INTRODUCTION AND OBJECTIVES: Neutrophil extracellular traps (NETs) have been associated with several steps of tumor progression, including primary growth and metastasis. We recently demonstrated that NETs drive the pro-metastatic phenotype in human breast cancer cells through the activation of the epithelial-mesenchymal transition (EMT). EMT has associated with the expression of Tissue Factor (TF), a transmembrane protein that initiates the blood coagulation cascade. In this study, we evaluated the ability of isolated NETs in modulating the procoagulant phenotype of human breast cancer cells. MATERIAL AND METHODS: Neutrophils were isolated from the blood of healthy donors and stimulated with PMA to generate NETs. T47D and MCF7 breast cancer cells were starved in serum-free medium and further treated with isolated NETs for 16 hours. Then, samples were generated for real-time PCR, flow cytometry, and plasma coagulation assays. RNA-seq data from breast cancer patients deposited in The Cancer Genome Atlas (TCGA) database were assessed. RESULTS AND CONCLUSION: In vitro analysis showed upregulation of TF gene expression in breast cancer cells treated with NETs. TF expression was confirmed by flow cytometric analysis. Accordingly, the treatment of breast cancer with isolated NETs induced a procoagulant phenotype, as demonstrated by the acceleration of plasma clotting. TCGA analysis revealed a significant positive correlation between TF and neutrophil signature gene expression. Besides, TF gene expression positively correlated with the gene expression of EMT-related proteins, including ZEB1, fibronectin, N-cadherin, and beta-catenin. Our results show that NETs upregulate TF expression in human breast cancer cells. In human patients, TF gene expression correlates with EMT-related proteins. We conclude that TF expression may contribute to the increased tumor cell aggressiveness as a result of the NETs-induced EMT program.