Abstract A065: The oncogenic role of PVT1 exon 9 overexpression in prostate Cancer is mediated by DNA methylation and CDX1

Abstract Prostate cancer (PCa) is the second leading cause of cancer-related deaths among men in the U.S. Overexpression of PVT1 exon 9 has been shown to transform non-tumorigenic prostate epithelial cells into aggressive tumor-forming cells. We have recently identified a non-canonical promoter within PVT1 that is associated with PVT1 exon 9 expression and hypothesize that epigenetic factors like DNA methylation and transcription factors regulate its overexpression in prostate cancer, given that gene expression is modulated by epigenetic alterations. Using enzymatic methyl-sequencing (EM-Seq), we profiled tumor and adjacent normal prostate tissues. At a differential methylation threshold of ≥±5% and q ≤0.05, we identified 1050 differentially methylated cytosines (DMCs), with 108 hypomethylated and 80 hypermethylated sites in tumor tissues. Regional tiling analysis (1kb windows) also revealed 172 differentially methylated regions (DMRs), including 42 hypomethylated and 16 hypermethylated DMRs in tumor tissue. PVT1 exon 9-associated promoter was visibly hypomethylated in tumors relative to adjacent normal tissues. In vitro, 5-azacytidine (a DNA methyltransferase inhibitor) treatment induced significant upregulation of PVT1 exons 4A and 9 in WPE1-NA22, DU145, PC-3 and MDA-PCa-2b cell lines versus the non-tumorigenic RWPE-1 cell line. Computational transcription factor analysis revealed CDX1 binds to the newly-identified non-canonical promoter, while CRISPR-mediated base editing of its signal sequence reduced PVT1 exon 9 expression in PVT1 exon 9 overexpressing cells. In addition, CDX1 expression was also found to have a positive correlation with high grade PCa. These findings indicate that PVT1 exon 9 overexpression and oncogenicity in PCa is driven by promoter hypomethylation and CDX1 regulation. Citation Format: Chinedum C. Udekwu, Siti Khaula. Nurazizah, Seidu Adams, Bonnacci Rachel, E.Oluwabunmi Olapade-Olaopa, Olorunseun O. Ogunwobi. The oncogenic role of PVT1 exon 9 overexpression in prostate Cancer is mediated by DNA methylation and CDX1 [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr A065.