Acvr1b Loss Increases Formation of Pancreatic Precancerous Lesions From Acinar and Ductal Cells of Origin.

BACKGROUND & AIMS: Pancreatic ductal adenocarcinoma can develop from precursor lesions, including pancreatic intraepithelial neoplasia and intraductal papillary mucinous neoplasm (IPMN). Previous studies indicated that loss of Acvr1b accelerates the Kras-mediated development of papillary IPMN in the mouse pancreas; however, the cell type predominantly affected by these genetic changes remains unclear. METHODS: We investigated the contribution of cellular origin by inducing IPMN associated mutations (KRASG12D expression and Acvr1b loss) specifically in acinar (Ptf1aCreER;KrasLSL-G12D;Acvr1bfl/fl mice) or ductal (Sox9CreER;KrasLSL-G12D;Acvr1bfl/fl mice) cells in mice. We then performed magnetic resonance imaging and a thorough histopathologic analysis of their pancreatic tissues. RESULTS: The loss of Acvr1b increased the development of pancreatic intraepithelial neoplasia and IPMN-like lesions when either acinar or ductal cells expressed a Kras mutation. Magnetic resonance imaging, immunohistochemistry, and histology revealed large IPMN-like lesions in these mice that exhibited features of flat, gastric epithelium. In addition, cyst formation in both mouse models was accompanied by chronic pancreatitis. Experimental acute pancreatitis accelerated the development of large mucinous cysts and pancreatic intraepithelial neoplasia when acinar, but not ductal, cells expressed mutant Kras and lost Acvr1b. CONCLUSIONS: These findings indicate that loss of Acvr1b in the presence of the Kras oncogene promotes the development of large and small precancerous lesions from both ductal and acinar cells. However, the IPMN-like phenotype was not equivalent to that observed when these mutations were made in all pancreatic cells during development. Our study underscores the significance of the cellular context in the initiation and progression of precursor lesions from exocrine cells.

PanIN and CAF transitions in pancreatic carcinogenesis revealed with spatial data integration.

This study introduces a new imaging, spatial transcriptomics (ST), and single-cell RNA-sequencing integration pipeline to characterize neoplastic cell state transitions during tumorigenesis. We applied a semi-supervised analysis pipeline to examine premalignant pancreatic intraepithelial neoplasias (PanINs) that can develop into pancreatic ductal adenocarcinoma (PDAC). Their strict diagnosis on formalin-fixed and paraffin-embedded (FFPE) samples limited the single-cell characterization of human PanINs within their microenvironment. We leverage whole transcriptome FFPE ST to enable the study of a rare cohort of matched low-grade (LG) and high-grade (HG) PanIN lesions to track progression and map cellular phenotypes relative to single-cell PDAC datasets. We demonstrate that cancer-associated fibroblasts (CAFs), including antigen-presenting CAFs, are located close to PanINs. We further observed a transition from CAF-related inflammatory signaling to cellular proliferation during PanIN progression. We validate these findings with single-cell high-dimensional imaging proteomics and transcriptomics technologies. Altogether, our semi-supervised learning framework for spatial multi-omics has broad applicability across cancer types to decipher the spatiotemporal dynamics of carcinogenesis.

Pancreatic carcinoma, its variants and precursors: Overview of the current WHO classification.

Pancreatic carcinoma is a relatively common malignant tumor with increasing incidence and mortality. The tumor is usually diagnosed at an advanced stage and generally has a poor prognosis, with only 5% of patients surviving 5 years from the time of diagnosis. The stage of the disease at the time of diagnosis is a crucial factor for the prognosis; 25% of patients with localized tumors survive 3 years from diagnosis, compared to only 1% of those with generalized tumors. Radical surgical removal of the tumor (partial or total pancreatectomy) is a key factor in improving survival. Therefore, the topic is highly relevant to surgeons. Statistics on pancreatic carcinoma mainly focus on ductal adenocarcinoma, which is the most common and least favorable malignant tumor of the pancreas. This review focuses on ductal adenocarcinoma, its variants, and precancerous lesions. The article summarizes information from the latest WHO classification of 2019, which was released 11 years after the previous edition. Compared to the previous version, this new WHO classification introduced rather minor changes in the field of ductal adenocarcinoma. The delineation of rare variants of ductal adenocarcinoma is justified based on genetic and morphological similarities and clinical relevance, as individual subtypes significantly differ in prognosis. The article also includes a description of macroscopic and microscopic precursors of ductal adenocarcinoma and their definitions. Genetic and immunohistochemical differential diagnostic aspects are briefly discussed, as these are more relevant to pathologists than to surgeons.

