As the prototypical member of this cytokine family, the role of IL6 in particular has been extensively studied [22,23,24]: although in vitro studies have reported both pro- and anti-tumourigenic effects, the role of IL6 as a negative prognosticator in BC is firmly established [25,26], with circulating serum levels in patients correlating with disease stage and higher levels being associated with worse prognosis and survival and poorer response to chemo- and endocrine therapy [27,28,29,30]. Here, IL6 is linked to breast cancer.