A significant proportion of non-small cell lung cancer(NSCLC)patients experience accumu-lating chemotherapy-related adverse events,motivating the design of chemosensitizating strategies.The main cytotoxic damage induced by chemotherapeutic agents is DNA double-strand breaks(DSB).It is thus conceivable that DNA-dependent protein kinase(DNA-PK)inhibitors which attenuate DNA repair would enhance the anti-tumor effect of chemotherapy.The present study aims to systematically evaluate the efficacy and safety of a novel DNA-PK inhibitor M3814 in synergy with chemotherapies on NSCLC.We identified increased expression of DNA-PK in human NSCLC tissues which was associated with poor prognosis.M3814 potentiated the anti-tumor effect of paclitaxel and etoposide in A549,H460 and H1703 NSCLC cell lines.In the four combinations based on two NSCLC xenograft models and two chemo-therapy,we also observed tumor regression at tolerated doses in vivo.Moreover,we identified a P53-dependent accelerated senescence response by M3814 following treatment with paclitaxel/etoposide.The present study provides a theoretical basis for the use of M3814 in combination with paclitaxel and etoposide in clinical practice,with hope to aid the optimization of NSCLC treatment.