IL6 and breast cancer: Chemotherapy triggers expression of IL-6 and TNF-α in endothelial cells [105,130], fostering a pro-tumor inflammatory microenvironment (IL-6) and conferring chemoresistance to breast cancer cells (TNF-α) [130]; at the same time, endothelial cells gain chemoresistance by exposure to bFGF and VEGF present in the TME (Figure 1b) [131,132].