbed to their illness. Genetic testing on the family identified the same in-frame deletion in the SNF5 homology domain of SMARCB1 and loss of heterozygosity of chromosome 22 in the two sisters; their mother was found to be a carrier. CONCLUSION This case series describes a family affected by RTPS, demonstrating the risk of familial recurrence in SMARCB1 germline mutations and emphasizing the need for genetic testing and counseling for these families should they wish to have additional children.

PATH-59. SYSTEMATIC CHARACTERIZATION OF ANTIBODY-DRUG CONJUGATE TARGETS IN CENTRAL NERVOUS SYSTEM TUMORS

Abstract BACKGROUND Antibody-drug conjugates (ADCs) enhance the specificity of cytotoxic drugs by directing them to cells expressing target antigens. Multiple ADCs are FDA-approved for solid cancers, including those expressing ERBB2/HER2, TACSTD2/TROP2, NECTIN4, folate receptor 1 (FOLR1), and tissue factor (CD142/TF). Recently, a next-generation ADC targeting HER2 (Trastuzumab-Deruxtecan) increased survival and reduced growth of brain metastases in treatment-refractory metastatic breast cancer, even in tumors with low HER2 expression. Thus, low-level ADC target expression may be sufficient for treatment responsiveness, and CNS tumors may be responsive to next-generation ADC. However, ADC target expression is poorly characterized in most CNS tumors. METHODS To systematically characterize ADC target expression in CNS tumors, we analyzed publicly available RNA-sequencing and proteomic data from the Children’s Brain Tumor Network (n=188 tumors) and GEO RNA-expression datasets (n=356 tumors) to evaluate expression of 14 potential ADC targets that are FDA-approved or under clinical investigation in solid cancers. We also used immunohistochemistry to score the levels of HER2, HER3, NECTIN4, TROP2, CLDN6, CLDN18.2, and CD276/B7-H3 protein in glioblastoma (GBM), oligodendroglioma, meningioma, ependymoma, pilocytic astrocytoma, medulloblastoma, atypical teratoid/rhabdoid tumor (AT/RT), adamantinomatous craniopharyngioma (ACP), papillary craniopharyngioma (PCP), and primary CNS lymphoma (n=575 total tumors). RESULTS Multi-modal pan-CNS analysis showed consistent subtype-specific expression of ADC target proteins. Most tumors expressed HER3, B7-H3, and NECTIN4. Ependymomas (n=44) strongly expressed HER2 (36/44; 81% of cases by IHC), while meningiomas weakly-moderately expressed HER2 in most tumors (201/234; 86%). ACP (n=15) and PCP (n=3) strongly expressed B7-H3 (100% of cases), with TROP2 and HER2 expression in whorled ACP epithelium (100% of cases). AT/RT strongly expressed CLDN6 (8/9; 89%). GBM showed little subtype-specific marker expression, suggesting a need for further target development. CONCLUSIONS CNS tumors exhibit subtype-specific expression of ADC targets including several FDA-approved for other indications. Clinical trials of ADCs in CNS tumors may therefore be fruitful.

PATH-61. NGS DATA INFLUENCE ON CLINICIAN DECISION-MAKING ACROSS PRIMARY BRAIN TUMORS AT NORTHWESTERN UNIVERSITY

Abstract BACKGROUND Next-generation sequencing (NGS) is routinely completed for systemic solid tumors; however, its utility is unclear in brain tumors. Our study sought to investigate and compare the impact of NGS on treatment decision-making for glioblastoma and other primary brain tumors. METHODS An IRB-approved retrospective chart review was conducted with patients at Northwestern University who were diagnosed with a primary brain tumor receiving NGS sequencing between October 2013 and February 2020. Tempus reports for each in-house sequencing event along with pertinent medical information from the electronic medical record (EMR) was extracted. Primary brain tumor types assessed included glioblastoma, astrocytoma, oligodendroglioma, and other rare subtypes (including meningioma, ependymoma, ganglioma, pleomorphic xanthoastrocytoma, atypical teratoid rhabdoid tumors, glioneuronal tumors, and CNS lymphomas). NGS-impacted decision-making was defined as a physician prescribing a targeted treatment that corresponded with an actionable mutation in the Tempus report. RESULTS NGS was completed in 261 patients with glioblastoma and 121 patients with other primary brain tumors. NGS impacted decision-making in 12.6% (33) of glioblastoma patients and 9.1% (11) of other brain tumor patients. These figures in grades 1-3 astrocytoma and oligodendroglioma were 9.1% (4 of 44) and 8.1% (3 of 37), respectively. NGS impacted treatment in 10.0% (4 of 40) of all remaining subtypes analyzed. Overall, NGS sequencing data influenced clinical decision-making 11.5% of the time across all brain tumor types. Across the 382 patients assessed, EGFR copy number gain or GOF mutations were targeted most often (52.3% of all mutations targeted), followed by BRAF (11.4%) and IDH1 (11.4%). CONCLUSIONS NGS influences treatment decisions less often in primary brain tumors compared to other systemic cancers; however, NGS should still be considered in primary brain tumor patients, as it impacts treatment decision-making across subtypes. As more targeted therapies become available for CNS tumors, the utility of NGS will only increase.

