MT-ND2 and cancer: The potential antitumor properties of Nd complexes (Nd0, Nd1, Nd2, Nd3, Nd4, and Nd5) in normal HaCaT cells and in A375, MCF-7, and PANC-1 cancer cells were investigated following a 48 h treatment with increasing concentrations—50, 100, 250, 500, and 1000 μg·mL−1, respectively.