ESR1 and cancer: To identify the nature of the activating factors driving neutrophil migration, we first used multiplex ELISA to quantify the relative presence of potential neutrophil chemoattractants/activators associated with cancer, including a number of CXCL and CCL chemokines, cytokines, and growth factors (1, 66) in TCM derived from M4, MDA-MB-231, and ER+ MCF-7 cell lines (Figure 6B).