Targeting ATM enhances radiation sensitivity of colorectal cancer by potentiating radiation-induced cell death and antitumor immunity

Abstract

Proposed working model of targeting ATM for enhancing the radiation sensitivity of colorectal cancer. Targeting ATM increased IR-induced ROS levels, which not only triggers apoptosis but also aggravates mitochondrial damage, and facilitates cytosolic mtDNA-induced STING type-I IFN signaling. Activation of this pathway enhances the overall radiation response by boosting antitumor immune responses, thereby improving the effectiveness of radiation therapy in treating CRC. • High ATM phosphorylation correlates with poor radiotherapy response in patients with colorectal cancer. • ATM inhibition amplifies radiation-induced ROS accumulation and mitochondrial damage, activating the STING pathway. • The combination of radiotherapy and ATM inhibition boosts CD8+ T cell recruitment and activation. • ATM inhibition mitigates radiation-induced PD-L1 upregulation via the NEMO/NF-κB pathway, enhancing immune responses. • A novel combination of radiotherapy, ATM inhibitor, and PD-L1 blockade enhances tumor regression and survival. The efficacy of radiotherapy in colorectal cancer (CRC) is often limited by radiation resistance. Ataxia telangiectasia mutated (ATM) is well known for its role in repairing double-strand DNA breaks within the DNA damage response (DDR) pathway. However, whether ATM mediates other mechanisms contributing to radiation resistance remains insufficiently investigated. This study investigates how targeting ATM enhances CRC radiation sensitivity and evaluates combination strategies to improve radiotherapy outcomes. Clinical specimens were analyzed to correlate ATM activation with radiotherapy response. Functional assays, including EdU, cell viability, clonogenic survival, and apoptosis assays, were used to assess the impact of ATM inhibition on radiation sensitivity. Mechanistic insights were gained through RNA-seq, RT-qPCR, western blotting, ELISA, immunofluorescence, flow cytometry, ChIP-qPCR, and co-immunoprecipitation. In vivo efficacy was evaluated using subcutaneous tumor models in nude, BALB/c, and C57BL/6J mice. High ATM phosphorylation levels correlated with poor radiotherapy response in CRC patients. ATM inhibition enhanced radiation sensitivity in both in vitro and in vivo models. Mechanistically, ATM inhibition increased radiation-induced ROS accumulation and mitochondrial damage, leading to the release of mitochondrial DNA (mtDNA) into the cytosol and activation of the STING-type I interferon pathway. This enhanced CD8+ T cell infiltration and boosted antitumor immunity. Additionally, ATM inhibition partially alleviated the radiation-induced upregulation of PD-L1, likely through the ATM/NEMO/NF-κB pathway. Notably, triple therapy combining radiotherapy, an ATM inhibitor, and anti-PD-L1 achieved superior tumor control and remission in mouse models, including large, treatment-resistant tumors. Targeting ATM enhances radiation-induced tumor cell death and boosts antitumor immune responses, offering a promising strategy to overcome CRC radiation resistance. The synergy of radiotherapy, ATM inhibitior, and immune checkpoint blockade highlights a novel therapeutic approach for CRC management.

Topics & Concepts