Lrig1 Regulates Epithelial to Mesenchyme Transition (EMT) in Pancreatic Duct Glands (PDG), an Epithelial Stem Cell Compartment Important in Regeneration and Cancer

Lrig1, an epithelial stem cell marker and tumor suppressor, is uniquely expressed within PDGs in pancreas. PDGs are an epithelial progenitor compartment and likely compartment-of-origin for PDAC. Here, in vivo GFP-lineage tagging of Lrig1 expressing PDG cells identify GFP tagged cells in mesenchyme but not in the main duct epithelium, identifying a cell within a PDG epithelial compartment capable of EMT to regenerate its own micro-environment. Mechanisms regulating this EMT switch results from a loss of Lrig1. Characterization of the GFP-positive mesenchyme and PDG cells confirms EMT. ScRNASeq of epithelial spheroids revealed enhanced mesenchymal features in Lrig1 deficient cells, while Lrig1 overexpression abrogates mesenchymal differentiation. In vivo, in vitro and ex vivo studies reveal the Lrig1 loss within this stem cell compartment results in enhanced EGF and TGF-β signaling, expansion of stem cell, proliferative and mesenchymal markers in addition to the up-regulation of a master regulator of stemness and EMT, PSPC1. In vivo murine models of PDAC (KPC) which tag and lose Lrig1 in the PDG compartment results in the expansion of the PDG stem cell compartment which now resembles low-grade PanINs in addition to the formation of an extensive GFP-positive desmoplasia. In vitro, Lrig1 regulates proliferation and EMT in cancer cell lines. These studies identify Lrig1 as a regulator of stemness and EMT in regeneration and cancer.