MECOM permits pancreatic acinar cell dedifferentiation avoiding cell death under stress conditions

Elyne Backx,Ilse Rooman,Isabelle Houbracken,Patrick Jacquemin,Yves Heremans,Mineo Kurokawa,Diedert Luc De Paep,Elke Wauters,Luc Bouwens,Susumu Goyama,Ellis Michiels,Jonathan Baldan,Mathias Van Bulck

doi:10.1038/s41418-021-00771-6

Abstract

Maintenance of the pancreatic acinar cell phenotype suppresses tumor formation. Hence, repetitive acute or chronic pancreatitis, stress conditions in which the acinar cells dedifferentiate, predispose for cancer formation in the pancreas. Dedifferentiated acinar cells acquire a large panel of duct cell-specific markers. However, it remains unclear to what extent dedifferentiated acini differ from native duct cells and which genes are uniquely regulating acinar cell dedifferentiation. Moreover, most studies have been performed on mice since the availability of human cells is scarce. Here, we applied a non-genetic lineage tracing method of human pancreatic exocrine acinar and duct cells that allowed cell-type-specific gene expression profiling by RNA sequencing. Subsequent to this discovery analysis, one transcription factor that was unique for dedifferentiated acinar cells was functionally characterized. RNA sequencing analysis showed that human dedifferentiated acinar cells expressed genes in “Pathways of cancer” with a prominence of MECOM (EVI-1), a transcription factor that was not expressed by duct cells. During mouse embryonic development, pre-acinar cells also transiently expressed MECOM and in the adult mouse pancreas, MECOM was re-expressed when mice were subjected to acute and chronic pancreatitis, conditions in which acinar cells dedifferentiate. In human cells and in mice, MECOM expression correlated with and was directly regulated by SOX9. Mouse acinar cells that, by genetic manipulation, lose the ability to upregulate MECOM showed impaired cell adhesion, more prominent acinar cell death, and suppressed acinar cell dedifferentiation by limited ERK signaling. In conclusion, we transcriptionally profiled the two major human pancreatic exocrine cell types, acinar and duct cells, during experimental stress conditions. We provide insights that in dedifferentiated acinar cells, cancer pathways are upregulated in which MECOM is a critical regulator that suppresses acinar cell death by permitting cellular dedifferentiation.

Highlights

Few cancers have such poor survival rates as pancreatic ductal adenocarcinoma (PDAC) [1]
MECOM is a cancer-related transcription factor uniquely expressed in human dedifferentiated acinar cells
Other enriched pathways included “PI3K-AKT signaling”, which is involved in acinar cell dedifferentiation and pancreatic tumorigenesis [32,33,34], and “Complement and coagulation cascades” encompassing genes belonging to the tissue damage pathway (Fig. 1e) and that code for F8, fibrinogen, and F3 (CD142), the marker used above [11] (Fig. 1b)

Summary

Introduction

Few cancers have such poor survival rates as pancreatic ductal adenocarcinoma (PDAC) [1]. Understanding the molecular mechanisms that are at play in early-stage cancer formation is important to improve disease outcomes, but clinical samples of early disease, in this case, are rare. Genetically modified mouse models are pivotal to provide us insight into the contribution of the different pancreatic cell types to tumor formation [2,3,4]. In order to become susceptible to tumorigenesis, acinar cells have to lose their differentiated phenotype to some extent. Tumorigenesis is restrained by mechanisms that control acinar cell differentiation [5,6,7,8,9,10]. Duct cells can give rise to tumors but likely under different conditions and through other mechanisms [14,15,16]

Methods

Results

Conclusion