It is possible that short-term treatment (0–48 h) with tamoxifen or AIs increases Bcl-2 and/or Bcl-xL levels, priming ERα+ breast tumor cells for Bcl-2/Bcl-xL inhibition, as was seen in ERα+ patient-derived xenograft models13. The gene discussed is BCL2L1; the disease is breast neoplasm.