LNCaP, LNCaP-AI, and LAPC4 cells were starved in 1% stripped medium for 24 hours. The cells were then treated with various concentrations of Heregulin-α for 24 hours (A). The cells were also treated with Lapatinib (10 uM) and Bortezomib (5 uM) without or with Heregulin-α (50 ng/ml) for 24 hours (B-D). The cell extracts were prepared and subjected to western blot analysis for sPLA2-IIa, HER2, P-HER2, HER3, and P-HER3.