Inhibitory effects of prostaglandin E2 on collagen synthesis and cell proliferation in human stellate cells from pancreatic head adenocarcinoma

Pancreatic stellate cell-induced gemcitabine resistance in pancreatic cancer is associated with LDHA- and MCT4-mediated enhanced glycolysis

BACKGROUND

Profound resistance to chemotherapy remains a major challenge in achieving better clinical outcomes for patients with pancreatic ductal adenocarcinoma (PDAC). Recent studies indicate that gemcitabine (GEM) resistance is promoted both by pancreatic stellate cells (PSCs) and through increased glycolysis. However, it remains unknown whether PSCs affect GEM sensitivity via glycolytic regulation.

METHODS

Human pancreatic cancer cell (PCC) lines (BxPC-3, Capan-2, HPAF-II, Mia PaCa-2, Panc-1, SW-1990) were exposed to three different PSC-conditioned media (PSC-CM; PSC-1, PSC-2, HPaSteC), following either pre-treatment with glycolysis inhibitor NV-5440 or transfection for transient silencing of key glycolytic regulators (LDHA and MCT4). Proliferation, glucose transport, extracellular lactate, and GEM sensitivity were assessed. Protein expression was determined by Western blot and immunostaining. Moreover, secreted proteins in PSC-CMs were profiled by mass spectrometry (MS).

RESULTS

While exposure to PSC-CMs did not affect glucose transport in PCCs, it increased their lactate release and proliferation, and reduced the sensitivity for GEM. Both NV-5440 treatment and transient silencing of LDHA and MCT4 inhibited these PSC-induced changes in PCCs. MS analysis identified 688 unique proteins with differential expression, of which only 87 were common to the three PSC-CMs. Most PSC-secreted proteins were extracellular matrix-related, including SPARC, fibronectin, and collagens. Moreover, exposure to PSC-CMs increased the phosphorylation of ERK in PCCs, but the treatment of PCCs with the MEK/ERK inhibitor PD98059 resulted in a reduction of PSC-CM-induced glycolysis and improved GEM sensitivity.

CONCLUSIONS

The study findings suggest that PSC-secreted factors promote both glycolysis and GEM resistance in PCCs, and that glycolysis inhibition by NV-5440 and blocking of ERK phosphorylation by PD98059 protect PCCs from PSC-CM-induced loss of GEM sensitivity. Taken together, PSCs appear to promote GEM resistance in PDAC via glycolysis. Thus, targeting glycolysis may improve the effect of chemotherapy in PDAC.

Cinobufacini Inhibits the Development of Pancreatic Cancer Cells through the TGFβ/Smads Pathway of Pancreatic Stellate Cells

This study aimed to test cinobufacini therapeutic potential for pancreatic cancer, verify its potential molecular mechanism, and evaluate the cinobufacini impact on pancreatic cancer microenvironment. First, the effect of cinobufacini-treated pancreatic stellate cells (PSCs) supernatant on the value-added ability of pancreatic cancer (PCCs) was tested. The results show that cinobufacini can effectively reduce the ability of PSCs supernatant to promote the value-added PCCs. Further results show that cinobufacini can effectively reduce the concentration of TGFβ in the supernatant of PSCs. Subsequently, the impact of cinobufacini on the transcription and translation levels of key genes in the TGFβ/Smads pathway was examined. The results showed that the impact of cinobufacini on the transcription levels of Smad2, Smad3, and Smad7 was in a concentration-dependent manner, while the transcriptional activity of collagen I mRNA was decreased with the increase of cinobufacini concentration. The results of protein expression showed that cinobufacini could upregulate the expression of inhibitory protein Smad7, inhibit the phosphorylation level of p-Smad2/3, and then suppress the expression of type I collagen (collagen I). On the one hand, this study shows that cinobufacini can inhibit the promotion of PSCs on the proliferation of PCCs. On the other hand, cinobufacini can upregulate the expression of the inhibitory molecule, Smad7, through the TGFβ/Smads pathway and reduce the phosphorylation level of p-Smad2/3, thereby inhibiting the expression of collagen I and pancreatic fibrosis. cinobufacin can inhibit the proliferation of SW1900 cells by blocking the TGFβ/Smads pathway of pancreatic stellate cells. These results provide a clinical basis for the treatment of pancreatic cancer.

