# Project 1: Remodeling Chromatin and the Tumor Microenvironment: Direct Oncogenesis and Therapeutic Targeting

> **NIH NIH P01** · MASSACHUSETTS GENERAL HOSPITAL · 2020 · $343,436

## Abstract

PROJECT SUMMARY
A synthetic lethality screen was performed to identify hyper-dependencies in melanomas harboring
deficiencies in ARID genes—components of the SWI/SNF chromatin remodelers—which occur in 20-30% of
human cancers. ARID mutant melanomas exhibited extreme dependency on the H3K9-dimethylase G9a, a
druggable enzyme. This led to discovery of 6 melanoma cases harboring recurrent point mutation at an
identical residue in G9a’s catalytic domain. The mutation hyper-activates G9a and aligns to oncogenic
mutations in EZH2, a previously known oncogenic methyltransferase that targets a different histone-3 lysine
(K27). Beyond these rare activating G9a mutations we identified more common genomic G9a copy gains in
27.8% of melanomas in TCGA and found G9a dependency (via genetic or pharmacologic means) in human
melanoma lines with as little as one extra G9a copy. Corroborating our results, the Achilles Project (genome-
scale loss-of-function viability screening in many deeply annotated cancer cell lines) confirmed G9a
dependency among melanoma lines harboring either G9a amplification or ARID deficiency. The same
dependencies were also seen in multiple cancers beyond melanoma in Achilles. Furthermore, G9a copy gain
was accompanied by global elevations in H3K9 dimethylation, which correlated as a biomarker of G9a
dependency in G9a gained/amplified melanoma cells. Mechanistic studies revealed activation of the canonical
Wnt pathway as a vital dependency target, which is induced by G9a’s suppression of Wnt antagonist DKK1.
Tumor intrinsic Wnt activation is common in melanomas, though usually without pathway-intrinsic mutations—a
phenomenon now largely explained by G9a activation. Importantly, Wnt activity has been strongly implicated
by others as a trigger of tumor-induced immune evasion—of keen interest for efficacy of immunotherapy. Here,
Aim 1 will validate dependencies of G9a copy-gained and ARID loss-of-function human melanoma lines on
G9a, GLP, MITF, DKK1, and Wnt signaling. Global ATAC-seq, RNA-seq, and H3K9me2-ChIP-seq will be used
to identify additional G9a targets and mediators of viability in these melanomas. Aim 2 will test pharmacologic
G9a inhibition in multiple mouse and zebrafish models containing copy gains of G9a or GLP, or ARID2
deficiency, combined with either BRAF-targeted therapy or anti-PD1 immunotherapy. The latter study will
utilize novel isogenic engineered syngeneic murine melanomas containing or lacking UV-neoantigens,
permitting measurements of G9a targeting as a strategy to blunt the Wnt pathway’s immunosuppressive
activity, together with direct targeting of G9a’s cell-intrinsic oncogenic function. Human melanoma biopsies will
also be interrogated to corroborate preclinical models. These studies identify a novel oncogene (G9a) and,
through vital collaborations with Dr. Zon (zebrafish melanoma model), Drs. Liu and Zon (epigenetic
mechanisms), and Drs. Wucherpfennig and Rodig (immunological profiling), will reveal mechanisms,...

## Key facts

- **NIH application ID:** 9989066
- **Project number:** 5P01CA163222-07
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** DAVID E FISHER
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $343,436
- **Award type:** 5
- **Project period:** 2013-03-12 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9989066

## Citation

> US National Institutes of Health, RePORTER application 9989066, Project 1: Remodeling Chromatin and the Tumor Microenvironment: Direct Oncogenesis and Therapeutic Targeting (5P01CA163222-07). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9989066. Licensed CC0.

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