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

Background: The DNA-dependent protein kinase (DNA-PK) plays a critical role in the non-homologous end joining (NHEJ) double-strand break (DSB) repair pathway and DNA damage response (DDR). Consequently, blocking DNA-PK activity is being pursued as therapeutic strategy for treatment of cancer combination with ionizing radiation (IR). Towards developing new class inhibitors, our laboratory previously reported development Ku-DNA binding inhibitors (Ku-DBis) that act via inhibition catalytic by interaction. Ku-DBis display nanomolar vitro, possess cellular NHEJ inhibitory activity, sensitize non-small cell lung (NSCLC) cells to DSB generating chemotherapeutics bleomycin etoposide. Material Methods: Using multiple NSCLC lines possessing mutations specific DDR genes we interrogated molecular mechanism involved sensitization DSBs function treatment. We employed viability assays coupled Western blot immunofluorescence determination activation assess how alteration impact Ku-DBi activity. Results: Our findings demonstrate DSB-inducing agents (bleomycin or IR), showed significant reduction autophosphorylation events DNA-PKcs at S2056 cluster compared agent alone. In addition, analysis phospho-ATM phospho-p53 levels these suggested ATM followed bleomycin, evidenced an increase phosphorylation Ser1981, modest p53 Ser15. results block DNA-DSB dependent autophosphorylation, resulting potentiating sensitivity IR, likely effect on ATM-dependent signaling pathway. Conclusions: this study, chemical interaction potentiates effects IR through This concomitant (pS2056). These data are consistent novel action abrogates potentially signaling, becoming promising approach part anticancer DSBs-inducing agents. No conflict interest.