DNA methylation landscapes in DIPG reveal methylome variability that can be modified pharmacologically

Ashley R Tetens; Allison M Martin; Antje Arnold; Orlandi V Novak; Adrian Idrizi; Rakel Tryggvadottir; Jordyn Craig-Schwartz; Athanasia Liapodimitri; Kayleigh Lunsford; Michael I Barbato; Charles G Eberhart; Adam C Resnick; Eric H Raabe; Michael A Koldobskiy

doi:10.1093/noajnl/vdae023

DNA methylation landscapes in DIPG reveal methylome variability that can be modified pharmacologically

Neurooncol Adv. 2024 Feb 19;6(1):vdae023. doi: 10.1093/noajnl/vdae023. eCollection 2024 Jan-Dec.

Authors

Ashley R Tetens^{1

2}, Allison M Martin³, Antje Arnold², Orlandi V Novak², Adrian Idrizi¹, Rakel Tryggvadottir¹, Jordyn Craig-Schwartz^{1

2}, Athanasia Liapodimitri^{1

2}, Kayleigh Lunsford^{1

2}, Michael I Barbato^{1

2}, Charles G Eberhart⁴, Adam C Resnick^{5

6}, Eric H Raabe^{2

4}, Michael A Koldobskiy^{1

2}

Affiliations

¹ Center for Epigenetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
² Pediatric Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
³ Pediatric Hematology-Oncology, Albert Einstein College of Medicine, Bronx, New York, USA.
⁴ Neuropathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
⁵ Center for Data-Driven Discovery in Biomedicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
⁶ Division of Neurosurgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.

Abstract

Background: Diffuse intrinsic pontine glioma (DIPG) is a uniformly lethal brainstem tumor of childhood, driven by histone H3 K27M mutation and resultant epigenetic dysregulation. Epigenomic analyses of DIPG have shown global loss of repressive chromatin marks accompanied by DNA hypomethylation. However, studies providing a static view of the epigenome do not adequately capture the regulatory underpinnings of DIPG cellular heterogeneity and plasticity.

Methods: To address this, we performed whole-genome bisulfite sequencing on a large panel of primary DIPG specimens and applied a novel framework for analysis of DNA methylation variability, permitting the derivation of comprehensive genome-wide DNA methylation potential energy landscapes that capture intrinsic epigenetic variation.

Results: We show that DIPG has a markedly disordered epigenome with increasingly stochastic DNA methylation at genes regulating pluripotency and developmental identity, potentially enabling cells to sample diverse transcriptional programs and differentiation states. The DIPG epigenetic landscape was responsive to treatment with the hypomethylating agent decitabine, which produced genome-wide demethylation and reduced the stochasticity of DNA methylation at active enhancers and bivalent promoters. Decitabine treatment elicited changes in gene expression, including upregulation of immune signaling such as the interferon response, STING, and MHC class I expression, and sensitized cells to the effects of histone deacetylase inhibition.

Conclusions: This study provides a resource for understanding the epigenetic instability that underlies DIPG heterogeneity. It suggests the application of epigenetic therapies to constrain the range of epigenetic states available to DIPG cells, as well as the use of decitabine in priming for immune-based therapies.

Keywords: DNA hypomethylating agents; diffuse intrinsic pontine glioma; diffuse midline glioma; epigenetic variability.