Replication repair deficiency (RRD) leading to hypermutation is an important driving mechanism of high-grade glioma (HGG) occurring predominantly in the context of germline mutations in ...RRD-associated genes. Although HGG presents specific patterns of DNA methylation corresponding to oncogenic mutations, this has not been well studied in replication repair-deficient tumors. We analyzed 51 HGG arising in the background of gene mutations in RRD utilizing either 450 k or 850 k methylation arrays. These were compared with HGG not known to be from patients with RRD. RRD HGG harboring secondary mutations in glioma genes such as
IDH1
and
H3F3A
displayed a methylation pattern corresponding to these methylation subgroups. Strikingly, RRD HGG lacking these known secondary mutations clustered together with an incompletely described group of HGG previously labeled “Wild type-C” or “Paediatric RTK 1”. Independent analysis of two comparator HGG cohorts showed that other RRD/hypermutant tumors clustered within these subgroups, suggesting that undiagnosed RRD may be driving some HGG clustering in this location. RRD HGG displayed a unique CpG Island Demethylator Phenotype in contrast to the CpG Island Methylator Phenotype described in other cancers. Hypomethylation was enriched at gene promoters with prominent demethylation in genes and pathways critical to cellular survival including cell cycle, gene expression, cellular metabolism, and organization. These data suggest that methylation arrays may provide diagnostic information for the detection of RRD HGG. Furthermore, our findings highlight the unique natural selection pressures in these highly dysregulated, hypermutant cancers and provide the novel impact of hypermutation and RRD on the cancer epigenome.
Abstract
The genetic contribution of rare pathogenic germline variation in cancer patients without a family history remains unclear. We sought to characterize the prevalence, spectrum, and clinical ...significance of pathogenic germline variation in cancer predisposition genes (CPGs) in pediatric brain tumor patients. Paired tumor and normal whole genome or exome sequencing was performed for 838 patients in the Pediatric Brain Tumor Atlas (PBTA). Rare variants in 196 CPGs were annotated as pathogenic (P) or likely pathogenic (LP) in an automated manner consistent with American College of Medical Genetics criteria and reviewed by an interdisciplinary panel. To assess enrichment, the frequency of CPG P-LP variants in cases was compared to the gnomAD v3.1 cancer-free control cohort (n=74,023). Second hit, mutational signature, and gene set enrichment analyses (GSEA) were performed on matched tumor sequencing to characterize differences in patients with and without germline P-LP variants in DNA repair genes. We observed 178 germline CPG P-LP variants in 163 PBTA patients (19.5%). CPG P-LP variants were most prevalent among Neurofibroma plexiform patients (64.3%), and NF1 and TSC2 harbored the most significant P-LP variant burden compared to controls (OR=69.5, p=2.4E-23, CI=34.6-137 and OR=357, p=1.1E-14, CI=71-3669, respectively). DNA repair gene P-LP variants were enriched in cases compared to controls (OR=4.4, p=8.3E-30). Patients harboring mismatch repair (MMR) gene P-LP variants exhibited significantly higher tumor-associated MMR-deficiency mutational signature exposures (p<0.05) and DNA repair GSEA scores relative to other patients (p=0.04). Second hit SNVs in tumors were identified in four patients with P-LP germline variants in NF1 (n=2), APC (n=1), and SUFU (n=1). Germline P-LP variants are enriched in PBTA patients, and DNA repair variants are predictive of repair-deficiency signatures in tumor samples. Our work emphasizes the need for germline sequencing to inform patient care.
