Dysregulation of PI3K and Hippo signaling pathways synergistically induces chronic pancreatitis via CTGF upregulation

FRA1 controls acinar cell plasticity during murine KrasG12D-induced pancreatic acinar to ductal metaplasia

Acinar cells have been proposed as a cell-of-origin for pancreatic ductal adenocarcinoma (PDAC) after undergoing acinar-to-ductal metaplasia (ADM). ADM can be triggered by pancreatitis, causing acinar cells to de-differentiate to a ductal-like state. We identify FRA1 (gene name Fosl1) as the most active transcription factor during KrasG12D acute pancreatitis-mediated injury, and we have elucidated a functional role of FRA1 by generating an acinar-specific Fosl1 knockout mouse expressing KrasG12D. Using a gene regulatory network and pseudotime trajectory inferred from single-nuclei ATAC-seq and bulk RNA sequencing (RNA-seq), we hypothesized a regulatory model of the acinar-ADM-pancreatic intraepithelial neoplasia (PanIN) continuum and experimentally validated that Fosl1 knockout mice are delayed in the onset of ADM and neoplastic transformation. Our study also identifies that pro-inflammatory cytokines, such as granulocyte colony stimulating factor (G-CSF), can regulate FRA1 activity to modulate ADM. Our findings identify that FRA1 is a mediator of acinar cell plasticity and is critical for acinar cell de-differentiation and transformation.

High-mobility group box 1 fragment ameliorates chronic pancreatitis induced by caerulein in mice

BACKGROUND

Chronic pancreatitis (CP) is a progressive disease characterized by pancreatic fibrosis for which effective treatment options are lacking. Mesenchymal stem cells (MSCs) have shown potential for fibrosis treatment but face limitations in clinical application. The high-mobility group box 1 (HMGB1) fragment mobilizes MSCs from bone marrow into the blood and has emerged as a promising therapeutic agent for tissue regeneration in various pathological conditions. The aim of this study was to investigate the potential therapeutic effects of systemic administration of the HMGB1 fragment in a mouse model of CP.

METHODS

A caerulein-induced CP mouse model was used, and the HMGB1 fragment was administered by tail vein injection. Parameters such as body weight, pancreatic tissue damage, fibrosis, inflammatory cytokine expression, and collagen-related gene expression were evaluated using various assays, including immunohistochemistry, real-time PCR, serum analysis, and single-cell transcriptome analysis. And the migration of MSCs to the pancreas was evaluated using the parabiosis model.

RESULTS

Administration of the HMGB1 fragment was associated with significant improvements in pancreatic tissue damage and fibrosis. It suppressed the expression of inflammatory cytokines and activated platelet-derived growth factor receptor-α+ MSCs, leading to their accumulation in the pancreas. The HMGB1 fragment also shifted gene expression patterns associated with pancreatic fibrosis toward those of the normal pancreas. Systemic administration of the HMGB1 fragment demonstrated therapeutic efficacy in attenuating pancreatic tissue damage and fibrosis in a CP mouse model.

CONCLUSION

These findings highlight the potential of the HMGB1 fragment as a therapeutic target for the treatment of CP.

Pancreatic stellate cells: Key players in pancreatic health and diseases (Review)

As a pluripotent cell, activated pancreatic stellate cells (PSCs) can differentiate into various pancreatic parenchymal cells and participate in the secretion of extracellular matrix and the repair of pancreatic damage. Additionally, PSCs characteristics allow them to contribute to pancreatic inflammation and carcinogenesis. Moreover, a detailed study of the pathogenesis of activated PSCs in pancreatic disease can offer promise for the development of innovative therapeutic strategies and improved patient prognoses. Therefore, the present study review aimed to examine the involvement of activated PSCs in pancreatic diseases and elucidate the underlying mechanisms to provide a viable therapeutic strategy for the management of pancreas‑related diseases.