Systematic characterization of antibody-drug conjugate targets in central nervous system tumors.

Antibody-drug conjugates (ADCs) enhance the specificity of cytotoxic drugs by directing them to cells expressing target antigens. Multiple ADCs are FDA-approved for solid and hematologic malignancies, including those expressing HER2, TROP2, and NECTIN4. Recently, an ADC targeting HER2 (Trastuzumab-Deruxtecan) increased survival and reduced growth of brain metastases in treatment-refractory metastatic breast cancer, even in tumors with low HER2 expression. Thus, low-level expression of ADC targets may be sufficient for treatment responsiveness. However, ADC target expression is poorly characterized in many central nervous system (CNS) tumors. We analyzed publicly available RNA-sequencing and proteomic data from the children's brain tumor network (N = 188 tumors) and gene-expression-omnibus RNA-expression datasets (N = 356) to evaluate expression of 14 potential ADC targets that are FDA-approved or under investigation in solid cancers. We also used immunohistochemistry to measure the levels of HER2, HER3, NECTIN4, TROP2, CLDN6, CLDN18.2, and CD276/B7-H3 protein in glioblastoma, oligodendroglioma, meningioma, ependymoma, pilocytic astrocytoma, medulloblastoma, atypical teratoid/rhabdoid tumor (AT/RT), adamantinomatous craniopharyngioma (ACP), papillary craniopharyngioma (PCP), and primary CNS lymphoma (N = 575). Pan-CNS analysis showed subtype-specific expression of ADC target proteins. Most tumors expressed HER3, B7-H3, and NECTIN4. Ependymomas strongly expressed HER2, while meningiomas showed weak-moderate HER2 expression. ACP and PCP strongly expressed B7-H3, with TROP2 expression in whorled ACP epithelium. AT/RT strongly expressed CLDN6. Glioblastoma showed little subtype-specific marker expression, suggesting a need for further target development. CNS tumors exhibit subtype-specific expression of ADC targets including several FDA-approved for other indications. Clinical trials of ADCs in CNS tumors may therefore be warranted.

Management of Atypical Teratoid/Rhabdoid Tumors in the Pediatric Population: A Systematic Review and Meta-Analysis

Atypical teratoid/rhabdoid tumors are rare and aggressive tumors that mainly affect children <3 years of age. Despite aggressive treatment, the overall survival rate for pediatric atypical teratoid/rhabdoid tumors remains poor. Due to their rarity, little is known regarding prognostic factors, and there is no official standard of treatment. A comprehensive database search was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Search terms included "atypical teratoid rhabdoid tumor" and "atypical (teratoid OR rhabdoid) tumor." Variables of interest included, but were not limited to, age, sex, tumor location, treatment modality, extent of resection, and overall survival. The study included 294 articles and 936 patients. The median age of patients was 22 months. There was a significant difference in survival among patients receiving surgery compared with patients receiving nonoperative treatment (50.3 months vs. 28 months; P < 0.005). Extent of resection did not significantly improve survival (P= 0.832 for gross total resection, P= 0.650 for partial resection). Combination therapy with surgical resection, radiotherapy, and chemotherapy demonstrated the largest median overall survival (54.9 months) and significantly improved survival on multivariate analysis (hazard ratio, 0.48; 95% confidence interval, 0.23-0.97; P=0.042). The results of this study indicate that while surgery is a crucial treatment modality for pediatric atypical teratoid/rhabdoid tumors, the effect of extent of resection is unclear. Multimodal therapy including surgery, radiotherapy, and chemotherapy is effective in improving overall survival. Future studies should focus on using larger datasets to efficiently account for confounding factors and biases.

