Ubiquitin-mediated DNA damage response is synthetic lethal with G-quadruplex stabilizer CX-5461

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• CX-5461 is a G-quadruplex (G4) ligand showing clinical activity in cancers with homologous recombination repair defects.
• Identifying additional genetic vulnerabilities can expand therapeutic strategies for CX-5461.

Purpose of the Study:

• To identify genetic defects that sensitize tumors to CX-5461 through synthetic lethality screening.
• To investigate the role of DNA repair and genome maintenance genes in response to G4 ligands.

Main Methods:

• Conducted a synthetic lethality screen of 480 DNA repair and genome maintenance genes against CX-5461, pyridostatin (PDS), and BMH-21.
• Utilized cell-based assays to assess cell survival and analyzed gene expression and protein localization.

Main Results:

• Identified synthetic lethality with homologous recombination deficiency (HRD) and Fanconi Anemia pathway genes, as well as POLQ.
• Found significant synthetic lethality with UBE2N and RNF168, key regulators of DNA damage response and ubiquitin signaling.
• Observed increased RNF168 recruitment and histone ubiquitination upon CX-5461 treatment, co-localizing with G4 structures.

Conclusions:

• Uncovered novel genetic vulnerabilities, including UBE2N and RNF168, that sensitize cancer cells to CX-5461 and PDS.
• Demonstrated that pharmacological inhibition of UBE2N synergizes with CX-5461.
• These findings have potential significance for selecting patients likely to benefit from CX-5461 in clinical trials.