Pancreatic stellate cells and the interleukin family: Linking fibrosis and immunity to pancreatic ductal adenocarcinoma (Review).

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive form of cancer with a low survival rate. A successful treatment strategy should not be limited to targeting cancer cells alone, but should adopt a more comprehensive approach, taking into account other influential factors. These include the extracellular matrix (ECM) and immune microenvironment, both of which are integral components of the tumor microenvironment. The present review describes the roles of pancreatic stellate cells, differentiated cancer­associated fibroblasts and the interleukin family, either independently or in combination, in the progression of precursor lesions in pancreatic intraepithelial neoplasia and PDAC. These elements contribute to ECM deposition and immunosuppression in PDAC. Therapeutic strategies that integrate interleukin and/or stromal blockade for PDAC immunomodulation and fibrogenesis have yielded inconsistent results. A deeper comprehension of the intricate interplay between fibrosis, and immune responses could pave the way for more effective treatment targets, by elucidating the mechanisms and causes of ECM fibrosis during PDAC progression.

CREB activation drives acinar to ductal reprogramming and promote pancreatic cancer progression in animal models of alcoholic chronic pancreatitis.

BACKGROUND AND AIMS: In vivo induction of alcoholic chronic pancreatitis (ACP) causes significant acinar damage, increased fibroinflammatory response, and heightened activation of cyclic response element binding protein 1 (CREB) when compared with alcohol (A) or chronic pancreatitis (CP) mediated pancreatic damage. However, the study elucidating the cooperative interaction between CREB and the oncogenic Kras G12D/+ (Kras*) in promoting pancreatic cancer progression with ACP remains unexplored. METHODS: Experimental ACP induction was established in multiple mouse models, followed by euthanization of the animals at various time intervals during the recovery periods. Tumor latency was determined in these mice cohorts. Here, we established CREB deletion (Creb fl/fl ) in Ptf1a CreERTM/+ ;LSL-Kras G12D+/-(KC) genetic mouse models (KCC-/-). Western blot, phosphokinase array, and qPCR were used to analyze the pancreata of Ptf1a CreERTM+/-, KC and KCC -/- mice. The pancreata of ACP-induced KC mice were subjected to single-cell RNA sequencing (scRNAseq). Further studies involved conducting lineage tracing and acinar cell explant cultures. RESULTS: ACP induction in KC mice had detrimental effects on the pancreatic damage repair mechanism. The persistent existence of acinar cell-derived ductal lesions demonstrated a prolonged state of hyperactivated CREB. Persistent CREB activation leads to acinar cell reprogramming and increased pro-fibrotic inflammation in KC mice. Acinar-specific Creb ablation reduced advanced PanINs lesions, hindered tumor progression, and restored acinar cell function in ACP-induced mouse models. CONCLUSIONS: Our findings demonstrate that CREB cooperates with Kras* to perpetuate an irreversible ADM and PanIN formation. Moreover, CREB sustains oncogenic activity to promote the progression of premalignant lesions toward cancer in the presence of ACP.

The role of biomarkers in the early detection of pancreatic cancer.

Pancreatic surveillance can detect early-stage pancreatic cancer and achieve long-term survival, but currently involves annual endoscopic ultrasound and MRI/MRCP, and is recommended only for individuals who meet familial/genetic risk criteria. To improve upon current approaches to pancreatic cancer early detection and to expand access, more accurate, inexpensive, and safe biomarkers are needed, but finding them has remained elusive. Newer approaches to early detection, such as using gene tests to personalize biomarker interpretation, and the increasing application of artificial intelligence approaches to integrate complex biomarker data, offer promise that clinically useful biomarkers for early pancreatic cancer detection are on the horizon.

Extremely Rare Synchronous Primary Neoplasms of Meckel's Diverticulum and Colon: a Report of Three Cases.

Synchronous primary neoplasms of Meckel's diverticulum and colon malignancies are rarely reported in the literature. We present three patients with synchronous primary neoplasms of Meckel's diverticulum and colon malignancies. All tumors located in Meckel's diverticulum were incidentally found at laparotomy and the definitive diagnosis was made with microscopic examination of surgical specimens. Synchronous primary neoplasms of Meckel's diverticulum and colon malignancies are rarely encountered. Moreover, this is the first case of synchronous colon cancer and pancreatic intraepithelial neoplasia (PanIN) arising from pancreatic heterotopia within Meckel's diverticulum. The diagnosis of Meckel's diverticulum should be kept in mind in patients who underwent laparotomy for any reason; when found incidentally at laparotomy, it should be carefully examined for any suspicious abnormality and surgery should be considered that it can be performed without any problems.

