ATF3 induces RAB7 to govern autodegradation in paligenosis, a conserved cell plasticity program

Differentiated cells across multiple species and organs can re-enter the cell cycle to aid in injury-induced tissue regeneration by a cellular program called paligenosis. Here, we show that activating transcription factor 3 (ATF3) is induced early during paligenosis in multiple cellular contexts, transcriptionally activating the lysosomal trafficking gene Rab7b. ATF3 and RAB7B are upregulated in gastric and pancreatic digestive-enzyme-secreting cells at the onset of paligenosis Stage 1, when cells massively induce autophagic and lysosomal machinery to dismantle differentiated cell morphological features. Their expression later ebbs before cells enter mitosis during Stage 3. Atf3-/- mice fail to induce RAB7-positive autophagic and lysosomal vesicles, eventually causing increased death of cells en route to Stage 3. Finally, we observe that ATF3 is expressed in human gastric metaplasia and during paligenotic injury across multiple other organs and species. Thus, our findings indicate ATF3 is an evolutionarily conserved gene orchestrating the early paligenotic autodegradative events that must occur before cells are poised to proliferate and contribute to tissue repair.

Identification of potential serum exosomal microRNAs involved in acinar-ductal metaplasia that is a precursor of pancreatic cancer associated with chronic pancreatitis

BACKGROUNDS

Due to difficulty in early diagnosis of chronic pancreatitis (CP), it is urgent to find novel biomarkers to detect CP. Exosomal microRNAs (Exo-miRNAs) located in the serum may be potential diagnostic and therapeutic targets for CP.

OBJECTIVE

To identify differentially expressed Exo-miRNAs (DE-Exo-miRNAs) in the serum of CP patients, we performed a bioinformatics analysis.

METHODS

The dataset GSE128508 was downloaded from the Gene Expression Omnibus (GEO) database. The analysis was carried out using BRB-ArrayTools and significance analysis of microarrays (SAM). The target genes of DE-S-Exo-miRNAs were predicted by miRWalk databases. Further gene ontology (GO) term and Kyoto Encyclopedia of Genomes (KEGG) pathway analyses were performed with plug-in ClueGO in Cytoscape software 3.7.0. Subsequently, the interaction regulatory network between encoded proteins of target genes was performed with the Search Tool for the Retrieval of Interacting Genes (STRING) database and analyzed using plug-in Molecular Complex Detection (MCODE) and cytoHubba in Cytoscape software 3.7.0.

RESULTS

We identified 227 DE-Exo-miRNAs in the serum. Further analysis using the miRWalk database identified 5164 target genes of these miRNAs. The protein-protein interaction (PPI) regulatory network of 1912 potential target genes for hub 10 up-regulated miRNAs with high degrees and one down-regulated miRNAs were constructed using the STRING database and Cytoscape software. The functional analysis using Cytoscape software tool highlighted that target genes involved in pancreatic cancer. Acinar-ductal metaplasia (ADM) in the inflammatory environment of CP is a precursor of pancreatic cancer. Subsequently, we constructed a network of target genes associated with ADM and their miRNAs.

CONCLUSIONS

Exo-miRNAs in the serum as well as their target genes may be promising targets for the early diagnosis and treatment of CP. In addition, we identified potential Exo-miRNAs involved in ADM that is a precursor of pancreatic cancer associated with CP.

A Dedicated Evolutionarily Conserved Molecular Network Licenses Differentiated Cells to Return to the Cell Cycle

Differentiated cells can re-enter the cell cycle to repair tissue damage via a series of discrete morphological and molecular stages coordinated by the cellular energetics regulator mTORC1. We previously proposed the term "paligenosis" to describe this conserved cellular regeneration program. Here, we detail a molecular network regulating mTORC1 during paligenosis in both mouse pancreatic acinar and gastric chief cells. DDIT4 initially suppresses mTORC1 to induce autodegradation of differentiated cell components and damaged organelles. Later in paligenosis, IFRD1 suppresses p53 accumulation. Ifrd1^-/- cells do not complete paligenosis because persistent p53 prevents mTORC1 reactivation and cell proliferation. Ddit4^-/- cells never suppress mTORC1 and bypass the IFRD1 checkpoint on proliferation. Previous reports and our current data implicate DDIT4/IFRD1 in governing paligenosis in multiple organs and species. Thus, we propose that an evolutionarily conserved, dedicated molecular network has evolved to allow differentiated cells to re-enter the cell cycle (i.e., undergo paligenosis) after tissue injury. VIDEO ABSTRACT.

