The TSA-induced ATX protects cancer cells from TSA-induced apoptosis through its lysoPLD activity. A, SW480 cells were treated with or without TSA (250 nM) for 24 hrs in the presence of LPC (100 μM) or LPA (5 μM) in the serum-free conditional medium containing 250 μg/ml fatty-acid free BSA, and then the apoptosis of SW480 cells were measured. B, SW480 cells were treated with or without TSA (250 nM) for 24 hrs, and then the concentrated conditional media (30-fold) were incubated with 100 μM LPC (18:1) for 6 hrs at 37°C. Lipids were extracted and analyzed by liquid chromatography-mass spectrometry (LC-MS). The levels of LPA (18:1) were obtained from three experiments. C, ATX siRNA was transfected into SW480 cells to block the ATX induction by TSA with non-specific siRNA (siNC) as the control. After siRNA transfection for 48 hrs, SW480 cells were treated with or without TSA (250 nM) in the presence of LPC (100 μM) or LPA (5 μM). The apoptosis of SW480 cells was measured after TSA treatment for 24 hrs. The p value derived from Student's t test is (**) p < 0.001.