Cancer-associated adipocytes promotes breast tumor radioresistance

► Tumor-surrounding adipocytes contribute to breast cancer progression. ► Breast tumor cells previously co-cultivated with mature adipocytes exhibit radioresistance. ► Increased in Chk1 phosphorylation is observed in irradiated co-cultivated tumor cells. ► IL-6 is over-expressed in tumor cells co-cultivated with adipocytes. ► IL-6 exposure confers increased Chk1 phosphorylation and radioresistance in tumor cells.