Role of Hippo pathway dysregulation from gastrointestinal premalignant lesions to cancer

BACKGROUND

First identified in Drosophila melanogaster, the Hippo pathway is considered a major regulatory cascade controlling tissue homeostasis and organ development. Hippo signaling components include kinases whose activity regulates YAP and TAZ final effectors. In response to upstream stimuli, YAP and TAZ control transcriptional programs involved in cell proliferation, cytoskeletal reorganization and stemness.

MAIN TEXT

While fine tuning of Hippo cascade components is essential for maintaining the balance between proliferative and non-proliferative signals, pathway signaling is frequently dysregulated in gastrointestinal cancers. Also, YAP/TAZ aberrant activation has been described in conditions characterized by chronic inflammation that precede cancer development, suggesting a role of Hippo effectors in triggering carcinogenesis. In this review, we summarize the architecture of the Hippo pathway and discuss the involvement of signaling cascade unbalances in premalignant lesions of the gastrointestinal tract, providing a focus on the underlying molecular mechanisms.

CONCLUSIONS

The biology of premalignant Hippo signaling dysregulation needs further investigation in order to elucidate the evolutionary trajectories triggering cancer inititation and develop effective early therapeutic strategies targeting the Hippo/YAP pathway.

Activation and Regulation of Pancreatic Stellate Cells in Chronic Pancreatic Fibrosis: A Potential Therapeutic Approach for Chronic Pancreatitis

In the complex progression of fibrosis in chronic pancreatitis, pancreatic stellate cells (PSCs) emerge as central figures. These cells, initially in a dormant state characterized by the storage of vitamin A lipid droplets within the chronic pancreatitis microenvironment, undergo a profound transformation into an activated state, typified by the secretion of an abundant extracellular matrix, including α-smooth muscle actin (α-SMA). This review delves into the myriad factors that trigger PSC activation within the context of chronic pancreatitis. These factors encompass alcohol, cigarette smoke, hyperglycemia, mechanical stress, acinar cell injury, and inflammatory cells, with a focus on elucidating their underlying mechanisms. Additionally, we explore the regulatory factors that play significant roles during PSC activation, such as TGF-β, CTGF, IL-10, PDGF, among others. The investigation into these regulatory factors and pathways involved in PSC activation holds promise in identifying potential therapeutic targets for ameliorating fibrosis in chronic pancreatitis. We provide a summary of recent research findings pertaining to the modulation of PSC activation, covering essential genes and innovative regulatory mediators designed to counteract PSC activation. We anticipate that this research will stimulate further insights into PSC activation and the mechanisms of pancreatic fibrosis, ultimately leading to the discovery of groundbreaking therapies targeting cellular and molecular responses within these processes.

Regulation of Hippo-YAP/CTGF signaling by combining an HDAC inhibitor and 5-fluorouracil in gastric cancer cells

Histone deacetylase (HDAC) inhibitors diminish carcinogenesis, metastasis, and cancer cell proliferation by inducing death in cancer cells. Tissue regeneration and organ development are highly dependent on the Hippo signaling pathway. Targeting the dysregulated hippo pathway is an excellent approach for cancer treatment. According to the results of this study, the combination of panobinostat, a histone deacetylase inhibitor, and 5-fluorouracil (5-FU), a chemotherapy drug, can act synergistically to induce apoptosis in gastric cancer cells. The combination of panobinostat and 5-FU was more effective in inhibiting cell viability than either treatment alone by elevating the protein levels of cleaved PARP and cleaved caspase-9. By specifically targeting E-cadherin, vimentin, and MMP-9, the combination of panobinostat and 5-FU significantly inhibited cell migration. Additionally, panobinostat significantly increased the anticancer effects of 5-FU by activating Hippo signaling (Mst 1 and 2, Sav1, and Mob1) and inhibiting the Akt signaling pathway. As a consequence, there was a decrease in the amount of Yap protein. The combination therapy of panobinostat with 5-FU dramatically slowed the spread of gastric cancer in a xenograft animal model by deactivating the Akt pathway and supporting the Hippo pathway. Since combination treatment exhibits much higher anti-tumor potential than 5-FU alone, panobinostat effectively potentiates the anti-tumor efficacy of 5-FU. As a result, it is believed that panobinostat and 5-FU combination therapy will be useful as supplemental chemotherapy in the future.

