To evaluate possible involvement of cytokines in effects of macrophages on ER+ breast cancer cells, we incubated a cytokine antibody array with CM collected from supernatants of: (i) MCF-7 cultured alone; (ii) KG-1 macrophages cultured alone; (iii) MCF-7 co-cultured with KG-1; (iv) MCF-7 co-cultured with KG-1 in the presence of tamoxifen. This evidence concerns the gene ESR1 and breast cancer.