Mujeeb, A. | Search bioRxiv

bioRxiv2023

H3.3-G34R Mutation-Mediated Epigenetic Reprogramming Leads to Enhanced Efficacy of Immune Stimulatory Gene Therapy in Pediatric High-Grade Gliomas

Diffuse hemispheric glioma (DHG), H3 G34-mutant, representing 9-15% of cases, are aggressive Central Nervous System (CNS) tumors with poor prognosis. This study examines the role of epigenetic reprogramming of the immune microenvironment and the response to immune-mediated therapies in G34-mutant DHG. To this end, we utilized human G34-mutant DHG biopsies, primary G34-mutant DHG cultures, and genetically engineered G34-mutant mouse models (GEMMs). Our findings show that the G34 mutation alters histone marks deposition at promoter and enhancer regions, leading to the activation of the JAK/STAT pathway, which in turn results in an immune-permissive tumor microenvironment. The implementation of Ad-TK/Ad-Flt3L immunostimulatory gene therapy significantly improved median survival, and lead to over 50% long term survivors. Upon tumor rechallenge in the contralateral hemisphere without any additional treatment, the long-term survivors exhibited robust anti-tumor immunity and immunological memory. These results indicate that immune-mediated therapies hold significant potential for clinical translation in treating patients harboring H3.3-G34 mutant DHGs, offering a promising strategy for improving outcomes in this challenging cancer subtype affecting adolescents and young adults (AYA). STATEMENT OF SIGNIFICANCEThis study uncovers the role of the H3.3-G34 mutation in reprogramming the tumor immune microenvironment in diffuse hemispheric gliomas. Our findings support the implementation of precision medicine informed immunotherapies, aiming at improving enhanced therapeutic outcomes in adolescents and young adults harboring H3.3-G34 mutant DHGs.

cancer biology↗

bioRxiv2022

Zinc Finger MYND-Type Containing 8 (ZMYND8) is epigenetically regulated in mutant Isocitrate Dehydrogenase 1 (IDH1) glioma to promote radioresistance

Mutant isocitrate dehydrogenase 1 (mIDH1) alters the epigenetic regulation of chromatin, leading to a hypermethylation phenotype in adult glioma. Establishment of glioma-specific methylation patterns by mIDH1 reprogramming drives oncogenic features of cancer metabolism, stemness and therapeutic resistance. This work focuses on identifying gene targets epigenetically dysregulated by mIDH1. Treatment of glioma cells with mIDH1 specific inhibitor AGI-5198, upregulated gene networks involved in replication stress. Specifically, we found that the expression of ZMYND8, a regulator of DNA damage response was decreased in three patient-derived glioma cell cultures (GCC) after treatment with AGI-5198. ZMYND8 functions as a chromatin reader to modulate enhancer activity and recruit DNA repair machinery. Knockdown of ZMYND8 expression sensitized mIDH1 GCCs to radiotherapy marked by decreased cellular viability. Following IR, mIDH1 glioma cells with ZMYND8 knockout (KO) exhibit significant phosphorylation of ATM and sustained {gamma}H2AX activation. ZMYND8 KO mIDH1 GCCs were further responsive to IR when treated with either BRD4 or HDAC inhibitors. The accumulation of DNA damage in ZMYND8 KO mIDH1 GCCs promoted the phosphorylation of cell cycle checkpoint proteins Chk1 and Chk2. In addition, the recruitment of ZMYND8 to sites of DNA damage has been shown to be PARP- dependent. PARP inhibition further enhanced the efficacy of radiotherapy in ZMYND8 KO mIDH1 glioma cells. These findings indicate the impact of ZMYND8 in the maintenance of genomic integrity and repair of IR-induced DNA damage in mIDH1 glioma. Translational RelevanceOur understanding of radioresistance mechanisms in patient-derived glioma cell cultures (GCC) that endogenously express mIDH1-R132H are limited. We have uncovered a novel gene target Zinc Finger MYND-Type Containing 8 (ZMYND8) that is downregulated following treatment of human mIDH1 GCCs with mIDH1 specific inhibitors. We demonstrate that suppression of ZMYND8 expression by shRNA knockdown or genetic knockout reduces the cellular viability of mIDH1 GCCs to ionizing radiation (IR). Our findings reveal an epigenetic vulnerability of mIDH1 GCCs to ZMYND8 knockout (KO) which results in impaired resolution of IR-induced DNA damage and induction of cell cycle arrest. Additionally, ZMYND8 KO mIDH1 GCCs display increased radiosensitivity to inhibition of epigenetic regulators BRD4, HDAC, and PARP which could be mediated by enhanced replicative stress.

cancer biology↗