Pancreatic Acinar Cells-Derived Sphingosine-1-Phosphate Contributes to Fibrosis of Chronic Pancreatitis via Inducing Autophagy and Activation of Pancreatic Stellate Cells

BACKGROUND & AIMS

Studies have demonstrated that activated pancreatic stellate cells (PSCs) play a crucial role in pancreatic fibrogenesis in chronic pancreatitis (CP); however, the precise mechanism for PSCs activation has not been fully elucidated. We analyzed the role of injured pancreatic acinar cells (iPACs) in the activation of PSCs of CP.

METHODS

Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling was evaluated in experimental CP induced by cerulein injection or pancreatic duct ligation, as well as in PACs injured by cholecystokinin. The activation of PSCs and pancreatic fibrosis in CP samples was evaluated by immunohistochemical and immunofluorescence analyses. In vitro coculture assay of iPACs and PSCs was created to evaluate the effect of the SPHK1/S1P pathway and S1P receptor 2 (SIPR2) on autophagy and activation of PSCs. The pathogenesis of CP was assessed in SPHK1-/- mice or PACs-specific SPHK1-knockdown mice with recombinant adeno-associated virus serotypes 9-SPHK1-knockdown, as well as in mice treated with inhibitor of SPHK1 and S1P receptor 2 (S1PR2).

RESULTS

SPHK1/S1P was remarkably increased in iPACs and acinar cells in pancreatic tissues of CP mice. Meanwhile, the pathogenesis, fibrosis, and PSCs activation of CP was significantly prevented in SPHK1-/- mice and recombinant adeno-associated virus serotypes 9-SPHK1-knockdown mice. Meanwhile, iPACs obviously activated PSCs, which was prevented by SPHK1 knockdown in iPACs. Moreover, iPACs-derived S1P specifically combined to S1PR2 of PSCs, by which modulated 5' adenosine monophosphate-activated protein kinase/mechanistic target of rapamycin pathway and consequently induced autophagy and activation of PSCs. Furthermore, hypoxia-inducible factor 1-α and -2α promoted SPHK1 transcription of PACs under hypoxia conditions, which is a distinct characteristic of the CP microenvironment. Coincidently, inhibition of SPHK1 and S1PR2 activity with inhibitor PF-543 and JTE-013 obviously impeded pancreatic fibrogenesis of CP mice.

CONCLUSIONS

The activated SPHK1/S1P pathway in iPACs induces autophagy and activation of PSCs by regulating the S1PR2/5' adenosine monophosphate-activated protein kinase/mammalian target of rapamycin pathway, which promotes fibrogenesis of CP. The hypoxia microenvironment might contribute to the cross talk between PACs and PSCs in pathogenesis of CP.

Rescue of murine hind limb ischemia via angiogenesis and lymphangiogenesis promoted by cellular communication network factor 2

Critical limb ischemia (CLI) is caused by severe arterial blockage with reduction of blood flow. The aim of this study was to determine whether therapeutic angiogenesis using cellular communication network factor 2 (CCN2) would be useful for treating CLI in an animal model. Recombinant CCN2 was administered intramuscularly to male C57BL/6J mice with hind limb ischemia. The therapeutic effect was evaluated by monitoring blood flow in the ischemic hind limb. In an in vivo assay, CCN2 restored blood flow in the ischemic hind limb by promoting both angiogenesis and lymphangiogenesis. VEGF-A and VEGF-C expression levels increased in the ischemic limb after treatment with CCN2. In an in vitro assay, CCN2 promoted proliferation of vascular and lymphatic endothelial cells, and it upregulated expression of Tgfb1 followed by expression of Vegfc and Vegfr3 in lymphatic endothelial cells under hypoxia. Suppression of Tgfb1 did not affect the activity of CCN2, activation of the TGF-β/SMAD signaling pathway, or expression of Vegfr3 in lymphatic endothelial cells. In summary, treatment using recombinant CCN2 could be a promising therapeutic strategy for CLI.

