VTCN1 and cancer: In addition to PD-L2, there are immune checkpoint molecules (such as CD47 and CLEC4G) showing positive correlation with SPHK1 among bladder cancer patients, but not seen in the others such as VTCN1, CEACAM1, and IGSF11 (Fig. S3), implying SPHK1 might have other effects on cancer immune evasion by interacting with these molecules.