Abstract PS2-12-23: Persistent Morphological and DNA Damage Changes Following Ultra-Low Dose and Dose Rate Radiation in a 3D Human Mammary Organoid Model with Wild-Type and p16-Mutant Isogenic Lines

Abstract Radiation exposure at ultra-low doses and dose rates—such as those encountered in medical imaging or by radiation workers—may still induce persistent biological effects in human tissue. Understanding these effects in genetically relevant models is essential for breast cancer risk assessment. We used a 3D human mammary acinar organoid system and isogenic epithelial cell lines, including one with a p16 mutation commonly found in normal women without cancer, to investigate long-term consequences of radiation. Isogenic human mammary epithelial cells (wild-type and p16 mutant) were cultured in Matrigel to form polarized acini. Organoids were irradiated with X-rays at a total dose of 10 mGy, delivered at 5 or 20 mGy/h. Morphology, DNA double-strand breaks (γH2AX), and preliminary markers of oxidative damage (ROS, 8-oxo-dG) were assessed 6 days post-exposure. Even at these extremely low doses, both wild-type and p16-mutant acini showed persistent changes in size and abnormal morphology. γH2AX foci were significantly elevated in irradiated samples. Preliminary ROS and oxidative DNA damage results are underway. The impact of the p16 mutation is being further investigated for each endpoint. This study demonstrates that 10 mGy of radiation at low dose rates can produce measurable long-term effects on tissue structure and DNA integrity in 3D mammary organoids. Inclusion of a common p16 mutation increases the relevance to population-level breast cancer risk modeling and highlights the need to consider low-dose exposures in genetically diverse individuals. Citation Format: A. Antypiuk, M. Kang, F. Cucinotta, J. Pluth. Persistent Morphological and DNA Damage Changes Following Ultra-Low Dose and Dose Rate Radiation in a 3D Human Mammary Organoid Model with Wild-Type and p16-Mutant Isogenic Lines [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-12-23.