Selection Of Specific Targeted Cell-binding Mimicry Peptides In Neuroglioma Through Random Peptide Phage Display

Objective: To isolate targeted mimicry peptides that binding and internalizing into human neuroglioma cell line SWO-38's two sublines Z1 and Z2, respectively, which have differ biological characters. Through these obtained peptides, try to find which ligands or proteins that can be able to bind specially with neuroglioma cells. Further, to identified the sites of amino acid epitopes when ligands binding on the cells' surface, and to be expected to present some basic data for study on targeted anticancer drug and idiosyncratic tumor diagnostic marker.Methods: The tumor cells were screened five rounds through the Ph.D.-12 phage display library. Pick out random phage monoclones from peptide libraries screened, and analyze the monoclones' specific binding efficiency compare with the wild type phage VcsM13 and specificity to five cell lines come from differ tissues(HepG-2, MCF-7, JEC, 3T3, C2C12). The DNA of phages were extracted, sequenced and translated to the sequences of amino acid and compared with the international protein database. Using cell immunofluorescence, to inspect whether phages can bind with tumor cells and the binding sites. From the sequence results, find the peptides having high consistency and predict possible protein structure.Results: After five rounds of binding-eluting-amplifying-rebinding's biopanning, the displayed peptide phages have high specificity and strong affinity for their cognate cell types relative to wild type phage VcsM13 and different cell lines. The quantity of output phages can reach 107~108 not only the cell surface-bound phages or the internalized portion. Through sequencing, we get three sequences of displayed peptides having high consistency. The sequences -SLHSKAYERPLS- and -TITNANKPSITL- were both found in the two cells. Whereas, -STKVLPVHTRPA- was only exist in Zl's surface. Immunofluorescence analysis revealed that the major proportion phages remains on the surface of cells and that a fraction is taken up into cells clustering and emitting green fluorescence.Conclusions: Whole cell screening against tumor cells through random phage peptide library can obtain phage peptides with a highly tissue specific binding and internalizing ability. These obtained targeted mimicry peptides maybe the epitopes in ligand proteins that be able to bind specially and tightly with some receptors on tumor cell's surface, and can be taken up into cells by receptor-mediated endocytosis. The peptides do provide a basis for tumor's targeted delivery as therapy vector.