Msi1 'knockdown' by a shRNA preferentially reduces CD133+ cells and stem cell marker expression. A. Lentivirus expression of an Msi1 shRNA. Left, 'Knockdown' (KD) of Msi1 in MCF-7 and T47D spheroid cells by an Msi1 shRNA (Msi1 shRNA) reduces Msi1, CD133, ErbB2 and pERK expression vs. the control shRNA (Contr shRNA). Right panel, quantitation of the western blot indicates that Msi1 was reduced by 77-84% in MCF-7 and T47D cells. B. Msi1 KD reduces stem cell marker expression in MCF-7 and T47D cells. CD133, Nanog, Oct4, Sox2, c-Myc and Bmi1 mRNA levels were determined by qRT-PCR. All stem cell markers, with the exception of Oct4 in T47D cells, were reduced by Msi1 knockdown. C. Left panel, Msi1 KD reduces Notch1 and increases p21CIP1 in MCF-7 and T47D spheroid cells. IC, Notch intracellular domain; FL, full-length Notch1. Middle panel, quantitation of Notch1 expression. Right panel, quantitation of p21CIP1 expression. D. Msi1 KD reduces Notch1 mRNA 2.7-5-fold, but not p21CIP1, in MCF-7 and T47D spheroid cells, respectively.