Tff2 defines transit-amplifying pancreatic acinar progenitors that lack regenerative potential and are protective against Kras-driven carcinogenesis

Regulatory network analysis of Dclk1 gene expression reveals a tuft cell-ILC2 axis that inhibits pancreatic tumor progression

Doublecortin-like kinase 1 (Dclk1) expression identifies cells that are rare in normal pancreas but occur with an increased frequency in pancreatic neoplasia. The identity of these cells has been a matter of debate. We employed Dclk1 reporter mouse models and single-cell RNA sequencing (scRNA-seq) to define Dclk1-expressing cells. In normal pancreas, Dclk1 identifies subsets of ductal, islet, and acinar cells. In pancreatic neoplasia, Dclk1 identifies several cell populations, among which acinar-to-ductal metaplasia (ADM)-like cells and tuft-like cells are predominant. These two populations play opposing roles, with Dclk1+ ADM-like cells sustaining and Dclk1+ tuft-like cells restraining tumor progression. The generation of Dclk1+ tuft-like cells requires the transcription factor SPIB and is sustained by a paracrine loop involving type 2 innate lymphoid cells (ILC2s) and cancer-associated fibroblasts (CAFs) that provide interleukin (IL)-13 and IL-33, respectively. Dclk1+ tuft-like cells release angiotensinogen to restrain tumor progression. Overall, our study defines pancreatic Dclk1+ cells and unveils a protective tuft cell-ILC2 axis against pancreatic neoplasia.

Tff2 marks gastric corpus progenitors that give rise to pyloric metaplasia/SPEM following injury

In Brief

Tu et al. show that Tff2 + corpus isthmus cells are TA progenitors, and they, not chief cells, are the primary source of SPEM following injury. Upon Kras mutation, these progenitors directly progress to dysplasia, bypassing metaplasia, highlighting them as a potential origin of gastric cancer.

Highlights

Tff2 + corpus cells are TA progenitors that give rise to secretory cells. Tff2 + progenitors, not chief cells, are the primary source of SPEM after injury. Kras-mutant Tff2 + progenitors progress directly to dysplasia, bypassing metaplasia. Multi-omics analysis reveals distinct trajectories for SPEM and gastric cancer.

Abstract Figure

Pyloric metaplasia, also known as spasmolytic polypeptide-expressing metaplasia (SPEM), arises in the corpus in response to oxyntic atrophy, but its origin and role in gastric cancer remain poorly understood. Using Tff2-CreERT knockin mice, we identified highly proliferative Tff2 + progenitors in the corpus isthmus that give rise to multiple secretory lineages, including chief cells. While lacking long-term self-renewal ability, Tff2 + corpus progenitors rapidly expand to form short-term SPEM following acute injury or loss of chief cells. Genetic ablation of Tff2 + progenitors abrogated SPEM formation, while genetic ablation of GIF + chief cells enhanced SPEM formation from Tff2 + progenitors. In response to H. pylori infection, Tff2 + progenitors progressed first to metaplasia and then later to dysplasia. Interestingly, induction of Kras G12D mutations in Tff2 + progenitors facilitated direct progression to dysplasia in part through the acquisition of stem cell-like properties. In contrast, Kras-mutated SPEM and chief cells were not able to progress to dysplasia. Tff2 mRNA was downregulated in isthmus cells during progression to dysplasia. Single-cell RNA sequencing and spatial transcriptomics of human tissues revealed distinct differentiation trajectories for SPEM and gastric cancer. These findings challenge the conventional interpretation of the stepwise progression through metaplasia and instead identify Tff2 + progenitor cells as potential cells of origin for SPEM and possibly for gastric cancer.

KRASG12D Cells Override Homeostatic Cell Elimination Mechanisms in Adult Pancreas Via Wnt5a and Cell Dormancy

BACKGROUND & AIMS

The adult pancreas protects against cancer by actively expelling genetically mutated cells. Pancreatic cancer starts with cells carrying KRAS mutations; however, it is not clear how some KRAS mutant cells override cell elimination mechanisms to survive in tissues.

