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Epigenetic profiling demarcates molecular subtypes of muscle-invasive bladder cancer.

ABSTRACT: Muscle-invasive bladder cancer (MIBC) is a heterogeneous disease that often recurs despite aggressive treatment with neoadjuvant chemotherapy and (radical) cystectomy. Basal and luminal molecular subtypes have been identified that are linked to clinical characteristics and have differential sensitivities to chemotherapy. While it has been suggested that epigenetic mechanisms play a role in defining these subtypes, a thorough understanding of the biological mechanisms is lacking. This report details the first genome-wide analysis of histone methylation patterns of human primary bladder tumours by chromatin immunoprecipitations and next-generation sequencing (ChIP-seq). We profiled multiple histone marks: H3K27me3, a marker for repressed genes, and H3K4me1 and H3K4me3, which are indicators of active enhancers and active promoters. Integrated analysis of ChIP-seq data and RNA sequencing revealed that H3K4 mono-methylation demarcates MIBC subtypes, while no association was found for the other two histone modifications in relation to basal and luminal subtypes. Additionally, we identified differentially methylated H3K4me1 peaks in basal and luminal tumour samples, suggesting that active enhancers play a role in defining subtypes. Our study is the first analysis of histone modifications in primary bladder cancer tissue and provides an important resource for the bladder cancer community.

SUBMITTER: van der Vos KE

PROVIDER: S-EPMC7331601 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Epigenetic profiling demarcates molecular subtypes of muscle-invasive bladder cancer.

van der Vos K E KE Vis D J DJ Nevedomskaya E E Kim Y Y Choi W W McConkey D D Wessels L F A LFA van Rhijn B W G BWG Zwart W W van der Heijden M S MS

Scientific reports 20200702 1

Muscle-invasive bladder cancer (MIBC) is a heterogeneous disease that often recurs despite aggressive treatment with neoadjuvant chemotherapy and (radical) cystectomy. Basal and luminal molecular subtypes have been identified that are linked to clinical characteristics and have differential sensitivities to chemotherapy. While it has been suggested that epigenetic mechanisms play a role in defining these subtypes, a thorough understanding of the biological mechanisms is lacking. This report deta ...[more]

PMID: 32616859

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Project description:BackgroundMuscle-invasive bladder cancer (MIBC) is a molecularly diverse disease with heterogeneous clinical outcomes. Several molecular classifications have been proposed, but the diversity of their subtype sets impedes their clinical application.ObjectiveTo achieve an international consensus on MIBC molecular subtypes that reconciles the published classification schemes.Design, setting, and participantsWe used 1750 MIBC transcriptomic profiles from 16 published datasets and two additional cohorts.Outcome measurements and statistical analysisWe performed a network-based analysis of six independent MIBC classification systems to identify a consensus set of molecular classes. Association with survival was assessed using multivariable Cox models.Results and limitationsWe report the results of an international effort to reach a consensus on MIBC molecular subtypes. We identified a consensus set of six molecular classes: luminal papillary (24%), luminal nonspecified (8%), luminal unstable (15%), stroma-rich (15%), basal/squamous (35%), and neuroendocrine-like (3%). These consensus classes differ regarding underlying oncogenic mechanisms, infiltration by immune and stromal cells, and histological and clinical characteristics, including outcomes. We provide a single-sample classifier that assigns a consensus class label to a tumor sample's transcriptome. Limitations of the work are retrospective clinical data collection and a lack of complete information regarding patient treatment.ConclusionsThis consensus system offers a robust framework that will enable testing and validation of predictive biomarkers in future prospective clinical trials.Patient summaryBladder cancers are heterogeneous at the molecular level, and scientists have proposed several classifications into sets of molecular classes. While these classifications may be useful to stratify patients for prognosis or response to treatment, a consensus classification would facilitate the clinical use of molecular classes. Conducted by multidisciplinary expert teams in the field, this study proposes such a consensus and provides a tool for applying the consensus classification in the clinical setting.

Dataset Information

Epigenetic profiling demarcates molecular subtypes of muscle-invasive bladder cancer.

Publications

Epigenetic profiling demarcates molecular subtypes of muscle-invasive bladder cancer.

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