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Neurodevelopmental cognitive disorders provide insights into mechanisms of human brain development. Here, we report an intellectual disability syndrome caused by the loss of APC7, a core component of the E3 ubiquitin ligase anaphase promoting complex (APC). In mechanistic studies, we uncover a critical role for APC7 during the recruitment and ubiquitination of APC substrates. In proteomics analyses of the brain from mice harboring the patient-specific APC7 mutation, we identify the chromatin-associated protein Ki-67 as an APC7-dependent substrate of the APC in neurons. Conditional knockout of the APC coactivator protein Cdh1, but not Cdc20, leads to the accumulation of Ki-67 protein in neurons in vivo, suggesting that APC7 is required for the function of Cdh1-APC in the brain. Deregulated neuronal Ki-67 upon APC7 loss localizes predominantly to constitutive heterochromatin. Our findings define an essential function for APC7 and Cdh1-APC in neuronal heterochromatin regulation, with implications for understanding human brain development and disease.

We explored the clinical and pathological impact of epidermal growth factor receptor (EGFR) extracellular domain missense mutations. Retrospective assessment of 260 de novo glioblastoma patients revealed a significant reduction in overall survival of patients having tumors with EGFR mutations at alanine 289 (EGFR(A289D/T/V)). Quantitative multi-parametric magnetic resonance imaging analyses indicated increased tumor invasion for EGFR(A289D/T/V) mutants, corroborated in mice bearing intracranial tumors expressing EGFR(A289V) and dependent on ERK-mediated expression of matrix metalloproteinase-1. EGFR(A289V) tumor growth was attenuated with an antibody against a cryptic epitope, based on in silico simulation. The findings of this study indicate a highly invasive phenotype associated with the EGFR(A289V) mutation in glioblastoma, postulating EGFR(A289V) as a molecular marker for responsiveness to therapy with EGFR-targeting antibodies., QC 20180730

We explored the clinical and pathological impact of epidermal growth factor receptor (EGFR) extracellular domain missense mutations. Retrospective assessment of 260 de novo glioblastoma patients revealed a significant reduction in overall survival of patients having tumors with EGFR mutations at alanine 289 (EGFR(A289D/T/V)). Quantitative multi-parametric magnetic resonance imaging analyses indicated increased tumor invasion for EGFR(A289D/T/V) mutants, corroborated in mice bearing intracranial tumors expressing EGFR(A289V) and dependent on ERK-mediated expression of matrix metalloproteinase-1. EGFR(A289V) tumor growth was attenuated with an antibody against a cryptic epitope, based on in silico simulation. The findings of this study indicate a highly invasive phenotype associated with the EGFR(A289V) mutation in glioblastoma, postulating EGFR(A289V) as a molecular marker for responsiveness to therapy with EGFR-targeting antibodies.

We present the case of a patient with a left frontal glioblastoma with primitive neuroectodermal tumor features and hypermutated genotype in the setting of a POLE germline alteration. During standard-of-care chemoradiation, the patient developed a cervical spine metastasis and was subsequently treated with pembrolizumab. Shortly thereafter, the patient developed an additional metastatic spinal lesion. Using whole-exome DNA sequencing and clonal analysis, we report changes in the subclonal architecture throughout treatment. Furthermore, a persistently high neoantigen load was observed within all tumors. Interestingly, following initiation of pembrolizumab, brisk lymphocyte infiltration was observed in the subsequently resected metastatic spinal lesion and an objective radiographic response was noted in a progressive intracranial lesion, suggestive of active central nervous system (CNS) immunosurveillance following checkpoint blockade therapy.SignificanceIt is unclear whether hypermutated glioblastomas are susceptible to checkpoint blockade in adults. Herein, we provide proof of principle that glioblastomas with DNA-repair defects treated with checkpoint blockade may result in CNS immune activation, leading to clinically and immunologically significant responses. These patients may represent a genomically stratified group for whom immunotherapy could be considered. Cancer Discov; 6(11); 1230-6. ©2016 AACR.See related commentary by Snyder and Wolchok, p. 1210This article is highlighted in the In This Issue feature, p. 1197.