Short-term changes in energy metabolism of breast cancer cells under ultra-high dose rate irradiation

Objective To investigate the time-dependent effects of electron ultra-high dose rate irradiation (Ultra-high dose rate FLASH irradiation, FLASH-IR) and conventional dose rate irradiation (Conventional dose rate irradiation, CONV-IR) at different doses on energy metabolism in triple-negative breast cancer cells (MDA-MB-231).Methods MDA-MB-231 cells were exposed to FLASH-IR and CONV-IR (6 MeV electrons) at doses of 2 Gy and 14 Gy. Mitochondrial metabolism and glycolytic metabolism were analyzed using the Seahorse XF Pro Cell Metabolic Analyzer at 4 h, 24 h, and 48 h post-irradiation.Results Compared to normal breast epithelial cells (MCF-10A), breast cancer cells (MDA-MB-231) exhibit a greater reliance on glycolytic metabolism. Compared with the sham-irradiated group, 2 Gy CONV-IR significantly increased ATP-linked respiration in MDA-MB-231 cells at 4 h, 24 h, and 48 h post-irradiation (t= 2.69-3.70, P < 0.05). Glycolysis rate and glycolytic capacity were elevated only at 4 h, followed by a significant decrease at 48 h (t= 2.79, -4.44, P < 0.05). In contrast, no statistically significant differences were observed between the FLASH and CONV groups regarding these parameters (P > 0.05). However, FLASH-IR resulted in a relative decrease in proton leak at 4 h post-irradiation and a significant increase at 24 h and 48 h (t= -2.45, 3.19, 6.51, P < 0.05).Under the 14 Gy irradiation condition, CONV-IR gradually increased mitochondrial and glycolytic metabolic activities at all measured time points (t= 2.48-12.14, P < 0.05). Notably, compared to the CONV group, the FLASH group exhibited greater increases in basal respiration, ATP-linked respiration, and non-mitochondrial oxygen consumption (t= 2.56-6.51, P < 0.05), as well as significantly higher glycolytic potential at 24 h post-irradiation (t= 2.86, P < 0.05).Conclusions At a low dose (2 Gy), FLASH-IR induces higher levels of proton leak in MDA-MB-231 breast cancer cells, while at a high dose (14 Gy), it triggers a more pronounced mitochondrial metabolic stress response.