[Identification of novel targeting peptides for PC3 cells by the screening of a phage display peptide library]

Objective: Prostate cancer is the second cause of cancer-associated death in men. In recent years, targeted therapy for cancer has attracted the attention of researchers. Targeted therapy leads to a decrease in drug adverse effects. Studies indicate that targeting peptides for cancer cells represent valuable tools for diagnostics and therapeutics. Recently, phage display peptide libraries have been used to identify target peptides to a variety of cancer cells. In the current study, we aim to isolate peptides that target PC3 cells [human prostate adenocarcinoma cells]

Methods: Four rounds of subtractive panning on control cells that included 5637 [bladder], Huh-7 [liver], SW480 [colon], AGS [stomach] and human fibroblast normal in addition to four rounds of positive panning on PC3 [target cell] were performed. Polyclonal phage ELISA was used to evaluate the process of enrichment during biopanning. Subsequently, phage clones were randomly selected from titer plates, amplified by plaque-PCR, and their genomic DNA was sequenced. We conducted bioinformatic analysis for further characterization of the isolated peptides

Results: Several rounds of panning resulted in the enrichment of a number of peptides. The results of polyclonal phage ELISA indicated that the biopanning process was successful. In silico analysis showed the presence of several consensus amino acid motifs in the peptides

Conclusion: The peptides identified through biopanning can be considered as potential specific binders to PC3 cells. Peptides with specificity binding to target cells can be used for targeted gene and drug delivery to malignant tumor cells. Further analyses of these peptides are required to show their capacity for targeted delivery of various genes and drugs into prostate cancer cells

[Screening phage display library for isolation of human colon cancer cell-binding peptide ligands]

Recently, phage display libraries have received enormous attention for identification and isolation of pharmaceutical molecules with diagnostic and therapeutic properties. Peptide libraries are known as one of the most important and widely used types of phage display libraries. In the current study, we aimed to screen the Ph.D.[TM]-7 phage display peptide library through biopanning for the identification of human colon adenocarcinoma-binding peptide ligands. Three rounds of biopanning were performed on SW480 as the target cell and fibroblast [HF-SF-PI3], AGS, KYSE-30 and Huh-7 as control cells. The displayed peptide-encoding regions in the genome of SW480-binding phages obtained from the final round of panning were amplified by plaque-PCR and subsequently sequenced. Bioinformatic tools were used to determine the sequence of target cell-binding peptides and further characterization of these peptides. Biopanning of the phage library led to the enrichment of several peptides among which the peptide with sequence "HAMRAQP" was the most dominant. Bioinformatic analysis of the isolated peptides indicated that they are not target unrelated peptides [TUP]. The peptides, in particular those with the highest frequency, due to having the capability of specific binding to SW480 cells represent the potential for use in targeting of therapeutic genes and drugs to colon cancer cells