A New Breast Cancer Cell Adhesion Molecule Function Of LSECtin

C-type lectin is non-enzymatic and non-antibody protein,which can selectively bind sugar non-covalently and reversibly.It plays a significant role in anti-infective,anti-tumor, antigen-presenting,immune regulation,transplant rejection and inflammatory response.Recently we cloned a novel C-type lectin LSECtin,which was expressed specifically on sinus endothelial cells in the liver and lymph nodes,and played a significant role in these cells.Recent studies found that LSECtin was also expressed in macrophages, peripheral blood dendritic cells(DC) and Kupffer cells.Human LSECtin(hLSECtin) have similar function structure domain and spatial structure as the known C-type lectin DC-SIGN,DC-SIGNR and CD23.It has typical glycosylation recognition domain(CRD),and can recognize mannose, N-acetyl glucosamine,fucose and G1cNAcβ1-2Man,but not glalctose.In particular,the interactin with G1cNAcβ1-2Man was the strongest. Tumor is transformed from some normal cells which lose the control of growth and dysdifferentiaion in organism.Cell membrane will change when cells are becoming malignant Its glycans will also have the corresponding changes which are widespread and diverse.DC-SIGN is the DC pathogen pattern recognition and the adhesive acceptor on DC.It also acts as the DC characteristic multi-function immune molecules in the DC immune regulation.DC may recognize specific glycans of CEA via DC-SIGN and bind colon tumor ceils to participate in the anti-tumor immune response,and tumor cells may also regulate t negatively and suppress DC fucntion via DC-SIGN,and then escape immune surveillance.Many researches have discovered that agglutinin can be as a marker of tumor organization origin,specific diagnosis,malignant transform and differentiation.Studies related to its members DC-SIGN and DC-SIGNR,and similarities among their spatial structures deeply suggest that LSECtin may play a crucial role in immune response and deserve further research.Dr.Li Tang and Dr.Juntao Yang showed that LSECtin interacted with CD44 on active T cells. CD44 is an adhesion molecule which participates in cell-cell interactions,lymphocyte homing and tumor metastasis.It is a typeⅠtransmembrane glycoprotein expressed widely on the cell surface. Human CD44 has two types.Standard-type CD44(CD44s or CD44H) only contains constitutive exons,however,another variant type is composed of constitutive exons and variant district(V district) splicing exons.Extracellular domain of CD44 has many potential N-glycosidic connecting sites,and their intracellular tail region has anchor-binding domain,which can be phosphorylated as protein kinase substrate and participate in signal transduction.A series of studies have shown that expression of CD44 in tumor cells is related to infiltration and metastasis of tumor cells.(1) C-type lectin and LSECtin family members make function in tumor genesis.(2) LSECtin ligand on T cell is CD44.(3) CD44 is deeply associated with occurrence and development of breast cancer.Based on views above,we developed a series of related studies. Purpose:To illustrate whether LSECtin binds breast cancer cells,and to identify its ligand on surface of breast cancer cells and specific glyco-structure of its ligand.Methods:We used RT-PCR and immunohistochemistry to detect distribution of LSECtin.We detected expression of recombinant Fc-LSECtin protein by Western Blotting and analyzed the binding of Fc-LSECtin to breast cancer cells or not by flow cytometry.We used Western Blotting and flow cytometry to analyze expression of CD44 on breast cancer cells,and adopted blocking antibodies against CD44 to identify candidate ligand of LSECtin on breast cancer cells.Furthermore,we used specific ELISA assay to demonstrate interaction between LSECtin and CD44 on breast cancer cells.Then we used a series of LSECtin mutation proteins binding experiments to prove their interaction depends on protein-carbohydrate recognition.Results:We showed that LSECtin can bind highly metastatic breast cancer cells MDA-MB-231,MDA-MB-435s and MCF-7.LSECtin was a novel tumor cells adhesive molecule.CD44 was proved as its ligand on breast cancer cells.Interaction between LSECtin and CD44 depends on protein-carbohydrate recognition.Conclusion:LSECtin is a newly identified tumor cell adhesive molecule which depends on interaction of protein-carbohydrate to recognizing CD44 on breast cancer cells MDA-MB-231,MDA-MB-435s and MCF-7 and likely plays an important role in breast cancer metastasis.