Western blotting analysis was performed as usually reported [34 (link)]. The GIST-T1 and GIST-T1/IMR cells were challenged with rabbit polyclonal anti-S1P (ab59870), anti-SPK1 (ab260073), anti-β-actin antibodies (ab8826) (Abcam company) and ABCC1 (DF7148) (Affinity company). Proteins were visualized with enhanced chemiluminescence detection reagent according to the manufacturer’s instructions (Pierce, Rockford, Illinois).