Fig. 5.

Mammospheres and CD133⁺ cells are resistant to conventional therapeutic agents. CD133⁺ and CD133⁻ cells were treated with increasing concentrations of (A) doxorubicin (^*P = 0.026) or (B) mitoxantrone (^**P = 0.029) and cell viability was assayed 48 h post-treatment. Mammospheres and adherent cells were treated with 1 nM vincristine (^#P < 0.003), 1 nM mitoxantrone (^##P < 0.001) or 1 nM doxorubicin (^###P < 0.001) and cell viability relative to untreated controls (0 nM) was assayed 48 h after treatment (C). Mammospheres and adherent cells were treated with increasing doses of γ-radiation and assayed for (D) cell viability (^*P = 0.029; ^**P = 0.015; ^***P = 0.001) and (E) colony formation ability (^#P = 0.009; ^##P = 0.003; ^###P = 0.089).