IL6 and breast cancer: Moreover, IL-6 activated the STAT3 was specifically enriched in co-culture system between macrophages and breast cancer MCF-7 cells as compared to control, which also showed significant upregulation of transforming growth factor β (TGF-β1) and hypoxia-inducible factor-1α (HIF-1α) mRNA levels [82] (Fig. 2d).