Cytosolic DNA in radiotherapy: relevance, mechanisms, and detection

Ionizing radiation (IR) is a cornerstone of cancer therapy, exerting cytotoxic effects primarily through the induction of DNA damage. Beyond direct tumor cell death, IR has been increasingly recognized for its capacity to modulate antitumor immune responses, in part through the accumulation of dispersed cytosolic double-stranded DNA (dsDNA) and micronuclei (MN) formation. These abnormally localized DNA structures are capable of engaging innate immune sensors such as the cGAS-STING pathway, linking IR and antitumor immune responses. This review highlights methodologies for the detection, quantification, and isolation of cytosolic DNA species, with a specific focus on dispersed cytosolic dsDNA and MN in the setting of IR. Together, these tools enhance our understanding of the role of MN and dispersed cytosolic dsDNA in IR-induced cellular responses and beyond. As the presence of MN and dispersed dsDNA in the cytosol act as interconnected but separate mediators of IR-induced immunogenicity, understanding their biology provides a foundation for optimizing combination therapies aimed at enhancing antitumor immunity. Modulating MN formation, MN rupture, and release of dispersed cytosolic dsDNA represents a promising avenue to enhance the efficacy of radiation-based cancer treatments.