Laminin Gamma 2 (LAMC2)-Targeting F(ab′) ₂ for ⁸⁹ Zr Immuno-PET Imaging of Human NSCLC Xenograft Models

Laminin gamma 2 (LAMC2) is upregulated in various tumors and is strongly associated with tumorigenesis, aggressiveness, metastasis, and a poor prognosis. This study evaluated the feasibility of 89Zr-labeled F(ab′)2 fragments of an anti-LAMC2 monoclonal antibody (αLAMC2) for the noninvasive PET/CT imaging of LAMC2-positive nonsmall cell lung cancer (NSCLC) xenografts. LAMC2 expression in NSCLC cell lines was assessed with immunofluorescence staining and Western blotting, and NCIH292 (LAMC2-high) and A549 (LAMC2-low) cells were selected for further analyses. The F(ab′)2 fragment of αLAMC2 was radiolabeled with 89Zr and evaluated in vitro for radiochemical purity, stability, cellular uptake, and internalization. PET/CT imaging and biodistribution analyses were conducted in NSCLC xenograft models to determine probe uptake and tumor targeting, with 89Zr-DFO-IgG-F(ab′)2 used as a nontargeted control. The radiochemical purity of the 89Zr-DFO-αLAMC2-F(ab′)2 probe started at 99.55 ± 0.37% and decreased to 98.00 ± 0.99% in PBS and 96.68 ± 1.66% in 5% FBS by day 5. Compared with A549 cells, NCIH292 cells exhibited substantial probe internalization and uptake at 24 h and 37 °C. Probe uptake was consistently higher in NCIH292 cells than in A549 cells, with NCIH292 exhibiting greater uptake than the control 89Zr-DFO-IgG-F(ab′)2 at all time points, whereas A549 showed higher uptake than the control only at 24 h. PET imaging revealed significantly greater uptake in LAMC2-high xenografts (NCIH292) than in LAMC2-low xenografts (A549). Biodistribution studies corroborated these findings, showing high accumulation in NCIH292 xenografts (30.66 ± 3.72%ID/g at 72 h) versus low uptake in A549 xenografts (19.06 ± 3.03%ID/g at 72 h). The control probe 89Zr-DFO-IgG-F(ab′)2 exhibited consistently low uptake in both PET imaging and biodistribution analyses. Immuno-PET with 89Zr-DFO-αLAMC2-F(ab′)2 enabled the robust and specific visualization of LAMC2-expressing xenografts, supporting its potential as a noninvasive molecular imaging probe for the in vivo detection and quantification of LAMC2-positive tumors.