Silibinin decreases serum- and DHT-stimulated PSA expression in LNCaP cells. (A) Effect of silibinin on intracellular PSA in cells grown in 10% FBS. Cells were treated with silibinin for 20 hr or for indicated times at 75 μg/ml; C, control cells treated with ethanol for 48 hr. (B) Effect of silibinin on secreted (medium) PSA in cells grown in 10% FBS. Cells were treated with silibinin for the indicated doses and time, and medium was collected. (C) Effect of silibinin on intracellular PSA in cells grown in 10% cFBS + 1 nM DHT. Cells were grown in: 1, 10% serum; 2, 10% cFBS; 3, 10% cFBS + 1 nM DHT; or 4, 10% cFBS supplemented with 1 nM DHT + 50 μg/ml of silibinin, and cell lysates were prepared. The data in C are at 5 days of cultures; silibinin was added at day 4. PSA protein levels were determined in cell lysates and medium as detailed in Materials and Methods. The Western blot data shown are representative of three independent experiments with similar findings.