Abstract P6-11-11: Breast cancer stem cell marker, CD24 regulates metabolic reprogramming in triple negative breast cancer

Abstract

Abstract Breast cancer stem cell (BCSC) is a subset of cancer cells that can dictate the tumor initiation, metastatic progression, and therapeutic resistance in BC. The eradication of this unusual population is emerging as a new paradigm in cancer treatment. Molecularly, CD24 negativity in conjunction with high expression of CD44 is considered a hallmark for the BCSCs. While extensive studies have been performed to delineate the role of CD44 in BCSCs, the regulation of CD24 and its functional role have not been fully understood. In this study, we investigated the regulatory mechanisms responsible for low CD24 expression in BCSCs and their functional relevance in BCSCs. Analysis of DNA from tumor tissues and blood from BC patients as well as BCSCs sorted from BC cell lines suggest that CD24 is epigenetically regulated via DNMT-1/HDAC1-dependent increased methylation of CpG islands in the CD24 proximal promoter region. To understand the role of CD24 in triple-negative BC (TNBC), an aggressive subgroup of BC, we knocked down (CD24-KD) and overexpressed (CD24-OE) CD24 in metastatic TNBC cells. While CD24-KD resulted in increased proliferation and stemness, CD24-OE diminished the proliferative and stem-like potential. To further identify the signaling cascade underpinning these effects, we performed phospho-proteome analysis using Reverse Phase Protein Array (RPPA). Remarkably, we observed an enhanced activation of AMPK and NF-kB signaling cascades, and reduced PDGFRβ signaling upon depletion of CD24. As signaling cascades are intricately linked to cellular metabolism, we performed a metabolomic analysis of CD24-KD and CD24-OE cells. Our comprehensive analysis revealed heightened activation of mitochondrial fatty acid β-oxidation (FAO) in CD24-KD and increased glutamine metabolism in CD24-OE cells. In coherence with these findings, we observed significant regulation of genes related to fatty acid metabolism in the TNBC patient cohort expressing low levels of CD24. Consistently, the CD24-KD cells demonstrated increased sensitivity towards FAO inhibitors while CD24-OE cells were more sensitive to glutamine metabolism inhibitors. In vivo studies to further understand the translational significance of this metabolic axis is underway. Taken together, our study demonstrates, for the first time, that CD24 presents a novel metabolic vulnerability that can target BCSCs to gain a therapeutic advantage in the treatment of drug-resistant TNBC patients. Citation Format: Divya Murthy, Debasmita Dutta, Sukjin Yang, Junhyoung Park, Benny Kaipparettu. Breast cancer stem cell marker, CD24 regulates metabolic reprogramming in triple negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-11-11.