METHODS

An in vivo mouse model of sporadic tumorigenesis was used to induce Kras and/or Tp53 mutations in low numbers of cells in the adult pancreas. The mutant cell fate was monitored over time using quantitative fluorescence imaging. Gene signatures of noneliminated mutant cell populations were identified using bulk RNA sequencing. Differential gene expression was overlapped with publicly available datasets. Key molecular pathways were validated in murine pancreas using immunofluorescence and functionally tested using inhibitor studies in vivo and epithelial coculture systems in vitro.

RESULTS

Although most genetically mutant cells are eliminated from the adult pancreas, a population of KRASG12D- or p53R172H-expressing cells are stably retained. Wnt5a signaling, cell dormancy, and stemness were identified as key features of surviving KrasG12D cells in vivo. Wnt5a specifically inhibits apical extrusion of RasV12 cells by promoting stable E-cadherin-based cell-cell adhesions at RasV12: normal cell-cell boundaries in vitro. In the pancreas, Wnt signaling, E-cadherin, and β-catenin are increased at cell-cell contacts between noneliminated KrasG12D cells and normal neighbors. Active Wnt signaling is a general mechanism required to promote KrasG12D and p53R172H cell retention and cell survival in vivo.

CONCLUSIONS

RAS mutant cells activate Wnt5a and cell dormancy to avoid cell expulsion and to survive in the adult pancreas.

Spatial analysis of IPMNs defines a paradoxical KRT17-positive, low-grade epithelial population harboring malignant features

Background & Aims

Intraductal papillary mucinous neoplasms (IPMNs) are pancreatic cysts that represent one of the few radiologically identifiable precursors to pancreatic ductal adenocarcinoma (PDAC).Though the IPMN-bearing patient population represents a unique opportunity for early detection and interception, current guidelines provide insufficient accuracy in determining which patients should undergo resection versus surveillance, resulting in a sizable fraction of resected IPMNs only harboring low-grade dysplasia, suggesting that there may be overtreatment of this clinical entity.

Methods

To investigate the transcriptional changes that occur during IPMN progression, we performed spatial transcriptomics using the Nanostring GeoMx on patient samples containing the entire spectrum of IPMN disease including low-grade dysplasia, high-grade dysplasia, and IPMN-derived carcinoma. Single cell RNA sequencing was performed on side branch and main duct IPMN biospecimens.

Results

We identified a subpopulation of histologically low-grade IPMN epithelial cells that express malignant transcriptional features including KRT17 , S100A10 and CEACAM5 , markers that are enriched in PDAC. We validated and refined this high-risk gene signature by integrating our ST analysis with an external ST dataset containing a larger number of IPMN samples including non-tumor bearing IPMN (i.e. low-grade IPMN in isolation). We confirmed the presence of the KRT17+ population using immunofluorescence on a large cohort of patient tissues, revealing a widespread but patchy distribution of KRT17+ cells in histologically low-grade IPMN.

Conclusions

Our study demonstrates that KRT17 marks a distinct transcriptional signature in a subpopulation of epithelial cells within histologically low-grade IPMN. This population of cells likely represents a transitional state of histologically low-grade epithelial cells undergoing progression to a higher grade of dysplasia and thus may represent a higher risk of progression to carcinoma.

Graphical abstract

The Stmn1-lineage contributes to acinar regeneration but not to neoplasia upon oncogenic Kras expression

BACKGROUND & AIMS

The exocrine pancreas has a limited regenerative capacity, but to what extent all acinar cells are involved in this process is unclear. Nevertheless, the heterogenous nature of acinar cells suggests that cells exhibiting higher plasticity might play a more prominent role in acinar regeneration. In that regard, Stmn1 -expressing acinar cells have been identified as potential facultative progenitor-like cells in the adult pancreas. Here, we studied Stmn1-progeny under physiological conditions, during regeneration, and in the context of Kras G12D expression.

