Level of nuclear proteins in mammospheres. MCF7-derived mammospheres were isolated and nuclear protein extracts were prepared. Equal protein quantities were examined by Western blot analysis for topo I, topo II, β-actin, and lamin B (A). Densitometric analysis of the results was performed using the EZQuant-Gel software and the percentage of nuclear proteins level was calculated relative to the adherent MCF7 (B) or to β-actin (C). Results represent means ± SE values of at least 3 experiments. Statistical significance was determined by the student’s t-test analysis: *p < 0.05; **p < 0.01.