We found the Mcl-1 inhibitor S63845 [18] to selectively induce apoptosis in Bcl-2-negative or Bcl-2low cell lines, but to be ineffective by itself in Bcl-2hi cell lines, suggesting that Bcl-2 and Mcl-1 are mutually exclusively expressed and can substitute for one another in preventing apoptosis in DLBCL. The gene discussed is BCL2; the disease is diffuse large B-cell lymphoma.