Abstract 300: Senescence and secreted factors: implication of DNA damage response pathways
Authors: Jordan Desmul, Nicolas Malaquin, Francis Rodier
Journal: Cancer Research (2025)

Introduction Senescence is a tumor-suppressive mechanism characterized by a halt in cellular proliferation. It can be triggered by various genotoxic sources, such as exposure to ionizing radiation during anticancer therapies to prevent the proliferation of cells with DNA damage. These cells adopt a senescence-associated secretory phenotype (SASP), which consists of hundreds of molecules, including cytokines, chemokines, and other pro-inflammatory factors. These secretions have beneficial anti-proliferative effects. However, their long-term accumulation can lead to detrimental outcomes, such as aging and tumorigenesis, driven by chronic inflammation. The senescence mechanism develops progressively in multiple steps over several days following genotoxic stress. In our model of irradiation-induced senescence (IR-10Gy) in human fibroblasts (BJ, HCA2), IR activates DNA damage response (DDR) pathways. These cells enter senescence 7 to 10 days post-exposure and develop their SASP. It is well established that there is a link between DDR activation and SASP induction. The genetic depletion of key DDR players (ATM, CHK2, NBS1) results in SASP suppression. However, the timing of these processes does not coincide. While DDR pathways are activated within minutes of DNA damage, the SASP takes several days to develop. Thus, the mechanism by which DDR influences SASP activation remains poorly understood. We identified a late non-canonical branch of the DDR (ncDDR) that appears to activate several days after the initial stress and is associated with the late pro-inflammatory SASP. In contrast, the canonical DDR pathway seems responsible for early non-inflammatory secretions. These findings suggest that the composition of senescent cell secretions evolves over time. Objective: We hypothesize that during the multi-step process of senescence establishment, the composition of the SASP evolves based on the activation or deactivation of DDR pathways. Modulating DDR activation through irradiation or genetic/pharmacological approaches will allow us to understand its impact on SASP. Our objective is to determine how the activation of different DDR pathways drives SASP induction and how these pathways influence its composition over time. Results: We irradiated fibroblasts with increasing doses of irradiation (10, 20, 40, 80 Gy) to sustain a high level of canonical DDR activation. At day 10 post-IR, we observed: • a dose-dependent decrease in the number of cells with genomic instability, • an almost complete suppression of the pro-inflammatory factor IL-6, • a significant increase in the secretion of GDF15, another SASP factor. Interestingly, these results were reversed when analyzing the secretome 24 hours post-irradiation. In conclusion, increased DDR activation induced a significant increase in various components of the early SASP and demonstrated distinct regulation between the early and late SASP. Citation Format: Jordan Desmul, Nicolas Malaquin, Francis Rodier. Senescence and secreted factors: implication of DNA damage response pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 300.