Imaging and multi-omics datasets converge to define different neural progenitor origins for ATRT-SHH subgroups

Atypical teratoid rhabdoid tumors (ATRT) are divided into MYC, TYR and SHH subgroups, suggesting diverse lineages of origin. Here, we investigate the imaging of human ATRT at diagnosis and the precise anatomic origin of brain tumors in the Rosa26-CreERT2::Smarcb1flox/flox model. This cross-species analysis points to an extra-cerebral origin for MYC tumors. Additionally, we clearly distinguish SHH ATRT emerging from the cerebellar anterior lobe (CAL) from those emerging from the basal ganglia (BG) and intra-ventricular (IV) regions. Molecular characteristics point to the midbrain-hindbrain boundary as the origin of CAL SHH ATRT, and to the ganglionic eminence as the origin of BG/IV SHH ATRT. Single-cell RNA sequencing on SHH ATRT supports these hypotheses. Trajectory analyses suggest that SMARCB1 loss induces a de-differentiation process mediated by repressors of the neuronal program such as REST, ID and the NOTCH pathway.

Review of surgical spproaches for posterior fossa tumors in pediatric population and illustrative cases

Introduction/Background: Posterior fossa tumors are common in the pediatric population, and various surgical approaches have been described to reach them based on their specific location. This paper aims to review the most common posterior fossa approaches in pediatric patients and present illustrative cases to provide insights into their successful application in specific clinical scenarios. Case report: Three cases are presented, each demonstrating a different approach and surgical outcome. Case 1 involved a telovelar approach for the resection of a medulloblastoma, resulting in complete removal without neurological deficits. Case 2 required a combination of telovelar and supracerebellar infratentorial approaches to achieve gross total resection of a pilocytic astrocytoma. In Case 3, an occipital transtentorial approach was utilized to access and completely resect an atypical teratoid rhabdoid tumor. Connclusion: The paper discusses the telovelar and transvermian approaches, the supracerebellar infratentorial approach, the transtentorial suboccipital approach, and intraventricular endoscopy as individual or combined approaches for posterior fossa tumors. The presented cases highlight the importance of tailoring the surgical approach to each patient and provide valuable insights for neurosurgeons managing similar clinical scenarios.

Sellar atypical teratoid/rhabdoid tumor in adults: survival analysis of treatment strategies. Illustrative case.

Atypical teratoid/rhabdoid tumor (ATRT) is a rare, highly aggressive central nervous system tumor predominantly found in children. Limited information exists on ATRT in adults, posing challenges in diagnosis and treatment. This study presents the case of an adult patient with ATRT in the sellar region and explores the impact of different treatment regimens on patient survival. A 60-year-old female with an ATRT underwent resection of the tumor, followed by adjuvant chemoradiotherapy. Molecular genetic analysis revealed compound heterozygous SMARCB1 point mutations. Survival analysis was performed on previously published adult ATRT cases, comparing treatment approaches. The cohort's overall median survival was 6 months, with patients receiving combined chemoradiotherapy showing the longest median survival of 23.5 months. Statistical analysis demonstrated a significant difference in survival between patients treated with surgery alone and those receiving surgery followed by chemoradiotherapy (p < 0.001). However, no significant difference was observed between patients treated with surgery alone and those with postoperative radiotherapy (p = 0.105). Early initiation of adjuvant chemoradiotherapy following surgery improves survival outcomes in adult patients with ATRT. Because of limited data on standardized treatment protocols for adults with ATRT, further research and larger-scale studies are needed to establish effective treatment guidelines for this population.

Atypical Teratoid/Rhabdoid Tumor of the Nervous System in Adults: Location-Related Features and Outcome

Atypical teratoid/rhabdoid tumor (AT/RT) of the nervous system is a rare and highly malignant neoplasm, mainly affecting children, first recognized as a pathologic entity in 1996 and added to the World Health Organization Classification of the Tumors of the Central Nervous System in 2000. AT/RT is even rarer among adults and is associated with a worse prognosis. The aim of the present study was to analyze the different tumor features according to the location in adults. A comprehensive and detailed literature review of AT/RTs in adults was made. The demographic, management, and outcome data associated with tumor location were analyzed and compared; histopathologic and molecular features were also discussed. Furthermore, we added our personal case with brain hemispheric localization and reported a progression-free survival of 103 months after gross total resection and adjuvant radiotherapy showing a peculiar histopathologic pattern. Female sex is mainly affected by AT/RT on median localizations, both intracranial and spinal, and by all sellar region cases. Gross total resection is mainly achieved among lateral compared with median localizations. Combined radiotherapy and chemotherapy is the most adopted adjuvant treatment in all tumor localizations and is related to better outcome. Postoperative death is reported only among sellar region localizations, whereas brain hemispheric cases show the best overall survival. AT/RTs show different and peculiar features according to their location, which significantly affects the outcome; precise knowledge of them helps the neurosurgeon in planning the best strategy for treatment.

