In addition, IL-6, an inflammatory cytokine, is secreted locally in the TME of breast cancer such as monocytes (Masjedi et al., 2018), and it has been demonstrated to directly regulate systemic iron homeostasis through IL6/IL6R/Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway (Hentze et al., 2010; Ganz and Nemeth, 2011; Guo et al., 2015). Here, STAT3 is linked to breast cancer.