Familial pancreatic cancer: a long fruitful journey.

In the early years of my GI fellowship, a healthy 40-year-old man came to my clinic and announced that he was going to die of pancreatic cancer. His brothers, father and uncles had all died of the disease; he felt his fate was inescapable. I asked whether his family members had seen doctors or had any tests. His answer was yes to both. Even so, doctors could not diagnose the pancreatic cancer at early stages. CT scans were always negative. I thought to myself, in order to help this patient-CT scans may not be reliable for early detection. Perhaps other methods of imaging the pancreas might be of more benefit. This patient opened a door that led to a 30-year journey of trying to detect pancreatic cancer at earlier stages when it is curable.

A neuroligin-2-YAP axis regulates progression of pancreatic intraepithelial neoplasia.

Pancreatic ductal adenocarcinoma (PDAC) is a tumor with a dismal prognosis that arises from precursor lesions called pancreatic intraepithelial neoplasias (PanINs). Progression from low- to high-grade PanINs is considered as tumor initiation, and a deeper understanding of this switch is needed. Here, we show that synaptic molecule neuroligin-2 (NLGN2) is expressed by pancreatic exocrine cells and plays a crucial role in the regulation of contact inhibition and epithelial polarity, which characterize the switch from low- to high-grade PanIN. NLGN2 localizes to tight junctions in acinar cells, is diffusely distributed in the cytosol in low-grade PanINs and is lost in high-grade PanINs and in a high percentage of advanced PDACs. Mechanistically, NLGN2 is necessary for the formation of the PALS1/PATJ complex, which in turn induces contact inhibition by reducing YAP function. Our results provide novel insights into NLGN2 functions outside the nervous system and can be used to model PanIN progression.

Label-free assessment of pathological changes in pancreatic intraepithelial neoplasia by biomedical multiphoton microscopy.

Pancreatic intraepithelial neoplasia (PanIN) is the most common precursor lesion that has the potential to progress to invasive pancreatic cancer, and early and rapid detection may offer patients a chance for treatment before the development of invasive carcinoma. Therefore, the identification of PanIN holds significant clinical importance. In this study, we first used multiphoton microscopy (MPM) combining two-photon excitation fluorescence and second-harmonic generation imaging to label-free detect PanIN and attempted to differentiate between normal pancreatic ducts and different grades of PanIN. Then, we also developed an automatic image processing strategy to extract eight morphological features of collagen fibers from MPM images to quantify the changes in collagen fibers surrounding the ducts. Experimental results demonstrate that the combination of MPM and quantitative information can accurately identify normal pancreatic ducts and different grades of PanIN. This study may contribute to the rapid diagnosis of pancreatic diseases and may lay the foundation for further clinical application of MPM.

Dichotomous role of the serine/threonine kinase MAP4K4 in pancreatic ductal adenocarcinoma onset and metastasis through control of AKT and ERK pathways.

MAP4K4 is a serine/threonine kinase of the STE20 family involved in the regulation of actin cytoskeleton dynamics and cell motility. It has been proposed as a target of angiogenesis and inhibitors show potential in cardioprotection. MAP4K4 also mediates cell invasion in vitro, is overexpressed in various types of cancer, and is associated with poor patient prognosis. Recently, MAP4K4 has been shown to be overexpressed in pancreatic cancer, but its role in tumour initiation, progression, and metastasis is unknown. Here, using the KrasG12D Trp53R172H Pdx1-Cre (KPC) mouse model of pancreatic ductal adenocarcinoma (PDAC), we show that deletion of Map4k4 drives tumour initiation and progression. Moreover, we report that the acceleration of tumour onset is also associated with an overactivation of ERK and AKT, two major downstream effectors of KRAS, in vitro and in vivo. In contrast to the accelerated tumour onset caused by loss of MAP4K4, we observed a reduction in metastatic burden with both the KPC model and in an intraperitoneal transplant assay indicating a major role of MAP4K4 in metastatic seeding. In summary, our study sheds light on the dichotomous role of MAP4K4 in the initiation of PDAC onset, progression, and metastatic dissemination. It also identifies MAP4K4 as a possible druggable target against pancreatic cancer spread, but with the caveat that targeting MAP4K4 might accelerate early tumorigenesis. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Bioinformatics analyses of infiltrating immune cell participation on pancreatic ductal adenocarcinoma progression and in vivo experiment of the therapeutic effect of Shuangshen granules.