Distinct Metalloproteinase Expression and Functions in Systemic Sclerosis and Fibrosis: What We Know and the Potential for Intervention

Systemic sclerosis (SSc) is a chronic debilitating idiopathic disorder, characterized by deposition of excessive extracellular matrix (ECM) proteins such as collagen which leads to fibrosis of the skin and other internal organs. During normal tissue repair and remodeling, the accumulation and turnover of ECM proteins are tightly regulated by the interaction of matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of metalloproteinases (TIMPs). SSc is associated with dysregulation of the activity of these proteolytic and inhibitory proteins within the tissue microenvironment, tipping the balance toward fibrosis. The resultant ECM accumulation further perpetuates tissue stiffness and decreased function, contributing to poor clinical outcomes. Understanding the expression and function of these endogenous enzymes and inhibitors within specific tissues is therefore critical to the development of therapies for SSc. This brief review describes recent advances in our understanding of the functions and mechanisms of ECM remodeling by metalloproteinases and their inhibitors in the skin and lungs affected in SSc. It highlights recent progress on potential candidates for intervention and therapeutic approaches for treating SSc fibrosis.

Molecular mechanisms of pancreatic myofibroblast activation in chronic pancreatitis and pancreatic ductal adenocarcinoma

Pancreatic fibrosis (PF) is an essential component of the pathobiology of chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC). Activated pancreatic myofibroblasts (PMFs) are crucial for the deposition of the extracellular matrix, and fibrotic reaction in response to sustained signaling. Consequently, understanding of the molecular mechanisms of PMF activation is not only critical for understanding CP and PDAC biology but is also a fertile area of research for the development of novel therapeutic strategies for pancreatic pathologies. This review analyzes the key signaling events that drive PMF activation including, initiating signals from transforming growth factor-β1, platelet derived growth factor, as well as other microenvironmental cues, like hypoxia and extracellular matrix rigidity. Further, we discussed the intracellular signal events contributing to PMF activation, and crosstalk with different components of tumor microenvironment. Additionally, association of epidemiologically established risk factors for CP and PDAC, like alcohol intake, tobacco exposure, and metabolic factors with PMF activation, is discussed to comprehend the role of lifestyle factors on pancreatic pathologies. Overall, this analysis provides insight into the biology of PMF activation and highlights salient features of this process, which offer promising therapeutic targets.

Pancreatic Stellate Cells: The Key Orchestrator of The Pancreatic Tumor Microenvironment

Pancreatic cancer is one of the most challenging adenocarcinomas due to its hostile molecular behavior and complex tumor microenvironment. It has been recently postulated that pancreatic stellate cells (PSCs), the resident lipid-storing cells of the pancreas, are important components of the tumor microenvironment as they can transdifferentiate into highly proliferative myofibroblasts in the context of tissue injury. Targeting tumor-stromal crosstalk in the tumor microenvironment has emerged as a promising therapeutic strategy against pancreatic cancer progression and metastasis. This chapter brings a broad view on the biological and pathological role of PSCs in the pancreas, activated stellate cells in the onset of tissue fibrosis, and tumor progression with particular emphasis on the bidirectional interactions between tumor cells and PSCs. Further, potential therapeutic regimens targeting activated PSCs in the pre-clinical and clinical trials are discussed.

Effects of a prostaglandin F2alpha derivative glaucoma drug on EGF expression and E-cadherin expression in a corneal epithelial cell line

Purpose: We examined the effects of travoprost on cell proliferation-related signals and E-cadherin expression in vitro and in situ in order to obtain evidence to support the hypothesis that topical travoprost impairs the integrity of the corneal epithelium.Methods: A human corneal epithelial cell culture was treated with travoprost (0.4 mg/ml) and/or PD168393 (an EGF receptor inhibitor, 10 μM). The culture was then processed for cell proliferation, an mRNA expression analysis of epidermal growth factor (EGF) and E-cadherin, and protein expression analysis of E-cadherin by immunocytochemistry and Western blotting. The eyes of C57/BL6 mice were incubated in serum-free medium plus travoprost (0.4 mg/ml) and/or PD168393 (10 μM). After being cultured for 24 h, the expression patterns of phospho-EGFR, phospho-ERK, E-cadherin, and Ki67 were immunohistochemically examined in paraffin sections.Results: The addition of travoprost up-regulated EGF mRNA expression and cell proliferation in the corneal epithelial cell culture, and this was cancelled by the addition of PD168393. This FP agonist also decreased E-cadherin expression levels in the cell-cell contact zone, and this was cancelled by the addition of PD168393. In the organ culture, the addition of travoprost to the medium up-regulated the expression of phospho-EGFR and phospho-ERK as well as cell proliferation, and down-regulated the expression of E-cadherin in the corneal epithelium, particularly in basal cells, whereas PD168393 reversed these effects.Conclusions: Travoprost activates epithelial cell proliferation by up-regulating an EGF-related signal in association with the suppression of E-cadherin localization in the cell-cell contact zone. Modulation of the EGF signal may be a strategy to minimize the negative impact of this mitogen on reformation of corneal barrier function during epithelial renewal.

