Detection of PD-L1 expression levels in malignant pleural mesothelioma with a targeted MRI nanoprobe in vivo

Abstract

ObjectivesImmune checkpoint inhibitors (ICIs) have demonstrated potential in inhibiting the growth of malignant pleural mesothelioma (MPM), and their efficacy is associated with the expression of programmed death-ligand 1(PD-L1). This study evaluated a PD-L1-targeted nanoprobe for detecting PD-L1 expression in a nude mouse model of malignant pleural mesothelioma (MPM).MethodsA PD-L1-binding peptide (WL-12) was conjugated with superparamagnetic iron oxide nanoparticles (SPIONs) to create the nanoprobe WL-12@Fe₃O₄. The nanoprobe’s stability, biotoxicity, targeting ability, and in vivo magnetic resonance (MR) imaging effects were assessed and compared to non-targeted Fe₃O₄ nanoparticles. ΔT2 values and PD-L1 expression were measured in H226 and MSTO-211H tumor tissues over 4 weeks to analyze correlations.ResultsThe WL-12@Fe₃O₄ nanoprobe demonstrated uniform distribution and a spherical shape, with a larger size (43.82 nm) and lower surface potential (−9.34 ± 0.54 mV) compared to Fe₃O₄ (32.67 nm, −20.20 ± 0.88 mV, P < 0.05). The XPS and FT-IR analysis results indicate the successful coupling of WL-12 with Fe3O4. It was well dispersed in serum and saline and showed no cytotoxicity or organ damage in vivo. The probe selectively accumulated in PD-L1-expressing MPM cells, especially MSTO-211H, and exhibited significantly higher uptake in high PD-L1-expressing H460 cells (930.22 ± 11.75 ng/mL) compared to low PD-L1-expressing A549 cells (254.89 ± 17.33 ng/mL, P < 0.05). Tumor iron levels in the WL-12@Fe₃O₄ group were significantly elevated (141.02 ± 17.33 μg/g) compared to controls (36.43 ± 3.56 μg/g, P < 0.05), with no significant differences in other organs (P > 0.05). The T2 values of H226 and MSTO-211H tumors decreased after probe injection, with ΔT2 values significantly higher in the targeted group than the nontargeted group (P < 0.05). ΔT2 values increased over 4 weeks, correlating strongly with PD-L1 expression (P < 0.05).ConclusionThe PD-L1-targeted nanoprobe with MRI is a promising tool for noninvasive, real-time assessment of PD-L1 expression in MPM.