Investigate the Roles, Mechanisms and Therapeutics for H2BG53D Mutant Pancreatic Ductal Adenocarcinoma In vitro and In vivo

Abstract

Histone mutations are pervasive across various cancer types and represent a novel mechanism of epigenetic dysfunction. These mutations disrupt chromatin dynamics and nucleosome stability, leading to aberrant gene expression that drives cancerous phenotypes. Our group recently identified a specific cancer-associated histone mutation, H2BGly53-to-Asp (H2BG53D), in approximately 7% of pancreatic ductal adenocarcinoma (PDAC) cases. The G53D-mutant H2B is enriched at gene loci associated with cell migration pathways, leading to elevation in gene expression and enhanced oncogenic properties of PDAC. However, the molecular mechanisms underlying these effects were unclear. In this study, I found that H2BG53D mutation intensifies the interaction between nucleosomes and the facilitates chromatin transcription complex (FACT). RNA-seq and CUT&RUN-seq data reveal that FACT mediates the transcriptional changes induced by H2BG53D, facilitates the enrichment of G53D-H2B at target loci, and contributes to the oncogenic phenotypes observed in PDAC cells. Furthermore, using a genetic PDAC mouse model (KPC: Kras ^WT/LSL-G12D; Trp53 ^loxp/loxp; Pdx1-CreER), I found that H2BG53D mutation increases PDAC incidence, promotes liver and diaphragm metastasis, and significantly reduces the survival rate of the KPC mice. RNA-seq data reveals that H2BG53D mutation induces a distinct transcriptional profile supporting its oncogenic driver properties. To develop potential therapeutics for H2BG53D-PDAC, genome-wide CRISPR/Cas9 functional screening was conducted and Ribonucleotide Reductase Regulatory Subunit M2 (RRM2) was identified as a druggable target for H2BG53D. Combinatory treatment of Clofarabine (ribonucleotide reductase inhibitor) and Curaxin (FACT inhibitor) exhibits a synergistic inhibitory effect on H2BG53D-PDAC cells with lower toxicity in pancreatic ductal epithelial cells, unveiling a promising therapeutic avenue for PDAC patients with & without the H2BG53D mutation.

In conclusion, this study 1) delineates the molecular mechanisms by which the H2BG53D mutation alters the expression of genes in cancer-related pathways, 2) elucidates the roles and mechanisms of the H2BG53D mutation on PDAC development in vivo, and 3) identifies potential therapeutic interventions for H2BG53D-PDAC.

Date of Award	21 Nov 2024
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kui Ming CHAN (Supervisor)