CD8A and neoplasm: Of note, Mn2+ itself acts as a potent cGAS‐STING activator, significantly enhancing CD8+T anti‐tumor immunity.[21] Employing inductively coupled plasma mass spectrometry (ICP‐MS), we detected the presence of Mn2+ (≈20 nm) in the cell culture supernatant upon Mn‐N/C plus H2O2 treatment (Figure S4C, Supporting Information).