Senescence, Necrosis, and Apoptosis Govern Circulating Cell-free DNA Release Kinetics

The kinetics of circulating cell-free DNA (cfDNA) release may provide a real-time assessment of induced cell death. However, there is a limited understanding of the underlying biological rationale for cfDNA release following distinct treatments and cell death mechanisms. Here, we uncover a complex interplay between apoptosis, necrosis, and senescence in determining cfDNA release kinetics. Utilizing multiple in vitro and in vivo preclinical models, we show how cfDNA release is modulated through a combination of apoptotic and senescent triggers and inhibitors. Interestingly, we identify treatment-induced senescence as a previously unrecognized determinant of cfDNA kinetics that can counteract its release. Necrosis is the predominant cell death mechanism that consistently contributes to cfDNA release in response to ionizing radiation, and, surprisingly, apoptosis plays a comparatively minor role in some tumors. Based on our results, we propose a model to explain cfDNA release from cells over time, with important implications for future studies.