Establishment and Characterization of Paired Primary Cultures of Human Pancreatic Cancer Cells and Stellate Cells Derived from the Same Tumor

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extremely poor prognosis, and its treatment remains a challenge. As the existing in vitro experimental models offer only a limited resemblance to human PDAC, there is a strong need for additional research tools to better understand PDAC tumor biology, particularly the impact of the tumor stroma. Here, we report for the first time the establishment and characterization of human PDAC-derived paired primary monolayer cultures of (epithelial) cancer cells (PCCs) and mesenchymal stellate cells (PSCs) derived from the same tumor by the outgrowth method. Characterization of cell morphology, cytostructural, and functional profiles and proteomics-based secretome analysis were performed. All PCCs harbored KRAS and TP53 mutations, and expressed cytokeratin 19, ki-67, and p53, while the expression of EpCAM and vimentin was variable. All PSCs expressed α-smooth muscle actin (α-SMA) and vimentin. PCCs showed a significantly higher growth rate and proliferation than PSCs. Secretome analysis confirmed the distinct nature of PCCs as compared to PSCs and allowed identification of potential molecular regulators of PSC-conditioned medium (PSC-CM)-induced migration of PCCs. Paired primary cultures of PCCs and PSCs derived from the same tumor specimen represent a novel experimental model for basic research in PDAC tumor biology.

Novel Microglia Cell Line Expressing the Human EP2 Receptor

Recently, EP2 signaling pathways were shown to regulate the classical activation and death of microglia in rat primary microglial culture. The study of microglial cells has been challenging because they are time-consuming to isolate in culture, they are demanding in their growth requirements, and they have a limited lifespan. To circumvent these difficulties, we created a murine BV2 microglial cell line stably expressing human EP2 receptors (BV2-hEP2) and further explored EP2 modulation of microglial functions. The BV2-hEP2 cells displayed cAMP elevation when exposed to the selective EP2 receptor agonists (ONO-AE1-259-1 and CP544326), and this response was competitively inhibited by TG4-155, a selective EP2 antagonist (Schild K_B = 2.6 nM). By contrast, untransfected BV2 cells were unresponsive to selective EP2 agonists. Similar to the case of rat primary microglia, BV2-hEP2 microglia treated with lipopolysaccharide (LPS) (100 ng/mL) displayed rapid and robust induction of the inflammatory mediators COX-2, IL-1β, TNFα, and IL-6. EP2 activation depressed TNFα induction but exacerbated that of the other inflammatory mediators. Like primary microglia, classically activated BV2 microglia phagocytose fluorescent-labeled latex microspheres. The presence of EP2, but not its activation by agonists, in BV2-hEP2 microglia reduced phagocytosis and proliferation by 65% and 32%, respectively, compared to BV2 microglia. Thus, BV2-hEP2 is the first microglial cell line that retains the EP2 modulation of immune regulation and phagocytic ability of native microglia. Suppression of phagocytosis by the EP2 protein appears unrelated to classical EP2 signaling pathways, which has implications for therapeutic development of EP2 antagonists.

Lysophosphatidylcholine-induced mitochondrial fission contributes to collagen production in human cardiac fibroblasts