ETHNOPHARMACOLOGICAL RELEVANCE: Shuangshen granules (SSG), a nationally patented Chinese medicinal formula, including Panax quinquefolium L., Panax notoginseng (Burkill) F. H. Chen, and Cordyceps sinensis (Berk.) Sacc., has demonstrated remarkable therapeutic effects on pancreatic cancer in clinical treatment for nearly 10 years. Previous pharmacological researches have found that its main components, including ginsenosides and cordycepin have anticancer or preventive effects on pancreatic ductal adenocarcinoma (PDAC), which may be associated with immune metabolism. However, the underlying pharmacological mechanism of SSG in the truncation effect of PDAC progression is still unclear. AIM OF THE STUDY: To comprehensively understand the infiltrating immune cells during the different stages of the PDAC development chain and search for immune-related biomarkers that could potentially serve as drug targets through bioinformatic analysis. Meanwhile, the truncation effect of SSG on PDAC progression was also investigated. MATERIALS AND METHODS: The gene expression profiles at different PDAC developmental stages, including normal pancreas, pancreatic intraepithelial neoplasia (PanIN), and PDAC, were retrieved from the GEO database. The GEO2R tool was used to identify differentially expressed genes among the three groups. Functional enrichment analysis was performed with the GSEA software and Metascape platform. The CIBERSORT algorithm evaluated immune cell infiltration in the three groups, and immune-related biomarkers were identified. Correlation analysis was employed to examine the association between immune cells and the biomarkers. One of these biomarkers was selected for immunohistochemistry validation in human samples. Lastly, the effectiveness of SSG against PDAC progression and the influence on the selected biomarker were validated in vivo. The underlying pharmacological mechanisms were also explored. RESULTS: One dataset was obtained, where the functional enrichment of DEGs primarily involved immune effector processes and cytokine production of immune cells. The differential immune cells reflected during the progression from PanIN to PDAC were B memory cells, monocytes, M2 macrophages, and activated dendritic cells. The upregulation of ACTA2 was closely associated with M2 macrophage regulation. The immunohistochemistry on human samples validated significant differences in ACTA2 expression levels as the PDAC progressed. Moreover, animal experiments revealed that the national patented drug SSG ameliorated the pathological changes, decreased the expression of ACTA2 and its functional protein α-smooth muscle actin during PDAC progression. The underlying pharmacological mechanism was related to the regulation of macrophage polarization and downregulation of TGF-ß/Smad signaling pathway. CONCLUSIONS: The immunosuppressive environment changes during the PDAC progression. ACTA2 is a potential immuned-target for drug prevention of PDAC, while SSG could be a promising drug candidate.

A new histopathological phenomenon: Pancreatic islet cell loss in the elderly population.

BACKGROUND: We observed the phenomenon of pancreatic islet cell loss (ICL) in our previous histopathological study. Multiple studies have reported that a decrease in ß-cells is correlated with diabetes or chronic pancreatitis. Few studies have reported ICL in a healthy population. METHODS: Thirty-three pancreatic tissue samples were obtained from cadavers (age: 65-104 years) who had never been diagnosed with any pancreatic diseases before death. The pancreatic body sections were used for an immunohistochemical study of pancreatic islet cells, and area calculations were performed using ImageJ to determine the degree of ICL and islet cell proportions. RESULTS: The proportion of ß-cells showed a downward trend as the degree of ICL increased (r=-0.414, P = 0.011), and the proportion of women with severe ICL was significantly higher than that of men with severe ICL (P = 0.016). The probability of severe ICL decreased with age in the population over 70 years of age (P = 0.069, linear correlation). Severe ICL may be associated with higher pancreatic intraepithelial neoplasia lesions (P = 0.059). CONCLUSION: The phenomenon of ICL in the elderly population was mainly due to pancreatic ß-cell reduction. It may be one of the direct causes of age-related diabetes.

Krüppel-like Factor 5 Plays an Important Role in the Pathogenesis of Chronic Pancreatitis.

