Abstract 1317: The role of PAX8 in copy number-high uterine cancers: Inflammatory cytokine modulation

Abstract Paired Box 8 (PAX8) is a transcription factor clinically utilized as a histologic biomarker for cancers arising in tissues derived from the embryonic Mullerian tract. Although dysregulated PAX8 expression has recently been shown to promote the growth of ovarian and renal cancers, its role in uterine cancer remains poorly understood. Here, we hypothesized that overexpression of PAX8 promotes uterine cancer growth and metastasis. When 108 uterine cancer specimens were evaluated by mass spectroscopy, the highest levels of PAX8 were found in TP53-mutated, copy number (CN)-high specimens. In vitro, we found that targeting PAX8 expression resulted in decreased rates of both proliferation and apoptosis in multiple representative cell lines (ARK2 and ARK4). PAX8 knockdown also negatively impacted rates of in vitro migration and invasion assessed using commercially available Boyden chamber assays. Using whole-exome and transcriptomic profiling performed by Next Generation Sequencing, we found that PAX8 knockdown resulted in increased expression of 268 gene products by >1.5-fold, and decreased expression of 179 gene products (adj p<0.01; FDR<1%). Specific gene products whose expression was altered by targeting PAX8 expression included IL-1β, IL-11, and MUC1. With qPCR, we confirmed that levels of IL-1β were 13.8-fold and 3.4-fold higher in cultures of ARK2 and ARK4 cells transfected with PAX8-specific siRNA, respectively, when compared to cultures transfected with a nontargeting control (p<0.01). Using these transfections, we also confirmed increased expression of IL-11 in ARK2 cells (RQ=3.22, p<0.01) and ARK4 cells (RQ = 2.28, p<0.01), and increased expression of MUC1 in ARK2 cells (RQ=1.13, p<0.01). Collectively, our findings demonstrate that PAX8 regulates the proliferation of CN-high uterine cancers, potentially through the regulation of IL-1β expression. Notably, our data also implicates PAX8 expression as a key mediator of the inflammatory response to these aggressive cancers. Key differences in PAX8’s relationship with proliferation and these select few signaling molecules, compared to what is seen in other PAX8-dependent cancers, suggest unique roles for PAX8 as an oncogene in uterine cancers. Citation Format: Lauren Karnolt, Maja Okuka, Susan Read, Yongchao Dou, Bing Zhang, Thomas J. Rutherford, Matthew L. Anderson. The role of PAX8 in copy number-high uterine cancers: Inflammatory cytokine modulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1317.