The complicated, changing pattern of protein expression should contain important information about the pathologic process taking place in the cells of actual tissue. Utilization of this information ...for the selection of druggable targets could be possible if a means existed to rapidly analyze and display changes in protein expression in defined microscopic cellular subpopulations. As a demonstration of feasibility, we show the generation of sensitive, rapid, and reproducible molecular weight protein profiles of patient‐matched normal, premalignant, malignant, and metastatic microdissected cell populations from stained human esophageal, prostate, breast, ovary, colon, and hepatic tissue sections through the application of an affinity‐based biochip. Reproducible, discriminatory protein biomarker profiles can be obtained from as few as 25 cells in less than 5 min from dissection to the generation of the protein fingerprint. Furthermore, these protein pattern profiles reveal reproducible changes in expression as cells undergo malignant transformation, and are discriminatory for different tumor types. Consistent protein changes were identified in the microdissected cells from patient‐matched tumor and normal epithelium from eight out of eight different malignant esophageal tissue sets and three out of three malignant prostate tissue sets. A means to rapidly generate a display of expressed proteins from microscopic cellular populations sampled from tissue could be an important enabling technology for pharmacoproteomics, molecular pathology, drug intervention strategies, therapeutic assessment of drug entities, disease diagnosis, toxicity, and gene therapy monitoring. Drug Dev. Res. 49:34–42, 2000. Published 2000 Wiley‐Liss, Inc.
Abstract
Replication repair deficiency (RRD) is an important driving mechanism of pediatric high grade glioma (pHGG) occurring predominantly in the context of germline mutations in RRD-associated ...genes. Although pHGG present specific patterns of DNA methylation corresponding to driving oncogenic processes, methylation patterns have not been well studied in RRD tumors. We analyzed 52 RRD pHGG using either 450k or 850k methylation arrays. These arrays were compared with 234 PHGG driven by other genetic or epigenetic mechanisms and 10 additional pHGG samples known to be hypermutant. RRD pHGG displayed a methylation pattern corresponding to specific secondary mutations such as IDH1 and H3K27M. Strikingly, RRD pHGG lacking these known secondary mutations largely clustered together with a poorly described group previously labelled Wild type-C. Most of the hypermutant tumors clustered in a similar location suggesting undiagnosed RRD may be a driving force for tumors clustering in this location. Analysis of methylation patterns revealed that RRD pHGG displayed a unique CpG Island Demethylator Phenotype in contrast to the Methylator Phenotype described in other cancers. This effect was most concentrated at gene promotors. Prominent demethylation was observed in genes and pathways critical to cellular survival including cell cycle, gene expression, cellular metabolism and cellular organization. These data suggest that methylation profiles may provide diagnostic information for the detection of RRD pHGG. Furthermore, our findings highlight the unique natural selection pressures in these highly dysregulated, hypermutant cancers and provide novel impact of hypermutation and RRD on the cancer epigenome.
Abstract
High-grade gliomas harboring H3 G34R/V mutations exclusively occur in the cerebral hemispheres of adolescents and young adults, suggesting a distinct neurodevelopmental origin. Combining ...multimodal bulk and single-cell genomics with unbiased genome-scale CRISPR/Cas9 approaches, we here describe a GABAergic interneuron progenitor lineage as the most likely context from which these H3 G34R/V mutations drive gliomagenesis, conferring unique and tumor-selective gene targets essential for glioma cell survival, as validated genetically and pharmacologically. Phenotypically, we demonstrate that while H3 G34R/V glioma cells harbor the neurotransmitter GABA, they are developmentally stalled, and do not induce the neuronal hyperexcitability described in other glioma subtypes. These findings offer a striking counter-example to the prevailing view of glioma origins in glial precursor cells, resulting in distinct cellular, microenvironmental, and therapeutic consequences.
Abstract
BACKGROUND
Hypermutation constitute an important subgroup of cancers and confers sensitivity to immune checkpoint inhibition (ICI). Glioblastoma arising in children with Constitutional ...Mismatch Repair Deficiency Syndrome (CMMRD) are ultrahypermutant. Our objective was to quantify the frequency of hypermutant tumors in children, determine whether mutational signatures can predict germline mutations, and treat hypermutant tumors with ICIs.
METHODS
Deep panel sequencing of 2984 pediatric tumors (585 brain tumors). Tumor mutation burden was correlated to mutation burden from exome and genome sequencing (R2 = 0.94). Mutational signatures were analyzed to predict source of hypermutation. Data on 36 patients with hypermutant tumors identified by sequencing were enrolled on an ICI registry trial.
