SELENOS and cancer: Among nanosystems, selenium nanoparticles (SeNPs) have demonstrated potent antiproliferative properties against several types of cancers, including breast and lung cancers.[12, 13] Selenium (Se) is incorporated into several selenoproteins, which are known for their roles in protecting against reactive oxygen species (ROS) and modulating immune and inflammation processes.[14, 15] Consequently, Se has garnered considerable attention for its potential to prevent or treat several diseases, including cancer, as malignant cells are more susceptible to Se‐induced cytotoxic effects.