Induction of apoptosis by clioquinol (CQ) + copper and pyrrolidine dithiocarbamate (PDTC) + copper complexes in premalignant- and malignant-MCF10 cells. CQ and PDTC were mixed in a 1:1 molar ratio with CuCl2. Normal-, premalignant, and malignant-MCF10 cells were treated with CQ alone (CQ), copper alone (Cu), or CQ + copper (CQ+Cu) at 20 μM, or PDTC alone or PDTC + copper (PDTC+Cu) at 5 μM for 24 h. Dimethylsulfoxide (DMSO) was used as a control. After treatment, cells were stained with Hoescht for determination of apoptotic nuclei. Nuclei that were punctate or granular and bright were considered apoptotic. (a) The normal MCF10 cell line showed no apoptosis induction from the ligand, copper, or mixture (<2% in all cases). However, both (b) the premalignant MCF10AT1K.cl2 and (c) the malignant MCF10DCIS.com cells showed a dramatic induction of apoptotic nuclei after treatment with the mixture. (b) The percentages of apoptosic nuclei in MCF10AT1K.cl2 cells were: CQ+Cu, 10%; PDTC+Cu, 63%; and others <2%. (c) The percentages of apoptotic nuclei in MCF10DCIS.com cells were: CQ+Cu, 65%; PDTC+Cu, 75%; and others <2%.