Ku-DNA binding inhibitors modulate the DNA damage response in response to DNA double-strand breaks

Area of Science:

• Molecular Biology
• Cancer Therapeutics
• DNA Repair Mechanisms

Background:

• DNA-dependent protein kinase (DNA-PK) is crucial for DNA damage response (DDR) and double-strand break (DSB) repair via non-homologous end joining (NHEJ).
• DNA-PK is a therapeutic target for cancer, particularly in DNA repair-deficient cancers and when combined with ionizing radiation (IR).
• Previous work identified novel Ku-DNA binding inhibitors (Ku-DBi's) targeting the Ku 70/80 heterodimer interaction with DNA.

Purpose of the Study:

• To investigate the potentiation of cellular effects of DNA-damaging agents by chemical inhibition of the Ku-DNA interaction.
• To elucidate the downstream signaling pathways affected by Ku-DBi's, including ATM activation and p53 phosphorylation.
• To assess the impact of Ku-DBi's on DNA-PKcs and H2AX phosphorylation as indicators of DSB repair and DDR modulation.

Main Methods:

• Utilized chemical inhibitors targeting the Ku-DNA interaction (Ku-DBi's).
• Assessed cellular responses to bleomycin and IR in the presence of Ku-DBi's.
• Measured p53 and H2AX phosphorylation, and DNA-PKcs autophosphorylation at S2056.

Main Results:

• Ku-DBi's potentiated the cellular effects of bleomycin and IR, leading to p53 phosphorylation via ATM pathway activation.
• Inhibition of Ku-DNA interaction reduced DNA-PKcs autophosphorylation at S2056.
• Observed a time-dependent increase in H2AX phosphorylation at S139, indicating DDR activation.

Conclusions:

• Ku-DBi's abrogate DNA-PKcs autophosphorylation, impacting DSB repair and DDR signaling through a novel mechanism.
• These inhibitors represent a promising strategy for enhancing anticancer therapy when combined with DNA DSB-inducing agents.
• The findings support Ku-DBi's as a novel therapeutic approach for specific cancer treatments.