The effect of over-expressing PPARβ/δ and/or ligand activation of PPARβ/δ on cell proliferation in MDA-MB-231 and MCF7 cells. Cell proliferation was examined in real time in (A) MDA-MB-231 cells, MDA-MB-231-MigR1 (MigR1) or MDA-MB-231-hPPARβ/δ (hPPARβ/δ) or (E) MCF7 cells, MCF7-MigR1 (MigR1) or MCF7-hPPARβ/δ (hPPARβ/δ). Cell proliferation was examined in real time for (B) MDA-MB-231, (C) MDA-MB-231-MigR1 (MigR1) or (D) MDA-MB-231-hPPARβ/δ (hPPARβ/δ) cells with or without the indicated concentration of GW0742. Cell proliferation was examined in real time for (F) MCF7, (G) MCF7-MigR1 (MigR1) or (H) MCF7-hPPARβ/δ (hPPARβ/δ) cells with or without the indicated concentration of GW0742. *Significantly different than control, P ≤ 0.05.