SPHK1 and cancer: Furthermore, we systematically examined the potential functions of SPHK1 in antitumor immunity and found significant associations between SPHK1 expression levels and the abundance of suppressive tumor-infiltrating immune cell subsets, including regulatory T cells (Tregs; median Rs = 0.36), myeloid-derived suppressor cells (MDSCs; median Rs = 0.37), and tumor-associated macrophages (TAMs; median Rs = 0.32) across 33 cancer types (Fig. 1d).