ESR1 and breast cancer: We report here that mTOR-dependent MCL1 translation rapidly drives Mcl-1 upregulation in ER+ breast cancer cells treated with ABT-263, or with BH3 mimetics that target Bcl-2 alone (ABT-199) or Bcl-xL alone (A1155463), consistent with the well-established oncogenic role of mTOR in ER+ breast cancers [31, 32].