NR4A1 and breast cancer: In the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial, which compared the efficacy of anastrozole against tamoxifen as an adjuvant treatment for hormone receptor-positive post-menopausal breast cancer patients, anastrozole, a non-steroidal AI, was significantly less effective in post-menopausal breast cancer patients with a high BMI, whereas an equal efficacy of tamoxifen was shown across all BMI levels (Sestak et al., 2010).