Abstract
This study was undertaken to generate human single chain variable antibody fragments (scFvs) reacting specifically against multiple myeloma (MM) cells using the phage display technique. To isolate myeloma-specific scFvs, we used a simple subtractive strategy by adsorbing the Griffin #1 antibody phage library against myeloma cells in the presence of excess decoy biotinylated HL60 cells, and then removing the unwanted decoy cells using streptavidin coated plates. From eleven scFvs that were isolated, two antibodies, D4A4 and D6B10 stained MM cell lines and patient MM cells with higher intensity than normal plasma cells. Both D4A4 and D6B10 scFvs immunoprecipitated syndecan-1 from myeloma cells and recognized sulfated motifs on syndecan-1-associated heparan sulfate (HS) chains. ScFv D4A4 competed with D6B10 for binding to MM cells. However, they differed in their fine specificities. ScFv D6B10 recognized HS 2,6-O-, N-sulfated motifs and, in contrast, binding of scFv D4A4 required N-sulfation combined with either 2-O- or 6-O-sulfation. Increased D6B10 binding on MM cells suggests that their HS chains contain a greater number of 2,6-O-, N-sulfated motifs than normal plasma cells. Since these highly sulfated motifs bind various angiogenic and growth factors and present them to their respective receptors, they could be instrumental for MM cell survival, proliferation and metastasis. Therefore, scFvs D4A4 and D6B10 provide a means to easily monitor changes in sulfation patterns of heparan sulfate during myeloma tumor progression.