ABSTRACT
OBJECTIVES: In advanced head and neck squamous cell carcinoma (HNSCC), there is a need for an adjuvant treatment. We aim to evaluate the biodistribution and therapeutic effect of radioimmunotherapy using the alpha emitting, astatine-211-labeled, chimeric monoclonal antibody U36 (U36) on the HNSCC cell line UT-SCC7 in vivo. STUDY DESIGN: Xenograft tumors were inoculated subcutaneously in nude mice. Astatine-211-labeled U36 was injected intravenously with or without blocking of target with nonlabeled U36. METHODS: In the biodistribution experiments, radioactivity was measured in tumors and various organs at set time points. In the therapeutic experiments, two groups (with or without blocking) received therapy, and the tumor growth was compared with that of controls. In addition, one group received nonlabeled U36 only. RESULTS: The biodistribution experiments demonstrated that astatine-211-labeled U36 could target UT-SCC7 xenografts in nude mice. With time, uptake increased in tumors and decreased in normal organs. Nonlabeled U36 did not influence tumor growth. In the two therapy groups, 18 of 20 tumors responded to therapy by decreasing or stabilizing their volumes. Significant difference was seen between the treated groups and the controls (P < .05). CONCLUSION: The study illustrates the specific binding of astatine-211-labeled U36 to HNSCC and suggests radioimmunotherapy with the alpha emitting radionuclide to be a useful treatment modality.
Subject(s)
Antibodies, Monoclonal/therapeutic use , Astatine/therapeutic use , Carcinoma, Squamous Cell/metabolism , Carcinoma, Squamous Cell/therapy , Chimerin Proteins/metabolism , Head and Neck Neoplasms/metabolism , Head and Neck Neoplasms/therapy , Radioimmunotherapy/methods , Animals , Carcinoma, Squamous Cell/pathology , Cell Growth Processes/immunology , Cell Growth Processes/radiation effects , Cell Line, Tumor/metabolism , Cell Line, Tumor/radiation effects , Cell Line, Tumor/transplantation , Cell Movement , Disease Models, Animal , Head and Neck Neoplasms/pathology , Mice , Mice, Nude , Random Allocation , Staining and LabelingABSTRACT
The humanized antibody A33 binds to the A33 antigen, expressed in 95% of primary and metastatic colorectal carcinomas. The restricted pattern of expression in normal tissue makes this antigen a possible target for radioimmunotherapy of colorectal micrometastases. In this study, the A33 antibody was labeled with the therapeutic nuclide (211)At using N-succinimidyl para-(tri-methylstannyl)benzoate (SPMB). The in vitro characteristics of the (211)At-benzoate-A33 conjugate ((211)At-A33) were investigated and found to be similar to those of (125)I-benzoate-A33 ((125)I-A33) in different assays. Both conjugates bound with high affinity to SW1222 cells (K(d) = 1.7 +/- 0.2 nM, and 1.8 +/- 0.1 nM for (211)At-A33 and (125)I-A33, respectively), and both showed good intracellular retention (70% of the radioactivity was still cell associated after 20 hours). The cytotoxic effect of (211)At-A33 was also confirmed. After incubation with (211)At-A33, SW1222 cells had a survival of approximately 0.3% when exposed to some 150 decays per cell (DPC). The cytotoxic effect was found to be dose-dependent, as cells exposed to only 56 DPC had a survival of approximately 5%. The (211)At-A33 conjugate shows promise as a potential radioimmunotherapy agent for treatment of micrometastases originating from colorectal carcinoma.
Subject(s)
Colonic Neoplasms/therapy , Colorectal Neoplasms/immunology , Membrane Glycoproteins/chemistry , Antibodies, Monoclonal/chemistry , Antibodies, Neoplasm/chemistry , Antigens, Neoplasm/chemistry , Astatine/metabolism , Carcinoma/immunology , Carcinoma/therapy , Cell Line, Tumor , Cell Proliferation , Cell Survival , Colorectal Neoplasms/metabolism , Colorectal Neoplasms/therapy , Dose-Response Relationship, Drug , Humans , Immunoglobulins/chemistry , In Vitro Techniques , Neoplasm Metastasis , Protein Binding , Radioimmunotherapy/methods , Time FactorsABSTRACT
The EGFR-TKI (epidermal growth factor receptor tyrosine kinase inhibitor) gefitinib ['Iressa' (trademark of the AstraZeneca group of companies), ZD1839] increases the cellular uptake of radiolabelled epidermal growth factor (EGF). We investigated gefitinib treatment combined with astatine-211 EGF targeting in vitro using two cell lines expressing high levels of EGFR: A431 (sensitive to gefitinib) and U343MGaCl2:1 (resistant to gefitinib). In both cell lines, the uptake of 211At-EGF was markedly increased by concomitant treatment with gefitinib. Survival was investigated using both a clonogenic survival assay and a cell growth assay. Combined gefitinib and 211At-EGF treatment reduced the survival of U343 cells 3.5-fold compared with 211At-EGF alone. In A431 cells, 211At-EGF treatment resulted in very low survival, but combined treatment with gefitinib increased the survival by about 20-fold. These results indicate that combined treatment with gefitinib might increase the effect of ligand-mediated radionuclide therapy in gefitinib-resistant tumours and decrease the effect of such therapy in gefitinib-sensitive tumours.
