Targeting repressive histone methylation in cancer
File(s)
Author(s)
Dye, Izzy
Type
Thesis
Abstract
EZH2 and G9a are repressive histone lysine methyltransferases that are heavily implicated in tumourigenesis. Both enzymes silence transposable elements, the expression of which stimulates viral mimicry immune signalling. Additionally, EZH2 and G9a promote oncogenic cMYC activity. Analyses of pan-cancer cell lines demonstrated cell-intrinsic anticorrelation between immune signalling and cMYC-G9a/EZH2 repression, supporting contribution of EZH2 and G9a to cMYC-mediated immune repression.
These features recommend EZH2 or G9a inhibition (EZH2i/G9ai) as an anti-tumour approach. However, physical interaction and redundancy between the two enzymes may limit the efficacy of single EZH2i/G9ai. HKMTi-1-005 is a novel compound based on a peptide-competitive G9ai, modified with the aim of introducing EZH2i activity. ATACseq and RNAseq performed in ovarian high-grade serous carcinoma (HGSC) models supported EZH2i and G9ai effects; dual EZH2/G9a repression targets gained chromatin accessibility and were transcriptionally upregulated by treatment. Additionally, HKMTi-1-005 sensitivity was highly correlated with that of single EZH2i or G9ai in analyses of over 600 cancer cell lines. Biochemical assays revealed minimal direct EZH2i by HKMTi-1-005, suggesting an indirect EZH2 targeting effect.
Further investigations demonstrated that HKMTi-1-005 upregulated transposable elements and induced viral mimicry in HGSC models. Immune signalling was characterised by upregulation of a 7-
gene signature (7ISG). In parallel, HKMTi-1-005 de-repressed targets of cMYC-G9a/EZH2 repression
and downregulated canonical cMYC targets. Reflecting cMYC and immune effects, in vitro HKMTi-
1-005 sensitivity was greater in MYC-deregulated lines and those with low basal 7ISG expression. HKMTi-1-005 has been shown to prolong survival of HGSC mouse models, a tumour type with extensive MYC deregulation. The KM2 murine model of lung adenocarcinoma was used to verify treatment efficacy in another MYC-deregulated tumour; HKMTi-1-005 induced immune stimulation and prolonged survival.
The data support HKMTi-1-005 as an EZH2 and G9a targeting approach with anti-tumour efficacy. Further, they propose MYC deregulation and the 7ISG as stratification biomarkers for HKMTi-1-005 sensitivity.
These features recommend EZH2 or G9a inhibition (EZH2i/G9ai) as an anti-tumour approach. However, physical interaction and redundancy between the two enzymes may limit the efficacy of single EZH2i/G9ai. HKMTi-1-005 is a novel compound based on a peptide-competitive G9ai, modified with the aim of introducing EZH2i activity. ATACseq and RNAseq performed in ovarian high-grade serous carcinoma (HGSC) models supported EZH2i and G9ai effects; dual EZH2/G9a repression targets gained chromatin accessibility and were transcriptionally upregulated by treatment. Additionally, HKMTi-1-005 sensitivity was highly correlated with that of single EZH2i or G9ai in analyses of over 600 cancer cell lines. Biochemical assays revealed minimal direct EZH2i by HKMTi-1-005, suggesting an indirect EZH2 targeting effect.
Further investigations demonstrated that HKMTi-1-005 upregulated transposable elements and induced viral mimicry in HGSC models. Immune signalling was characterised by upregulation of a 7-
gene signature (7ISG). In parallel, HKMTi-1-005 de-repressed targets of cMYC-G9a/EZH2 repression
and downregulated canonical cMYC targets. Reflecting cMYC and immune effects, in vitro HKMTi-
1-005 sensitivity was greater in MYC-deregulated lines and those with low basal 7ISG expression. HKMTi-1-005 has been shown to prolong survival of HGSC mouse models, a tumour type with extensive MYC deregulation. The KM2 murine model of lung adenocarcinoma was used to verify treatment efficacy in another MYC-deregulated tumour; HKMTi-1-005 induced immune stimulation and prolonged survival.
The data support HKMTi-1-005 as an EZH2 and G9a targeting approach with anti-tumour efficacy. Further, they propose MYC deregulation and the 7ISG as stratification biomarkers for HKMTi-1-005 sensitivity.
Version
Open Access
Date Issued
2024-04
Date Awarded
2024-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Brown, Robert
McNeish, Iain
Sponsor
Medical Research Council (Great Britain)
Publisher Department
Department of Surgery & Cancer
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)