Abstract 309: Mapping oncogenic signal transduction in PKA-driven cancers

Abstract

Abstract Protein Kinase A (PKA) is a major effector of cyclic-AMP (cAMP) signaling and has recently been appreciated to play a role in multiple malignancies. Mutations of its catalytic subunit (PRKACA) have been identified in a substantial proportion of adrenocortical tumors, and are also detected in a wide spectrum of tumor types in the TCGA dataset, although at a low frequency. A unique fusion protein of PRKACA and DNAJB1 is seen in the majority of fibrolamellar liver cancers (FLC), a rare malignancy of young adults, where it is suspected to be the primary oncogenic driver. However, the key effectors of oncogenic signaling in FLC and other PRKACA driven cancers remain unknown. To understand PKA's downstream targets, we generated genetic cell models with doxycycline-inducible PRKACA or its dominant negative counterpart, a mutant form of the PRKAR1A regulatory subunit. These cell models were then subjected to mass spectrometry for kinome profiling in order to detect kinases with significant altered activity following PKA modulation. This was integrated with small molecule inhibition and siRNA knockdown to identify PKA-regulated kinases that impact cell proliferation. Our analysis revealed activation of the aurora-family kinase AURKA, with preferential sensitivity to the confirmation-disrupting AURKA inhibitor (CD-AURKAi) CD532 compared to other AURKA inhibitors. CD-AURKAi not only selectively inhibit AURKA's kinase activity, but also disrupt its interaction with MYC-family transcription factors. These key oncogenic mediators are necessary to drive the proliferation of multiple tumor types, although they have not yet been connected with oncogenic PKA signaling. Our follow up quantitative PCR experiments confirm that CD-532 treatment results in reduced expression of MYC family members and their transcriptional targets. We next confirmed that MYC family members support the proliferation of PKA-driven cell models with live cell imaging. Finally, we have begun to investigate other kinases identified in our siRNA screen for potential effects on MYC, and have identified several potential combination partners to augment the activity of CD-532 and other CD-AURKAi. These data suggest that CD-AURKAi, either alone or in combination, have the potential to serve as therapeutic agents for PKA-driven cancers. Citation Format: Gary Kwan Leung Chan, Samantha M. Maisel, Y. Christina Hwang, Rebecca Wolber, Danielle L. Swaney, Nabeel Bardeesy, John D. Gordan. Mapping oncogenic signal transduction in PKA-driven cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 309.