Abstract 4377: Biodistribution and therapeutic effects of a monoclonal antibody against Eph receptor A10 in a breast cancer xenograft model (2015)

Abstract Introduction HER2-targeting antibodies and anti-hormone drugs are effective agents for breast cancer patients. However, such treatments are not applicable to triple negative breast cancers (TNBCs) which don't express HER2, estrogen, and progesterone receptors. Thus, effective molecular targets for TNBC are urgently needed. In this respect, we searched for new targets using a proteomics approach and identified Eph receptor A10 (EphA10) to be highly expressed in breast cancer including TNBCs, compared with normal breast tissues. Moreover, we previously found that EphA10 is expressed in testis but not in other normal tissues, thus suggesting that EphA10 could become a promising therapeutic target in breast cancer patients. Here, we developed a novel monoclonal antibody (mAb) against EphA10 and showed that it accumulates in the tumor and has anti-tumor properties in a breast cancer xenograft model. Materials and Methods Characterization of the anti-EphA10 mAb; Specificity of the mAb was evaluated by mAb binding to EphA family proteins (EphA1-A8, A10). Affinity of the mAb was analyzed by surface plasmon resonance method. Tumor accumulation analysis of anti-EphA10 mAb; Alexa647-conjugated anti-EphA10 mAb or control mAb were administrated intravenously and observed daily using an in vivo imaging system. Anti-EphA10 mAb treatment in a mouse xenograft model; A mouse model was generated by orthotopic transplantation of EphA10 expressing MDA-MB-435 (TNBC) cells. When the tumor size reached approximately a volume of 100 mm3, anti-EphA10 mAb and control mAb were administrated intraperitoneally twice a week. Results and Discussion The results showed that the anti-EphA10 mAb had an affinity for EphA10 in the nanomolar range. Moreover, the mAb specifically bound to EphA10 but not to the other EphA family proteins; therefore, our mAb had the same specificity and affinity for EphA10 as other existing antibody drugs. Furthermore, the mAb also displayed cross-reactivity with mouse EphA10, suggesting that we could evaluate the mAb in a mouse model. The administration of the fluorescein-labeled mAb to the mice bearing EphA10-positive breast tumors showed that the anti-EphA10 mAb accumulated in the tumors to a greater extent than the control mAb and tended to be restricted to the tumor. Furthermore, tumor growth was significantly suppressed in the mAb-treated mice in a dose-dependent manner. On the other hand, body weight and biochemical markers of tissue damage did not change between the mAb or control mAb-treated groups. These data indicate that our mAb might become a promising therapeutic tool for treating EphA10-positive breast cancers. Conclusion Our anti-EphA10 mAb mainly accumulated in EphA10-positive tumor cells and showed anti-tumor effects. We believe that these findings will contribute to the development of a novel drug in the treatment of breast cancer patients refractory to traditional therapies. Citation Format: Kazuya Nagano, Yuka Maeda, Takuya Yamashita, Yohei Mukai, Haruhiko Kamada, Kazuma Higashisaka, Yasuo Yoshioka, Yasuo Tsutsumi, Shin-ichi Tsunoda. Biodistribution and therapeutic effects of a monoclonal antibody against Eph receptor A10 in a breast cancer xenograft model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4377. doi:10.1158/1538-7445.AM2015-4377