Identification and validation of LGR5-binding peptide for molecular imaging of gastric cancer

• Published in: Biochemical and biophysical research communications 2021-11, Vol.580, p.93-99
• Main Authors: Kwak, Moon Hwa, Yang, Seung Mok, Yun, Seul Ki, Kim, Sol, Choi, Myung-Gyu, Park, Jae Myung
• Format: Article
• Language: English
• Subjects: Animals; Biomarker; Carbocyanines - chemistry; Cell Line, Tumor; Diagnosis; Fluorescein-5-isothiocyanate - chemistry; Fluorescence; Fluorescent Dyes - chemistry; Gastric cancer; Humans; LGR5; Mice; Mice, Nude; Molecular Imaging - methods; Optical Imaging - methods; Peptides - chemistry; Receptors, G-Protein-Coupled - analysis; Stomach Neoplasms - diagnostic imaging
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2021.09.073

Leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) is a stem cell marker in gastric cancer. In this study, we aimed to produce the LGR5-targeting peptide probe for the use of molecular imaging for gastric cancer. We used phage display libraries to produce a LGR5-specific peptide probe. This peptide was validated for targeting gastric cancer with in vitro and in vivo studies. This peptide was tagged with fluorescein isothiocyanate (FITC) and cyanine 5.5 (Cy5.5). We used two normal and three gastric cancer cell lines. Immunocytochemistry (ICC) and fluorescence-activated cell sorting (FACS) analysis were used to validate the target specificity of the peptide. After three rounds of bio-panning, we found a novel 7-mer peptides, IPQILSI (IPQ∗). FITC-conjugated IPQ∗ showed 2 to 10 times higher fluorescence in gastric cancer cells vs. control cells in ICC. This discrimination was consistently observed using Cy5.5-conjugated IPQ∗ in ICC. FACS analysis showed right shift of peak point in gastric cancers compared to the control cells. In the peritoneal metastasis animal model, we could find Cy5.5-conjugated IPQ∗ accumulated specifically to gastric tumors. In conclusion, IPQ∗ peptide showed a specific probe for gastric cancer diagnosis. This probe can be applied to theragnosis for gastric cancer diagnosis including peritoneal metastasis. •There is little information for biomarkers of gastric cancer, although the prevalence of this disease is high world-widely.•We developed a new heptapeptide, IPQILSI, which targets LGR5 protein, a putative cancer stem cell marker.•We validated this peptide in gastric cancers through in vitro and in vivo model simulating peritoneal metastasis.•Our newly developed heptapeptide, IPQILSI, can be used as a molecular biomarker for gastric cancer.