Medulloblastomas, CNS embryonal tumors, and cerebellar mutism syndrome: advances in care and future directions.

Central nervous system (CNS) embryonal tumors, commonly found in pediatric patients, represent a heterogeneous mix of lesions with an overall poor (though improving) prognosis. Medulloblastomas are by far the most frequently encountered and most widely studied subtype, though others include atypical teratoid/rhabdoid tumors (AT/RTs), embryonal tumor with multilayered rosettes (ETMRs), and CNS neuroblastomas, FOX-R2 activated. The classification, diagnosis, and treatment of these lesions have evolved drastically over the years as their molecular underpinnings have been elucidated. We describe the most recent 2021 WHO Classification system, discuss current understanding of the genetic basis, and demonstrate current thinking in treatment for these highly complex tumors. Since surgical resection continues to remain a mainstay of treatment, preventing and managing surgical complications, especially cerebellar mutism syndrome (CMS), is paramount. We describe the current theories for the etiology of CMS and two centers' experience in mitigating its risks. As our surgical toolbox continues to evolve along with our understanding of these tumors, we hope future patients can benefit from both improved overall survival and quality of life.

Survival Benefit from Multimodal Treatment for Patients with Atypical Teratoid Rhabdoid Tumor in a Surveillance, Epidemiology, and End Results Database Analysis

Introduction: Atypical teratoid rhabdoid tumor (ATRT) is among the most aggressive central nervous system malignancies. Although rare, this tumor typically afflicts young children and results in mortality within months. Here, we aim to determine key clinical features and treatment options that impact the survival of patients with ATRT. Methods: From the year 2000 to 2019, 363 patients with ATRT were identified from the Surveillance, Epidemiology, and End Results database. Univariate analysis was used to identify variables that had a significant impact on the primary endpoint of overall survival (OS). Multivariable analysis was then used to identify independent predictors of survival. Results: The median OS of the entire cohort was 13 months. Univariate analysis identified ages between 1 and 3 years, ages between 4 and 17 years, years of diagnosis between 2010 and 2019, and the receipt of treatment to have a significant impact on survival. In multivariable analysis, ages between 1 and 3 years and receipt of treatment were the only significant independent predictors of survival. The median OS was significantly greater in patients who received surgical treatment, chemotherapy, or radiation when compared to those who did not receive any treatment. In general, the receipt of any combination of therapies improved the median OS significantly. The receipt of triple therapy had the greatest impact on survival. Discussion: This study highlights the survival benefit of a multimodal approach in the treatment of ATRT. The use of triple therapy, including surgery, radiation, and chemotherapy, was found to have the greatest survival benefit for patients. Overall, these findings may guide future care for patients with ATRT.

Modeling human brain rhabdoid tumor by inactivating tumor suppressor genes in induced pluripotent stem cells

Atypical teratoid/rhabdoid tumor (ATRT) is a rare childhood malignancy that originates in the central nervous system. Over ninety-five percent of ATRT patients have biallelic inactivation of the tumor suppressor gene SMARCB1. ATRT has no standard treatment, and a major limiting factor in therapeutic development is the lack of reliable ATRT models. We employed CRISPR/Cas9 gene-editing technology to knock out SMARCB1 and TP53 genes in human episomal induced pluripotent stem cells (Epi-iPSCs), followed by brief neural induction, to generate an ATRT-like model. The dual knockout Epi-iPSCs retained their stemness with the capacity to differentiate into three germ layers. High expression of OCT4 and NANOG in neurally induced knockout spheroids was comparable to that in two ATRT cell lines. Beta-catenin protein expression was higher in SMARCB1-deficient cells and spheroids than in normal Epi-iPSC-derived spheroids. Nucleophosmin, Osteopontin, and Ki-67 proteins were also expressed by the SMARCB1-deficient spheroids. In summary, the tumor model resembled embryonal features of ATRT and expressed ATRT biomarkers at mRNA and protein levels. Ribociclib, PTC-209, and the combination of clofilium tosylate and pazopanib decreased the viability of the ATRT-like cells. This disease modeling scheme may enable the establishment of individualized tumor models with patient-specific mutations and facilitate high-throughput drug testing.