RESULTS
Hypermutant tumors (>10 mut/MB) comprised 5% of all pediatric tumors (n=143). These were highly enriched for replication repair mutations (p<0.0001) and mutation loads correlated with hypermutant adult tumors that have shown demonstrable clinical response to ICI. Hypermutation was found in 5% of childhood and 6% of adult glioblastoma. All glioblastomas with greater than 100 Mut/MB harbored MMR/polymerase mutations suggesting germline bMMRD (p =10-7). Clinical data collected on 19 ultrahypermutant tumors revealed germline mutations in replication repair genes in all patients. Of the 36 patients with hypermutant cancers treated with ICI, 24 had brain tumors, and favorable sustained responses are observed.
CONCLUSION
High mutation burden is a sensitive predictor of germline CMMRD. Hypermutant tumors are more common in the pediatric setting than previously appreciated, opening novel therapeutic avenues. ICI shows promise for hypermutant pediatric cancers including glioblastoma.
We recently identified a novel gene (PB39) (HGMW-approved symbol POV1) whose expression is up-regulated in human prostate cancer using tissue microdissection-based differential display analysis. In ...the present study we report the full-length sequencing of PB39 cDNA, genomic localization of the PB39 gene, and genomic sequence of the mouse homologue. The full-length human cDNA is 2317 nucleotides in length and contains an open reading frame of 559 amino acids which does not show homology with any reported human genes. The N-terminus contains charged amino acids and a helical loop pattern suggestive of an srp leader sequence for a secreted protein. Fluorescencein situhybridization using PB39 cDNA as probe mapped the gene to chromosome 11p11.1–p11.2. Comparison of PB39 cDNA sequence with murine sequence available in the public database identified a region of previously sequenced mouse genomic DNA showing 67% amino acid sequence homology with human PB39. Based on alignment and comparison to the human cDNA the mouse genomic sequence suggests there are at least 14 exons in the mouse gene spread over approximately 100 kb of genomic sequence. Further analysis of PB39 expression in human tissues shows the presence of a unique splice variant mRNA that appears to be primarily associated with fetal tissues and tumors. Interestingly, the unique splice variant appears in prostatic intraepithelial neoplasia, a microscopic precursor lesion of prostate cancer. The current data support the hypothesis that PB39 plays a role in the development of human prostate cancer and will be useful in the analysis of the gene product in further human and murine studies.
Abstract
Patients with constitutional mismatch repair deficiency (CMMRD) are prone to developing high-grade glioma (HGG). These tumours acquire DNA polymerase mutations and become ultra-hypermutant ...harbouring hundreds of mutations per megabase. The impact of these mutations on methylation profile and the ability of the tool to differentiate MMRD tumours from others is unknown. In order to answer these questions, we performed either 450k/850K methylation analysis on a cohort of 52 CMMRD-HGG and compared them to 148 non-CMMRD HGG and normal brain controls. CMMRD HGG harbouring classic mutations in histone 3 or IDH genes had a methylation profile which clustered closely with non-MMRD tumours harbouring these mutations. Tumours without these alterations exhibited a tendency to hypomethylation with some tumours being extremely hypomethylated in comparison to other HGG. Hypomethylation was unrelated to mutational burden and type of DNA polymerase mutation present. Gene set analysis of methylation patterns revealed enrichment of hypomethylation for cellular pathways involved in cellular metabolism, organelle maintenance, mitotic cell cycle and gene expression. This pattern persisted in subgroup analysis of IDH mutant tumours in patients with and without MMRD. Importantly, this pattern was present in MMRD HGG with mutational burdens <10 mutations/MB and shared between primary and recurrent tumours suggesting that hypomethylation is an early event. CMMR-HGG have unique pattern of hypomethylation which can distinguish them from other paediatric HGG. Several plausible explanations include that hypomethylation in specific pathways confer a survival advantage on the cells which acquire it, or that hypermutations in specific CpG affect methylation patterns in these genes.
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