Sialic acid-binding immunoglobulin-like lectin 9 as a potential therapeutic target for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease(COPD)has become the third-leading cause of death worldwide,which is a severe economic burden to the healthcare system.Chronic bronchitis is the most common condition that contributes to COPD,both locally and systemically.Neutrophilic inflammation predominates in the COPD airway wall and lumen.Logically,repression of neutrophilia is an essential fashion to COPD treatment.However,currently available anti-neutrophilic therapies provide little benefit in COPD patients and may have serious side effects.Thus,there is an urgent need to explore an effective and safe anti-neutrophilic approach that might delay progression of the disease.Sialic acid-binding immunoglobulin-like lectin(Siglec)-9 is a member of the Siglec cell surface immunoglobulin family.It is noteworthy that Siglec-9 is highly expressed on human neutrophils and monocytes.Ligation of Siglec-9 by chemical compounds or synthetic ligands induced apoptosis and autophagic-like cell death in human neutrophils.Furthermore,administration of antibody to Siglec-E,mouse functional ortholog of Siglec-9,restrained recruitment and activation of neutrophils in mouse models of airway inflammation in vivo.Given the critical role that neutrophils play in chronic bronchitis and emphysema,targeting Siglec-9 could be beneficial for the treatment of COPD,asthma,fibrosis,and related chronic inflammatory lung diseases.

Engagement of sialylated glycans with Siglec receptors on suppressive myeloid cells inhibits anticancer immunity via CCL2

The overexpression of sialic acids on glycans,called hypersialylation,is a common alteration found in cancer cells.Sialylated glycans can enhance immune evasion by interacting with sialic acid-binding immunoglobulin-like lectin(Siglec)receptors on tumorinfiltrating immune cells.Here,we investigated the effect of sialylated glycans and their interaction with Siglec receptors on myeloid-derived suppressor cells(MDSCs).We found that MDSCs derived from the blood of lung cancer patients and tumor-bearing mice strongly express inhibitory Siglec receptors and are highly sialylated.In murine cancer models of emergency myelopoiesis,Siglec-E knockout in myeloid cells resulted in prolonged survival and increased tumor infiltration of activated T cells.Targeting suppressive myeloid cells by blocking Siglec receptors or desialylation strongly reduced their suppressive potential.We further identified CCL2 as a mediator involved in T-cell suppression upon interaction between sialoglycans and Siglec receptors on MDSCs.Our results demonstrated that sialylated glycans inhibit anticancer immunity by modulating CCL2 expression.