Cited by 291Chromatin Remodeling and CancerProtein Degradation and InhibitorsGenomics and Chromatin Dynamics

The SMARCA2/4 ATPase Domain Surpasses the Bromodomain as a Drug Target in SWI/SNF-Mutant Cancers: Insights from cDNA Rescue and PFI-3 Inhibitor Studies

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Vangamudi, Bhavatarini, Paul, Thomas A., Shah, Parantu K., Kost-Alimova, Maria, Nottebaum, Lisa, Shi, Xi, Zhan, Yanai, Leo, Elisabetta +16 more·2015·Cancer Research

Published version of a preprint

Abstract

The SWI/SNF multisubunit complex modulates chromatin structure through the activity of two mutually exclusive catalytic subunits, SMARCA2 and SMARCA4, which both contain a bromodomain and an ATPase domain. Using RNAi, cancer-specific vulnerabilities have been identified in SWI/SNF-mutant tumors, including SMARCA4-deficient lung cancer; however, the contribution of conserved, druggable protein domains to this anticancer phenotype is unknown. Here, we functionally deconstruct the SMARCA2/4 paralog dependence of cancer cells using bioinformatics, genetic, and pharmacologic tools. We evaluate a selective SMARCA2/4 bromodomain inhibitor (PFI-3) and characterize its activity in chromatin-binding and cell-functional assays focusing on cells with altered SWI/SNF complex (e.g., lung, synovial sarcoma, leukemia, and rhabdoid tumors). We demonstrate that PFI-3 is a potent, cell-permeable probe capable of displacing ectopically expressed, GFP-tagged SMARCA2-bromodomain from chromatin, yet contrary to target knockdown, the inhibitor fails to display an antiproliferative phenotype. Mechanistically, the lack of pharmacologic efficacy is reconciled by the failure of bromodomain inhibition to displace endogenous, full-length SMARCA2 from chromatin as determined by in situ cell extraction, chromatin immunoprecipitation, and target gene expression studies. Furthermore, using inducible RNAi and cDNA complementation (bromodomain- and ATPase-dead constructs), we unequivocally identify the ATPase domain, and not the bromodomain of SMARCA2, as the relevant therapeutic target with the catalytic activity suppressing defined transcriptional programs. Taken together, our complementary genetic and pharmacologic studies exemplify a general strategy for multidomain protein drug-target validation and in case of SMARCA2/4 highlight the potential for drugging the more challenging helicase/ATPase domain to deliver on the promise of synthetic-lethality therapy. Cancer Res; 75(18); 3865–78. ©2015 AACR.

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Crossref · 10.1158/0008-5472.can-14-3798

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  • The targeted bromodomain proteins also harbored multiple other functional domains and often participate in protein-protein interactions that appeared bromodomain independent.

    “In all cases, the targeted proteins also harbored multiple other functional domains and are often participating in intricate protein–protein interactions that appeared to be bromodomain independent.”
  • Potent, specific, and well-characterized ligands for individual bromodomains largely lack cellular efficacy.

    “While these efforts culminated in potent, specific, and well-characterized ligands for the individual bromodomains, ensuing functional analyses revealed that they are largely lacking cellular efficacy.21”
  • SMARCA2/4 bromodomain inhibitors have failed to inhibit tumor cell growth because the ATPase domain but not the bromodomain is essential for tumor cell growth.

    “However, such inhibitors have failed to inhibit tumor cell growth [48] because the ATPase domain but not the bromodomain is essential for tumor cell growth [169].”

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Authors
Vangamudi, B., Paul, T. A., Shah, P. K., Kost-Alimova, M., Nottebaum, L., Shi, X., Zhan, Y., Leo, E., Mahadeshwar, H. S., Protopopov, A., Futreal, A., Tieu, T. N., Peoples, M., Heffernan, T. P., Marszalek, J. R., Toniatti, C., Petrocchi, A., Verhelle, D., Owen, D. R., Draetta, G., Jones, P., Palmer, W. S., Sharma, S., & Andersen, J. N.
Affiliations
  • The University of Texas MD Anderson Cancer Center (US)
  • Pfizer (United States) (US)
  • 1Institute for Applied Cancer Science, The University of Texas MD Anderson Cancer Center, Houston, Texas.
  • 3Department of Genomic Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Corresponding author
  • Sharma, Shikhar
  • Andersen, Jannik N.
Venue
Cancer Research
Published
2015-09-14
Volume
75
Issue
18
Pages
3865-3878
ISSN
  • 0008-5472 (ISSN-L)
  • 1538-7445
OpenAlex
W2137511124
Cited by
281
References
50
Citations by year
2026: 22 · 2025: 31 · 2024: 28 · 2023: 36 · 2022: 22 · 2021: 24 · 2020: 25 · 2019: 19 · 2018: 20 · 2017: 26 · 2016: 22 · 2015: 6
FWCI
11.30
Type
journal article
Language
en
Open access
Locations
  • Cancer Research (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion)
  • PubMed Central (acceptedVersion)
Funders
  • American Association for Cancer Research
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
  • National Cancer Institute (P30CA016672)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Chromatin Remodeling and Cancer
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Degradation and Inhibitors
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Chromatin Dynamics
Keywords
SMARCA2, SMARCA4, SWI/SNF complex, ATPase domain, bromodomain, bromodomain inhibitors, drug target validation, synthetic lethality, chromatin binding, cDNA rescue, rhabdoid tumor, synovial sarcoma, leukemia, transcriptional programs, chromatin immunoprecipitation
MeSH terms
Binding, Competitive, Catalysis, Chromatin, Chromosomal Proteins, Non-Histone, DNA Helicases, Genetic Complementation Test, Humans, Lung Neoplasms, Neoplasm Proteins, Neoplasms, Nuclear Proteins, Pyridines, Sarcoma, Synovial, Transcription Factors, Protein Structure, Tertiary, DNA, Complementary, Rhabdoid Tumor, RNA Interference, RNA, Small Interfering, Chromatin Assembly and Disassembly, Cell Line, Tumor, Microarray Analysis, Azabicyclo Compounds, Gene Knockout Techniques, Molecular Targeted Therapy

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