PHF19 Promotes Cell Growth and Confers Drug Resistance through EZH2 Phosphorylation in Multiple Myeloma

To determine the effect of overexpression PHF19 in ARP1 myeloma cells Drug resistance is a major reason for the recurrence of multiple myeloma (MM). In addition to genetic mutations, epigenetic abnormalities are involved in the whole process of MM relapse and drug resistance. In this study, we investigate the roles of polycomb like protein 19 (PHF19), a critical gene involved in the epigenetic regulation of gene expression, in the development of MM. The gene expression profiling (GEP) data shows that PHF19 is significantly up-regulated in MM cells and associated with shortened progression-free survival and overall survival in MM patients. PHF19 promotes MM cell growth both in vitro and in a subcutaneous xenograft mouse model. Up-regulated PHF19 is also associated with the development of resistance to multiple drugs, including bortezomib, in MM cells. Moreover, miR-15a can directly target PHF19 by binding to its 3'-UTR. Since miR-15a is down-regulated in MM cells, PHF19 is considered to be up-regulated due to loss of the suppression by miR-15a. The mechanistic investigations indicate that PHF19 can activate AKT which in turn leads to an increase in the phosphorylation of EZH2, a core component of PRC2 that mediates the histone H3K27 methylation. Subsequently suppresses histone H3K27 methylation and causes up-regulated expression of several anti-apoptotic genes, including BCL-xL, MCL-1 and HIF-1alpha. Moreover, PDK1 activation is significantly increased in PHF19 overexpressing MM cells. Overall design: ARP1 cells were transfected by lenti-virus plasmids with PHF19 ORF, then PHF19 overexpressed cells were sorted. And RNA was extracted.