Abstract 4129: Phosphorylation of AMPKβ by EDIL3/Del-1 regulates the progression of triple negative breast cancer

Abstract Background: Developmental Endothelial Locus-1 (Del-1), also known as EGF Like Repeats and Discoidin Domains 3 or Edil-3, is a secreted glycoprotein enriched in extracellular vesicles circulating in the plasma of breast cancer patients. Various papers have suggested that Del-1 might be important in Triple Negative Breast Cancer (TNBC), the subtype with the highest mortality rate, even though it only accounts for 15%-20% of all breast cancers. However, the precise role of Del-1 in TNBC regulation remains poorly characterized. AMP-activated protein kinase (AMPK), a heterotrimeric energy sensor, is composed of α (catalytic), β (scaffolding), and γ (nucleotide-binding regulatory) subunits. AMPKβ subunits, characterized by their carbohydrate-binding modules (β-CBM), facilitate glycogen binding and are often amplified in tumor cells. Although AMPKβ has been extensively studied for its metabolic functions, its contributions to oncogenic signaling pathways in TNBC remain poorly understood. Methods: RNA sequencing of Del-1-suppressed MDA-MB-231 cells revealed reduced expression of AMPK subunits. Western blot assays confirmed that AMPKβ protein levels were significantly elevated in TNBC cell lines, and RT-PCR analysis further verified increased AMPKβ mRNA levels in breast cancer patient samples. CRISPR/Cas9 genome editing Del-1 knockout cell lines and pharmacological activator of AMPKβ, and tumor progression assays (MTT, MTS, BrdU and Matrigel transwell assays) were used to evaluate the effects of Del-1 and AMPKβ on TNBC cell proliferation, invasion, and survival. To understand how Del-1 positively activates AMPKβ, genetically mutated phospho-mimetic AMPKβ was overexpressed, and assessed the progression of TNBC cells. Results: In TNBC cells (particularly TNBC mesenchymal stem-like cells), the expression levels of Del-1 and AMPKβ were significantly upregulated. While AMPKα remain unchanged, β subunit of AMPK was increased. Both overexpression of Del-1 and pharmacological activation of AMPKβ stimulated proliferation and invasion, whereas CRISPR/Cas9 genome editing Del-1 knockout inhibited AMPKβ and blocked proliferation and invasion. Notably, overexpression of Del-1 upregulated AMPKβ, but AMPKβ activation did not affect Del-1. Furthermore, DEL-1 phosphorylates AMPKβ at S108, and phosphor-mimetic AMPKβ overexpression significantly enhanced TNBC cell progression. Conclusions: Our findings identify AMPKβ as a novel downstream target of Del-1 in TNBC mesenchymal stem-like cells. Elevated Del-1 and AMPKβ levels accelerate proliferation, invasion, and survival. These results uncover a previously unrecognized Del-1-AMPKβ axis, offering new insights into the molecular mechanisms of TNBC progression and potential therapeutic targets. Citation Format: Seolhwa Jeong, Soo Jung Lee, Jeeyeon Lee, In Hee Lee, Byeongju Kang, Ho Yong Park, Eun Ae Kim, Jieun Kang, Yee Soo Chae. Phosphorylation of AMPKβ by EDIL3/Del-1 regulates the progression of triple negative 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 4129.