In our research, we clearly evidenced that copper (II) promotes the phosphorylation of RTK as well as essential intracellular AKT and ERK pathways in two different cancer cells, i.e., A549 and DU145, supporting the hypothesis that the presence of high amounts of copper (II) in a tumor microenvironment may promote the cancer cell proliferation even if the natural ligands are deficient [28]. Here, MAPK1 is linked to cancer.