METHODS

We followed the fate of Stmn1-progenies both under baseline conditions, following caerulein-induced acute or chronic pancreatitis, pancreatic duct ligation, and in the context of Kras G12D expression.

RESULTS

The Stmn1-lineage contributes to baseline acinar cell turnover under physiological conditions. Furthermore, these cells rapidly proliferate and repopulate the acinar compartment in response to acute injury in an ADM-independent manner. Moreover, acinar regeneration during chronic pancreatitis progression is in conjunction with a decline in the proliferative capacity of the Stmn1-lineage. Interestingly, newly generated acinar cells display increased susceptibility to additional injury during recurrent acute pancreatitis (RAP). Finally, given their inability to form ADMs, the Stmn1-lineage fails to form PanINs upon oncogenic Kras expression.

CONCLUSIONS

Our findings establish the Stmn1-lineage as a pivotal subpopulation for acinar tissue homeostasis and regeneration. The ability of these cells to restore acinar tissue in an ADM-independent manner distinguishes them as a critical regenerative population. This study presents a new paradigm for acinar regeneration and repair in the context of pancreatitis and neoplasia.

Beta cells are essential drivers of pancreatic ductal adenocarcinoma development

Pancreatic endocrine-exocrine crosstalk plays a key role in normal physiology and disease. For instance, endocrine islet beta (β) cell secretion of insulin or cholecystokinin (CCK) promotes progression of pancreatic adenocarcinoma (PDAC), an exocrine cell-derived tumor. However, the cellular and molecular mechanisms that govern endocrine-exocrine signaling in tumorigenesis remain incompletely understood. We find that β cell ablation impedes PDAC development in mice, arguing that the endocrine pancreas is critical for exocrine tumorigenesis. Conversely, obesity induces β cell hormone dysregulation, alters CCK-dependent peri-islet exocrine cell transcriptional states, and enhances islet proximal tumor formation. Single-cell RNA-sequencing, in silico latent-space archetypal and trajectory analysis, and genetic lineage tracing in vivo reveal that obesity stimulates postnatal immature β cell expansion and adaptation towards a pro-tumorigenic CCK+ state via JNK/cJun stress-responsive signaling. These results define endocrine-exocrine signaling as a driver of PDAC development and uncover new avenues to target the endocrine pancreas to subvert exocrine tumorigenesis.

Emerging strategies to investigate the biology of early cancer

Early detection and intervention of cancer or precancerous lesions hold great promise to improve patient survival. However, the processes of cancer initiation and the normal-precancer-cancer progression within a non-cancerous tissue context remain poorly understood. This is, in part, due to the scarcity of early-stage clinical samples or suitable models to study early cancer. In this Review, we introduce clinical samples and model systems, such as autochthonous mice and organoid-derived or stem cell-derived models that allow longitudinal analysis of early cancer development. We also present the emerging techniques and computational tools that enhance our understanding of cancer initiation and early progression, including direct imaging, lineage tracing, single-cell and spatial multi-omics, and artificial intelligence models. Together, these models and techniques facilitate a more comprehensive understanding of the poorly characterized early malignant transformation cascade, holding great potential to unveil key drivers and early biomarkers for cancer development. Finally, we discuss how these new insights can potentially be translated into mechanism-based strategies for early cancer detection and prevention.

