In-Vitro Internalization and In-Vivo Tumor Uptake of Anti-EGFR Monoclonal Antibody LA22 in A549 Lung Cancer Cells and Animal Model

Purpose: Internalization is one of the key steps for anticancer immunoconjugates to deliver the drugs inside of cancer cells. Herein, the internalization property of antiepidermal growth factor receptor (EGFR) monoclonal antibody (mAb) LA22 was evaluated. Materials and Methods: The binding and internalization properties of LA22 on A549 cells were investigated by using ¹²⁵I-LA22. In vitro internalization was also confirmed by indirect fluorescent staining. In vivo tumor targeting and internalization of ¹²⁵I-LA22 were evaluated in the A549 nude mice model. Results: The mAb LA22 showed a high affinity to EGFRs expressed on A549 cells (Kd = 0.69 ± 0.13 nM). The in vitro internalization of LA22 was time- and temperature dependent. The cell-surface-bound LA22 was rapidly internalized at 37°C. The experimental results of LA22 internalization obtained from radioassay and fluorescent staining were consistent with a good linear correlation. At 72 hours postinjection, a clear γ-image of tumor was obtain in A549 tumor xenografts, and the tumor uptake of ¹²⁵I-LA22 was 8.00 ± 0.61 percent injected dose per gram (%ID/g) (2.19 ± 0.37 %ID/g for ¹²⁵I-mIgG). Similar to the in vitro observation, 64.06% of the cell-bound mAb LA22 was internalized into the tumor cells in vivo. Conclusions: The mAb, LA22, is a rapid, high-internalizing antibody, and this property makes it a promising vehicle for tumor-targeted drug delivery.