Document Type : Research Articles
Department of Molecular Biology and Genetics, Istanbul Technical University, Istanbul, Turkey.
Department of Medicine and Cancer Center, Howard University, Washington, DC, United States of America.
Department of Internal Medicine, Meharry Medical College, Nashville, TN, United States of America.
Background: Gastric cancer is the second most common cancer among the malign cancer types. Inefficiency of
traditional techniques both in diagnosis and therapy of the disease makes the development of alternative and novel
techniques indispensable. As an alternative to traditional methods, tumor specific targeting small peptides can be used
to increase the efficiency of the treatment and reduce the side effects related to traditional techniques. The aim of this
study is screening and identification of individual peptides specifically targeted to human gastric cancer cells using
a phage-displayed peptide library and designing specific peptide sequences by using experimentally-eluted peptide
sequences. Methods: Here, MKN-45 human gastric cancer cells and HFE-145 human normal gastric epithelial cells
were used as the target and control cells, respectively. 5 rounds of biopannning with a phage display 12-peptide library
were applied following subtraction biopanning with HFE-145 control cells. The selected phage clones were established
by enzyme-linked immunosorbent assay and immunofluorescence detection. We first obtain random phage clones
after five biopanning rounds, determine the binding levels of each individual clone. Then, we analyze the frequencies
of each amino acid in best binding clones to determine positively overexpressed amino acids for designing novel
peptide sequences. Results: DE532 (VETSQYFRGTLS) phage clone was screened positive, showing specific binding
on MKN-45 gastric cancer cells. DE-Obs (HNDLFPSWYHNY) peptide, which was designed by using amino acid
frequencies of experimentally selected peptides in the 5th round of biopanning, showed specific binding in MKN-45
cells. Conclusion: Selection and characterization of individual clones may give us specifically binding peptides, but
more importantly, data extracted from eluted phage clones may be used to design theoretical peptides with better
binding properties than even experimentally selected ones. Both peptides, experimental and designed, may be potential
candidates to be developed as useful diagnostic or therapeutic ligand molecules in gastric cancer research.