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Principal Investigator: Sarki A. Abdulkadir
Organization: NORTHWESTERN UNIVERSITY AT CHICAGO
Fiscal Year: 2024
Award: $542,383
Funding agency: National Cancer Institute
ABSTRACT
MYC oncoproteins (including c-MYC, L-MYC and N-MYC) play critical roles in the initiation, progression and
recurrence of many human malignancies. Extensive studies indicate that MYC is required to maintain tumor cell
survival and proliferation. We have recently used a novel approach that combined computer-aided modeling with
a rapid in vivo screen to develop a new series of direct small molecule inhibitors (MYCi’s) that show excellent
selectivity, potency and tolerability in multiple MYC-driven cancer models. These compounds demonstrate a
dual mechanism of action. First, direct binding of MYCi to MYC in the basic helix-loop-helix (bHLH) region
disrupts complex formation with MYC which is required for MYC transcriptional activity. Secondly, binding of
MYCi enhances MYC phosphorylation on threonine-58 (pT58) which promotes MYC degradation via the
ubiquitin-proteasome pathway. However the key downstream effectors of these events and how they might
impact cellular function are unknown. Reduction of MYC protein and enhanced pT58MYC may be expected to
have profound effects on MYC family protein interactions with each other and with chromatin. In this regard, we
have observed in preliminary studies that MYCi leads to selective loss of MYC at genomic loci enriched for
master chromatin regulators (CTCF and FOX), suggesting disruption of the 3D architecture of the MYC-bound
genome in response to MYCi. Additionally, unfolded MYC due to MYCi binding and/or enhanced MYC
degradation may provoke a cellular stress response. Using unbiased ATAC-seq and RNA-seq approaches, we
found that MYCi treatment activates the ATF4/CHOP stress response pathway. Importantly, activation of
ATF4/CHOP by MYCi is an on-target, MYC-dependent effect. ATF4 mediates MYCi antitumor activity as ATF4
depletion partially ameliorates the antitumor effects of MYCi. Furthermore, we propose that MYCi-induced ATF4
cytokines modulate the tumor microenvironment. Activation of the ATF4 pathway by MYCi exposes potential
therapeutic vulnerabilities for rational combination approaches, such as combination of MYCi with proteasome
inhibitors that activates ATF4. Based on the preliminary findings, our central hypotheses is that MYCi inhibits
MYC-dependent tumorigenesis by a dual-pronged mode of action. First, MYCi affects MYC family target gene
expression by disrupting MYC/MAX interaction and by promoting MYC degradation. Secondly, binding of MYCi
to MYC and/or MYC degradation activates an ATF4/CHOP stress response pathway that suppresses tumor cell
viability. We propose the following specific aims to test these hypotheses: Aim 1). To investigate the mechanisms
by which MYC inhibitor modulates MYC transcriptional activity and the epigenetic landscape. We will investigate
the consequences of MYCi treatment on the recruitment of MYC, pT58MYC, and associated factors to chromatin;
changes to 3D chromatin architecture; as well as the effects on MYC-driven transcriptional output in tumor cells
vitro and in vivo. Aim 2). To define the mechanisms and functional consequences of ATF4/CHOP pathway
activation by MYCi. We will determine mechanism of ARF4 upregulation by MYCi; define the role of MYCi-
induced ATF4 in regulating target gene expression, cell viability and tumorigenicity; and assess strategies that
exploit the consequences of ATF4 activation as a means of enhancing MYCi anti-tumor efficacy.
These studies are significant as MYC is implicated in the majority of human cancers. The studies advance the
use of MYCi as chemical probes to unmask distinct biology that complements the knowledge derived from
genetic manipulations of MYC proteins. The findings will contribute to the efforts aimed at developing small
molecule MYCi as potential therapeutics. Specifically, this work indicates that small-molecule MYC inhibitors
have an additional anti-tumor effect due to the activation of the ATF4 pathway beyond the antitumor effects of
suppressing MYC function. Finally, understanding this on-target ATF4 response provoked by small-molecule
MYCi will provide rational strategies for combination therapy to enhance MYCi efficacy.
