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Published on: May 17, 2016
Identification of G-Quadruplex-Binding Inhibitors of Myc Expression through Affinity Selection-Mass Spectrometry
Deborah A Flusberg1, Noreen F Rizvi2, Victoria Kutilek2
11 Oncology, Merck & Co., Inc., Boston, MA, USA.
Abstract:
The Myc oncogene is overexpressed in many cancers, yet targeting it for cancer therapy has remained elusive. One strategy for inhibition of Myc expression is through stabilization of the G-quadruplex (G4), a G-rich DNA secondary structure found within the Myc promoter; stabilization of G4s has been shown to halt transcription of downstream gene products. Here we used the Automated Ligand Identification System (ALIS), an affinity selection-mass spectrometry method, to identify compounds that bind to the Myc G4 out of a pool of compounds that had previously been shown to inhibit Myc expression in a reporter screen. Using an ALIS-based screen, we identified hits that bound to the Myc G4, a small subset of which bound preferentially relative to G4s from the promoters of five other genes. To determine functionality and specificity of the Myc G4-binding compounds in cell-based assays, we compared inhibition of Myc expression in cells with and without Myc G4 regulation. Several compounds inhibited Myc expression only in the Myc G4-containing line, and one compound was verified to function through Myc G4 binding. Our study demonstrates that ALIS can be used to identify selective nucleic acid-binding compounds from phenotypic screen hits, increasing the pool of drug targets beyond proteins.
Insights
Researchers identified compounds targeting the Myc oncogene by stabilizing its G-quadruplex (G4) structure. This approach successfully inhibited cancer gene expression, demonstrating a novel therapeutic strategy beyond protein targets.
Area of Science:
- Oncology
- Medicinal Chemistry
- Molecular Biology
Background:
- The Myc oncogene is frequently overexpressed in various cancers, presenting a significant therapeutic challenge.
- Stabilizing G-rich DNA secondary structures, known as G-quadruplexes (G4s), in the Myc promoter offers a strategy to inhibit Myc transcription.
- Targeting non-protein structures like G4s expands the scope of potential cancer therapeutics.
Purpose of the Study:
- To identify compounds that selectively bind to and stabilize the Myc G-quadruplex (G4) structure.
- To validate the efficacy and specificity of identified compounds in inhibiting Myc expression in cancer cells.
- To demonstrate the utility of affinity selection-mass spectrometry for discovering nucleic acid-binding compounds.
Main Methods:
- Utilized the Automated Ligand Identification System (ALIS), an affinity selection-mass spectrometry technique.
- Screened a library of compounds previously shown to inhibit Myc expression via reporter assays.
- Assessed compound binding affinity and selectivity for the Myc G4 compared to other gene promoter G4s.
- Conducted cell-based assays to evaluate Myc expression inhibition in G4-dependent and independent cell lines.
Main Results:
- Identified several compounds that bind to the Myc G4 structure.
- A subset of these compounds exhibited preferential binding to the Myc G4 over other G4s.
- Specific compounds demonstrated Myc expression inhibition exclusively in cell lines with Myc G4 regulation.
- One compound was confirmed to exert its inhibitory effect through direct binding to the Myc G4.
Conclusions:
- The Automated Ligand Identification System (ALIS) is effective for discovering selective nucleic acid-binding compounds.
- Stabilizing the Myc G-quadruplex is a viable strategy for inhibiting Myc oncogene expression in cancer.
- This study expands the landscape of potential drug targets to include nucleic acid structures, moving beyond traditional protein-centric approaches.
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