Regulatory network analysis of Dclk1 gene expression reveals a tuft cell-ILC2 axis that inhibits pancreatic tumor progression

Dclk1 expression defines a rare population of cells in the normal pancreas whose frequency is increased at early stages of pancreatic tumorigenesis. The identity and the precise roles of Dclk1 expressing cells in pancreas have been matter of debate, although evidence suggests their involvement in a number of key functions, including regeneration and neoplasia. We employed a recently developed Dclk1 reporter mouse model and single cell RNAseq analysis to define Dclk1 expressing cells in normal pancreas and pancreatic neoplasia. In normal pancreas, Dclk1 epithelial expression identifies subsets of ductal, islet and acinar cells. In pancreatic neoplasia, Dclk1 expression identifies five epithelial cell populations, among which acinar-to-ductal metaplasia (ADM)-like cells and tuft-like cells are predominant. These two cell populations play opposing roles in pancreatic neoplasia, with Dclk1+ ADM-like cells sustaining tumor growth while Dclk1+ tuft-like cells restraining tumor progression. The differentiation of Kras mutant acinar cells into Dclk1+ tuft-like cells requires the activation of the transcription factor SPIB and is further supported by a cellular paracrine loop involving cancer group 2 innate lymphoid cells (ILC2) and cancer activated fibroblasts (CAFs) that provide IL13 and IL33, respectively. In turn, Dclk1+ tuft-like cells release angiotensinogen that plays protective roles against pancreatic neoplasia. Overall, our study provides novel insights on the biology of Dclk1+ cells in normal pancreas and unveils a protective axis against pancreatic neoplasia, involving CAFs, ILC2 and Dclk1+ tuft-like cells, which ultimately results in angiotensinogen release.

Pathways regulating intestinal stem cells and potential therapeutic targets for radiation enteropathy

Radiotherapy is a pivotal intervention for cancer patients, significantly impacting their treatment outcomes and survival prospects. Nevertheless, in the course of treating those with abdominal, pelvic, or retroperitoneal malignant tumors, the procedure inadvertently exposes adjacent intestinal tissues to radiation, posing risks of radiation-induced enteropathy upon reaching threshold doses. Stem cells within the intestinal crypts, through their controlled proliferation and differentiation, support the critical functions of the intestinal epithelium, ensuring efficient nutrient absorption while upholding its protective barrier properties. Intestinal stem cells (ISCs) regulation is intricately orchestrated by diverse signaling pathways, among which are the WNT, BMP, NOTCH, EGF, Hippo, Hedgehog and NF-κB, each contributing to the complex control of these cells' behavior. Complementing these pathways are additional regulators such as nutrient metabolic states, and the intestinal microbiota, all of which contribute to the fine-tuning of ISCs behavior in the intestinal crypts. It is the harmonious interplay among these signaling cascades and modulating elements that preserves the homeostasis of intestinal epithelial cells (IECs), thereby ensuring the gut's overall health and function. This review delves into the molecular underpinnings of how stem cells respond in the context of radiation enteropathy, aiming to illuminate potential biological targets for therapeutic intervention. Furthermore, we have compiled a summary of several current treatment methodologies. By unraveling these mechanisms and treatment methods, we aspire to furnish a roadmap for the development of novel therapeutics, advancing our capabilities in mitigating radiation-induced intestinal damage.

Trefoil Factor 2 Expressed by the Murine Pancreatic Acinar Cells Is Required for the Development of Islets and for β-Cell Function During Aging

Exocrine-to-endocrine cross talk in the pancreas is crucial to maintain β-cell function. However, the molecular mechanisms underlying this cross talk are largely undefined. Trefoil factor 2 (Tff2) is a secreted factor known to promote the proliferation of β-cells in vitro, but its physiological role in vivo in the pancreas is unknown. Also, it remains unclear which pancreatic cell type expresses Tff2 protein. We therefore created a mouse model with a conditional knockout of Tff2 in the murine pancreas. We find that the Tff2 protein is preferentially expressed in acinar but not ductal or endocrine cells. Tff2 deficiency in the pancreas reduces β-cell mass on embryonic day 16.5. However, homozygous mutant mice are born without a reduction of β-cells and with acinar Tff3 compensation by day 7. When mice are aged to 1 year, both male and female homozygous and male heterozygous mutants develop impaired glucose tolerance without affected insulin sensitivity. Perifusion analysis reveals that the second phase of glucose-stimulated insulin secretion from islets is reduced in aged homozygous mutant compared with controls. Collectively, these results demonstrate a previously unknown role of Tff2 as an exocrine acinar cell-derived protein required for maintaining functional endocrine β-cells in mice.