Lysophosphatidylcholine (LPC) may accumulate in the heart to cause fibrotic events, which is mediated through fibroblast activation and collagen accumulation. Here, we evaluated the mechanisms underlying LPC-mediated collagen induction via mitochondrial events in human cardiac fibroblasts (HCFs), coupling application of the pharmacologic cyclooxygenase-2 (COX-2) inhibitor, celecoxib, and genetic mutations in FOXO1 on the fibrosis pathway. In HCFs, LPC caused prostaglandin E2 (PGE2)/PGE2 receptor 4 (EP4)-dependent collagen induction via activation of transcriptional activity of forkhead box protein O1 (FoxO1) on COX-2 gene expression. These responses were mediated through LPC-induced generation of mitochondrial reactive oxygen species (mitoROS), as confirmed by ex vivo studies, which indicated that LPC increased COX-2 expression and oxidative stress. LPC-induced mitoROS mediated the activation of protein kinase C (PKC)α, which interacted with and phosphorylated dynamin-related protein 1 (Drp1) at Ser616, thereby increasing Drp1-mediated mitochondrial fission and mitochondrial depolarization. Furthermore, inhibition of PKCα and Drp1 reduced FoxO1-mediated phosphorylation at Ser256 and nuclear accumulation, which suppressed COX-2/PGE2 expression and collagen production. Moreover, pretreatment with celecoxib or COX-2 siRNA suppressed WT FoxO1; mutated Ser256-to-Asp256 FoxO1-enhanced collagen induction, which was reversed by addition of PGE2 Our results demonstrate that LPC-induced generation of mitoROS regulates PKCα-mediated Drp1-dependent mitochondrial fission and COX-2 expression via a PKCα/Drp1/FoxO1 cascade, leading to PGE2/EP4-mediated collagen induction. These findings provide new insights about the role of LPC in the pathway of fibrotic injury in HCFs.

Secretion of fibronectin by human pancreatic stellate cells promotes chemoresistance to gemcitabine in pancreatic cancer cells

Background

Gemcitabine remains a cornerstone in chemotherapy of pancreatic ductal adenocarcinoma (PDAC) despite suboptimal clinical effects that are partly due to the development of chemoresistance. Pancreatic stellate cells (PSCs) of the tumor stroma are known to interact with pancreatic cancer cells (PCCs) and influence the progression of PDAC through a complex network of signaling molecules that involve extracellular matrix (ECM) proteins. To understand tumor-stroma interactions regulating chemosensitivity, the role of PSC-secreted fibronectin (FN) in the development of gemcitabine resistance in PDAC was examined.

Methods

PSC cultures obtained from ten different human PDAC tumors were co-cultured with PCC lines (AsPC-1, BxPC-3, Capan-2, HPAF-II, MIA PaCa-2, PANC-1 and SW-1990) either directly, or indirectly via incubation with PSC-conditioned medium (PSC-CM). Gemcitabine dose response cytotoxicity was determined using MTT based cell viability assays. Protein expression was assessed by western blotting and immunofluorescence. PSC-CM secretome analysis was performed by proteomics-based LC-MS/MS, and FN content in PSC-CM was determined with ELISA. Radiolabeled gemcitabine was used to determine the capacity of PCCs to uptake the drug.

Results

In both direct and indirect co-culture, PSCs induced varying degrees of resistance to the cytotoxic effects of gemcitabine among all cancer cell lines examined. A variable degree of increased phosphorylation of ERK1/2 was observed across all PCC lines upon incubation with PSC-CM, while activation of AKT was not detected. Secretome analysis of PSC-CM identified 796 different proteins, including several ECM-related proteins such as FN and collagens. Soluble FN content in PSC-CM was detected in the range 175–350 ng/ml. Neither FN nor PSC-CM showed any effect on PCC uptake capacity of gemcitabine. PCCs grown on FN-coated surface displayed higher resistance to gemcitabine compared to cells grown on non-coated surface. Furthermore, a FN inhibitor, synthetic Arg-Gly-Asp-Ser (RGDS) peptide significantly inhibited PSC-CM-induced chemoresistance in PCCs via downregulation of ERK1/2 phosphorylation.

Conclusions

The findings of this study suggest that FN secreted by PSCs in the ECM plays a key role in the development of resistance to gemcitabine via activation of ERK1/2. FN-blocking agents added to gemcitabine-based chemotherapy might counteract chemoresistance in PDAC and provide better clinical outcomes.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5803-1) contains supplementary material, which is available to authorized users.

EphA2-positive human umbilical cord-derived mesenchymal stem cells exert anti-fibrosis and immunomodulatory activities via secretion of prostaglandin E2

OBJECTIVE

Previous study has demonstrated that EphA2 is a biomarker of mesenchymal stem cells (MSCs) from human placenta or umbilical cord and is able to distinguish MSCs from fibroblasts. In this study, we further examine the potential efficacy of EphA2⁺ human umbilical cord-derived MSCs (hUC-MSCs).

