ESR1 and breast cancer: Upon thorough investigation of the effects of UBE2M on fulvestrant resistance in breast cancer, we found the following results: (a) The combination of UBE2M silencing and fulvestrant treatment synergistically inhibited the downstream signalling pathways of both ERα and UBE2M (Fig. 5); (b) The combination of UBE2M silencing and fulvestrant treatment synergistically inhibited the growth of breast cancer cells both in vitro and in vivo (Figs. 5 and 6).