A proof-of-concept study for the pathogenetic role of enhancer hypomethylation of MYBPHL in multiple myeloma.

Enhancer DNA methylation and expression of MYBPHL was studied in multiple myeloma (MM). By bisulfite genomic sequencing, among the three CpGs inside the MYBPHL enhancer, CpG1 was significantly hypomethylated in MM cell lines (6.7-50.0%) than normal plasma cells (37.5-75.0%) (P = 0.007), which was negatively correlated with qPCR-measured MYBPHL expression. In RPMI-8226 and WL-2 cells, bearing the highest CpG1 methylation, 5-azadC caused enhancer demethylation and expression of MYBPHL. In primary samples, higher CpG1 methylation was associated with lower MYBPHL expression. By luciferase assay, luciferase activity was enhanced by MYBPHL enhancer compared with empty vector control, but reduced by site-directed mutagenesis of each CpG. RNA-seq data of newly diagnosed MM patients showed that MYBPHL expression was associated with t(11;14). MOLP-8 cells carrying t(11;14) express the highest levels of MYBPHL, and its knockdown reduced cellular proliferation and increased cell death. Herein, as a proof-of-concept, our data demonstrated that the MYBPHL enhancer, particularly CpG1, was hypomethylated and associated with increased MYBPHL expression in MM, which was implicated in myelomagenesis.