Abstract 4634: Development of novel monoclonal antibody detection of ERα36 in breast cancer

Abstract Approximately 75% of breast cancer tumors express the estrogen receptor alpha steroid receptor. Canonical estrogen receptors ERα66 and ERβ1 are the main mediators of estrogen-dependent pathophysiology in mammals. However, numerous isoforms have been identified, stimulating unconventional estrogen response pathways leading to complex cellular and tissue responses. Estrogen receptor alpha plays essential roles in the human body, such as the reproductive organs and metabolic and inflammatory systems. Recent studies suggest that a 36 kD variant of ERα (ERα36, ERα isoform 4) may play a role in endocrine therapy resistance in breast carcinoma (BCa). However, a key limitation to discovering the precise role of ERα36 in BCa is the lack of reliable, commercially available antibodies. Most ERα polyclonal antibodies show poor antigen specificity, hindering the evaluation of ERα36 as a clinical biomarker in BCa. Our goal is to develop a reliable monoclonal antibody targeting ERα36, which could facilitate its development as a clinical biomarker in BCa. Here, we describe the development of hybridoma producing an ERα36 monoclonal antibody (34F11) followed by rigorous enrichment (ultrafiltration), purification (fast protein liquid chromatography), and affinity (spectral shift assay) characterization. We assessed the utility of 34F11 antibody in several applications (immunoblot, immunohistochemistry, and fluorescence cytometry). Here, we provide the first comparative characterization of a monoclonal antibody directed toward ERα36 for the potential implementation of biomarker detection in BCa. Citation Format: Alexandra C. Selico Dunn, Hogyoung Kim, DeZha A. Robinson, Sihyoung Kim, Clark J. Perkins, Sichan Kim, Emily L. Smith, Emma Elkins, Christopher Williams. Development of novel monoclonal antibody detection of ERα36 in breast cancer [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 4634.