Topoisomerases activity in mammospheres. MCF7-derived mammospheres were isolated and nuclear extracts were made. Equal quantities of total nuclear proteins were added to a topo I- or topo II-specific reaction mixture and reaction products were analyzed by agarose gel electrophoresis. (A) Representative result of topo I DNA-relaxation activity. (B) Quantification analysis of topo I activity. (C) Representative result of topo II decatenation activity. (D) Quantification analysis of topo II activity. Results represent means ± SE of 3 experiments. Statistical significance was determined by the student’s t-test analysis: *p < 0.00001; **p < 0.05, compared to the adherent control.