MB and cancer: Considering the marked potential of Dp4e4mT as an anti-cancer agent, the current investigation examined for the first time the influence of its complexation with Fe(iii), Co(iii), Ni(ii), Cu(ii), Zn(ii), Ga(iii), and Pd(ii) to examine the effect on anti-proliferative activity and the oxidation of oxy-Hb and oxy-Mb.