Abstract 3489: A novel monoclonal antibody to native HER2 epitope detects HER2-positive CTCs, HER2 in blood, and HER2 in tissue: realistic approach for monitoring breast carcinoma.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Background: Amplification of the HER2 gene and/or overexpression of its protein product have been reported in 25% to 30% of breast carcinomas and have been associated with poorer outcomes. However, there are still highly controversial aspects of HER2 testing. In the present study, we generated a novel monoclonal antibody against human native epitope of HER2 and investigated its clinical potential in managing breast carcinoma. Methods and findings: We generated a novel monoclonal antibody (mAb), AB-HER2 using hybridoma technology and native folding of the protein as an immunogen. This mAb is of IgG1 (kappa) type. It specifically recognized both native and denatured human HER2 protein and displayed high affinity as assessed by Circulating Tumor Cells (CTCs), ELISA, immunohistochemistry assay, western blot and flow cytometry applications. We have developed a CTCs assay to detect specific HER2-positive tumor cells circulating in blood, while we did not observe any background staining in blood cells. Using AB-HER2 mAb in ELISA, we showed soluble HER2 level is significantly increased in breast cancer patients’ plasma which directly correlated with HER2 expression pattern in breast cancer tissues. Tissue expression of HER2 was determined by using immunohistochemical techniques. Most of normal tissues showed negative staining, while different levels of membrane staining were observed in cancer sections. To evaluate the immunoreactivity of HER2 associated with tumor histological types, the staining intensity in membranes were scored according to the guidelines of ASCO/CAP. We also have compared AB-HER2 mAB with commercial HER2 antibodies in all immunoassays. Conclusion: The novel AB-HER2 mAb showed improved accuracy in all immunoassays and clinical outcome. Circulating HER2-positive tumor cells, HER2 protein levels in plasma and in breast tissues significantly increased in patients with breast carcinoma compared to normal healthy controls. Our data suggest the potential clinical use of AB-HER2 mAB as a powerful immunoreagent in measuring real-time HER2 levels in managing breast cancer. Citation Format: Ozge Alper, Achille Akoa, Ozgul M. Alper, Cui P. Chen. A novel monoclonal antibody to native HER2 epitope detects HER2-positive CTCs, HER2 in blood, and HER2 in tissue: realistic approach for monitoring breast carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3489. doi:10.1158/1538-7445.AM2013-3489