Assessment of ferroptosis inducers and Nrf2 inhibitors as radiosensitisers in 2D and 3D breast cancer cell cultures

Ferroptosis is a form of programmed cell death that is modulated in some cancer cells as a pro-survival mechanism. Induction of ferroptosis is a potential anti-cancer strategy, and enhancement of ferroptosis has the potential to current anti-tumour mechanisms. In this study, we assessed the effect of the ferroptosis inducers Erastin, RSL-3 and FIN-56 on the radiosensitivity of MCF-7 and MDA-MB-231 breast cancer cell lines in 2D and 3D cell culture. Since some tumours modulate ferroptosis via increased Nrf2 production, and MCF-7 and MDA-MB-231 both produce Nrf2 protein, we also assessed the effects of the Nrf2 inhibitor ML385 on radiosensitivity. MDA-MB-231 was highly sensitive to all ferroptosis inducers, and ferroptosis was reversed by the ferroptosis inhibitors Ferrostatin-1, Liproxstatin-1 and Deferoxamine. MCF-7 was resistant to all ferroptosis inducers. MDA-MB-231 and MCF-7 cells were sensitive to irradiation in 2D cell culture but resistant in 3D alginate spheroids. There was also no robust enhancement to irradiation effects with ferroptosis inducers or ML385 in 2D or 3D cell culture or colony formation assays. Ferroptosis inducers did, however, show heterogeneous responses in 3D cell culture. These studies suggest targeting ferroptosis does not induce enhancement of ferroptotic cell death in breast cancer cells.