In particular, HER2- patients showed lower levels of IL-2, previously associated with relapse of the disease [45,46], reduced amounts of the pro-inflammatory cytokines IL-1β and IL-6 (repressors of in vitro cell cycle progression) [47], and reduced levels of IL-8, recently reported also in the in vitro comparison of HER2- and HER2+ breast cancers cell lines and in serum samples from metastatic breast cancer patients [25]. This evidence concerns the gene IL6 and breast cancer.