Background/Aim: New anticancer drugs are usually tested on cancer cells in culture in a standard medium. We stimulated immune polynuclear cells by lipopolysaccharides to obtain an enriched medium (EM) containing inflammatory cytokines more closely reflecting the tumor microenvironment and tested a rhenium-diselenium (Re-diSe) drug in this new model. Concentrations of cytokines were compared with a control medium (CM). Materials and Methods: Human-derived breast cancer cells were grown in culture either in CM or EM with or without Re-diSe. Assays of tumor necrosis factor alpha (TNF alpha), interleukin 6 (IL6), intereukin 1 beta (IL1 beta), transforming growth factor-beta (TGF beta), insulin growth factor 1 (IGF1) and vascular epidermal growth factor A (VEGFA) were performed by enzyme-linked immunosorbent assays. The production of reactive oxygen species (ROS) was determined by 2,7-dichlorofluorescein test. The cell growth was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tests. Results: Concentrations of TNF alpha, IL6 and Il1 beta were observed to be significantly higher in EM than in CM. There was no difference for TGF beta, IGF1 and VEGFA. The cells were sensitive to Re-diSe, with reduced concentrations of TGF beta, IGF1, VEGFA and ROS, but the half-maximal inhibitory concentration was significantly higher in EM than in CM. Conclusion: The efficacy of the Re-diSe drug was confirmed in this model of aggressive cancer.