Abstract 5624: Dec2, a circadian rhythm gene facilitates pancreatic cancer dormancy through evasion of antitumor immunity

Abstract Metastatic recurrence following curative intent oncologic surgery is a major clinical problem in patients with pancreatic ductal adenocarcinoma (PDAC). These recurrences are from disseminated tumor cells (DTCs) and can sometimes occur years after surgery indicating that DTCs undergo a period of dormancy. The mechanisms that drive cancer dormancy and its awakening are poorly understood in part due to a lack of animal models that recapitulate dormant tumor cell biology. We created a novel model of PDAC dormancy where mice undergo surgery to remove the primary tumor and are followed for evidence of metastatic recurrence. Dormant DTCs can be isolated from mice without clinical evidence of recurrence for molecular studies. Single cell RNAseq of dormant DTCs detected that the circadian rhythm gene, Dec2 is upregulated. We knocked out (KO) Dec2 from murine pancreatic cancer cells and when implanted into the model we found almost no mice developed metastatic recurrence. When immunodeficient or immunocompetent mice depleted of CD4 and CD8 T cells were used as hosts, we observed no difference in survival in mice engrafted with Dec WT vs. KO cells indicating the survival benefit in the Dec KO group was due to an immune mediated mechanism. We performed a differential expression analysis on bulk RNAseq data comparing the Dec2 WT vs. KO cells and found antigen presentation a top upregulated pathway. We then observed that surface MHC-I was significantly upregulated in Dec2 KO cells as compared to wild type cells. Further mechanistic studies revealed that proteosome activity was significantly higher in Dec2 KO cells and treatment with proteosome inhibitors decreased surface MHCI levels in Dec2 KO cells. Cut and tag experiments revealed that Dec2 binds the promoter of a number of genes that regulate the proteosome. In conclusion, Dec2 promotes cancer dormancy by down regulating cell surface MHCI which facilitates immune evasion. Citation Format: Lan Wang, Chris Harris, Orjola Prela, Wade C. Narrow, Darren R. Carpizo. Dec2, a circadian rhythm gene facilitates pancreatic cancer dormancy through evasion of antitumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5624.