Rhabdoid tumors in patients conceived following ART: is there an association?

In children affected by rhabdoid tumors (RT), are there clinical, therapeutic, and/or (epi-)genetic differences between those conceived following ART compared to those conceived without ART? We detected a significantly elevated female predominance, and a lower median age at diagnosis, of children with RT conceived following ART (RT_ART) as compared to other children with RT. Anecdotal evidence suggests an association of ART with RT. This was a multi-institutional retrospective survey. Children with RT conceived by ART were identified in our EU-RHAB database (n = 11/311 children diagnosed between January 2010 and January 2018) and outside the EU-RHAB database (n = 3) from nine different countries. A population-representative German EU-RHAB control cohort of children with RTs conceived without ART (n = 211) (EU-RHAB control cohort) during the same time period was used as a control cohort for clinical, therapeutic, and survival analyses. The median follow-up time was 11.5 months (range 0-120 months) for children with RT_ART and 18.5 months (range 0-153 months) for the EU-RHAB control cohort. We analyzed 14 children with RT_ART diagnosed from January 2010 to January 2018. We examined tumors and matching blood samples for SMARCB1 mutations and copy number alterations using FISH, multiplex ligation-dependent probe amplification, and DNA sequencing. DNA methylation profiling of tumor and/or blood samples was performed using DNA methylation arrays and compared to respective control cohorts of similar age (n = 53 tumors of children with RT conceived without ART, and n = 38 blood samples of children with no tumor born small for gestational age). The median age at diagnosis of 14 individuals with RT_ART was 9 months (range 0-66 months), significantly lower than the median age of patients with RT (n = 211) in the EU-RHAB control cohort (16 months (range 0-253), P = 0.03). A significant female predominance was observed in the RT_ART cohort (M:F ratio: 2:12 versus 116:95 in EU-RHAB control cohort, P = 0.004). Eight of 14 RT_ART patients were diagnosed with atypical teratoid rhabdoid tumor, three with extracranial, extrarenal malignant rhabdoid tumor, one with rhabdoid tumor of the kidney and two with synchronous tumors. The location of primary tumors did not differ significantly in the EU-RHAB control cohort (P = 0.27). Six of 14 RT_ART patients presented with metastases at diagnosis. Metastatic stage was not significantly different from that within the EU-RHAB control cohort (6/14 vs 88/211, P = 1). The incidence of pathogenic germline variants was five of the 12 tested RT_ART patients and, thus, not significantly different from the EU-RHAB control cohort (5/12 versus 36/183 tested, P = 0.35). The 5-year overall survival (OS) and event free survival (EFS) rates of RT_ART patients were 42.9 ± 13.2% and 21.4 ± 11%, respectively, and thus comparable to the EU-RHAB control cohort (OS 41.1 ± 3.5% and EFS 32.1 ± 3.3). We did not find other clinical, therapeutic, outcome factors distinguishing patients with RT_ART from children with RTs conceived without ART (EU-RHAB control cohort). DNA methylation analyses of 10 tumors (atypical teratoid RT = 6, extracranial, extrarenal malignant RT = 4) and six blood samples from RT_ART patients showed neither evidence of a general DNA methylation difference nor underlying imprinting defects, respectively, when compared to a control group (n = 53 RT samples of patients without ART, P = 0.51, n = 38 blood samples of patients born small for gestational age, P = 0.1205). RTs are very rare malignancies and our results are based on a small number of children with RT_ART. This cohort of patients with RT_ART demonstrated a marked female predominance, and a rather low median age at diagnosis even for RTs. Other clinical, treatment, outcome, and molecular factors did not differ from those conceived without ART (EU-RHAB control cohort) or reported in other series, and there was no evidence for imprinting defects. Long-term survival is achievable even in cases with pathogenic germline variants, metastatic disease at diagnosis, or relapse. The female preponderance among RT_ART patients is not yet understood and needs to be evaluated, ideally in larger international series. M.C.F. is supported by the 'Deutsche Kinderkrebsstiftung' DKS 2020.10, by the 'Deutsche Forschungsgemeinschaft' DFG FR 1516/4-1 and by the Deutsche Krebshilfe 70113981. R.S. received grant support by Deutsche Krebshilfe 70114040 and for infrastructure by the KinderKrebsInitiative Buchholz/Holm-Seppensen. P.D.J. is supported by the Else-Kroener-Fresenius Stiftung and receives a Max-Eder scholarship from the Deutsche Krebshilfe. M.H. is supported by DFG (HA 3060/8-1) and IZKF Münster (Ha3/017/20). BB is supported by the 'Deutsche Kinderkrebsstiftung' DKS 2020.05. We declare no competing interests. N/A.

