Inhibition of PI3K in serum-starved LNCaP cells induces apoptosis that is abrogated by introduction of EGF or serum. LNCaP cells serum-starved for 20 h were treated with fresh medium containing 10% serum (serum), serum-free medium (No serum), medium containing 10% serum and 25 μ M LY (LY+serum), serum-free medium with 25 μ M LY (LY) or serum-free medium containing 25 μ M LY and 100 ng/ml EGF (LY+EGF) for 6, 12 and 20 h before (a) cell death was determined by propidium iodide staining and (c) caspase 3 and (d) caspase 9 activity as described in Materials and methods. Percentage of cells in sub-G1 was analysed using the WINMDI 2.8 software. DNA histograms depicting % cell in sub-G1 of one of the experiments after 20 h incubation in different treatments is shown in (b). Results shown in (a), (c) and (d) are a mean of three experiments performed in duplicates±s.e.