Pancreatic stellate cells are an important source of MMP-2 in human pancreatic cancer and accelerate tumor progression in a murine xenograft model and CAM assay

INS-1 cells inhibit the production of extracellular matrix from pancreatic stellate cells

In type 2 diabetes mellitus, pancreatic stellate cells (PSCs) are present within and surrounding pancreatic islets and may cause progressive fibrosis and deterioration of pancreatic beta cell function. However, it is unknown whether pancreatic beta cells influence the biological behavior of PSCs. In the present study, we examined the impact of pancreatic beta cells on the proliferation, migration and extracellular matrix (ECM) production of PSCs. PSCs were treated with conditioned media from INS-1 cells (supernatant, SN). Although the proliferation of PSCs incubated with INS-1-SN was increased compared to control, INS-1-SN treatment induced matrix metalloproteinase-2 activity and reduced the production of ECM and TGF-β1. In addition, PSCs treated with INS-1-SN reduced the secretion of cytokines that are known to mediate pancreatic beta cell death, such as FADD, Fas, IFN-γ, IL-1, TNF-α, and TRAIL. Our findings suggest that pancreatic beta cells may ameliorate islet fibrosis and the progression of islet dysfunction.

Role of pancreatic stellate cells in chemoresistance in pancreatic cancer

Pancreatic cancer is highly chemoresistant. A major contributing factor is the characteristic extensive stromal or fibrotic reaction, which comprises up to 90% of the tumor volume. Over the last decade there has been intensive research into the role of the pro-fibrogenic pancreatic stellate cells (PSCs) and their interaction with pancreatic cancer cells. As a result of the significant alterations in the tumor microenvironment following activation of PSCs, tumor progression, and chemoresistance is enhanced. This review will discuss how PSCs contribute to chemoresistance in pancreatic cancer.

Pancreatic stellate cells promote hapto-migration of cancer cells through collagen I-mediated signalling pathway

Background:

Pancreatic stellate cells (PSCs) promote metastasis as well as local growth of pancreatic cancer. However, the factors mediating the effect of PSCs on pancreatic cancer cells have not been clearly identified.

Methods:

We used a modified Boyden chamber assay as an in vitro model to investigate the role of PSCs in migration of Panc1 and UlaPaCa cells and to identify the underlying mechanisms.

Results:

PSC supernatant (PSC-SN) dose-dependently induced the trans-migration of Panc1 and UlaPaCa cells, mainly via haptokinesis and haptotaxis, respectively. In contrast to poly-L-lysine or fibronectin, collagen I resembled PSC-SN with respect to its effect on cancer cell behaviours, including polarised morphology, facilitated adhesion, accelerated motility and stimulated trans-migration. Blocking antibodies against integrin α2/β1 subunits significantly attenuated PSC-SN- or collagen I-promoted cell trans-migration and adhesion. Moreover, both PSC-SN and collagen I induced the formation of F-actin and focal adhesions in cells, which was consistent with the constantly enhanced phosphorylation of focal adhesion kinase (FAK, Tyr397). Inhibition of FAK function by an inhibitor or small interference RNAs significantly diminished the effect of PSC-SN or collagen I on haptotaxis/haptokinesis of pancreatic cancer cells.

Conclusion:

Collagen I is the major mediator for PSC-SN-induced haptokinesis of Panc1 and haptotaxis of UlaPaCa by activating FAK signalling via binding to integrin α2β1.

The stromal compartments in pancreatic cancer: are there any therapeutic targets?

Pancreatic ductal adenocarcinoma (PDAC) is characterised by an abundant stromal response also known as a desmoplastic reaction. Pancreatic Stellate Cells have been identified as playing a key role in pancreatic cancer desmoplasia. There is accumulating evidence that the stroma contributes to tumour progression and to the low therapeutic response of PDAC patients. In this review we described the main actors of the desmoplastic reaction within PDAC and novel therapeutic approaches that are being tested to block the detrimental function of the stroma.

(18)F-FDG PET/CT imaging detects therapy efficacy of anti-EMMPRIN antibody and gemcitabine in orthotopic pancreatic tumor xenografts

PURPOSE

The objective of this study is to evaluate the therapeutic response to a novel monoclonal antibody targeting human extracellular matrix metalloproteinase inducer (EMMPRIN) in combination with gemcitabine in a pancreatic-tumor xenograft murine model by sequential 2-deoxy-2-[18F]fluoro-D-glucose ((18)F-FDG) positron emission tomography/computed tomgraphy (PET/CT) imaging.

