Inhibition of ATM, ATR and DNA-PK radiosensitises 3D uveal melanoma models to X-rays and proton beam therapy.

Introduction: Proton beam therapy (PBT) is a well-established treatment modality for uveal melanoma (UM), where it exerts its therapeutic effect primarily through the induction of significant DNA damage, particularly DNA double strand breaks (DSBs) that are the most challenging for the cell to repair. Following DSB induction, a coordinated repair response is orchestrated by the key protein kinases, ataxia telangiectasia mutated (ATM), ataxia telangiectasia and Rad3-related (ATR) and DNA-dependent protein kinase catalytic subunit (DNA-PK). These enzymes detect damage and activate the appropriate DSB repair pathways, namely homologous recombination or non-homologous end joining to maintain genomic integrity. Targeting these major DNA damage response kinases is a promising therapeutic target in cancers, including UM, to enhance the therapeutic effect of radiation and potentially reduce the radiation dosage required for treatment, thus reducing the frequency and severity of adverse effects. Methods: Here, we investigate the response of 3D spheroid models of UM to both X-rays and PBT in the presence of inhibitors of ATM (AZD1390), ATR (AZD6738) and DNA-PK (AZD7648). Results: We demonstrate that inhibition of these protein kinases significantly suppresses the growth of UM spheroids exposed to both X-rays and PBT, which is primarily driven by delayed and persistent DSBs, leading to the accumulation of chromosomal aberrations. Discussion: These results highlight the potential of combining ATM, ATR or DNA-PK inhibitors to enhance radiotherapy efficacy, and particularly with targeted PBT, to help improve clinical outcomes in UM.