Abstract C081: The lysine demethylase KDM4C is an oncogenic driver in pancreatic ductal adenocarcinoma

Abstract Deregulation of proteins involved in chromatin regulation is common in pancreatic ductal adenocarcinoma (PDAC), occurring via both genomic and non-genomic mechanisms. Lysine demethylase 4C (KDM4C) is one of the chromatin-modifying proteins frequently overexpressed across multiple solid cancers. We observed upregulation of Kdm4c protein in a panel of human and murine PDAC cell lines, as well as in PDAC patient samples compared to non-neoplastic controls. CRISPR/Cas9-mediated deletion of KDM4C in human and murine PDAC cells resulted in reduced proliferation and clonogenicity, and increased survival of orthotopically implanted murine PDAC allografts. Notably, in multiple KDM4C-null PDAC clones analyzed by reverse phase protein arrays (RPPA), we observed downregulation of activated mitogen-activated protein kinase (MAP kinase) pathway components (including phospho-MEK and phospho-ERK), which are key effector pathways downstream of mutant KRAS. In vitro propagation of KDM4C-null PDAC lines eventually led to adaptation and restitution of MAP kinase signaling via compensatory upregulation of other KDM4 family members (KDM4A and KDM4B). In order to bypass genetic compensation by KDM4 family members, we utilized a preclinical grade pan-KDM4 inhibitor (TACH107, Tachyon Therapeutics) in PDAC cell lines, which confirmed profound reduction in proliferation and colony formation; in vivo xenograft and allograft studies with TACH107 are now ongoing. To characterize signaling pathways perturbed by KDM4C deregulation, we investigated the transcriptional changes in PDAC cells with and without KDM4C deletion by RNA-seq and integrated these with alterations in H3K9me3 and H3K36me3 marks using histone ChIP-Seq. Regulatory network analysis identified ATF4 as one of the top downregulated transcription factor networks, validating a previously published observation linking KDM4C to amino acid biosynthesis and cell proliferation. Gene set enrichment analysis showed downregulation of RAS signatures, consistent with the RPPA data on attenuation of MAP Kinase pathway. DUSP2, a member of the dual specificity protein phosphatase subfamily that inactivates ERK, is transcriptionally upregulated and has increased H3K36me3 marks near the promoter region in KDM4C-depleted cells, nominating it as a candidate of KDM4C-mediated epigenetic regulation. To further delineate the essential binding partners of KDM4C in chromatin regulation, we have created HA-tagged catalytic domain and reader domain deletion constructs that will be used for immunoprecipitation followed by mass spectrometry analysis. Overall, our data suggests that KDM4C - and other KDM4 family members – regulate MAPK signaling in KRAS-mutant cells, at least partially via attenuation of transcripts encoding specific protein phosphatases. To the best of our knowledge, this is the first demonstration linking the requirement of sustained activity of the KDM4 family of lysine demethylases to MAPK signaling in cancer and presents an opportunity to leverage this oncogenic pathway for therapeutic purposes. Citation Format: Menna-t-Allah Shaheen, Laila Barkoudeh, Sarah Dhebat, Kimal I. Rajapakshe, Bidyut Ghosh, Anirban Maitra. The lysine demethylase KDM4C is an oncogenic driver in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C081.