PROCEDURES

Four groups of SCID mice bearing orthotopic pancreatic tumor xenografts were injected with phosphate-buffered saline, gemcitabine (120 mg/kg BW), anti-EMMPRIN antibody (0.2 mg), or combination, respectively, twice weekly for 2 weeks, while (18)F-FDG PET/CT imaging was performed weekly for 3 weeks. Changes in mean standardized uptake value (SUV(mean)) of (18)F-FDG and volume of tumors were determined.

RESULTS

The tumor SUV(mean) change in the group receiving combination therapy was significantly lower than those of the other groups. Tumor-volume changes of groups treated with anti-EMMPRIN monotherapy or combined therapy were significantly lower than that of the control group.

CONCLUSIONS

These data provide support for clinical studies of anti-EMMPRIN therapy with gemcitabine for pancreatic cancer treatment.

Tumour basement membrane laminin expression predicts outcome following curative resection of pancreatic head cancer

Background:

Although widely fragmented BMs have been associated with adverse outcome in several cancer types, comparatively little is known with respect to its effect on the prognosis of pancreatic cancer. The aim of the current study was therefore to determine the prognostic value of tumour basement membrane (BM) continuity in two anatomically closely related, however, prognostically different tumours, pancreatic head- and periampullary cancer.

Methods:

Tumour BM continuity was determined by immunohistochemical staining of its two major components, laminin and collagen type IV. Associations were made with recurrence free survival (RFS), cancer-specific survival (CSS), overall survival (OS) and conventional prognostic factors.

Results:

Fifty-nine and 61% of pancreatic head and periampullary tumours, respectively, showed limited BM laminin expression. Whereas 43% and 41% of pancreatic head and periampullary cancers, respectively, showed limited BM collagen type IV expression. Limited BM laminin was associated with poor outcome following curative resection of pancreatic head cancer (P=0.034, 0.013 and 0.017 for RFS, CSS and OS, respectively). Two and a half times as many patients with ⩾25% BM laminin were recurrence free and alive 5 years following resection compared with those with limited BM laminin. Although staining patterns of both BM components were weakly correlated with each other, BM collagen type IV expression was not significantly associated with outcome in either tumour type.

Conclusion:

Discontinuous BMs, determined by laminin expression, are associated with poor outcome following curative resection of pancreatic head cancer.

Targeting the cancer-stroma interaction: a potential approach for pancreatic cancer treatment

Recent studies have demonstrated that the interaction between the cancer and the stroma, play a key role in the development of pancreatic cancer. The desmoplasia, which consists of fibroblasts, pancreatic stellate cells, lymphatic and vascular endothelial cells, immune cells, pathologic increased nerves, and the extracellular matrix (ECM), creates a complex tumor microenvironment that promotes pancreatic cancer development, invasion, metastasis, and resistance to chemotherapy. Thus, the potential approach for targeting the components of this desmoplastic reaction or the pancreatic tumor microenvironment might represent a novel therapeutic approach to advanced pancreatic carcinoma. Novel therapies that target on the pancreatic tumor microenvironment should become one of the more effective treatments for pancreatic cancer.

