Combined AURKA and H3K9 Methyltransferase Targeting Inhibits Cell Growth By Inducing Mitotic Catastrophe

The current integrative pathobiologic hypothesis states that pancreatic cancer (PDAC) develops and progresses in response to an interaction between known oncogenes and downstream epigenomic regulators. Congruently, this study tests a new combinatorial therapy based on the inhibition of the Aurora kinase A (AURKA) oncogene and one of its targets, the H3K9 methylation-based epigenetic pathway. This therapeutic combination is effective at inhibiting the in vitro growth of PDAC cells both, in monolayer culture systems, and in three-dimensional spheroids and organoids. The combination also reduces the growth of PDAC xenografts in vivo Mechanistically, it was found that inhibiting methyltransferases of the H3K9 pathway in cells, which are arrested in G₂-M after targeting AURKA, decreases H3K9 methylation at centromeres, induces mitotic aberrations, triggers an aberrant mitotic check point response, and ultimately leads to mitotic catastrophe. Combined, these data describe for the first time a hypothesis-driven design of an efficient combinatorial treatment that targets a dual oncogenic-epigenomic pathway to inhibit PDAC cell growth via a cytotoxic mechanism that involves perturbation of normal mitotic progression to end in mitotic catastrophe. Therefore, this new knowledge has significant mechanistic value as it relates to the development of new therapies as well as biomedical relevance.Implications: These results outline a model for the combined inhibition of a genetic-to-epigenetic pathway to inhibit cell growth and suggest an important and provocative consideration for harnessing the capacity of cell-cycle inhibitors to enhance the future use of epigenetic inhibitors. Mol Cancer Res; 15(8); 984-97. ©2017 AACR.