Bortezomib is approved for use in multiple myeloma and the HDAC6-selective inhibitor, ACY-1215, was shown to synergise with bortezomib in MM.1S and RPMI8226 myeloma cells,37 and as opposed to single agent showed 37% clinical response rate in multiple myeloma patients.38 In this report, we show that either C1A or ACY-1215 at equimolar concentrations synergises with bortezomib to induce caspase-3/7 activity in OPM-2 multiple myeloma cells (Fig. 3b). This evidence concerns the gene CASP3 and plasma cell myeloma.