title: In-vitro internalization and in-vivo tumor uptake of anti-EGFR monoclonal antibody LA22 in A549 lung cancer cells and animal model.
abstract: OBJECTIVE
  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.
  
  
  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 degrees 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 gamma-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.
authors.affiliation: Medical Isotopes Research Center, Peking University, Beijing, China.
authors.forename: Zhaofei
authors.initials: Z
authors.lastname: Liu
authors.forename: Zilin
authors.initials: Z
authors.lastname: Yu
authors.forename: Weiwei
authors.initials: W
authors.lastname: He
authors.forename: Shujun
authors.initials: S
authors.lastname: Ma
authors.forename: Le
authors.initials: L
authors.lastname: Sun
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D066246:ErbB Receptors / Q000737:chemistry*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes / Q000737:chemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D011877:Radionuclide Imaging / Q000379:methods; D013696:Temperature
chemical_list: D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D066246:ErbB Receptors