MATERIALS AND METHODS

MSCs specific markers, EphA2 and CD146 expression on the surface of hUC-MSCs were determined by flow cytometry analysis. Quantitative real time polymerase chain reaction was used to examine pro-fibrotic gene expression of TGF-β1-stimulated lung fibroblast (MRC-5 cells). On the other hand, ELISA was used to analyze the content of pro-inflammatory cytokines (TNF-ɑ; and IP-10) in the LPS-activated macrophages culture supernatant.

RESULTS

The pro-fibrotic gene (TGF-β1, CTGF, fibronectin, collagen I and TIMP-1) expression in TGF-β1-activated MRC-5 cells and the pro-inflammatory cytokines (TNF-ɑ and IP-10) in the LPS-activated macrophages culture supernatant were both attenuated when in present of EphA2⁺ hUC-MSCs. Moreover, once EphA2⁺ hUC-MSCs treated with prostaglandin E2 specific inhibitor NS-398, both anti-fibrotic and anti-inflammatory effects of EphA2⁺ hUC-MSCs were abolished.

CONCLUSION

EphA2⁺ hUC-MSCs possess immunomodulatory and anti-fibrotic properties, and PGE2 plays an important role in these activities. This implies that EphA2⁺ hUC-MSCs have potentially effectiveness for treatment of acute inflammatory and chronic fibrotic lung diseases.

Commonly Used Pancreatic Stellate Cell Cultures Differ Phenotypically and in Their Interactions with Pancreatic Cancer Cells

Activated pancreatic stellate cells (PSCs) play a central role in the tumor stroma of pancreatic ductal adenocarcinoma (PDAC). Given the limited availability of patient-derived PSCs from PDAC, immortalized PSC cell lines of murine and human origin have been established; however, it is not elucidated whether differences in species, organ disease status, donor age, and immortalization alter the PSC phenotype and behavior compared to that of patient-derived primary PSC cultures. Therefore, a panel of commonly used PSC cultures was examined for important phenotypical and functional features: three primary cultures from human PDAC, one primary from normal human pancreas, and three immortalized (one from human, two from murine pancreas). Growth rate was considerably lower in primary PSCs from human PDAC. Basal collagen synthesis varied between the PSC cultures, and TGF-β stimulation increased collagen synthesis only in non-immortalized cultures. Differences in secretome composition were observed along with a divergence in the DNA synthesis, migration, and response to gemcitabine of PDAC cell lines that were grown in conditioned medium from the various PSC cultures. The findings reveal considerable differences in features and functions that are key to PSCs and in the interactions with PDAC. These observations may be relevant to researchers when selecting the most appropriate PSC culture for their experiments.

Long noncoding RNA myocardial infarction-associated transcript regulated the pancreatic stellate cell activation to promote the fibrosis process of chronic pancreatitis

BACKGROUND

Long noncoding RNAs (lncRNAs) play crucial roles in fibrosis process. In our previous RNA-seq study, we found that lncRNA myocardial infarction-associated transcript (MIAT) was differentially expressed in pancreatic tissues of chronic pancreatitis (CP) patients. However, the function of MIAT in CP remains unknown. This study was aimed to investigate the function and underlying mechanism of MIAT in pancreatic fibrosis.

MATERIALS AND METHODS

The expression levels of MIAT, miR-216a-3p, cyclooxygenase 2 (COX-2), α-smooth muscle actin (α-SMA), and collagen I were estimated by Western blot analysis and qualitative reverse transcription polymerase chain reaction. The relationships between miR-216a-3p, MIAT, and COX-2 were confirmed by luciferase reporter assay. The proliferation of human pancreatic stellate cells (HPaSteCs) was detected by cell counting kit-8 assay.

RESULTS

We found that MIAT, along with the levels of fibrosis-related proteins α-SMA and collagen I, as well as COX-2 were upregulated, while miR-216a-3p was downregulated in transforming growth factor (TGF)-β1-stimulated HPaSteCs. Mechanistically, MIAT acted as a molecular sponge for miR-216a-3p. Furthermore, we identified COX-2 as a direct target of miR-126a-3p. Additionally, MIAT overturned the inhibitory effect of miR-216a-3p overexpression and COX-2 knockdown on the activation and proliferation of HPaSteCs.

CONCLUSION

Our study provided mechanistic insights into a critical role for MIAT as a miRNA sponge in CP.

