Cell Transfection

The lentiviral vectors containing human SphK1 (LV-SphK1) or empty plasmid (LV-Cr) were procured from HANBIO Biotech (Shanghai, China). A 24-well plate was used to culture SK-HEP-1 to a confluence of 30–50%. They were then cultured in a fresh medium containing lentiviral vectors (MOI = 30) and polybrene (5 μg/ml) for 24 h, and then in a fresh medium for further culturing, followed by incubation for 48 h. The transfection efficiency of cells was studied using an inverted microscope and were incubated with a medium containing puromycin (1 μg/ml) to eliminate the untransfected cells. The transfected cells were cultured further, and the culture medium was used to isolate exosomes.