A very recent study conducted on C57Bl/6N female mice with implanted E0771 mammary carcinoma cells, highlights that in vivo iron supplementation increases the availability of this metal in the TME and that this is accompanied by suppression of T cells activation as well as by the reduction of anti-PD-L1-based therapy efficacy (Tymoszuk et al., 2020). The gene discussed is CD274; the disease is breast carcinoma.