Exploring the Role of YAP1 and TAZ in Pancreatic Acinar Cells and the Therapeutic Potential of VT-104 in Pancreatic Inflammation

Increasing evidences have linked the hippo pathway with the fibroinflammatory diseases. We generated a series of genetic knockout mice for targeting the key components of Hippo pathway to examine the individual effects of YAP1 and TAZ on pancreatic inflammation and evaluated the therapeutic potential of the YAP1/TAZ inhibitor VT-104. Mice with acinar-specific knockout of YAP1/TAZ did not exhibit any histological abnormalities in the pancreas. LATS1/2 deficiency induced acinar-to-ductal metaplasia, immune cell infiltration and fibroblast activation, which were rescued by the homozygous knockout YAP1, but not TAZ. Additionally, treatment with VT-104 also decreased pathological alterations induced by deletions of LATS1 and LATS2 in acinar cells. Our findings highlight the critical role of YAP1 in modulating pancreatic inflammation and demonstrate that VT-104 holds therapeutic potential to mitigate pancreatitis-associated pathological manifestations. Further exploration is necessary to unravel the underlying mechanisms and translate these insights into clinical applications.

Pancreatic acinar cell fate relies on system xC- to prevent ferroptosis during stress

Acinar cell dedifferentiation is one of the most notable features of acute and chronic pancreatitis. It can also be the initial step that facilitates pancreatic cancer development. In the present study, we further decipher the precise mechanisms and regulation using primary human cells and murine experimental models. Our RNAseq analysis indicates that, in both species, early acinar cell dedifferentiation is accompanied by multiple pathways related to cell survival that are highly enriched, and where SLC7A11 (xCT) is transiently upregulated. xCT is the specific subunit of the cystine/glutamate antiporter system xC-. To decipher its role, gene silencing, pharmacological inhibition and a knock-out mouse model were used. Acinar cells with depleted or reduced xCT function show an increase in ferroptosis relating to lipid peroxidation. Lower glutathione levels and more lipid ROS accumulation could be rescued by the antioxidant N-acetylcysteine or the ferroptosis inhibitor ferrostatin-1. In caerulein-induced acute pancreatitis in mice, xCT also prevents lipid peroxidation in acinar cells. In conclusion, during stress, acinar cell fate seems to be poised for avoiding several forms of cell death. xCT specifically prevents acinar cell ferroptosis by fueling the glutathione pool and maintaining ROS balance. The data suggest that xCT offers a druggable tipping point to steer the acinar cell fate in stress conditions.

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.

5-FU-miR-15a Inhibits Activation of Pancreatic Stellate Cells by Reducing YAP1 and BCL-2 Levels In Vitro

Chronic pancreatitis is characterized by chronic inflammation and fibrosis, processes heightened by activated pancreatic stellate cells (PSCs). Recent publications have demonstrated that miR-15a, which targets YAP1 and BCL-2, is significantly downregulated in patients with chronic pancreatitis compared to healthy controls. We have utilized a miRNA modification strategy to enhance the therapeutic efficacy of miR-15a by replacing uracil with 5-fluorouracil (5-FU). We demonstrated increased levels of YAP1 and BCL-2 (both targets of miR-15a) in pancreatic tissues obtained from Ptf1aCreERTM and Ptf1aCreERTM;LSL-KrasG12D mice after chronic pancreatitis induction as compared to controls. In vitro studies showed that delivery of 5-FU-miR-15a significantly decreased viability, proliferation, and migration of PSCs over six days compared to 5-FU, TGFβ1, control miR, and miR-15a. In addition, treatment of PSCs with 5-FU-miR-15a in the context of TGFβ1 treatment exerted a more substantial effect than TGFβ1 alone or when combined with other miRs. Conditioned medium obtained from PSC cells treated with 5-FU-miR-15a significantly inhibits the invasion of pancreatic cancer cells compared to controls. Importantly, we demonstrated that treatment with 5-FU-miR-15a reduced the levels of YAP1 and BCL-2 observed in PSCs. Our results strongly suggest that ectopic delivery of miR mimetics is a promising therapeutic approach for pancreatic fibrosis and that 5-FU-miR-15a shows specific promise.