Nerve-cancer interactions in the stromal biology of pancreatic cancer

Interaction of cancer cells with diverse cell types in the tumor stroma is today recognized to have a fate-determining role for the progression and outcome of human cancers. Despite the well-described interactions of cancer cells with several stromal components, i.e., inflammatory cells, cancer-associated fibroblasts, endothelial cells, and pericytes, the investigation of their peculiar relationship with neural cells is still at its first footsteps. Pancreatic cancer (PCa) with its abundant stroma represents one of the best-studied examples of a malignant tumor with a mutually trophic interaction between cancer cells and the intratumoral nerves embedded in the desmoplastic stroma. Nerves in PCa are a rich source of neurotrophic factors like nerve growth factor (NGF), glial-cell-derived neurotrophic factor (GDNF), artemin; of neuronal chemokines like fractalkine; and of autonomic neurotransmitters like norepinephrine which can all enhance the invasiveness of PCa cells via matrix-metalloproteinase (MMP) upregulation, trigger neural invasion (NI), and activate pro-survival signaling pathways. Similarly, PCa cells themselves provide intrapancreatic nerves with abundant trophic agents which entail a remarkable neuroplasticity, leading to emergence of more routes for NI and cancer spread, to augmented local neuro-surveillance, neural sensitization, and neuropathic pain. The strong correlation of NI with PCa-associated desmoplasia suggests the potential presence of a triangular relationship between nerves, PCa cells, and other stromal partners like myofibroblasts and pancreatic stellate cells which generate tumor desmoplasia. Hence, although not a classical hallmark of human cancers, nerve-cancer interactions can be considered as an indispensable sub-class of cancer-stroma interactions in PCa. The present article provides an overview of the so far known nerve-cancer interactions in PCa and illustrates their ominous role in the stromal biology of human PCa.

Galectin-1 secreted by activated stellate cells in pancreatic ductal adenocarcinoma stroma promotes proliferation and invasion of pancreatic cancer cells: an in vitro study on the microenvironment of pancreatic ductal adenocarcinoma

OBJECTIVES

This study aimed to clarify that the activated pancreatic stellate cells (PaSCs) are the origin of the highly expressed galectin-1 in the stroma of pancreatic ductal adenocarcinoma (PDAC) tissue and to evaluate the effect of the secreted galectin-1 on proliferation and invasion ability of pancreatic cancer cell line CFPAC-1 in vitro.

METHODS

Different kinds of PaSCs were isolated from the normal or cancerous pancreatic tissues and cultured. Immunohistochemistry study, quantitative polymerase chain reaction, and Western blot were carried out to check the cellular origin of galectin-1 in PDAC tissue. By using modified Boyden chambers, in vitro coculture system of PaSCs was established with the pancreatic cancer cell line CFPAC-1 and based on which we assessed the proliferation and invasion ability of CFPAC-1 with or without galectin-1 antagonists.

RESULTS

We identified PaSCs as the primary source of the highly expressed galectin-1 in PDAC stroma. Galectin-1 secreted by PaSCs increased CFPAC-1 proliferative rate in the proliferation assay and facilitated CFPAC-1 infiltration in the invasion assay.

CONCLUSIONS

Under malignant circumstances, PaSCs express and secret galectin-1, which could further promote the proliferation and invasion of cancer cells.

Analysis of the human pancreatic stellate cell secreted proteome

OBJECTIVE

Pancreatic stellate cells (PSCs) are important players in pancreatic fibrosis and are major contributors to the extracellular matrix proteins observed with the stromal response characteristic of pancreatic ductal adenocarcinoma (PDAC). Pancreatic stellate cells are also believed to secrete soluble factors that promote tumor progression; however, no comprehensive analysis of the PSC proteome in either the quiescent or the activated state has been reported.

METHODS

Using 2-dimensional tandem mass spectrometry and the RLT-PSC cell line, we present the first comprehensive study describing and comparing the quiescent and activated human PSC-secreted proteomes.

RESULTS

Very few proteins are secreted in the quiescent state. In stark contrast, activated PSCs secreted a vast array of proteins. Many of these proteins differed from those secreted by PDAC-derived cell lines. Proteins associated with wound healing, proliferation, apoptosis, fibrosis, and invasion were characterized. Selected proteins were verified in human tissue samples from PDAC, dysplastic pancreas, and normal pancreas using Western blot analysis and immunohistochemical staining.

CONCLUSIONS

Our study represents the first comprehensive analysis of proteins secreted by PSCs. These findings lay the foundation for characterizing PSC-derived proteins involved in stroma-tumor interactions and the promotion of pancreatitis and PDAC.

PSP/reg inhibits cultured pancreatic stellate cell and regulates MMP/ TIMP ratio

BACKGROUND

Pancreatic stellate cells (PSC) play a central role in fibrogenesis associated with acute and chronic pancreatitis. Pancreatic stone protein/regenerating protein (PSP/reg) belongs to a family of secretory stress proteins (SSP) that are constitutively synthesized by pancreatic acinar cells and upregulated dramatically during acute and chronic pancreatitis. Assuming a protective role of this stress protein, we investigated its effects on human PSC.

