Inhibition of SphK1 impairs migration and invasion ability of MDA-MB-231 cells, and reduced the metastatic ability of MDA-MB-231 cells in NOD/SCID mice. (A) MDA-MB-231 cells were infected with Ad-NC-siRNA, Ad-SPHK1-siRNA #1, or Ad-SPHK1-siRNA #2 at 10 MOI for 24 hours, migration was determined. (B) MDA-MB-231 cells were treated with SphK1 inhibitor PF543 (5 μM and 10 μM) for 24 hours, migration was determined. (C) MDA-MB-231 cells were infected with Ad-NC-siRNA, Ad-SPHK1-siRNA #1, or Ad-SPHK1-siRNA #2 at 10 MOI for 24 hours, invasion was determined. (D) MDA-MB-231 cells were treated with SphK1 inhibitor PF543 (5 μM and 10 μM) for 24 hours, invasion was determined. All data was shown by mean ±SD; * p<0.05; ** p<0.01. (E) Silencing of SphK1 expression in MDA-MB-231 cells, the in vivo metastatic ability was determined by intrasplenic injection of MDA-MB-231 cells in female NOD/SCID mice. In four to six weeks after injection, animals were scarified for examination of tumor metastasis in different organs.