ARTICLE HIGHLIGHTS

Tumor initiation and early tumorigenesis: molecular mechanisms and interventional targets

Tumorigenesis is a multistep process, with oncogenic mutations in a normal cell conferring clonal advantage as the initial event. However, despite pervasive somatic mutations and clonal expansion in normal tissues, their transformation into cancer remains a rare event, indicating the presence of additional driver events for progression to an irreversible, highly heterogeneous, and invasive lesion. Recently, researchers are emphasizing the mechanisms of environmental tumor risk factors and epigenetic alterations that are profoundly influencing early clonal expansion and malignant evolution, independently of inducing mutations. Additionally, clonal evolution in tumorigenesis reflects a multifaceted interplay between cell-intrinsic identities and various cell-extrinsic factors that exert selective pressures to either restrain uncontrolled proliferation or allow specific clones to progress into tumors. However, the mechanisms by which driver events induce both intrinsic cellular competency and remodel environmental stress to facilitate malignant transformation are not fully understood. In this review, we summarize the genetic, epigenetic, and external driver events, and their effects on the co-evolution of the transformed cells and their ecosystem during tumor initiation and early malignant evolution. A deeper understanding of the earliest molecular events holds promise for translational applications, predicting individuals at high-risk of tumor and developing strategies to intercept malignant transformation.

Genetic Signature of Human Pancreatic Cancer and Personalized Targeting

Pancreatic cancer is a highly lethal disease with a 5-year survival rate of around 11-12%. Surgery, being the treatment of choice, is only possible in 20% of symptomatic patients. The main reason is that when it becomes symptomatic, IT IS the tumor is usually locally advanced and/or has metastasized to distant organs; thus, early diagnosis is infrequent. The lack of specific early symptoms is an important cause of late diagnosis. Unfortunately, diagnostic tumor markers become positive at a late stage, and there is a lack of early-stage markers. Surgical and non-surgical cases are treated with neoadjuvant and/or adjuvant chemotherapy, and the results are usually poor. However, personalized targeted therapy directed against tumor drivers may improve this situation. Until recently, many pancreatic tumor driver genes/proteins were considered untargetable. Chemical and physical characteristics of mutated KRAS are a formidable challenge to overcome. This situation is slowly changing. For the first time, there are candidate drugs that can target the main driver gene of pancreatic cancer: KRAS. Indeed, KRAS inhibition has been clinically achieved in lung cancer and, at the pre-clinical level, in pancreatic cancer as well. This will probably change the very poor outlook for this disease. This paper reviews the genetic characteristics of sporadic and hereditary predisposition to pancreatic cancer and the possibilities of a personalized treatment according to the genetic signature.

An optimized protocol for isolation of murine pancreatic single cells with high yield and purity

Here, we present a protocol for rapidly isolating single cells from the mouse pancreas, minimizing damage caused by digestive enzymes in exocrine cells. We guide you through steps to optimize the dissection sequence, enzyme composition, and operational procedures, resulting in high yields of viable pancreatic single cells. This protocol can be applied across a wide range of research areas, including single-cell sequencing, gene expression profiling, primary cell culture, and even the development of spheroids or organoids. For complete details on the use and execution of this protocol, please refer to Jiang et al. (2023).1.

Pancreatic acinar heterogeneity hijacks carcinogenesis and homeostasis

In this issue, Jiang and colleagues employ multiple lineage-tracing approaches to elaborate on the role of Tff2+ transit-amplifying progenitor cells in the pancreatic acinar compartment of mice. This work provides insights into the steady-state homeostasis and tumor-suppressive features of certain progenitor cells and presents findings on acinar cell heterogeneity.