S1P, the product of SphK1 and SphK2, plays different roles: SphK1 drives HCC proliferation and angiogenesis through S1P signaling, while SphK2 has a dual role, with pro-apoptotic or pro-survival effects depending on subcellular localization and microenvironment signals. The gene discussed is MBTPS1; the disease is hepatocellular carcinoma.