Critical role of PAFR/YAP1 positive feedback loop in cardiac fibrosis

Aberrant activation of cardiac fibroblasts is the main cause and character of cardiac fibrosis, and inhibition of cardiac fibrosis becomes a promising treatment for cardiac diseases. Platelet-activating factor (PAF) and Hippo pathway is recently recognized as key signaling mechanisms in cardiovascular diseases. In this study we explored the potential roles of PAF and Hippo signaling pathway in cardiac fibrosis. Myocardial infarction (MI) was induced in mice by left anterior descending artery ligation. After 28 days, the mice were sacrificed, and the hearts were collected for analyses. We showed that PAF receptor (PAFR) and yes-associated protein 1 (YAP1, a key effector in the Hippo pathway) were significantly increased in the heart of MI mice. Increased expression of PAFR and YAP1 was also observed in angiotensin II (Ang II)-treated mouse cardiac fibroblasts. In mouse cardiac fibroblasts, forced expression of YAP1 increased cell viability, resulted in collagen deposition and promoted fibroblast-myofibroblast transition. We showed that PAF induced fibrogenesis through activation of YAP1 and promoted its nuclear translocation via interacting with PAFR, while YAP1 promoted the expression of PAFR by binding to and activating transcription factor TEAD1. More importantly, silencing PAFR or YAP1 by shRNA, or using transgenic mice to induce the conditional deletion of YAP1 in cardiac fibroblasts, impeded cardiac fibrosis and improved cardiac function in MI mice. Taken together, this study elucidates the role and mechanisms of PAFR/YAP1 positive feedback loop in cardiac fibrosis, suggesting a potential role of this pathway as novel therapeutic targets in cardiac fibrosis.

Liver sinusoidal endothelial cell expressed vascular cell adhesion molecule 1 promotes liver fibrosis

Background

During liver injury, liver sinusoidal endothelial cells (LSECs) dysfunction and capillarization promote liver fibrosis. We have previously reported that the LSEC vascular cell adhesion molecule 1 (VCAM1) plays a key role in liver inflammation in nonalcoholic steatohepatitis (NASH) and we now aim to uncover its role in LSEC capillarization and liver fibrosis.

Methods

Wild-type C57BL/6J mice were fed either chow or high fat, fructose and cholesterol diet to induce NASH and treated with either anti-VCAM1 neutralizing antibody or control isotype antibody. Inducible endothelial cell-specific Vcam1 deleted mice (Vcam1^Δend ) and control mice (Vcam1^fl/fl ) were fed choline-deficient high-fat diet (CD-HFD) to induce NASH or injected with carbon tetrachloride to induce liver fibrosis. LSECs isolated from Vcam1^fl/fl or Vcam1^Δend and hepatic stellate cells (HSCs) isolated from wild-type mice were cocultured in a 3-D system or a μ-Slide 2 well co-culture system.

Results

Immunostaining for Lyve1 (marker of differentiated LSECs) was reduced in Vcam1^fl/fl mice and restored in Vcam1^Δend mice in both NASH and liver fibrosis models. Co-immunostaining showed increased α-smooth muscle actin in the livers of Vcam1^fl/fl mice in areas lacking Lyve1. Furthermore, scanning electron microscopy showed reduced LSEC fenestrae in the Vcam1^fl/fl mice but not Vcam1^Δend mice in both injury models, suggesting that VCAM1 promotes LSEC capillarization during liver injury. HSCs profibrogenic markers were reduced when cocultured with LSECs from CD-HFD fed Vcam1^Δend mice compared to Vcam1^fl/fl mice. Furthermore, recombinant VCAM1 activated the Yes-associated protein 1 pathway and induced a fibrogenic phenotype in HSCs in vitro, supporting the profibrogenic role of LSEC VCAM1.

