Small-Molecule Inhibition of CBX4/7 Hypersensitises Homologous Recombination-Impaired Cancer to Radiation by...

Area of Science:

• Oncology
• Molecular Biology
• Cancer Therapeutics

Background:

• Targeting DNA repair pathways is a promising strategy in cancer treatment.
• DNA double-strand breaks (DSBs) are critical lesions, and their repair mechanisms, particularly homologous recombination (HR), are key targets.
• CBX4, a SUMO E3 ligase, modulates DNA end resection, a crucial step in HR repair.

Purpose of the Study:

• To investigate the therapeutic potential of UNC3866, a novel small molecule inhibitor of CBX4.
• To determine the effect of UNC3866 on DNA repair pathways and cancer cell sensitivity to ionizing radiation (IR).
• To explore the selective killing of homologous recombination-deficient (HR-deficient) cancer cells.

Main Methods:

• Treatment of cancer cells with UNC3866.
• Assessment of DNA repair pathway inhibition, including homologous recombination (HR), alternative end joining (alt-EJ), and single-strand annealing (SSA).
• Evaluation of cancer cell sensitivity to ionizing radiation (IR) in HR-proficient and HR-deficient contexts.

Main Results:

• UNC3866 significantly sensitizes HR-deficient, NHEJ-hyperactive cancer cells to IR.
• UNC3866 treatment is non-toxic to selected HR-proficient cancer cells.
• The compound inhibits multiple end-resection-dependent DNA repair pathways, including HR, alt-EJ, and SSA.

Conclusions:

• UNC3866 effectively targets CBX4, inhibiting critical DNA repair processes.
• UNC3866 demonstrates selective toxicity towards HR-deficient cancer cells when combined with IR.
• The findings suggest a potential therapeutic vulnerability in HR-ineffective cancers exploitable by UNC3866.