Characterizing the Inflammatory Profile of Neutrophil-Rich Triple-Negative Breast Cancer

Simple Summary The interaction between the highly aggressive triple-negative breast cancer, and the neutrophils is connected to the poor outcomes of this tumor. Using a wide array of cellular and molecular essays, we found that triple-negative breast cancer cells stressed out the neutrophil-like cells and reduced their viability in cell culture conditions. Furthermore, growing neutrophil-like cells with breast cancer cells enhanced the inflammatory activity of the neutrophil-like cells through the release and expression of chemical or structural inflammatory mediators. Given that cancer cells can exploit the active inflammatory milieu to the advantage of their growth and spread, targeting the crosstalk mechanisms that we illustrated here could help in defining potential therapeutic options in breast cancer management.Abstract Breast cancer (BC) is one of the most common types of cancer in women in the United Arab Emirates. Immunogenic tumours, such as triple-negative breast cancer (TNBC), show increased neutrophil infiltration, which is associated with poor prognosis and limited efficacy of immunotherapy. This study aims to investigate in vitro the bidirectional effect of neutrophils on metastatic TNBC (MDA-MB-231) compared to less-metastatic luminal breast cancer (MCF-7) cell lines. We found that BC cells or their conditioned medium (CM) reduced the viability of neutrophil-like cells (HL60). This was supported by increased cellular stress and NETosis in differentiated HL60 cells (dHL60) upon exposure to MDA-MB-231 compared to MCF-7-CM using nucleic acid staining essays. Flow cytometry showed comparable expression of inflammatory markers by polymorphonuclear cells (PMN) when treated with MDA-MB-231-CM and standard polarizing cocktails. Furthermore, MDA-MB-231-CM triggered an inflammatory pattern with evidence of stronger adhesion (CD62L) and degranulation (CD11b and CD66b) phenotypes. The proinflammatory polarization of dHL60 by MDA-MB-231-CM was additionally confirmed by the elevated CD54 expression, myeloperoxidase, and CD11b protein levels, which matched an increased transwell migratory capacity. In conclusion, BC might use neutrophils to their benefit through NETosis and complement system activation, which makes this crosstalk a potential mechanism for understanding tumour progression.