ESR1 and breast cancer: The role of IL6 and IL8 in breast cancer progression has been well studied in that both cytokines increase the invasiveness and the metastatic potential of ER+ and ER− breast cancers by activating signaling through their receptors, gp130 and CXCR1 (Ginestier et al., 2010, Iliopoulos et al., 2010, Korkaya et al., 2011, Sasser et al., 2007, Sheridan et al., 2006, Studebaker et al., 2008).