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BACKGROUND: The mortality from squamous cell carcinoma of the head and neck (SCCHN) remains high and almost unchanged throughout the last decades. Therefore, new therapeutic strategies are urgently needed. One promising approach is the application of radio-labeled antibodies directed against tumor-associated antigens. EpCAM is a transmembrane protein, which is overexpressed on almost all SCCHN, making it a suitable anchor molecule for targeted radioimmunotherapy (RIT). The aim of this study was to establish an animal model to investigate the biodistribution and the therapeutic effect of a radio-labeled EpCAM-specific monoclonal antibody (mAb). MATERIALS AND METHODS: The mAb C215 was labeled with 131I and tested for its antitumor effect against established SCCHN xenografts in SCID mice. Initially, the biodistribution of the mAb in the tumor and different organs was determined with a gamma counter and was calculated as % injected dose/gram tissue. For therapeutic approaches 5, 15 or 25 MBq 131I-labeled mAb was injected as a single bolus into tumor-bearing mice. Control animals received either sodium chloride or the unlabeled mAb. The tumor growth and body weight of the animals were measured at various times after administration of the antibody. RESULTS: Initially, high activity was seen in all organs after systemic administration of 13I-C215. Over time general activity decreased whereas an accumulation of activity was seen in the tumor. Tumor growth was delayed in the groups receiving either 15 MBq or 25 MBq 131I-C215 relative to control groups and the 5 MBq group. However, animals in the high-dose groups suffered from treatment-related toxicity, which led to body weight loss of more than 20%. CONCLUSION: Our data demonstrate that the EpCAM-specific radio-labeled mAb C215 is a promising tool to target SCCHN leading to significant tumor control. Further studies are necessary to increase efficacy and reduce toxicity of this new therapeutic approach.

The EBV latent membrane protein 1 (LMP1) is an integral membrane protein that acts like a constitutively activated receptor. LMP1 interacts with members of the tumor necrosis factor receptor-associated factor family, as well as with tumor necrosis factor receptor-associated death domain, resulting in induction of nuclear factor-κB, the p38 mitogen-activated protein kinase pathway, and the c-Jun NH2-terminal kinase activator protein 1-signaling cascade. The binding of Janus kinase 3 results in activation of signal transducers and activators of transcription. The domain structure of LMP1 has been mapped extensively, but the quantitative contribution of distinct LMP1 domains to the efficiency of B-cell proliferation by EBV has not been determined. On the basis of the maxi-EBV system, which allows us to introduce and study mutations in the context of the complete EBV genome, a panel of 10 EBV mutants with alterations in the LMP1 gene locus was established. The mutant EBVs were tested for their efficiency to induce and maintain proliferation of clonal B-cell lines in vitro. Surprisingly and with reduced frequency, EBV mutants which deleted LMP1’s COOH terminus, transmembrane domains, or the entire open reading frame were able to generate proliferating B-cell clones that were dependent on the presence of human fibroblast feeder cells. A B-cell clone carrying the LMP1-null mutant EBV genome was also analyzed for oncogenicity in severe combined immunodeficiency mice. Our results demonstrate that LMP1 is critical but not mandatory for the generation of proliferating B cells in vitro. LMP1 functions greatly contribute to EBV’s transformation potential and appear essential for its oncogenicity in severe combined immunodeficiency mice.