Chronic pancreatitis results in the formation of pancreatic intraepithelial neoplasia (PanIN) and poses a risk of developing pancreatic cancer. Our previous study demonstrated that Krüppel-like factor 5 (KLF5) is necessary for forming acinar-to-ductal metaplasia (ADM) in acute pancreatitis. Here, we investigated the role of KLF5 in response to chronic injury in the pancreas. Human tissues originating from chronic pancreatitis patients showed increased levels of epithelial KLF5. An inducible genetic model combining the deletion of Klf5 and the activation of KrasG12D mutant expression in pancreatic acinar cells together with chemically induced chronic pancreatitis was used. The chronic injury resulted in increased levels of KLF5 in both control and KrasG12D mutant mice. Furthermore, it led to numerous ADM and PanIN lesions and extensive fibrosis in the KRAS mutant mice. In contrast, pancreata with Klf5 loss (with or without KrasG12D) failed to develop ADM, PanIN, or significant fibrosis. Furthermore, the deletion of Klf5 reduced the expression level of cytokines and fibrotic components such as Il1b, Il6, Tnf, Tgfb1, Timp1, and Mmp9. Notably, using ChIP-PCR, we showed that KLF5 binds directly to the promoters of Il1b, Il6, and Tgfb1 genes. In summary, the inactivation of Klf5 inhibits ADM and PanIN formation and the development of pancreatic fibrosis.

Acinar-to-Ductal Metaplasia (ADM): On the Road to Pancreatic Intraepithelial Neoplasia (PanIN) and Pancreatic Cancer.

Adult pancreatic acinar cells show high plasticity allowing them to change in their differentiation commitment. Pancreatic acinar-to-ductal metaplasia (ADM) is a cellular process in which the differentiated pancreatic acinar cells transform into duct-like cells. This process can occur as a result of cellular injury or inflammation in the pancreas. While ADM is a reversible process allowing pancreatic acinar regeneration, persistent inflammation or injury can lead to the development of pancreatic intraepithelial neoplasia (PanIN), which is a common precancerous lesion that precedes pancreatic ductal adenocarcinoma (PDAC). Several factors can contribute to the development of ADM and PanIN, including environmental factors such as obesity, chronic inflammation and genetic mutations. ADM is driven by extrinsic and intrinsic signaling. Here, we review the current knowledge on the cellular and molecular biology of ADM. Understanding the cellular and molecular mechanisms underlying ADM is critical for the development of new therapeutic strategies for pancreatitis and PDAC. Identifying the intermediate states and key molecules that regulate ADM initiation, maintenance and progression may help the development of novel preventive strategies for PDAC.

Notch signaling pathway in pancreatic tumorigenesis.

The Notch signaling pathway is an evolutionary conserved signal transduction cascade that is critical to embryonic and postnatal development, but aberrant Notch signaling is also implicated in tumorigenesis of many organs including the pancreas. Pancreatic ductal adenocarcinoma (PDAC) is the most common malignancy in the pancreas, with a dismally low survival rate due to the late-stage diagnosis and peculiar therapeutic resistance. Upregulation of the Notch signaling pathway has been found in preneoplastic lesions as well as PDACs in genetically engineered mouse models and human patients, and inhibition of the Notch signaling suppresses tumor development and progression in mice as well as patient-derived xenograft tumor growth, suggesting a critical role for Notch in PDAC. However, the role of Notch signaling pathway remains contentious, exemplified by differential functions of Notch receptors and contrasting outcomes of abolishing Notch signaling in murine PDAC models with distinct cell-of-origin or at different stages. Glycosylation of Notch receptors represents a powerful regulatory mechanism of Notch signaling, and its functional significance in PDAC has begun to emerge. Beyond its impact on tumor cells, Notch signaling is an important regulator of the components of pancreatic tumor microenvironment, including blood vasculature, stellate cells, fibroblasts, and immune cells. Finally, Notch may act as a tumor suppressor in pancreatic neuroendocrine tumor, the second most common pancreatic neoplasm with the incidence on rise. This review summarizes the research on the complex roles of Notch signaling in pancreatic tumorigenesis and the development of potential Notch-targeting therapies for pancreatic cancer.

Role of EUS combined with a newly modified scoring system to detect pancreatic high-grade precancerous lesions.

