Overexpression of estrogen-related receptor alpha (ERRα) in breast cancer bone metastases activates the tumor-killing effect of CTLs, through the production of chemokines C-C chemokine receptor type 17 (CCL17) and C-C chemokine receptor type 20 (CCL20), which allows CTLs to evade the control of transforming growth factor-β (TGF-β) (32). The gene discussed is TGFB1; the disease is neoplasm.