Effect of herceptin, 4-hydroxy-tamoxifen (4-HOT) and RU486 on the mitochondrial respiration and on p70S6K status in BT474 cells. (A) Effect of antagonist of breast cancer receptors on AMPK and p70S6K status. BT474 cells were pre-treated with herceptin for 24 hours before adding 4-HOT/or RU486 for an additional 24 hours. Cell lysates were subjected to analysis of p70S6K and AMPK status. Data are representative of at least three independent experiments. (B) Mitochondrial respiration was determined using the Clark electrode after addition of the inhibitor as indicated in growth medium. BT474 cells (1 × 10^6 cells) were pre-treated with herceptin for 24 hours before adding 4-HOT/or RU486 for an additional 24 hours (the bar graph represents mean ± SD from three experiments).