Backgrounds and Objectives: Although pancreatic cancer (PC) has an extremely poor prognosis, the 5-year survival rate of patients with pancreatic high-grade precancerous lesion without invasive carcinoma (PHP) is favorable. PHP diagnosis and identification of patients requiring intervention are needed. We aimed to validate a modified PC detection scoring system regarding its detection ability for PHP and PC in the general population. Subjects and Methods: We modified an existing PC detection scoring system that incorporates low-grade risk (LGR) factors (family history, presence of diabetes mellitus [DM] or worsening DM, heavy drinking, smoking, stomach symptoms, weight loss, and pancreatic enzyme) and high-grade risk (HGR) factors (new-onset DM, familial PC, jaundice, tumor biomarkers, chronic pancreatitis, intraductal papillary mucinous neoplasm, cysts, hereditary PC syndrome, and hereditary pancreatitis). Each factor was scored as one point; LGR score ≥3 points and/or HGR score ≥1 point (positive scores) were indicative of PC. The newly modified scoring system incorporated main pancreatic duct dilation as an HGR factor. The PHP diagnosis rate using this scoring system combined with EUS was prospectively analyzed. Results: Among 544 patients with positive scores, 10 had PHP. The diagnosis rates were 1.8% for PHP and 4.2% for invasive PC. Although the number of LGR and HGR factors tended to increase with PC progression, none of the individual factors were significantly different between patients with PHP and those without lesions. Conclusion: The newly modified scoring system evaluating multiple factors associated with PC could potentially identify patients with higher risk of PHP or PC.

3'-sulfated LewisA/C: An oncofetal epitope associated with metaplastic and oncogenic plasticity of the gastrointestinal foregut.

Metaplasia, dysplasia, and cancer arise from normal epithelia via a plastic cellular transformation, typically in the setting of chronic inflammation. Such transformations are the focus of numerous studies that strive to identify the changes in RNA/Protein expression that drive such plasticity along with the contributions from the mesenchyme and immune cells. However, despite being widely utilized clinically as biomarkers for such transitions, the role of glycosylation epitopes is understudied in this context. Here, we explore 3'-Sulfo-Lewis A/C, a clinically validated biomarker for high-risk metaplasia and cancer throughout the gastrointestinal foregut: esophagus, stomach, and pancreas. We discuss the clinical correlation of sulfomucin expression with metaplastic and oncogenic transformation, as well as its synthesis, intracellular and extracellular receptors and suggest potential roles for 3'-Sulfo-Lewis A/C in contributing to and maintaining these malignant cellular transformations.

Aryl hydrocarbon receptor knockout accelerates PanIN formation and fibro-inflammation in a mutant Kras-driven pancreatic cancer model.

Objectives: The pathogenesis of pancreas cancer (PDAC) remains poorly understood, hindering efforts to develop a more effective therapy for PDAC. Recent discoveries show the aryl hydrocarbon receptor (AHR) plays a crucial role in the pathogenesis of several cancers, and can be targeted for therapeutic effect. However, its involvement in PDAC remains unclear. Therefore, we evaluated the role of AHR in the development of PDAC in vivo. Methods: We created a global AHR-null, mutant Kras-driven PDAC mouse model (A-/-KC) and evaluated the changes in PDAC precursor lesion formation (Pan-IN 1, 2, and 3) and associated fibro-inflammation between KC and A-/-KC at 5 months of age. We then examined the changes in the immune microenvironment followed by single-cell RNA-sequencing analysis to evaluate concomitant transcriptomic changes. Results: We found a significant increase in PanIN-1 lesion formation and PanIN-1 associated fibro-inflammatory infiltrate in A-/-KC vs KC mice. This was associated with significant changes in the adaptive immune system, particularly a decrease in the CD4+/CD8+ T-cell ratio, as well as a decrease in the T-regulatory/Th17 T-cell ratio suggesting unregulated inflammation. Conclusion: These findings show the loss of AHR results in heightened Kras-induced PanIN formation, through modulation of immune cells within the pancreatic tumor microenvironment.

Deciphering the roadmap of in vivo reprogramming toward pluripotency.

Differentiated cells can be converted into pluripotent stem cells by expressing the transcription factors OCT4, SOX2, KLF4, and MYC (OSKM) in a process known as reprogramming. Here, using single-cell RNA sequencing of pancreas undergoing reprogramming, we identify markers along the trajectory from acinar cell identity to pluripotency. These markers allow direct in situ visualization of cells undergoing dedifferentiation and acquiring features of early and advanced intermediate reprogramming. We also find that a fraction of cells do not dedifferentiate upon OSKM expression and are characterized by stress markers of the REG3 and AP-1 families. Importantly, most markers of intermediate reprogramming in the pancreas are also observed in stomach, colon, and cultured fibroblasts expressing OSKM. Among them is LY6A, a protein characteristic of progenitor cells and generally upregulated during tissue repair. Our roadmap defines intermediate reprogramming states that could be functionally relevant for tissue regeneration and rejuvenation.