Conclusion

VCAM1 is not just a scaffold for leukocyte adhesion during liver injury, but also a modulator of LSEC capillarization and liver fibrosis.

Emerging roles of the Hippo signaling pathway in modulating immune response and inflammation-driven tissue repair and remodeling

Inflammation is an evolutionarily conserved process and part of the body's defense mechanism. Inflammation leads to the activation of immune and non-immune cells that protect the host tissue/organs from injury or intruding pathogens. The Hippo pathway is an evolutionarily conserved kinase cascade with an established role in regulating cell proliferation, survival, and differentiation. It is involved in diverse biological processes, including organ size control and tissue homeostasis. Recent clinical and pre-clinical studies have shown that the Hippo signaling pathway is also associated with injury- and pathogen-induced tissue inflammation and associated immunopathology. In this review, we have summarized the recent findings related to the involvement of the Hippo signaling pathway in modulating the immune response in different acute and chronic inflammatory diseases and its impact on tissue repair and remodeling.

Cancer-Associated Fibroblasts and Tumor Cells in Pancreatic Cancer Microenvironment and Metastasis: Paracrine Regulators, Reciprocation and Exosomes

Simple Summary

Cancer-associated fibroblasts in the stromal tumor microenvironment play a key role in cancer progression, invasion, metastasis, and therapy resistance. Cancer-associated fibroblasts communicate with tumor cells through diverse factors, such as growth factors, hedgehog proteins, cytokines, and chemokines, regulating signaling activity in paracrine as well as paracrine-reciprocal ways. Furthermore, cancer-associated fibroblasts, not only tumor cells, secrete exosomes that drive pre-metastatic niche formation and metastasis.

Abstract

Pancreatic cancer is currently the fourth leading cause of cancer deaths in the United States, and the overall 5 year survival rate is still only around 10%. Pancreatic cancer exhibits a remarkable resistance to established therapeutic options such as chemotherapy and radiotherapy, in part due to the dense stromal tumor microenvironment, where cancer-associated fibroblasts are the major stromal cell type. Cancer-associated fibroblasts further play a key role in cancer progression, invasion, and metastasis. Cancer-associated fibroblasts communicate with tumor cells, not only through paracrine as well as paracrine-reciprocal signaling regulators but also by way of exosomes. In the current manuscript, we discuss intercellular mediators between cancer-associated fibroblasts and pancreatic cancer cells in a paracrine as well as paracrine-reciprocal manner. Further recent findings on exosomes in pancreatic cancer and metastasis are summarized.

Crosstalk between KRAS, SRC and YAP Signaling in Pancreatic Cancer: Interactions Leading to Aggressive Disease and Drug Resistance

Pancreatic ductal adenocarcinoma (PDAC), the predominant form of pancreatic cancer, remains a devastating disease. The purpose of this review is to highlight recent literature on mechanistic and translational developments that advance our understanding of a complex crosstalk between KRAS, YAP and Src tyrosine kinase family (SFK) in PDAC development and maintenance. We discuss recent studies indicating the importance of RAS dimerization in signal transduction and new findings showing that the potent pro-oncogenic members of the SFK phosphorylate and inhibit RAS function. These surprising findings imply that RAS may not play a crucial role in maintaining certain subtypes of PDAC. In support of this interpretation, current evidence indicates that the survival of the basal-like subtype of PDAC is less dependent on RAS but relies, at least in part, on the activity of YAP/TAZ. Based on current evidence, we propose that SFK propels PDAC cells to a state of high metastasis, epithelial-mesenchymal transition (EMT) and reduced dependence on KRAS signaling, salient features of the aggressive basal-like/squamous subtype of PDAC. Strategies for PDAC treatment should consider the opposite effects of tyrosine phosphorylation on KRAS and SFK/YAP in the design of drug combinations that target these novel crosstalk mechanisms and overcome drug resistance.