Luteolin reduces IGF-II secretion dose-dependently in HT-29 human colon cancer cells. (A) HT-29 cells were plated at a density of 2 × 106 cells/100 mm dish in DMEM/F12 supplemented with 10% FBS. After 24 h, cells were serum-starved with serum-free DMEM/F12 supplemented with 5 mg/L of transferrin and 5 μg/L of selenium for 24 h. Cells were treated with various concentrations (0 - 60 μmol/L) of luteolin. 24 h after luteolin treatment, conditioned media were collected and concentrated for immunoblot analysis with an anti-IGF-II antibody. The volumes of media loaded onto the gels were adjusted for equivalent cell numbers. Photographs of the chemiluminescent detection of the blot, which were representative of three independent experiments, are shown. (B) The relative abundance of each band was quantified via densitometric scanning of the exposed films, and the control levels were set at 100%. Each bar represents the mean ± SEM (n = 3). Means without a common letter differ, P < 0.05.