Function And Mechanism Study Of Lineage Specific PAX8 Regulon And Its Sensitity To HDAC Inhibitors In Ovarian Cancer

Ovarian cancer is a highly heterogeneous group of neoplasms,lacking of effective early screening strategies,and is the most common cause of gynaecological cancer death all over the world.PAX8 is currently referred to a diagnostic biomarker and prototype lineage-defining transcription factor in epithelial ovarian cancer.Nevertheless,the oncogenic role of PAX8 in the development of ovarian cancer and its potential therapeutic function have not been adequately elucidated.In this study,we unveiled an ovarian lineage-specific PAX8 regulon by conducting modified cancer outlier profile analysis complemented with pan-cancer analysis.All genes including PAX8 in the regulon were specifically overexpressed in ovarian cancer and displayed largely confined gene expression pattern in normal thyroid,kidney and fallopian tube tissues.Gene knockout assays by CRISPR-Cas9 system demonstrated that PAX8 could regulate other genes expression at transcription level except FOLR1,and resided at the very center of the regulon network.PAX8,SOX17 and CLDN16 each turned out to sustain cell proliferation,whereas PAX8,FGF18 and CDH6 evidently promoted cell migration.With more experimental evidence,the PAX8-FGF18 signaling axis was found to be responsible for improving cell migration in an autocrine fashion.In order to find compounds that suppress PAX8,a high-throughput image-based drug screen was performed,and histone deacetylase(HDAC)inhibitors,in particular class I HDAC inhibitors,could potently inhibit PAX8 expression.Mechanistically,HDAC inhibition altered histone H3K27 ac distribution ratios within PAX8 promoter zone compared to the intron regions and probably perturbed the super-enhancer topology associated with PAX8 gene locus,resulting in rapid and pronounced downregulation of PAX8 transcripts and its related targets.FDA-approved HDAC antagonists(panobinostat and romidepsin)efficaciously suppressed ovarian tumor growth and metastasis as single agents in xenograft mouse models and PDX mouse models in vivo,showed synergistic effects in combination with standard platinum-based chemotherapy and induced both cell apoptosis and cell pyroptosis.These findings extend previous knowledge of PAX8 and offer mechanistic and therapeutic insights for PAX8 dependent ovarian cancer.In general,our bioinformatic and experimental process presents an extensible model for revealing and targeting lineage-survival oncogenes in more human malignancies.