Abstract 267: ECD co-operates with ERBB2 to promote tumorigenesis through upregulation of unfolded protein response and glycolysis

Abstract Introduction: The mammalian ortholog of the Drosophila ecdysoneless (ECD) protein regulates cell cycle progression and cell survival. ECD levels are overexpressed in breast cancer (BC), and its overexpression correlates with poor prognosis and short patient survival, particularly in ERBB2-positive BC. This study explores the cooperative oncogenic mechanisms of ECD and ERBB2 to enhance cancer progression. Methods: We generated immortal human mammary immortalized epithelial cell lines (hMECs) overexpressing ECD, ERBB2, or both. Additionally, we developed transgenic mice overexpressing ECD and/or ERBB2 (huHER2) in mammary epithelium under the control of the MMTV promoter (ECD; HER2Tg) to elucidate the co-oncogenic role and mechanisms underlying this cooperation. Results: hMECs co-expressing ECD and ERBB2 demonstrated a significant increase in in vitro oncogenic traits as compared to cells expressing either ECD or ERBB2. Similarly, while huHER2Tg mice developed more homogenous solid nodular carcinomas, double transgenic mice (ECD; huHER2Tg) developed heterogenous and histologically aggressive mammary tumors with basal-like phenotype and epithelial mesenchymal transition (EMT) features, resembling tumors seen in ECDTg mice. RNA sequencing revealed significant upregulation of two major oncogenic pathways, unfolded protein response (UPR) and glycolysis in ECD+ERBB2 expressing cells as compared to ECD or ERBB2 overexpressing hMECs. Consistently, transcriptomic profile of ECD; huHER2Tg tumors also demonstrated upregulation of glycolysis and UPR pathways. RNA immunoprecipitation assays showed ECD associates to mRNAs of three key glycolytic enzymes (LDHA, PKM2, and HK2) and the major UPR-regulated gene GRP78. This association resulted in increased mRNA stability, leading to higher expression of these genes in ECD+ERBB2-expressing cells. Consequently, ECD+ERBB2-overexpressing cells exhibited higher glucose uptake, and a higher glycolytic rate compared to cells overexpressing either ECD or ERBB2 alone. Conclusions: Our findings support a co-oncogenic role of ECD and ERBB2 in ERBB2-driven BC oncogenesis by enhancing two major oncogenic pathways, UPR and glycolysis. Citation Format: Benjamin B. Kennedy, Mohsin Raza, Sameer Mirza, Asher Rajkumar Rajan, Farshid Oruji, Matthew M. Storck, Subodh M. Lele, Timothy E. Reznicek, Lusheng Li, M. Jordan Rowley, Shibiao Wan, Bhopal C. Mohapatra, Hamid Band, Vimla Band. ECD co-operates with ERBB2 to promote tumorigenesis through upregulation of unfolded protein response and glycolysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 267.