DNA methylation of the CRBN promoter and enhancer in MM patients and CD138⁺ plasma cells from healthy donors.CRBN has 2 regulatory regions, a 5' promoter (Prom.) and a 6039 bp downstream located active intronic enhancer (Enh.) region as shown in a UCSC plot of representative primary MM as well as naïve B cells from tonsil (NBCT) and plasma cells from tonsil (PCT) from healthy donors. DNA methylation was detected only in the enhancer region and accumulated in IMiD-resistant MM patients. Each line represents an individual sample, and each column represents a single CpG; blue encodes for an unmethylated state, red for a methylated state. The different study cohorts are marked by a second color code. UTR, untranslated region.