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Aggressive PDACs show hypomethylation of repetitive elements and the execution of an intrinsic IFN program linked to a ductal cell-of-origin

ABSTRACT: Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer embedded in an e , we FACS-purified epithelial cells from PDAC and healthy human pancreas and performed genome-wide transcriptome and DNA methylome analyses. Clustering based on DNA methylation revealed two distinct groups of PDAC with different methylation levels at genomic regions encoding repeat elements. Methylationlow tumors showed higher expression of endogenous retroviral (ERV) transcripts and a strong engagement of the dsRNA sensing machinery. This results in the cell intrinsic activation of an interferon response signature (IFNsign), leading to the reprogramming of stromal cells towards a pro-tumorigenic microenvironment and poor patient outcome. Methylationlow/IFNsignhigh and Methylationhigh/IFNsignlow PDAC cells harboured distinct lineage traits specific for normal ductal or acinar pancreatic epithelial cells at the methylation and transcriptional level. Moreover, ductal-cell-derived KrasG12D/Trp53-/- mutant mouse PDACs showed higher expression of IFNsign compared to tumors initiated by the same drivers in acinar cells. Collectively, our data point to two distinct origins and etiology of human PDACs, with the aggressive Methylationlow/IFNsignhigh tumor subtype potentially targetable by agents blocking cell intrinsic IFN-signaling. (H015)

PROVIDER: EGAS00001004660 | EGA |

REPOSITORIES: EGA

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Project description:Pancreatic ductal adenocarcinoma (PDAC) is characterized by desmoplastic stroma surrounding most tumors. Activated stromal fibroblasts, namely Cancer-associated fibroblasts (CAFs), play a major role in PDAC progression. Here we analyzed if CAFs influence acinar cells and impact PDAC initiation, namely “Acinar to Ductal Metaplasia” (ADM). ADM connection with PDAC pathophysiology is indicated but not yet established. Hence, we hypothesized that CAF secretome might play a significant role in ADM in PDAC initiation. Mouse and human acinar cell organoids, acinar cells cocultured with CAFs and exposed to CAF-conditioned media (CAF-CM), acinar cell explants, and CAF cocultures, etc., were examined by qRT-PCR, RNA-seq, immunoblotting and confocal microscopy. Data from LC-MS/MS analysis of CAF CM and RNAseq data of acinar cells post-CM exposure were integrated using bioinformatics tools to identify molecular mechanism for CAF-induced ADM. Using confocal microscopy, immunoblotting, and qRT-PCR analysis, we validated the depletion of key signaling axis in cell-line, acinar explant coculture, and mCAFs. Close association of acino-ductal (UEA1, Amylase, Ck19) markers and mCAFs (α-SMA) in LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx1Cre (KPC) and LSL-KrasG12D/+; Pdx1Cre (KC) autochthonous progression tumor tissue was observed. Caerulein treatment-induced mCAFs increased Ck19 and decreased Amylase in wild-type (WT) and KC pancreas. Likewise, acinar-mCAF cocultures revealed induction of ductal transdifferentiation in cell-line, acinar-organoid, and explant coculture formats in WT and KC mice pancreas. Proteomic and transcriptomic data integration revealed a novel Laminin5/Integrinα4/Stat3 axis responsible for CAF-mediated acinar to ductal cell transdifferentiation. Results collectively suggest the first evidence for CAF-influenced acino-ductal phenotypic switchover, thus highlighting the role of the tumor micro-environment in the inception of pancreatic carcinogenesis.