Assuncao, Thiago de

Abstract By regulating gene expression networks that mediate neoplastic behavior, epigenetic protein complexes are the ultimate effectors of oncogenic pathways. This hierarchical position of epigenetic pathways within the mechanisms that regulate cancer makes them ideal candidates for therapeutic targets. The current work was designed to characterize the role of the K9H3 Histone Methyltransferase (HMT) pathway in mediating oncogenic signals downstream of Aurora Kinase A (AurkA), with the goal of designing efficient combinatorial therapies against PDAC. Affinity protein purification, combined with mass spectrometry, demonstrates that HP1γ isolated from mitotic cells interacts with AurkA and the HMTs, G9a and GLP. We also find that this complex is critical for mitotic progression and cell proliferation. Congruently, treatment of PDAC cells with individual drugs against AurkA or HP1-HMT inhibits cell growth by inducing senescence, a cytostatic response. However, the combination of these agents has a synergistic effect of reducing cell growth in both, monolayer and spheroid cultures to result in a cytotoxic effect. Confocal and electron microscopy, along with cell cycle analysis, demonstrate that the cytotoxic effect of this combination is due to induction of mitotic catastrophe, a distinct form of cell death that occurs during mitosis. Molecularly, the combination of AurkA and HP1-HMT inhibition bypasses G2/M arrest with downregulation of the Chk1-Cdc25c pathway. In vivo treatment of PDAC orthotopic xenografts with the HP1-HMT inhibitor alone demonstrated reduced PDAC growth, and increased efficacy in PDAC growth reduction was observed in combination with the AurkA inhibitor over either individual treatment. Thus, our data demonstrate a novel AurkA-HP1-HMT mitotic pathway that holds promise for potential pharmacological targeting in combinatorial therapy for this malignancy. Citation Format: Angela Mathison, Ann Salmonson, Mckenna Missfeldt, Thiago de Assuncao, Jennifer Bintz, Trace Christensen, Sarah Kossak, Asha Nair, Juan Iovanna, Robert Huebert, Gwen Lomberk. Pharmacological targeting of the Aurora A and Histone 3 lysine 9 methyltransferase pathways in pancreatic cancer induces mitotic catastrophe [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4060. doi:10.1158/1538-7445.AM2017-4060