SYST-12 LP-184, A NOVEL ACYLFULVENE-DERIVED TUMOR SITE ACTIVATED SMALL MOLECULE INHIBITS ADULT AND PEDIATRIC CNS TUMOR CELL GROWTH

Abstract Blood-brain barrier (BBB) permeable agents effective against recurrent, chemotherapy-resistant central nervous system (CNS) tumors are urgently needed, particularly in Glioblastoma multiforme (GBM) and atypical teratoid/rhabdoid tumors (ATRT). These represent extremely aggressive and lethal types of CNS malignancies. LP-184 is a next-generation acylfulvene class drug candidate and has received FDA orphan drug designations for the treatment of malignant gliomas and ATRT. LP-184 creates covalent DNA adducts that are selectively repaired via nucleotide excision repair (NER). Repair of LP-184-induced DNA damage is mediated by ERCC complexes. Consistent with this, we observed 3-6X decreased cancer cell viability in U87, M1123 and Mayo39 GBM cells treated with LP-184 in combination with the ERCC3 degrader Spironolactone (SP) relative to LP-184 alone. Mice bearing pre-established subcutaneous U87 xenografts were treated with SP alone, LP-184 alone or their combination. Tumors recurred after initial regression in 5/5 animals treated with LP-184 alone whereas tumors showed durable complete regression without recurrence in 4/5 animals treated with LP-184 + SP. Thus, LP-184 likely functions as a synthetically lethal agent in the presence of DNA repair deficiencies. LP-184 inhibited cell growth in CHLA06 and BT37 ATRT cell lines, with IC50s in the 20-25nM range. LP-184 induced apoptosis 96 hours after treatment in these ATRT cell lines as measured by immunofluorescence for cleaved caspase-3 and Western blot for c-PARP. LP-184 intravenous treatment at 4 mg/kg twice weekly for 2 weeks showed tumor regression in mice implanted with CHLA06 ATRT subcutaneous xenografts, with 112% tumor growth inhibition and 2/10 treated mice being tumor-free at study termination. LP-184 further showed favorable intracranial tumor bioavailability along with in vivo BBB permeability comparable to other CNS cancer drugs. These findings identify LP-184 as a promising new agent and support its further development for treating CNS tumors in adult and pediatric populations.

Recurrent atypical teratoid/rhabdoid tumors (AT/RT) reveal discrete features of progression on histology, epigenetics, copy number profiling, and transcriptomics.

Atypical teratoid/rhabdoid tumors (AT/RT) are the most common malignant brain tumors manifesting in infancy. They split into four molecular types. The major three (AT/RT-SHH, AT/RT-TYR, and AT/RT-MYC) all carry mutations in SMARCB1, the fourth quantitatively smaller type is characterized by SMARCA4 mutations (AT/RT-SMARCA4). Molecular characteristics of disease recurrence or metastatic spread, which go along with a particularly dismal outcome, are currently unclear. Here, we investigated tumor tissue from 26 patients affected by AT/RT to identify signatures of recurrences in comparison with matched primary tumor samples. Microscopically, AT/RT recurrences demonstrated a loss of architecture and significantly enhanced mitotic activity as compared to their related primary tumors. Based on DNA methylation profiling, primary tumor and related recurrence were grossly similar, but three out of 26 tumors belonged to a different molecular type or subtype after second surgery compared to related primary lesions. Copy number variations (CNVs) differed in six cases, showing novel gains on chromosome 1q or losses of chromosome 10 in recurrences as the most frequent alterations. To consolidate these observations, our cohort was combined with a data set of unmatched primary and recurrent AT/RT, which demonstrated chromosome 1q gain and 10 loss in 18% (n = 7) and 11% (n = 4) of the recurrences (n = 38) as compared to 7% (n = 3) and 0% (n = 0) in the primary tumors (n = 44), respectively. Similar to the observations made by DNA methylation profiling, RNA sequencing of our cohort revealed AT/RT primary tumors and matched recurrences clustering closely together. However, a number of genes showed significantly altered expression in AT/RT-SHH recurrences. Many of them are known tumor driving growth factors, involved in embryonal development and tumorigenesis, or are cell-cycle-associated. Overall, our work identifies subtle molecular changes that occur in the course of the disease and that may help define novel therapeutic targets for AT/RT recurrences.