Autophagy, a self-digestive process, is a protective mechanism for tissue homeostasis. However, its importance during cell plasticity is not fully understood. Numerous human diseases are caused by epithelial cell plasticity, and animal models of pancreatic diseases are recognised as study models. Therefore, we developed a unique model in which VPS34, the highly conserved class III PI3K that promotes the autophagic flux, was inactivated in pancreatic exocrine epithelial acinar cells.

Models that reconstitute early pancreatic cancer are recognised models to study cell plasticity. We hence generated a murine model of inducible VPS34 inactivation specifically in pancreatic acinar cells (ElasCreER/VPS34flx/flx), combined or not with KRAS mutation (KC/VPS34flx/flx). Phenotypic, histopathologic and single cell RNA sequencing analysis (scRNAseq) were realized. We used lentiviral vectors to overexpress VPS34 and demonstrate causative roles of VPS34. Results were validated in Human samples.

VPS34 inactivation (ElasCreER/VPS34flx/flx) induced a heterogeneous increase of lipids and markers of autophagy in the pancreas compared to control mice. The scRNAseq highlighted that VPS34 inhibition triggered the loss of an acinar subpopulation with a high mitochondrial activity for the benefit of 3 subpopulations expressing REG mRNAs, linked with pancreas regeneration. These cells had an altered expression of genes related to canonical autophagy and expressed embryonic markers. Those populations of cells were identified in Human pancreas associated with decreased autophagy gene expression. VPS34-inactivated cells presented reduced protein levels of REG3A, due to an increased lysosomal activity. An overexpression of VPS34 was responsible for an increase of REG3A level and of AKT phosphorylation. A pharmacological activator of PI3K increased REG3A levels. Reversely, the PI3Kα pharmacological inhibition reduced the level of REG3A. The total inactivation of VPS34 in the pancreas protected from cell plasticity induced by inflammation and/or oncogenic KRAS alterations (KC/VPS34flx/flx).

VPS34 is a key protein for pancreatic cell plasticity, through positive control of autophagy, activation of class I PI3K and reduced selective degradation of REG3A by lysosome, which can be prevented solely with PI3Kα inactivation. Our unexpected findings transform the once unattainable goal of preventing environmentally-induced cancer initiation into a tangible possibility, paving the way for new protective strategies.