Inhibition of human CD24 binding to platelet-bound P-selectin by monoclonal antibody.
P-selectin, an adhesive molecule present on the surface of activated platelets, participates in the interactions between platelets and a variety of cells, including cancer cells. Such interaction is an important step toward the establishment of thriving secondary tumors during blood-borne metastasis. CD24, one of the mucin-type ligands of P-selectin, is expressed in various adenocarcinomas and may mediate the interaction between platelets and cancer cells. To demonstrate the involvement and specificity of P-selectin and/or CD24 in the interaction, we adapted a fluorometric binding procedure to assay the binding of calcein AM-labeled platelets to DU145 cells grown on 96-well microplates in the presence or absence of antibodies against CD24 or P-selectin. The platelet binding on DU145 cells was inhibited by anti-P-selectin antibody (GA-6) by 83.6% (p<0.01). The similar inhibition seen with anti-CD24 (FL80) antibody, (68%, p<0.01), was preventable by preincubating with a cognate CD24 peptide. In conclusion, our results indicate that P-selectin ligand CD24 mediates the binding of platelets to prostate cancer line DU145 cells in vitro. The fluorometric assay for platelet binding may have a promising role in further defining parameters of the interaction.
Chen
Chi
C
Brookdale University Hospital & Medical Center, New York, USA. chen1001@excite.com
He
Zili
Z
Sai
Padmaja
P
Faridi
Amir
A
Aziz
Ashraf
A
Kalavar
Madhumati
M
Griciene
Pasaka
P
Gintautas
Jonas
J
Steier
William
W
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000918:Antibody Specificity; D015703:Antigens, CD / Q000378:metabolism*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D051927:CD24 Antigen; D005456:Fluorescent Dyes; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019007:P-Selectin / Q000378:metabolism*; D010973:Platelet Adhesiveness / Q000187:drug effects
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D051927:CD24 Antigen; C497889:CD24 protein, human; D005456:Fluorescent Dyes; D008562:Membrane Glycoproteins; D019007:P-Selectin