Identification and characterization of nonapeptide targeting a human B cell lymphoma, Raji

Here, we identified a novel peptide specifically targeting a human B cell lymphoma, Raji, through a conventional phage display method. The amino acid sequence, 'CTLPHLKMC' was obtained with the highest frequency from a nonapeptide-expressing phage library. The phage clone encoding CTLPHLKMC peptide sequence avidly bound to Raji cells compared with control phage clones. Furthermore, flow-cytometric analysis on the biotinylated synthetic CTLPHLKMC peptide demonstrated the high binding affinity to Raji cells in a dose-dependent manner whereas it has binding activity to neither human peripheral blood mononuclear cells including normal B cell derived from healthy donors nor other leukemia cells including THP-1, HL-60, Jurkat and IM-9. MALDI-TOF mass spectrometry following immunoprecipitation assay showed that a potential host receptor for the peptide is a variable region of human immunoglobulin heavy chain which would be a specific phenotypic marker of Raji. In conclusion, these results suggest that the peptide, 'CTLPHLKMC', is a specific ligand to a Raji cell.