Impact of Optimized Ku-DNA Binding Inhibitors on the Cellular and In Vivo DNA Damage Response

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• DNA-dependent protein kinase (DNA-PK) is crucial for DNA damage response (DDR) and DNA double-strand break (DSB) repair via non-homologous end-joining (NHEJ).
• Ku protein binds to DSBs, activating DNA-PK, making DNA-PK inhibition a strategy to enhance cancer therapies like radiation.
• Previous Ku-DNA binding inhibitors (Ku-DBis) showed potential but lacked optimal cellular uptake.

Purpose of the Study:

• To discover novel oxindole Ku-DBis with enhanced cellular uptake and potent Ku-inhibitory activity.
• To evaluate the therapeutic potential of these new Ku-DBis as monotherapy and in combination with radiation in non-small cell lung cancer (NSCLC).
• To assess the in vivo efficacy of Ku-DBis in an NSCLC xenograft model.

Main Methods:

• Development and synthesis of novel oxindole Ku-DBis.
• In vitro assessment of Ku-inhibitory activity, cellular uptake, and NHEJ blocking.
• Evaluation of monotherapy and combination effects with ionizing radiation (IR) in various NSCLC cell lines (ATM-null, BRCA1-deficient).
• In vivo studies using an NSCLC xenograft model to assess drug efficacy, DNA-PK autophosphorylation, DDR modulation, and tumor proliferation.

Main Results:

• Novel oxindole Ku-DBis exhibited improved cellular uptake and retained potent Ku-inhibitory activity.
• ATM-null NSCLC cells were sensitive to Ku-DBi monotherapy and showed synergy with IR, while BRCA1-deficient cells were resistant and antagonistic with IR.
• In vivo, Ku-DBi treatment inhibited IR-dependent DNA-PKcs autophosphorylation, modulated DDR, and reduced tumor cell proliferation in an NSCLC xenograft model.

Conclusions:

• Oxindole Ku-DBis represent a promising new class of targeted cancer therapeutics with improved properties.
• Ku-DBis demonstrate potential for enhancing radiation therapy efficacy in specific cancer contexts, particularly ATM-null NSCLC.
• This study provides the first in vivo validation of Ku-targeted DNA-binding inhibitors impacting radiation response, highlighting their therapeutic utility.