Evidence for an essential role of activated STAT3 in preventing the apoptosis of human tumor cells was first shown in multiple myeloma.24 STAT3 activation supports tumor cell survival by upregulating expression of the anti-apoptotic proteins (i.e., Bcl-2, Bcl-xL, Mcl-1 and survivin), cyclin D1 and Myc.18, 25, 26, 27 In general, STAT3 is constitutively activated in diverse cancers. Here, MCL1 is linked to AL amyloidosis.