Coculture with macrophages alters ferroptosis susceptibility of triple-negative cancer cells

Various treatment options, such as molecular targeted drugs and immune checkpoint blockades, are available for patients with cancer. However, some cancer types are refractory to molecular targeted therapies or acquire drug resistance after long-term treatment. Thus, ferroptosis, a newly defined type of programmed cell death caused by the iron-dependent accumulation of lipid peroxidation, has gained attention as a novel cancer treatment strategy. Understanding cell–cell interactions in the tumor microenvironment is important for the clinical application of ferroptosis inducers. However, the effects of cell–cell interactions on ferroptosis sensitivity remain unclear. Thus, we aimed to evaluate the effects of macrophage–cancer cell interactions on ferroptosis induction. Coculture experiments showed that conditioned medium prepared from macrophages did not alter the ferroptosis sensitivity of cancer cells. By contrast, coculture via transwell, which enables cell–cell interactions through secretion, increased the sensitivity of cancer cells to ferroptosis inducers. Additionally, direct coculture increased the susceptibility of cancer cells to RSL3-induced ferroptosis. Mechanistically, coculture with macrophages upregulated the levels of intracellular ferrous ions and lipid peroxidation in cancer cells. These findings provide novel insights into the mechanisms by which cell–cell interactions influence ferroptosis induction and application of ferroptosis inducers as a cancer treatment option.