Aminopeptidase genes are differentially expressed in NDMM versus RRMM. (A) Five aminopeptidase genes (ERAP2, XPNPEP1, DPP3, RNPEP, CTSV) were differentially expressed in RRMM (n = 82) and NDMM (n = 41) samples (p < 0.05; adjusted p < 0.1) in the FIMM dataset. Differential gene expression between NDMM and RRMM was determined using the DESeq2 tool. (B) Among these five genes, only the expression level of ERAP2 was decreased in RRMM versus NDMM samples. NDMM: newly diagnosed multiple myeloma; RRMM: relapsed/refractory multiple myeloma; RPKM: reads per kilobase of transcript per million mapped reads; ap: adjusted p-value.