Detecting GPC3-Expressing Hepatocellular Carcinoma with L5 Peptide-Guided Pretargeting Approach: An In Vitro MRI Experiment

Background and Aim : Glypican-3 (GPC3) is a novel molecular target for hepatocellular carcinoma (HCC). This study investigated the potential of an L5 peptide-guided pretargeting approach to identify GPC3-expressing HCC cells using ultra-small super-paramagnetic iron oxide (USPIO) as the MRI probe. Methods : Immunofluorescence with carboxyfluorescein (FAM)-labeled L5 peptide was performed in HepG 2 and HL-7702 cells. Polyethylene glycol-modified ultrasmall superparamagnetic iron oxide (PEG-USPIO) and its conjugates with streptavidin (SA-PEG-USPIO) were synthesized, and hydrodynamic diameters, zeta potential, T 2 relaxivity, and cytotoxicity were measured. MR T 2 -weighted imaging of HepG 2 was performed to observe signal changes in the pretargeting group, which was first incubated with biotinylated L5 peptide and then with SA-PEG-USPIO. Prussian blue staining of cells was used to assess iron deposition. Results : Immunofluorescence assays showed high specificity of L5 peptide for GPC3. SA-PEG-USPIO nanoparticles had ≈36 nm hydrodynamic diameter, low toxicity, negative charge and high T2 relaxivity. MR imaging revealed that a significant negative enhancement was only observed in HepG 2 cells from the pretargeting group, which also showed significant iron deposition with Prussian blue staining. Conclusion : MR imaging with USPIO as the probe has potential to identify GPC3-expressing HCC through L5 peptide-guided pretargeting approach.