Breast Cancer Cell–Neutrophil Interactions Enhance Neutrophil Survival and Pro-Tumorigenic Activities

SIMPLE SUMMARY: Tumor cell–neutrophil interactions play an important role in tumor progression, metastasis, and overall survival. The purpose of this study was to examine the tumor cell–neutrophil survival and function. We observed that high neutrophil infiltration was associated with disease aggressiveness and therapy resistance, and breast cancer-derived factors significantly enhanced neutrophil survival, polarization, and expression of pro-inflammatory cytokines. The present study demonstrates the significance of tumor cell–neutrophil interaction in breast therapy resistance and neutrophils as a potential therapeutic target. ABSTRACT: Breast cancer remains the most prevalent cancer in women with limited treatment options for patients suffering from therapy-resistance and metastatic disease. Neutrophils play an important role in breast cancer progression and metastasis. We examined the pro-tumorigenic nature of the breast cancer cell–neutrophil interactions and delineated the differences in neutrophil properties between the chemotherapy-resistant and the parent tumor microenvironment. Our data demonstrated that high neutrophil infiltration is associated with disease aggressiveness and therapy resistance. In the human breast cancer dataset, expression of neutrophil-related signature gene expression was higher in tumors from therapy-resistant patients than therapy-sensitive patients. We observed that breast cancer-derived factors significantly enhanced neutrophil survival, polarization, and pro-inflammatory cytokine expression. Breast cancer cell-derived supernatant treated neutrophils significantly expressed high levels of interleukin-1β (IL-1β), CC-chemokine ligand-2-4 (CCL2, CCL3, CCL4), inducible nitric oxide synthase (iNOS), and matrix metallopeptidase-9 (MMP9), and formed extracellular traps (NETs). Moreover, neutrophils showed increased secretion of MMP9 when cultured with the supernatant of chemotherapy-resistant Cl66-Doxorubicin (Cl66-Dox) and Cl66-Paclitaxel (Cl66-Pac) cells in comparison with the supernatant of Cl66-parent cells. Together, these data suggest an important role of breast cancer cell–neutrophil interactions in regulating pro-tumor characteristics in neutrophils and its modulation by therapy resistance.