Selective targeting of liver cancer with the endothelial marker CD146

Abstract

Hepatocellular carcinomas are well-vascularized tumors; the endothelial cells in these tumors have a specific phenotype. Our aim was to develop a new approach for tumor-specific drug delivery with monoclonal antibody targeting of endothelial ligands. CD146, a molecule expressed on the endothelial surface of hepatocellular carcinoma, was identified as a promising candidate for targeting. In the present study, endothelial cells immediately captured circulating anti-CD146 (ME-9F1) antibody, while antibody binding in tumors was significantly higher than in hepatic endothelium. Macroscopically, after intravenous injection, there were no differences in the mean accumulation of anti-CD146 antibody in tumor compared to liver tissue, due to a compensating higher blood vessel density in the liver tissue. Additional blockade of nontumoral epitopes and intra-arterial administration, improved selective antibody capture in the tumor microvasculature and largely prevented antibody distribution in the lung and liver. The potential practical use of this approach was demonstrated by imaging of radionuclide-labeled ME-9F1 antibody, which showed excellent tumor-selective uptake. Our results provide a promising principle for the use of endothelial markers for intratumoral drug delivery. Tumor endothelium–based access might offer new opportunities for the imaging and therapy of hepatocellular carcinoma and other liver malignancies.

Microsurgical Technique of Locoregional Injection into the Hepatic Artery in Tumor-Bearing Mice

“…One variation (variation 2) was found in a fraction of C57BL/6 mice and corresponds well with material shown in the atlas of laboratory mouse anatomy [15]. This anatomic variation was previously described for AlbTag mice [8] (having C3H genetic background [16]). Another variation (variation 1) is not depicted in the atlas [15].…”

“…The preferential arterial supply is known in human liver tumors [13, 14] and has previously been shown in a transgenic tumor model [8] in mice. In the present work, application of unlabeled ME-9F1 mAb occupied free CD146 epitopes on the endothelium and prevented binding of the subsequently injected fluorescent mAb in the liver and tumor.…”

“…The procedure was performed as previously described with some modifications [8]. Mice were anesthetized with 40 mg/kg ketamine (Pfizer, Berlin, Germany) and 10 mg/kg xylazine (Bayer, Leverkusen, Germany).…”

“…Previous studies reported the first hepatic arterial infusion models in mice and showed the feasibility of this procedure [7, 8]. Recently, we reported the phenomenon of endothelial antibody capture which was demonstrated using the mouse model of selective injection into the hepatic artery [9].…”

Phenomenon of Endothelial Antibody Capture: Principles and Potential for Locoregional Targeting of Hepatic Tumors

“…The application of high antibody doses will lead to saturation of binding sites on endothelium and blunt the high efficacy of endocapt. The saturation of endothelial epitopes can be rapidly achieved; for example, with the ME‐9F1 mAb, this saturation amounts to approximately 2 μg/g tissue in the mouse liver …”