Abstract 3811: Circadian disruption enhances development of pancreatic inflammation and pancreatic cancer precursors

Introduction: Emerging data suggest a role for circadian disruption in tumor formation and progression. Yet little is known regarding the effects of circadian disruption on the oncogenesis of pancreatic ductal adenocarcinoma (PDAC). We sought to determine if circadian disruption enhances PDAC development through a genetically engineered mouse model, and evaluate possible mechanisms with transcriptomic analysis. Methods: KrasG12D/+ mice (K) were crossed with Pdx-1 Cre (C) mice on a C57BL/6 background to generate KC mice. At 4 weeks, mice were subjected to standard lighting conditions (KC normal circadian [KCNC]) or a chronic jet-lag protocol known to induce circadian disruption (KCCD), with light/dark cycles shifted 8 hours every 2-3 days. Mice were sacrificed at 9 months for histologic analysis, examining for PDAC and its precursor lesions (PanINs). Comparisons were made with Fischer's Exact Test. For pancreatic transcriptomic profiling, 144 4-week-old wild-type (WT) C57BL/6 mice underwent disruption (WTCD, n = 72) or standard lighting conditions (WTNC, n = 72) for 4 weeks to identify cycling genes over a 48 hour period. Four weeks was chosen to understand the effects of disruption on gene expression impacting tumor initiation. Standard gene cycling analysis was performed with meta2d utilizing a false discovery rate of q = 0.1, and comparisons were made with the Audic-Claverie Distribution tool. Results: All KC mice (27 KCNC & 7 KCCD) exhibited chronic pancreatitis and PanIN-1 (p = 1). However, KCCD mice developed higher rates of acute pancreatitis (86% vs 4%; p < 0.01) and PanIN-2 (43% vs 7%; p = 0.04) versus KCNC mice. PanIN-3 (14% vs 7% p = 0.48) and PDAC (29% vs 16% p = 0.6) were also increased but did not reach statistical significance. Given this phenotype, we sought a mechanism through transcriptomic analysis. In total, we found 12.8% of the protein-coding pancreatic transcriptome was cycling in either WTNC or WTCD. Pathway enrichment analysis demonstrated genes important for circadian rhythm were cycling in WTNC, while those important for catabolism and protein localization were cycling in WTCD. Only 129 genes, shared between male and female mice, exclusively cycled following circadian disruption. Of those, roughly 15% have been implicated in PDAC development, reported as prognostic biomarkers in PDAC or possibly contribute to chemotherapeutic resistance in PDAC. Conclusion: Little is known about the effects of circadian disruption on PDAC. We have