119 Enhancer of Zeste Homolog 2: A Pivotal Role in Pulmonary Artery Smooth Muscle Cell Proliferation

BACKGROUND: Pulmonary arterial hypertension (PAH) is a progressive and a devastating disease characterized by excessive proliferation of pulmonary artery smooth muscle cells (PASMCs). The pathogenesis of PAH is not fully understood and treatment options are limited. Studies suggest that PAH and cancers share apoptosis resistant state featuring excessive cell proliferation. Proliferation of cancer cells is mediated by increased expression of Enhancer of Zeste Homolog 2 (EZH2), a mammalian histone methyltransferase that contributes to the epigenetic silencing of target genes. However, the role of EZH2 in PAH has not been studied. In this study, we hypothesized that EZH2 could play a role in PASMCs proliferation. METHODS: In the present study the effects of EZH2 overexpression on human PASMCs proliferation were tested. PASMCs were transfected with wild type EZH2 cDNA or GFP using the Lonza 4D nucleofector system. After transfection, cells were incubated for 48 hours at 37°C. PASMCs proliferation and cell cycle analysis were performed by flow cytometry; PASMCs apoptosis was determined using annexin V staining, and cell migration was tested by the wound healing assay. Expression levels of EZH2 were confirmed by real time PCR. RESULTS: The overexpression of EZH2 in PASMCs enhances proliferation, migration, and decreases the rate of apoptosis when compared to GFP transfected cells. There was a 3.5-fold increase in proliferation and a 1.5-fold increase in the percentage of cells in the G2/M phase in the EZH2 transfected cells while there was a significant decrease in the rate of apoptosis in the PASMCs. CONCLUSIONS: These findings suggest that EZH2 plays a role in the migration and proliferation of PASMCs .It also suggest that EZH2 could play a role in PAH development and serve as a potential target for new therapies for PAH.