Human NK cells mainly express Siglec-7 and -9 [86], which engage with tumor-associated sialoglycans to suppress NK cell function through multiple mechanisms: (1) Siglec-9 binding to MUC16 on ovarian cancer cells inhibits anti-tumor responses [115]; (2) immune synapse formation induces Siglec-7 ligand accumulation and sustained inhibitory signaling through delayed glycoconjugate endocytosis [100]; and (3) in multiple myeloma, Siglec-7 engagement facilitates tumor escape from NK cell surveillance [9]. Here, MUC16 is linked to plasma cell myeloma.