A new promising approach to improve the outcome of head and neck squamous cell carcinoma (HNSCC) is the application of radio-labeled antibodies directed against tumor-associated antigens. Cytokeratin 8 (CK8), an intermediate filament forming protein, is shown to be de novo expressed in dysplastic lesions as well as in HNSCC. Therefore like the epithelial cell adhesion molecule CK8 seems to be a suitable anchor molecule for targeted radioimmunotherapy (RIT). The aim of this study was to investigate the biodistribution of a radio-labeled Cytokeratin 8-specific monoclonal antibody (mAb) in a SCID (severe combined immunodeficiency disease) mouse model.The mAb against CK8 was labeled with (131)I and biodistribution was tested in established HNSCC xenografts in SCID mice. 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.Initially, after systemic administration of (131)I-anti CK8 monoclonal antibody high activity was seen in all the organs. Over time the general activity decreased, whereas activity accumulated in the tumor. This activity decayed compared to the other tissues with a two- to threefold prolonged radioactive half-life.Specific antibody-antigen-binding is probably responsible for the prolonged radioactive half-life in the tumor and the resulting cumulative activity due to enrichment of the (131)I-anti CK8 mAb, so that Cytokeratin 8 seems to be a suitable anchor molecule for radioimmunotherapy in HNSCC.
Background: The epithelial cell adhesion molecule (EpCAM) is expressed in most normal epithelia, but is absent from squamous stratified epithelia. However, a de novo expression can be observed in squamous epithelia during carcinogenesis. Materials and Methods: In order to evaluate EpCAM as a molecular marker to indicate borders of high risk for the development of local recurrences, its expression was examined in the marginal zone of malignancies. Specimens of squamous cell carcinoma of the head and neck (SCCHN), of the histologically tumor-free defined resection margin and of healthy epithelia of 20 patients were examined by RT-PCR in order to identify the expression of EpCAM in these three different areas. Additionally, immunohistochemistry was performed on biopsies from 10 patients in order to confirm these findings and to investigate a potential correlation between EpCAM expression and the degree of dysplasia. Results: By RT-PCR, high expression of EpCAM was found in the tumor. An inverse correlation was observed between EpCAM expression and the distance from the tumor, with no expression being detectable in healthy oral mucosa. In 70% of the cases, EpCAM was expressed in the marginal zone, which had been defined as tumor-free by routine histopathological assessment. Additional immunohistology revealed no correlation between EpCAM expression and the grade of dysplasia. Conclusion: Our data provide evidence that EpCAM is restricted as a marker for redefining the real tumor margin by RT-PCR. To complement routine histology, immunohistochemical staining with EpCAM is limited due to its expression in hyperplastic tissue without dysplastic changes. Both observations limit the reliable use of EpCAM for the molecular definition of the critical tumor border and resection margins. The standard treatment of squamous cell carcinoma of the head and neck (SCCHN) is surgical resection of the tumor in combination with radio- and chemotherapy. The patient's survival strongly depends on a complete resection of the tumor, including an appropriate distance to the tumor margin. Therefore, histopathological assessment of the surgical margins is routinely performed. Due to the selective choice of few sections during routine histological workup and disseminated tumor cells in the margin, early stages of metastasis can be missed. Recently, new efforts have been made to improve histological diagnosis by using molecular methods (1).
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).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.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%.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.
