#1521 EZH2 promotes cyst growth in autosomal dominant polycystic kidney disease

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the leading hereditary kidney disease worldwide. Epigenetic modulations of genes and proteins play important roles in ADPKD pathogenesis. In this study, the role of enhancer of zeste homolog 2 (EZH2), a histone lysine methyltransferase, was investigated in ADPKD. Method To elucidate the role of EZH2 in ADPKD pathogenesis, we employed inducible knockout models, specifically targeting Pkd1 alone (Pkd1fl/fl) or both Pkd1 and EZH2 (Pkd1fl/fl: Ezh2fl/fl) in mouse models. Molecular analyses included assessing EZH2 expression levels and H3K27 trimethylation in Pkd1 knockout cells, kidney tissues from Pkd1 knockout mice, and samples from ADPKD patients. Functional investigations involved the use of EZH2-specific inhibitors, GSK126 and EPZ-6438, to inhibit EZH2 activity. Additionally, Ezh2 knockdown was employed to assess its impact on cystogenesis in MDCK cells. The embryonic kidney cyst model was utilized to evaluate the effects of GSK126 and EPZ-6438 on cyst growth. Results We found that EZH2 expression and the trimethylation of lysine 27 on histone H3 (H3K27) were upregulated in Pkd1 knockout cells and kidney tissues of Pkd1 knockout mice and ADPKD patients. Using EZH2-specific inhibitors GSK126/EPZ-6438 and knockdown of Ezh2 both suppressed cystogenesis in MDCK cells. GSK126 and EPZ-6438 delayed cyst growth in the embryonic kidney cyst model. Double knockout of Pkd1 and Ezh2 significantly decreased the kidney volume, cyst indexes, H3K27 methylation level, and the proliferation of renal cystic epithelial cells compared with Pkd1 knockout mice. Moreover, GSK126 delayed cyst growth and protected renal function in both early- and late-onset Pkd1 conditional knockout mice. EZH2 promoted the proliferation of renal cystic epithelial cells by activating STAT3 through H3K27 methylation. Conclusion Inhibiting EZH2 emerged as a promising strategy to impede cyst growth and attenuate disease progression across various PKD models. These findings establish a molecular foundation for the potential use of EZH2-specific inhibitors in delaying ADPKD cyst growth in the future.