We found abundant Mcl-1 expression (but not Bcl-2 or Bcl-xL) upon LTED in cell culture and in vivo (Figs. 1c and 2a,b), suggesting that Mcl-1, rather than Bcl-2 or Bcl-xL, may be the primary survival factor in AI-resistant ERα+ breast cancers. Here, ESR1 is linked to breast cancer.