SPHK1 and neoplasm: Notably, the SPHK1-MTA3 axis enhanced the tumor infiltration of CD4+CD25+FoxP3+ Tregs and F4/80+CD11b+CD206+MHC class II- M2-like tumor-associated macrophages, and this effect could be reversed by PD-1 mAb treatment (Supplementary Fig. 10b–d, i, j).