Sphingolipid modulation and anti-tumor activity of Jaspine B in HepG2 bearing mice

The cytotoxicity of Jaspine B was evaluated across a concentration range of 0.5-50 μM, yielding a half maximal inhibitory concentration (IC₅₀) of 2.6 μM for HepG2 human hepatocellular carcinoma cells. To explore the mechanisms of Jaspine B, we investigated the expression of sphingosine kinase 1 (SphK1), a rate-limiting enzyme involved in the production of sphingosine-1-phosphate (S1P) from sphingosine, and the modulation of sphingolipids in HepG2 cells. Jaspine B reduced SphK1 expression and S1P levels in a dose-dependent manner. Additionally, flow cytometry analysis indicated that Jaspine B induces apoptosis in HepG2. In HepG2-xenografted mice, Jaspine B treatment (20 mg/kg/every other day for four weeks) reduced tumor size without significant changes in either body or organ weight. The anti-cancer effect in these mice was linked to reduced SphK1 expression in tumor tissue and lower plasma S1P levels. The concentration of Jaspine B in tumor tissue was 4.64 ± 2.05 μM, which exceeded its IC₅₀ value (2.6 μM for cytotoxicity and 1.4 μM for SphK1 inhibition), further supporting its efficacy through SphK1inhibition. The anti-cancer effect and reduced plasma S1P levels induced by Jaspine B were comparable to PF543, a selective SphK1 inhibitor, in HepG2-xenografted mice. In conclusion, this study provides in vitro and in vivo evidence that Jaspine B is a promising anti-cancer agent for hepatocellular carcinoma, acting through SphK1 inhibition, with favorable pharmacokinetic and tumor distribution properties. This study also suggested that reduced plasma S1P levels may serve as a therapeutic biomarker for SphK1 inhibitors in hepatocellular carcinoma treatment.