Epithelial-Stromal Interactions in Pancreatic Cancer

Pancreatic cancer is characterized by an extensive fibroinflammatory reaction that includes immune cells, fibroblasts, extracellular matrix, vascular and lymphatic vessels, and nerves. Overwhelming evidence indicates that the pancreatic cancer microenvironment regulates cancer initiation, progression, and maintenance. Pancreatic cancer treatment has progressed little over the past several decades, and the prognosis remains one of the worst for any cancer. The contribution of the microenvironment to carcinogenesis is a key area of research, offering new potential targets for treating the disease. Here, we explore the composition of the pancreatic cancer stroma, discuss the network of interactions between different components, and describe recent attempts to target the stroma therapeutically. We also discuss current areas of active research related to the tumor microenvironment.

Cyclooxygenase-2 induces angiogenesis in pancreatic cancer mediated by prostaglandin E2

The purpose of the present study was to elucidate the effects of cyclooxygenase 2 (COX-2) on the expression of vascular endothelial growth factor (VEGF) and prostaglandin E2 (PGE2) in pancreatic cancer in vitro and in vivo, and to clarify the potential mechanism of COX-2-induced angiogenesis of pancreatic cancer. The study analysis was conducted in the pancreatic cancer PC-3 cell line. The expression of COX-2 and VEGF in human pancreatic cancer tissue was analyzed by immunohistochemistry. Angiogenesis was detected using immunohistochemistry with anti-collagen IV antibodies, and was calculated according to the microvascular density (MVD). In vitro analysis was performed using ELISA or radioimmunoassay (RIA). The effect of exogenous PGE2 on the downregulation of VEGF by Celebrex was also assessed. In vivo analysis was performed using western blotting or RIA. Concurrently, MVD was also investigated in nude mice using immunohistochemistry with anti-collagen IV antibodies. COX-2 was overexpressed in pancreatic cancer tissues, with an overall positive rate of 87.5%. There was a positive association between the expression of COX-2 and MVD. The in vitro study indicated that Celebrex suppressed the expression of VEGF and PGE2 in PC-3 cells in a dose- and time-dependent manner, while exogenous PGE2 rescued the expression of VEGF, which was suppressed by Celebrex, in a dose-dependent manner. The in vivo study revealed that the administration of Celebrex to xenograft nude mice significantly inhibited the expression of VEGF and PGE2. These data provide evidence that PGE2 may be an important mediator between COX-2 and VEGF expression in the process of angiogenesis in pancreatic cancer.

Functional heterogeneity in tumor-derived human pancreatic stellate cells: Differential expression of HGF and implications for mitogenic signaling and migration in pancreatic cancer cells

The pancreatic stellate cell (PSC) is the principal cell type of the desmoplastic stroma of pancreatic ductal adenocarcinoma (PDAC). PSCs interact with cancer cells and influence the progression of the disease through a complex network of signaling molecules including hepatocyte growth factor (HGF). Functional heterogeneity of PSCs within a tumor might conceivably influence tumor progression. We investigated PSC populations isolated from different human PDACs and examined the effects of PSC-conditioned medium on BxPC-3 and AsPC-1 pancreatic cancer cells. The different PSC populations exhibited a wide range of variation (120-3,000 pg/ml) in their ability to secrete HGF. Media from high-HGF-producing PSCs stimulated phosphorylation of Met, Gab1, and ERK in the cancer cells and induced increases in DNA synthesis and migration which were blocked by the Met inhibitor SU11274, indicating a role of HGF as a mediator. HGF levels produced by PSCs and the effects of PSC media on the cancer cells were increased by IL-1α and inhibited by TGFβ. The functional heterogeneity of PSCs in terms of HGF-mediated tumor-stroma interactions suggests that inhibition of the HGF pathway as a novel treatment approach in PDAC might have different effects in different subsets of patients.

