NR4A1 and breast cancer: Phase I studies showed that the IGF-1R inhibitors, ganitumab (AMG 479), AVE1642, R1507, and cixutumumab had promising activity against metastatic breast cancer,36–39 but a phase II study of ganitumab in combination with endocrine therapy did not improve the outcomes in patients with endocrine-resistant hormone-receptor-responsive metastatic breast cancer.40 These studies suggest that not all patients would benefit from IGF-1R inhibitor therapy; therefore, more studies, including biomarker analysis, are needed to validate the usefulness of IGF-1R inhibitors in breast cancer patients.