DPP4 and plasma cell myeloma: First, five myeloma cell lines KMS11, 26, 27, 28, and RPMI8226, were cultured in the presence or absence of HDACi; the broad inhibitors, panobinostat and vorinostat or the isoform-specific inhibitors, romidepsin (HDAC1i); BG45, entinostat and RG2833 (HDAC3i); and nexturastatA, ricolinostat, and tubastatinA (HDAC6i) for the indicated times (24, 48, 72 hours) and then, the expression levels of CD26 on myeloma cells were analyzed at each timepoints by flow cytometry.