Abstract C22: Loss of KDM6A promotes pancreatic cancer progression by upregulating epithelial-mesenchymal transition pathway

Abstract

Abstract Metastasis is one of the main reasons for poor survival in patients with pancreatic ductal adenocarcinoma (PDA). However, the molecular mechanism of PDA metastasis remains elusive. Recent studies failed to find metastasis-specific genetic mutations, and thus suggested that aberrant epigenetic regulation may be one of the crucial mechanisms. Many epigenetic regulator genes are altered in PDA, including KDM6A, a histone H3K27 demethylase, which has been identified by whole-genomic mutational analyses as a driver of PDA. Recent studies have shown that loss of KDM6A induces aggressive squamous-like PDA by activing superenhancers and promotes metastasis. However, the underlying mechanism by which KDM6A promotes metastasis remains elusive. Using stable KDM6A knockout PDA cell lines established by CRISPR/Cas9 system and siRNA, we knocked out or knocked down the expression of KDM6A in PDA cells. We also established an inducible KDM6A re-expressed PDA cell line that has homozygous KDM6A deletion. A novel Bru-seq technology was used to determine global changes of nascent RNA synthesis in KDM6A-null cells. Cell migration and invasion was assessed in vitro. To study the impact of KDM6A loss in vivo, we crossed KDM6Afl/fl mice with the well-established Ptf1aCre; Kras G12D; p53 R172H (KPC) PDA mouse model. Bru-seq data have shown that epithelial-mesenchymal transition (EMT) pathway is highly upregulated in KDM6A knockout cells and downregulated in KDM6A re-expressed PDA cells. EMT is a well-known process that is involved in tumor metastasis. KDM6A knockout cells demonstrated decreased cell proliferation but increased cell migration and invasion with mesenchymal cell morphology changes in vitro. Hallmark epithelial marker E-cadherin was significantly downregulated in KDM6A knockout cells, supporting the EMT process. Furthermore, genetic mouse model showed that mice that lose KDM6A expression developed PDA and metastasis much earlier than KPC mice. The morphology of the PDA developed in KDM6A-null KPC mice is more sarcomatoid or mesenchymal compared to PDA in KPC mice. Immunohistochemistry analysis also demonstrated loss of epithelial marker E-cadherin and gain of mesenchymal marker vimentin in tumor cells. In summary, these results suggest that loss of KDM6A promotes PDA development and metastasis by upregulating EMT signaling. These data linked epigenetic regulation to EMT signaling and provided insights into the role of KDM6A in PDA development. These novel findings also provided foundation for developing new therapeutic strategies. Citation Format: Sivakumar Jeyarajan, Zhujun Yi, Shanqiao Wei, Shuang Lu, Hong Kim, Michelle Paulsen, Karan Bedi, Mats Ljungman, Jiaqi Shi. Loss of KDM6A promotes pancreatic cancer progression by upregulating epithelial-mesenchymal transition pathway [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr C22.