STAT3 and neoplasm: (1) Copper increases PD-L1 levels by inhibiting UPS-mediated degradation, facilitating the phosphorylation of STAT3 and EGFR, which are crucial proteins for tumor growth and immune escape.20,189 Copper chelators have also been shown to enhance the effectiveness of immune cells such as CD8+ T cells and natural killer (NK) cells in the tumor microenvironment (TME), thereby slowing tumor growth and improving survival rates in mice.20 (2) Copper promotes the secretion of LOXL4 by tumor cells.