Abstract 3399: Using protein chips to develop a highly specific HER2 antibody for HER2 amplification testing

Human epidermal growth factor receptor 2 (HER2) is an orphan receptor tyrosine kinase member of the EGFR families and is found to be a key tumor driver gene. In breast cancer and gastric cancer, HER2 amplification can be effectively treated by its neutralizing antibody, trastuzumab. In clinic, the HER2 immunohistochemistry (IHC) was used as the primary screening method to diagnose HER2 amplification. However, recent evidence suggested that the frequently used rabbit HER2 antibody 4B5 cross reacted to another family member HER4. IHC staining also indicated that it has strong non-specific cytoplasmic and nucleus staining in normal gastric mucosal cells and some gastric cancer samples. Using a protein lysate array which covers 85% of the human proteome, we have successfully identified and confirmed that the 4B5 bound to HER4 and a nuclear protein ZSCAN18 besides HER2. The non-specific binding accounts for the unexpected cytoplasmic and unclear staining of 4B5 on normal gastric epithelium. Finally, we have developed a novel HER2 mouse monoclonal antibody UMAB36 with similar sensitivity to 4B5 but only reacted to HER2 across the 17,000 proteins on the protein chip. In 129 breast cancer and 158 gastric cancer samples, UMAB36 showed 100% sensitivity and specificity comparing to the HER2 FISH reference results with no unspecific staining in the gastric mucosa layer. UMAB36 could provide an alternative high specific IHC reagent for HER2 amplification testing in gastric cancer population. Citation Format: Lixin Zhou, Kehu Yuan, Fangfang Ren, Lili Qi, Zhongwu Li, Guiyin Wu, Xiaozheng Huang, Yi Shen, Min Zhao, Wei Fu, Huibo Liu, Boyang Chu, Guangli Wang, Youmin Shu, Donghui Ma, Wei-Wu He, Jian Chen. Using protein chips to develop a highly specific HER2 antibody for HER2 amplification testing. [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 3399. doi:10.1158/1538-7445.AM2015-3399