Figure 6

FOXM1 increases expression of markers of epithelial-to-mesenchymal transition and invasiveness and induces an aggressive phenotype in breast cancer cells. (A) Fluorescence-activated cell sorting (FACS) evaluation of the expression of ABCG2 in control (Ctrl) MCF-7 and FOXM1-overexpressing (OE) MCF-7 cells. A FACS profile from one of three representative experiments is shown. FITC, Fluorescein isothiocyanate; FSC-H, Forward scatter height. (B) Representative images obtained using a conventional inverted microscope show spheroids formed after modulation of the levels of FOXM1. Higher-magnification section (inset) shows details of invadopodia advancing into the matrix. (C) Invasion assay in Ctrl, siFOXM1 and FOXM1-OE MCF-7 cells after 48 hours. (D) Evaluation by quantitative RT-PCR (qRT-PCR) of the expression profiles of epithelial-to-mesenchymal transition markers and (E) Rho-GTPase genes CDC42 and RhoB in Ctrl or siFOXM1- or FOXM1-OE MCF-7 cells. Mean ± SEM. *p < 0.05; **p < 0.01 vs. Ctrl. (F) Evaluation by qRT-PCR of the expression profiles of FOXM1, CDC42 and RhoB in total TamR or ABCG2+ or ABCG2- cell populations. (G) Invasion assay in TamR and in sorted ABCG2+ and ABCG2- cells. Data are mean ± SEM. *P < 0.05; **P < 0.01 vs. total TamR cells. (H) Schematic model depicting our findings for the role of FOXM1 in engendering tamoxifen resistance, increased proliferation and invasion and the upregulation of stem cell markers, Rho-GTPases and mitosis-related genes. ER, Estrogen receptor; MAPK, Mitogen-activated protein kinase.