PDE4D and prostate cancer: To test if Eggmanone overcomes prostate cancer cell chemo-resistance via sonic Hedgehog signaling, we treated the chemo-resistant prostate cancer DU-145TxR and PC3-TxR cell with shh (200 ng/mL), shh (200 ng/mL) combined with 3 μM Eggmanone, shh (200 ng/mL) with siRNA control and shh (200 ng/mL) with siRNA PDE4D.