Similarly, in another ERα+ breast cancer cell line T47D, we observed that overexpression of WT but not D151N COPS5 led to agonistic conversion of 4OHT in ERα-dependent transcription (Supplementary Fig. 5a,b), and caused resistance to 4OHT-induced growth inhibition (Supplementary Fig. 5c). Here, COPS5 is linked to breast carcinoma.