The Intriguing Roles of Siglec Family Members in the Tumor Microenvironment

Sialic acid-binding receptors are expressed on the surfaces of a variety of immune cells and have complex and diverse immunoregulatory functions in health and diseases. Recent studies have shown that Siglecs could play diverse immune and nonimmune regulatory roles in the tumor microenvironment (TME) and participate in tumor progression through various mechanisms, such as regulating tumor growth and metastasis, mediating the inflammatory response, and promoting tumor immune escape, thereby affecting the prognoses and outcomes of patients. However, depending on the cell type in which they are expressed, each Siglec member binds to corresponding ligands in the microenvironment milieu to drive diverse cell physiological and pathological processes in tumors. Therefore, we herein summarize the expression spectra and functions of the Siglec family in human diseases, particularly cancer, and highlight the possibility of therapeutic interventions targeting the TME in the future.