Pancreatic stellate cell: Pandora's box for pancreatic disease biology

Pancreatic stellate cells (PSCs) were identified in the early 1980s, but received much attention after 1998 when the methods to isolate and culture them from murine and human sources were developed. PSCs contribute to a small proportion of all pancreatic cells under physiological condition, but are essential for maintaining the normal pancreatic architecture. Quiescent PSCs are characterized by the presence of vitamin A laden lipid droplets. Upon PSC activation, these perinuclear lipid droplets disappear from the cytosol, attain a myofibroblast like phenotype and expresses the activation marker, alpha smooth muscle actin. PSCs maintain their activated phenotype via an autocrine loop involving different cytokines and contribute to progressive fibrosis in chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC). Several pathways (e.g., JAK-STAT, Smad, Wnt signaling, Hedgehog etc.), transcription factors and miRNAs have been implicated in the inflammatory and profibrogenic function of PSCs. The role of PSCs goes much beyond fibrosis/desmoplasia in PDAC. It is now shown that PSCs are involved in significant crosstalk between the pancreatic cancer cells and the cancer stroma. These interactions result in tumour progression, metastasis, tumour hypoxia, immune evasion and drug resistance. This is the rationale for therapeutic preclinical and clinical trials that have targeted PSCs and the cancer stroma.

Cyclooxygenase-2 expression in hepatocytes attenuates non-alcoholic steatohepatitis and liver fibrosis in mice

Cyclooxygenase-2 (COX-2) is involved in different liver diseases but little is known about the significance of COX-2 in the development and progression of non-alcoholic steatohepatitis (NASH). This study was designed to elucidate the role of COX-2 expression in hepatocytes in the pathogenesis of steatohepatitis and hepatic fibrosis. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were either fed methionine-and-choline deficient (MCD) diet to establish an experimental non-alcoholic steatohepatitis (NASH) model or injected with carbon tetrachloride (CCl4) to induce liver fibrosis. In our animal model, hCOX-2-Tg mice fed MCD diet showed lower grades of steatosis, ballooning and inflammation than Wt mice, in part by reduced recruitment and infiltration of hepatic macrophages, with a corresponding decrease in serum levels of pro-inflammatory cytokines. Furthermore, hCOX-2-Tg mice showed a significant attenuation of the MCD diet-induced increase in oxidative stress and hepatic apoptosis observed in Wt mice. Even more, hCOX-2-Tg mice treated with CCl4 had significantly lower stages of fibrosis and less hepatic content of collagen, hydroxyproline and pro-fibrogenic markers than Wt controls. Collectively, our data indicates that constitutive hepatocyte COX-2 expression ameliorates NASH and liver fibrosis development in mice by reducing inflammation, oxidative stress and apoptosis and by modulating activation of hepatic stellate cells, respectively, suggesting a possible protective role for COX-2 induction in NASH/NAFLD progression.

Aspirin in pancreatic cancer: chemopreventive effects and therapeutic potentials

Pancreatic cancer is one of the most aggressive malignancies with dismal prognosis. Recently, aspirin has been found to be an effective chemopreventive agent for many solid tumors. However, the function of aspirin use in pancreatic cancer largely remains unknown. We herein argued that aspirin could also lower the risk of pancreatic cancer. Importantly, aspirin assumes pleiotropic effects by targeting multiple molecules. It could further target the unique tumor biology of pancreatic cancer and modify the cancer microenvironment, thus showing remarkable therapeutic potentials. Besides, aspirin could reverse the chemoradiation resistance by repressing tumor repopulation and exert synergistic potentials with metformin on pancreatic cancer chemoprevention. Moreover, aspirin secondarily benefits pancreatic cancer patients through modestly reducing cancer pain and the risk of venous thromboembolism. Furthermore, new aspirin derivatives and delivery systems might help to improve risk-to-benefit ratio. In brief, aspirin is a promising chemopreventive agent and exerts significant therapeutic potentials in pancreatic cancer.

The TGFβ-SMAD3 pathway inhibits IL-1α induced interactions between human pancreatic stellate cells and pancreatic carcinoma cells and restricts cancer cell migration

BACKGROUND

The most abundant cells in the extensive desmoplastic stroma of pancreatic adenocarcinomas are the pancreatic stellate cells, which interact with the carcinoma cells and strongly influence the progression of the cancer. Tumor stroma interactions induced by IL-1α/IL-1R1 signaling have been shown to be involved in pancreatic cancer cell migration. TGFβ and its receptors are overexpressed in pancreatic adenocarcinomas. We aimed at exploring TGFβ and IL-1α signaling and cross-talk in the stellate cell cancer cell interactions regulating pancreatic adenocarcinoma cell migration.

