Topo I activity in 4 T1-Luc-Oct3/
4pG-derived mammospheres. Adherent 4 T1-Luc mouse cells, expressing green fluorescent protein zsGreen under Oct-3/4 promoter, were grown as mammospheres under the conditions indicated. (A) Mammospheres were examined for Oct-3/4 expression by the visualization of fluorescence (green) under the same exposure setting expression. Images were obtained by fluorescent microscopy. After 6 days in culture, 4 T1-Luc-Oct3/4pG-derived mammospheres were isolated and nuclear extracts were made. Total nuclear proteins were added to a topo I-specific reaction mixture and reaction products were analyzed by agarose gel electrophoresis. (B) Representative result of topo I DNA-relaxation activity. (C) Quantification analysis of topo I activity. Results represent means ± SE of 3 experiments. Statistical significance was determined by the student’s t-test analysis: *p < 0.05.