ESR1 and breast cancer: For example, CXCL members CXCL8 (aka IL-8) and CXCL1/2 have been implicated in driving neutrophil recruitment in breast cancer (49–52), and overexpression of these chemokines is associated with breast tumor samples and breast cancer cell lines that have negative estrogen receptor expression status and higher aggressiveness (50, 53–55).