SPHK1 and neoplasm: Multiplex IHC staining showed that overexpression of SPHK1 or MTA3 significantly boosted PD-L1+ cells but decreased the density of CD8+ T cells in the tumor region, indicating that SPHK1-MTA3-PD-L1 axis-mediated immune escape contributes to melanoma progression (Fig. 5h–j and Supplementary Fig. 10k).