In radiation oncology, ionizing radiation is used to kill
cancer cells, in other words, the induction of different types of cell death. To investigate this cellular death and the associated
iron accumulation, the transfer, release, and participation of
iron after
radiation treatment was analyzed. We found that radiation-induced cell death varied in different
breast cancer cells and autophagy was induced in MDA-MB-231 and BT549 cells (
triple negative breast cancer cell line) rather than in MCF-7 and zr-75 cells.
Iron chelator deferoxamine (DFO), the autophagy inhibitor 3MA, silencing of the autophagy-related genes ATG5, and
Beclin 1 could decrease radiation induced cell death in MDA-MB-231 cells, while inhibitors of apoptosis such as
Z-VAD-FMK, ferroptosis inhibitor
ferrostatin-1 (Fer-1), and necroptosis inhibitor
Necrostatin-1 showed no change. This suggests the occurrence of autophagic cell death. Furthermore, we found that
iron accumulation and
iron regulatory proteins, including
transferrin (Tf),
transferrin receptor (CD71), and
Ferritin (FTH), increased after
radiation treatment, and the silencing of
transferrin decreased radiation-induced cell death. In addition, radiation increased lysosomal membrane permeabilization (LMP) and the release of lysosomal
iron and
cathepsins, while
cathepsins silencing failed to change cell viability. Radiation-induced
iron accumulation increased
Reactive oxygen species (ROS) generation via the Fenton reaction and increased autophagy in a time-dependent manner. DFO,
N-acetylcysteine (NAC), and overexpression of
superoxide dismutase 2 (SOD2) decreased ROS generation, autophagy, and cell death. To summarize, for the first time, we found that radiation-induced autophagic cell death was
iron-dependent in
breast cancer MDA-MB-231 cells. These results provide new insights into the cell death process of
cancers and might conduce to the development and application of novel therapeutic strategies for patients with apoptosis-resistant
breast cancer.