Magnetic resonance imaging of esophageal squamous cell carcinoma using magnetite particles coated with anti-epidermal growth factor receptor antibody.

A highly specific and effective magnetic resonance imaging (MRI) contrast agent was prepared by coating super-paramagnetite particles with monoclonal antibodies (MAbs) directed against epidermal growth factor receptors (EGFRs), which are over-expressed in esophageal squamous cell carcinoma. The preparation maintained both the immunoreactivity of the MAbs and the full relaxing capability of the magnetite particles. The particles of this EGFR-specific contrast agent are 13.2 +/- 1.9 nm in size, and thus, it is assumed that they are smaller than capillary pores and, hence, able to escape scavenging by reticulo-endothelial system cells. The EGFR-specific T2-relaxing ability of this contrast agent was ascertained first in vitro, using the EGFR-expressing cell line TE8 and the EGFR-deficient cell line H69. The results in athymic rats bearing TE8 or H69 tumors revealed that the agent has EGFR-specific MRI contrast capacity in vivo. The electron-microscopic findings in TE8 tumor-bearing rats revealed that the magnetite particles had been taken up by their lysosomes. In conclusion, immuno-specific MRI using magnetite particles coated with MAbs against EGFR appears to be useful in the diagnosis of squamous cell carcinoma of the esophagus.