Abstract 3937: An intracellular variant of zona pellucida glycoprotein 3 is expressed in cancer

Abstract This study describes the expression of an intracellular variant of the Zona Pellucida glycoprotein 3 (ZP3) that is predominantly expressed in cancer. ZP3 is an important constituent of the Zona Pellucida (ZP), the extracellular layer surrounding oocytes. It is highly expressed in maturing oocytes, but not in other adult human tissues. As ZP3 protein has also been detected in cancer, it may serve as an interesting diagnostic and therapeutic target. Here, we extend the cancer-related ZP3 expression data using immunohistochemistry (IHC) of tumor biopsies, interrogating publicly available RNA-sequencing (RNA-seq) data of cancer cell lines (CCLs) and tumor and normal tissues, as well as computational analysis and real-time quantitative PCR (qPCR) of CCLs. IHC data for several cancer types shows abundant ZP3 protein expression, which is confined to the cytoplasm, contradicting the extracellular ZP3 localization in oocytes. An alternative ZP3 mRNA variant, which we term ‘ZP3-Cancer’, is annotated in the NCBI and Ensembl databases, and lacks the genetic information encoding the N-terminal signal peptide that governs extracellular secretion. Analysis of publicly available RNA-seq data of 1339 CCLs indicates that ZP3-Cancer is the dominant variant as compared to ZP3-Oocyte, which was validated by independent computational analysis. Expression of ZP3-Cancer in CCLs was confirmed by qPCR. Publicly available RNAseq data of tumor and normal tissues confirms strongly enhanced expression of ZP3-Cancer in cancer cells. In addition, ZP3-Cancer expression is upregulated in advanced stages and shows a relationship with patient survival in a number of cancer types. The folliculogenesis specific transcription factor FIGLA, which activates transcription of ZP3-Oocyte in maturing oocytes, appears absent in cancer as inferred from publicly available transcriptome data, indicating alternative ZP3-Cancer transcriptional activation mechanisms in this disease. The cancer restricted expression of this ZP3 transcript variant renders it an attractive tumor specific antigen for the development of a therapeutic cancer vaccine, particularly using mRNA technology. Citation Format: Iman J. Schultz, Yvette Zimmerman, Cathy B. Moelans, Marcin Chrusciel, Jan Krijgh, Paul J. van Diest, Ilpo T. Huhtaniemi, Herjan J. Coelingh Bennink. An intracellular variant of zona pellucida glycoprotein 3 is expressed in cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3937.