MMP9 and breast cancer: NETs positively regulated gene expression of several factors linked to the pro-inflammatory and pro-metastatic properties of breast cancer cells, including interleukin-1β (IL-1β/IL1B), interleukin-6 (IL-6/IL6), interleukin-8 (IL-8/CXCL8), CXCR1, matrix metalloprotease-2 (MMP-2/MMP2), MMP9, and CD44. Further analyses of data from The Cancer Genome Atlas (TCGA) showed that samples from breast cancer patients exhibit a significant correlation between neutrophil signature and pro-tumoral genes, including several EMT and pro-metastatic factors.