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Abstract Breast cancer is the second leading cause of cancer-related death in women, with mortality most often due to metastatic recurrence. Elevated cholesterol is associated with poor prognosis, with several potential mechanisms proposed. Work in murine models found that many of the pro-metastatic actions of cholesterol required the enzymatic conversion of cholesterol to 27-hydroxycholesterol (27HC), which functions as a ligand for both the estrogen receptors (ERs) and liver X receptors (LXRs). Importantly, we have found that 27HC promotes metastasis, in part through its actions on neutrophils. When examining mechanisms, we have made the observation that 27HC resulted in increased secretion of small extracellular vesicles (sEVs) from neutrophils. These 27HC-neutrophil-sEVs independently promote metastatic colonization. Since we have found that breast cancer cell lines can take up neutrophil-derived sEVs, we hypothesized that 27HC results in altered cargo within sEVs which leads to functional changes within cancer cells, the ultimate consequence of which being their increased metastatic potential. Using a non-biased small RNA-seq approach we have found that sEVs from 27HC-treated neutrophils had an altered miRNA signature. Bioinformatic analysis revealed several downregulated miRNAs from the let-7 subgroup. Let-7 miRs are known to target several genes associated with the WNT/β-catenin pathway, a pathway strongly implicated in epithelial to mesenchymal transition (EMT) and cancer cell stemness. Strikingly, breast cancer cells treated with sEVs from neutrophils treated with 27HC lost their adherent properties and adopted a mesenchymal and stem-like phenotype. In order to elucidate the mechanism by which these sEVs promote EMT and stemness, we performed comprehensive transcriptomics through time. Weighted gene co-expression network analysis (WGCNA) confirmed these phenotypic shifts, and implicated the WNT/β-catenin pathway, providing support to our hypothesis that the loss of let-7 miRs is the upstream mediator. Collectively, our data suggests that 27HC increases metastasis in part through its effects on neutrophils, by shifting sEVs cargo towards a loss of protective microRNA, resulting in increased EMT and stemness, and thus the ability of cancer cells to migrate, invade and metastasize. Funding: National Cancer Institute (ERN: R01CA234025) Department of Defense (ERN: BCRP Era of Hope Award), and Beckman Institute for Advanced Science and Technology (NK) Citation Format: Natalia J. Krawczynska, Yu Wang, Anasuya Das Gupta, Jenny Drnevich, Julie Ostrander, Erik R. Nelson. A cholesterol metabolite can modulate neutrophil-derived extracellular vesicles to promote breast cancer cell epithelial to mesenchymal transition (EMT) and stemness abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 1258.
Krawczyńska et al. (Fri,) studied this question.