5-Azacitidine Remolds the Methylation Status and Inhibits Growth in Multiple Myeloma

Multiple myeloma (MM) is a malignant disorder characterized by the proliferation of a single clone of plasma cells derived from B cells. Previous studies have demonstrated that both gene-specific hypermethylation and global hypomethylation characterizes the multiple myeloma epigenome. 5-azacytidine as a DNA methylation inhibitor has therapeutic efficacy in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Nevertheless,the effects of 5-azacytidine on MM remains unclear. We used RT-PCR to detect the expression of PTPL1 and used MS-PCR to determine the methylation status of PTPL1 in MM cell lines and after 5-azacytidine treatment. ELISA-like reaction was used to detect global DNA methylation level. The cytotoxic activity of 5-azacytidine was tested using cell viability and apoptosis assays. Flow cytometry was used to detect cell cycle after 5-azacytidine treatment. Our experiments discovered that the PTPL1 gene was hypermethylated in the U266 and H929 cell lines, and the expression of PTPL1 mRNA could be re-inducible by 5-azacytidine. 5-azacytidine also inhibited the proliferation of multiple myeloma cell lines U266 and H929 in a time- and dose-dependent manner, induced G2/M cell cycle arrest and caspase-dependent apoptosis. But in our study 5-azacytidine increased the methylation level for both cell lines. Our study showed that PTPL1 was epigenetically regulated in MM which can be reversed by 5-azacytidine, and highlights 5-azacytidine is a potential therapeutic candidate for MM, but additional studies are needed to determine the effects of genome-wide methylation changes in MM.