STAT3 and cancer: In another study, TNFα was found to induce in macrophages the release of factors that have led the cancer cells resist estrogen withdrawal and express elevated resistance to tamoxifen and ICI 182,780; co-culture experiments of macrophages with cancer cells demonstrated that TNFα together with IL-6 have led to increased activation of STAT3, NF-κB and ERα, thus leading to its constitutive stimulation (124).