Abstract 2820: A human Claudin-3 monoclonal antibody as a potential multimodal theranostic probe in ovarian cancer

Abstract

Abstract Introduction: Claudin-3 (CLDN3), a tight junction protein, regulates cell-to-cell interactions in epithelial or endothelial cell sheets. During tumorigenesis, epithelial cells are transformed and tumor cells proliferate through out-of-plane division, resulting in external exposure of CLDN3. This alteration of CLDN3 expression is associated with cancer progression, correlating with malignancy in various carcinomas. Since CLDN3 is particularly overexpressed in most ovarian cancers and used as an effective diagnostic marker, we tested the possibility of using a CLDN3-specific antibody as a novel imaging probe. Materials and Methods: After reducing the CLDN3 specific antibody to expose the -SH group, click chemistry was used to conjugate radioactive isotope 111In or fluorescent protein FNR648. Human ovarian cancer OVCAR-3 cells and human glioblastoma (U87MG) cells were used as CLDN3 positive and negative cells, respectively. Flow cytometry was used to measure the binding of CLDN3 IgG1 monoclonal antibody to theses cell lines. To establish xenograft model, OVCAR-3 cells were injected subcutaneously into the mice. 111In-labeled CLDN3 antibody (370 kBq/50 μl) was administered intravenously to mice with. After 24 hours, organs including tumor were excised and measured with a γ-counter. Images were acquired with IVIS and SPECT/CT. Results: The labeling efficiency of NOTA-111In or antibody-NOTA-111In was 98.52% or 100%, respectively. FNR648 labeled CLDN3 antibody was bound to the cell surface of OVCAR-3 at 83.4% and to U87MG at 5.7%, respectively. In OVCAR-3 tumor xenografted mice, mice injected with CLDN3 antibody showed 2.5-fold higher tumor uptake (20.4 ± 7.4% ID/g) than mice injected with human IgG (8.8 ± 2.6% ID/g) at 24 hour p.i. The fluorescence signal of CLDN3 antibody peaked at 24 hour p.i. Conclusion: We successfully conjugated radioisotope and fluorescent protein using the CLDN3 specific antibody. Since the specific binding of CLDN3 antibodies to OVCAR-3 tumors has been validated in a mouse model and diagnostic radionuclides can be replaced with therapeutic radionuclides, this human monoclonal antibody could be used as a useful theranostic probe. Citation Format: Sera Oh, Hobin Yang, Ho Rim Oh, Chul-Hee Lee, Young-Hwa Kim, Gi Jeong Cheon, Keon Wook Kang, Young Kee Shin, Hyewon Youn. A human Claudin-3 monoclonal antibody as a potential multimodal theranostic probe in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2820.