LAUSR

Background: GD2-directed immunotherapeutic strategies have improved outcomes in neuroblastoma; however, the majority of patients treated suffer relapse and GD2 expression on pain fibers causes dose-limiting toxicities. Methods: To identify alternative cell surface immunotherapeutic targets, we compared high-risk neuroblastoma (n=126 tumors) and normal tissue RNA sequencing data (GTEx; n=7859 samples from 31 normal tissues) and prioritized genes by differential and absolute expression and cell surface prediction. Genes were further surveyed for somatic copy number gain and correlative expression with MYCN amplification. Differential protein expression and localization were confirmed in neuroblastoma primary tumors (n=98), patient-derived xenografts (n=32; PDXs), cell lines (n=23), and normal pediatric tissues (n=36). Cell lines were subjected to candidate gene gain and loss of function studies (n=11). Additional pediatric tumor RNA sequencing data was surveyed followed by confirmatory immunohistochemistry (IHC). Finally, candidate specific antibodies were isolated from a human Fab phage library and utilized for antibody-drug conjugate (ADC) engineering followed by cytotoxicity studies. Results: We identified 33 differentially expressed cell surface molecules from which we prioritized glypican-2 (GPC2) for validation given GPC2’s robust differential expression (log-fold change tumor vs. normal tissue = 1.71-9.22; p=1.99 x 10-9-1.88 x10-300), high-level absolute RNA expression (median FPKM=60), and frequent DNA copy number gain associated with higher GPC2 expression (35%, n=182 tumors; p Conclusions: GPC2 is an oncogene and immunotherapeutic target in neuroblastoma and potentially other cancers. Citation Format: Kristopher R. Bosse, Pichai Raman, Maria Lane, Robyn T. Sussman, Jo Lynne Harenza, Daniel Martinez, Sabine Heitzeneder, Zhongyu Zhu, Komal Rathi, Michael Randall, Laura Donovan, Sorana Morrissy, Doncho V. Zhelev, Yang Feng, Jennifer Hwang, Yanping Wang, Bruce Pawel, Tricia Bhatti, Mariarita Santi, Javed Khan, Michael Taylor, Dimiter S. Dimitrov, Crystal Mackall, John M. Maris. GPC2 is an oncogene and immunotherapeutic target in high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 685. doi:10.1158/1538-7445.AM2017-685