METHODS

Human pancreatic stellate cells were isolated from surgically resected pancreatic adenocarcinomas and cultured in the presence of TGFβ or pancreatic adenocarcinoma cell lines. The effects of TGFβ were blocked by inhibitors or amplified by silencing the endogenous inhibitor of SMAD signaling, SMAD7. Pancreatic stellate cell responses to IL-1α or to IL-1α-expressing pancreatic adenocarcinoma cells (BxPC-3) were characterized by their ability to stimulate migration of cancer cells in a 2D migration model.

RESULTS

In pancreatic stellate cells, IL-1R1 expression was found to be down-regulated by TGFβ and blocking of TGFβ signaling re-established the expression. Endogenous inhibition of TGFβ signaling by SMAD7 was found to correlate with the levels of IL-1R1, indicating a regulatory role of SMAD7 in IL-1R1 expression. Pancreatic stellate cells cultured in the presence of IL-1α or in co-cultures with BxPC-3 cells enhanced the migration of cancer cells. This effect was blocked after treatment of the pancreatic stellate cells with TGFβ. Silencing of stellate cell expression of SMAD7 was found to suppress the levels of IL-1R1 and reduce the stimulatory effects of IL-1α, thus inhibiting the capacity of pancreatic stellate cells to induce cancer cell migration.

CONCLUSIONS

TGFβ signaling suppressed IL-1α mediated pancreatic stellate cell induced carcinoma cell migration. Depletion of SMAD7 upregulated the effects of TGFβ and reduced the expression of IL-1R1, leading to inhibition of IL-1α induced stellate cell enhancement of carcinoma cell migration. SMAD7 might represent a target for inhibition of IL-1α induced tumor stroma interactions.

Profile of MMP and TIMP Expression in Human Pancreatic Stellate Cells: Regulation by IL-1α and TGFβ and Implications for Migration of Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma is characterized by a prominent fibroinflammatory stroma with both tumor-promoting and tumor-suppressive functions. The pancreatic stellate cell (PSC) is the major cellular stromal component and the main producer of extracellular matrix proteins, including collagens, which are degraded by metalloproteinases (MMPs). PSCs interact with cancer cells through various factors, including transforming growth factor (TGF)β and interleukin (IL)-1α. The role of TGFβ in the dual nature of tumor stroma, i.e., protumorigenic or tumor suppressive, is not clear. We aimed to investigate the roles of TGFβ and IL-1α in the regulation of MMP profiles in PSCs and the subsequent effects on cancer cell migration. Human PSCs isolated from surgically resected specimens were cultured in the presence of pancreatic cancer cell lines, as well as IL-1α or TGFβ. MMP production and activities in PSCs were quantified by gene array transcripts, mRNA measurements, fluorescence resonance energy transfer-based activity assay, and zymography. PSC-conditioned media and pancreatic cancer cells were included in a collagen matrix cell migration model. We found that production of IL-1α by pancreatic cancer cells induced alterations in MMP and tissue inhibitors of matrix metalloproteinase (TIMP) profiles and activities in PSCs, upregulated expression and activation of MMP1 and MMP3, and enhanced migration of pancreatic cancer cells in the collagen matrix model. TGFβ counteracted the effects of IL-1α on PSCs, reestablished PSC MMP and TIMP profiles and activities, and inhibited migration of cancer cells. This suggests that tumor TGFβ has a role as a suppressor of stromal promotion of tumor progression through alterations in PSC MMP profiles with subsequent inhibition of pancreatic cancer cell migration.

Pancreatic stellate cell: physiologic role, role in fibrosis and cancer

PURPOSE OF REVIEW

Ever since the first descriptions of methods to isolate pancreatic stellate cells (PSCs) from rodent and human pancreas 17 years ago, rapid advances have been made in our understanding of the biology of these cells and their functions in health and disease. This review updates recent literature in the field, which indicates an increasingly complex role for the cells in normal pancreas, pancreatitis and pancreatic cancer.

RECENT FINDINGS

Work reported over the past 12 months includes improved methods of PSC immortalization, a role for PSCs in islet fibrosis, novel factors causing PSC activation as well as those inducing quiescence, and translational research aimed at inhibiting the facilitatory effects of PSCs on disease progression in chronic pancreatitis as well as pancreatic cancer.

SUMMARY

Improved understanding of the role of PSCs in pancreatic pathophysiology has prompted a focus on translational studies aimed at developing novel approaches to modulate PSC function in a bid to improve clinical outcomes of two major fibrotic diseases of the pancreas: chronic pancreatitis and pancreatic cancer.