Pentraxin 3 as a Modulator of miRNAs and Extracellular Vesicles Release in Triple-Negative Breast Cancer Cells

<b>Background/Objectives</b>: Breast cancer is the most prevalent tumor among women worldwide, with the triple-negative (TNBC) being the most aggressive and therapeutically resistant subtype. It is crucial to investigate new therapeutic targets for the treatment of TNBC. Pentraxin 3 (PTX3), an acute-phase protein, has a complex role in tumor progression, with its expression associated with disease severity. We investigated the role of recombinant human PTX3 (rhPTX3) in modulating microRNA (miRNA) expression and extracellular vesicle (EV) release in TNBC MDA-MB-231 cells. <b>Methods</b>: PTX3 gene expression was evaluated by RT-qPCR. The miRNA expression profile was determined by small RNA Next-Generation Sequencing (NGS). EV release was analyzed by nanoparticle tracking analysis (NTA), flow cytometry, and protein quantification. <b>Results</b>: rhPTX3 treatment significantly increased PTX3 gene expression in MDA-MB-231 cells. Furthermore, rhPTX3 altered the expression profile of 142 miRNAs, with 112 being upregulated and 30 downregulated. These differentially expressed miRNAs were predicted to have 12,894 potential targets, impacting 29 canonical pathways related to carcinogenesis. Key molecules for cancer progression were inhibited (IL6, IL4, CXCL8, CXCR4, CXCL12; ICAM1, CD44 and BCL2), and pro-apoptotic BAD was activated. While rhPTX3-treatment increased total EV release, it specifically reduced the percentage of the CD44+ EV subpopulation. <b>Conclusions</b>: Our data demonstrates that PTX3 modulates the miRNA expression profile and EV release dynamics, particularly by reducing the CD44+ EV population, which points to a tumor-suppressor role in this TNBC context. Given the limited therapeutic avenues for TNBC, our results suggest that PTX3 and its downstream molecular effects represent promising and previously unexplored potential therapeutic targets.