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PATH-46. DETECTING MISDIAGNOSED ATYPICAL TERATOID/RHABDOID TUMOR (ATRT) BY DNA METHYLATION-BASED TUMOR CLASSIFICATION

ABSTRACT: Abstract Brain tumor diagnostics is achieved by combining morphology assessment and biomarker identification. However, the inter-observer variability of the histopathological diagnosis and lack of distinctive biomarkers makes these diagnoses particularly challenging. Recently, the potential for methylation-based characterization has been developed for brain tumors. To provide accurate and efficient brain tumor diagnostics, The Jackson Laboratory developed a DNA methylation array (Illumina Infinium HD Methylation EPIC), combining the “Classifier” established by the German Cancer Research Center (DKFZ), which can identify 82 distinct central nervous system tumors. Here we present a pediatric patient referred to us for medulloblastoma subtype classification by the methylation profile. Surprisingly, the array classified the tumor type as atypical teratoid/rhabdoid tumor (ATRT), subclass SHH. Also, the CNV profile indicated the SMARCB1/INI1 heterozygous deletion as part of the chromosome 22q deletion typically seen in ATRT, and absent was the isochromosome 17q commonly associated with medulloblastoma. Immunohistochemistry confirmed the loss of SMARCB1/INI1 expression leading to ATRT. Additionally, our NGS panel found a novel SMARCB1/INI1 frameshift variant c.1150delG (p.Ala384fs) in the last exon (exon 9). Although this variant is not expected to induce nonsense-mediated mRNA decay, it is located in the ATP-dependent nucleosome-remodeling complex domain Sfh1/SNF5 (IPR017393), which is associated with cell proliferation and differentiation. In addition, ClinVar reported several pathogenic/likely pathogenic variants in this domain, further supporting SMARCB1/INI1 c.1150delG which, together with the SMARCB1/INI1 deletion, may contribute to the loss of SMARCB1/INI1 expression, resulting in ATRT. We have identified the ATRT misclassification by the methylation profile and characterized a novel SMARCB1/INI1 variant c.1150delG most likely contributing to ATRT. We further propose that the DNA methylation profile will significantly improve the brain tumor diagnostics for cases with ambiguous, or contradictory histology and molecular profiles.

SUBMITTER: Hsiao M

PROVIDER: S-EPMC6847758 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Project description:Abstract Novel therapies are needed to for the treatment of atypical teratoid/rhabdoid tumor (ATRT), an aggressive brain tumor that predominantly affects young children and has an average 5-year survival under 50%. Claudin-6 (CLDN6) is a tight junction protein present during development and is expressed in up to 70% of ATRT specimens but not in normal tissue, making it a promising immunotherapeutic target. CLDN6-targeted chimeric antigen receptor (CAR) T cells in combination with a CAR T cell-amplifying mRNA vaccine have demonstrated antitumor activity against other CLDN6-expressing cancers in pre-clinical and a phase I adult trial (NCT04503278; Haanen J et al AACR, 2022). To assess the effectiveness of CLDN6-targeted CAR T cells against ATRT, we utilized a second-generation mRNA CAR with a 4-1BB costimulatory domain and single-chain variable fragment against CLDN6 (Reinhard et al, 2020). CLDN6 expression in patient-derived ATRT specimens was profiled by RNAseq (mean FPKM 11.4) and immunohistochemistry (positive staining in 53% of specimens). Tumor-derived cell lines were assessed for CLDN6 expression by flow cytometry. Co-culture of CLDN6-directed mRNA CAR T cells resulted in tumor-specific cytotoxicity compared to CD19-directed control CAR T cells in CLDN6-positive ATRT cell lines 7316-2187 (92% versus 15% at 10:1, p < 0.0001; 86% versus 0% at 5:1, p<0.0001) and 7316-2141 (75% versus 7% at 10:1, p<0.0001; 53% versus 0% at 5:1, p< 0.0001). Patient-derived, orthotopic xenograft ATRT models were created through intracranial injection of tumor cells into the cerebellum of NSG mice. Following engraftment with 7316-2141, repeated intratumoral administration of mRNA CLDN6 CAR T cells resulted in significant tumor regression (-1.9x108 vs. +2.4x109 p/sec/cm2/sr, p<0.001) and improved survival compared to mRNA CD19 CAR T cells (median OS not reached vs. 13 days, p=0.002). This work highlights the potential for targeting CLDN6 via CAR T cell therapy in patients with ATRT as a novel therapeutic strategy.

Project description:Atypical teratoid/rhabdoid tumor (AT/RT) is an extremely malignant neoplasm in the central nervous system (CNS) which occurs in infancy and childhood. Recent studies suggested that CD133 could be considered a marker for brain cancer stem-like cells (CSCs). However, the role of CD133 in AT/RT has never been investigated. Herein we report the isolation of CD133-positive cells (CD133(+)), found to have the potential to differentiate into three germ layer tissues, from tissues of nine AT/RT patients. The migration/invasion/malignancy and radioresistant capabilities of CD133(+) were significantly augmented when compared to CD133(-). The clinical data showed that the amount of CD133(+) in AT/RTs correlated positively with the degree of resistance to radiation therapy. Using cDNA microarray analysis, the genotoxic-response profiles of CD133(+) and CD133(-) irradiated with 10 Gy ionizing radiation (IR) were analyzed 0.5, 2, 6, 12 and 24 h post-IR. We then validated these microarray data and showed increased phosphorylation after IR of p-ATM, p-RAD17, and p-CHX2 as well as increased expression of BCL-2 protein in CD133(+) compared to CD133(-). Furthermore, we found that CD133(+) can effectively resist IR with cisplatin- and/or TRAIL-induced apoptosis. Immunohistochemical analysis confirmed the up-regulated expression of p-ATM and BCL-2 proteins in IR-treated CD133(+) xenotransgrafts in SCID mice but not in IR-treated CD133(-). Importantly, the effect of IR in CD133(+) transplanted mice can be significantly improved by a combination of BCL-2 siRNA with debromohymenialdisine, an inhibitor of checkpoint kinases. In sum, this is the first report indicating that CD133(+) AT/RT cells demonstrate the characteristics of CSCs. The IR-resistant and anti-apoptotic properties in CD133(+) may reflect the clinical refractory malignancy of AT/RTs and thus the activated p-ATM pathway and BCL-2 expression in CD133(+) could be possible targets to improve future treatment of deadly diseases like AT/RT.

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PATH-46. DETECTING MISDIAGNOSED ATYPICAL TERATOID/RHABDOID TUMOR (ATRT) BY DNA METHYLATION-BASED TUMOR CLASSIFICATION

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