ChIP-qPCR analysis confirmed that in the absence of HDACi, c-Myc is present on the CD26 promoter of myeloma cells via binding to Sp1 located on the proximal G-C box, thereby repressing the promoter and leading to reduced CD26 transcription in myeloma cells (Fig. 5D and E). Here, DPP4 is linked to plasma cell myeloma.