Terms: <20S Catalytic Proteasome><20S Core Proteasome><20S Proteasome><20S Proteosome><3-D><3-Dimensional><3D><APF-1><ATAC sequencing><ATAC-seq><ATACseq><ATF><ATP-Dependent Proteolysis Factor 1><Affect><Animal Model><Animal Models and Related Studies><Architecture><Assay for Transposase-Accessible Chromatin using sequencing><Avian Myelocytomatosis Viral Oncogene Homolog><Basal Transcription Factor><Basal transcription factor genes><Binding><Biochemical><Biology><Cancer Genes><Cancer Model><Cancer-Promoting Gene><CancerModel><Cancers><Cell Body><Cell Function><Cell Growth in Number><Cell Multiplication><Cell Physiology><Cell Process><Cell Proliferation><Cell Survival><Cell Viability><Cells><Cellular Function><Cellular Physiology><Cellular Process><Cellular Proliferation><Cellular Stress><Cellular Stress Response><Cessation of life><Chemicals><Chromatin><Chromatin Structure><Combined Modality Therapy><Complex><Computer Assisted><Consensus><Coupled><DNA><DNA Binding><DNA Binding Interaction><DNA bound><Death><Deoxyribonucleic Acid><Dependence><Drug Kinetics><Drugs><Engineering / Architecture><Epigenetic><Epigenetic Change><Epigenetic Mechanism><Epigenetic Process><Event><Family><GSK-3beta><GSK-3β><Gene Expression><Gene Transcription><General Transcription Factor Gene><General Transcription Factors><Genes><Genetic Transcription><Genome><Genomics><HMG-20><HTH DNA Binding Domain><HTH Motifs><Helix-Turn-Helix Motifs><High Mobility Protein 20><Human><In Vitro><Knowledge><L-Threonine><MYC Family Protein><MYC Protein><MYC gene><Macropain><Macroxyproteinase><Malignant Neoplasms><Malignant Tumor><Malignant Tumor of the Lung><Malignant Tumor of the Prostate><Malignant neoplasm of lung><Malignant neoplasm of prostate><Malignant prostatic tumor><Maps><Mediating><Medication><Modeling><Modern Man><Molecular Interaction><Multicatalytic Proteinase><Multimodal Therapy><Multimodal Treatment><Oncogene Products><Oncogene Proteins><Oncogenes><Oncogenesis><Oncogenic><Oncoproteins><Output><Pathway interactions><Pharmaceutical Preparations><Pharmacokinetics><Phosphorylation><Play><Proliferating><Prosome><Prostate CA><Prostate Cancer><Prostate malignancy><Prostatic Cancer><Proteasome><Proteasome Endopeptidase Complex><Proteasome Inhibitor><Protein Phosphorylation><Proteins><Proteosome><Publishing><Pulmonary Cancer><Pulmonary malignant Neoplasm><RNA Expression><RNA Seq><RNA sequencing><RNAseq><Recurrence><Recurrent><Role><Series><Site><Stress><Subcellular Process><Testing><Therapeutic><Threonine><Toxicology><Transcription><Transcription Activation><Transcription Factor Proto-Oncogene><Transcription factor genes><Transcriptional Activation><Transforming Genes><Tumor Cell><Tumorigenicity><Ubiquitin><Up-Regulation><Upregulation><Work><activating transcription factor><anti-tumor effect><antitumor effect><assay for transposase accessible chromatin followed by sequencing><assay for transposase accessible chromatin seq><assay for transposase accessible chromatin sequencing><assay for transposase-accessible chromatin with sequencing><biological adaptation to stress><c myc><c-myc Genes><cancer microenvironment><cell stress><cmyc><combination therapy><combined modality treatment><combined treatment><computer aided><cytokine><drug/agent><efficacy study><epigenetically><gene locus><gene manipulation><genetic locus><genetic manipulation><genetically manipulate><genetically perturb><genome scale><genome-wide><genomewide><genomic location><genomic locus><glycogen synthase kinase 3 beta><glycogen synthase kinase 3β><helix loop helix><helix turn helix><in silico><in vivo><inhibitor><knock-down><knockdown><leukemia><lung cancer><malignancy><member><model of animal><multi-modal therapy><multi-modal treatment><multicatalytic endopeptidase complex><myc Oncogenes><neoplasm/cancer><neoplastic cell><new approaches><novel><novel approaches><novel strategies><novel strategy><overexpress><overexpression><pathway><programs><reaction; crisis><recruit><response><screening><screenings><small molecular inhibitor><small molecule><small molecule inhibitor><social role><stress response><stress; reaction><three dimensional><transcription factor><transcriptome sequencing><transcriptomic sequencing><tumor><tumor microenvironment><tumorigenesis><v-myc Avian Myelocytomatosis Viral Oncogene Cellular Homolog>