Moderate alcohol intake promotes pancreatic ductal adenocarcinoma development in mice expressing oncogenic Kras

Kras mutations are associated with pancreatic ductal adenocarcinoma (PDAC). Although tobacco smoking, pancreatitis, and obesity are known environmental risk factors for PDAC, the contribution of moderate alcohol intake to PDAC remains elusive. In the present study, we tested whether a combination of risk factors or moderate alcohol intake induces PDAC development in mice. Control Pdx1^Cre and Pdx1^Cre;LSL-Kras^G12D mutant mice were fed a Western alcohol diet containing high levels of cholesterol and saturated fat, 3.5% alcohol, and lipopolysaccharide for 5 mo. In addition, mice were treated with cerulein, for induction of pancreatitis, and nicotine every month. Treatment with all of these risk factors promoted development of advanced pancreatic neoplasia and PDAC in the Pdx1^Cre;LSL-Kras^G12D mice but not in the control Pdx1^Cre mice. Moderate alcohol intake or Western diet feeding also significantly promoted advanced neoplasia and PDAC development in Pdx1^Cre;LSL-Kras^G12D mice compared with mice fed a regular chow. Alcohol, but not Western diet, increased tumor development in the liver in the Pdx1^Cre;LSL-Kras^G12D mice, but its origin remained elusive due to leakiness of Pdx1^Cre in hepatocytes. RNA-seq analysis revealed that alcohol feeding increases expression of markers for tumors (Epcam, Krt19, Prom1, Wt1, and Wwtr1), stroma (Dcn, Fn1, and Tnc), and cytokines (Tgfb1 and Tnf) and decreases expression of Fgf21 and Il6 in the pancreatic tumor tissues. Immunostaining showed heterogeneous expression of nephronectin, S100 calcium-binding protein A6, and vascular cell adhesion molecule 1 in pancreatic tumors surrounded by podoplanin-positive stromal cells. Our data indicate that moderate alcohol drinking is a risk factor for development of PDAC.NEW & NOTEWORTHY Heavy alcohol intake has been suspected to be a risk factor of pancreatic ductal adenocarcinoma (PDAC) in humans. However, the contribution of moderate alcohol intake to PDAC development remains elusive. In the present study, we experimentally show that moderate alcohol feeding significantly induces advanced stages of pancreatic intraepithelial neoplasia development and invasive PDAC in Pdx1^Cre;LSL-Kras^G12D mutant mice. Our data indicate that moderate alcohol drinking is a risk factor for PDAC.

Snail1 is required for the maintenance of the pancreatic acinar phenotype

The Snail1 transcriptional factor is required for correct embryonic development, yet its expression in adult animals is very limited and its functional roles are not evident. We have now conditionally inactivated Snail1 in adult mice and analyzed the phenotype of these animals. Snail1 ablation rapidly altered pancreas structure: one month after Snail1 depletion, acinar cells were markedly depleted, and pancreas accumulated adipose tissue. Snail1 expression was not detected in the epithelium but was in pancreatic mesenchymal cells (PMCs). Snail1 ablation in cultured PMCs downregulated the expression of several β-catenin/Tcf-4 target genes, modified the secretome of these cells and decreased their ability to maintain acinar markers in cultured pancreas cells. Finally, Snail1 deficiency modified the phenotype of pancreatic tumors generated in transgenic mice expressing c-myc under the control of the elastase promoter. Specifically, Snail1 depletion did not significantly alter the size of the tumors but accelerated acinar-ductal metaplasia. These results demonstrate that Snail1 is expressed in PMCs and plays a pivotal role in maintaining acinar cells within the pancreas in normal and pathological conditions.