MATERIAL AND METHODS

Pancreatic stellate cells were obtained by outgrowth from fibrotic human pancreas tissue. PSP/reg was expressed in the yeast Pichia pastoris and purified from medium supernatants. PSP/reg was added at concentrations of 100 ng/mL to cultured PSC. Cell proliferation was determined by bromodeoxyuridine incorporation. PSC migration was assessed by a wound healing assay. Extracellular matrix (collagen type I and fibronectin), matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) were demonstrated on protein level.

RESULTS

Pancreatic stone protein/regenerating protein inhibited PSC proliferation and migration. Soluble collagen I and fibronectin were reduced after the addition of PSP/reg. PSP/reg slightly decreased the synthesis of MMP-1 and MMP-2 and strongly decreased TIMP-1 and TIMP-2 concentrations in PSC supernatants.

CONCLUSIONS

Our work describes a novel aspect that in vitro PSP/reg reduces PSC activity (proliferation and migration) and stimulates fibrolysis by increasing MMP/TIMP ratio. The findings suggest that PSP/reg might have a protective function in the repair phase of acute and chronic pancreatitis by promoting resolution of fibrosis. We highlight PSP/reg as an antifibrogenic protein in pancreatic injury.

Pancreatic cancer: the role of pancreatic stellate cells in tumor progression

Pancreatic ductal adenocarcinoma is an aggressive and highly lethal disease frequently characterized by a dense stromal or desmoplastic response. Accumulating evidence exists that tumor desmoplasia plays a central role in disease progression and that e.g. activated pancreatic stellate cells (PSCs) are responsible for the excess matrix production. The mechanisms underlying the tumor versus stroma interplay are complex. Pancreatic cancer cells release mitogenic and fibrogenic stimulants, such as transforming growth factor β(1), platelet-derived growth factor (PDGF), sonic hedgehog, galectin 3, endothelin 1 and serine protease inhibitor nexin 2, all of which may promote the activated PSC phenotype. Stellate cells in turn secrete various factors, including PDGF, stromal-derived factor 1, epidermal growth factor, insulin-like growth factor 1, fibroblast growth factor, secreted protein acidic and rich in cysteine, matrix metalloproteinases, small leucine-rich proteoglycans, periostin and collagen type I that mediate effects on tumor growth, invasion, metastasis and resistance to chemotherapy. This review intends to shed light on the mechanisms by which PSCs in the stroma influence pancreatic cancer development. The increased understanding of this interaction will be of potential value in designing new modalities of targeted therapy. and IAP.

Membrane drug transporters and chemoresistance in human pancreatic carcinoma

Pancreatic cancer ranks among the tumors most resistant to chemotherapy. Such chemoresistance of tumors can be mediated by various cellular mechanisms including dysregulated apoptosis or ineffective drug concentration at the intracellular target sites. In this review, we highlight recent advances in experimental chemotherapy underlining the role of cellular transporters in drug resistance. Such contribution to the chemoresistant phenotype of tumor cells or tissues can be conferred both by uptake and export transporters, as demonstrated by in vivo and in vitro data. Our studies used human pancreatic carcinoma cells, cells stably transfected with human transporter cDNAs, or cells in which a specific transporter was knocked down by RNA interference. We have previously shown that 5-fluorouracil treatment affects the expression profile of relevant cellular transporters including multidrug resistance proteins (MRPs), and that MRP5 (ABCC5) influences chemoresistance of these tumor cells. Similarly, cell treatment with the nucleoside drug gemcitabine or a combination of chemotherapeutic drugs can variably influence the expression pattern and relative amount of uptake and export transporters in pancreatic carcinoma cells or select for pre-existing subpopulations. In addition, cytotoxicity studies with MRP5-overexpressing or MRP5-silenced cells demonstrate a contribution of MRP5 also to gemcitabine resistance. These data may lead to improved strategies of future chemotherapy regimens using gemcitabine and/or 5-fluorouracil.

Interaction of stellate cells with pancreatic carcinoma cells

Pancreatic cancer is characterized by its late detection, aggressive growth, intense infiltration into adjacent tissue, early metastasis, resistance to chemo- and radiotherapy and a strong “desmoplastic reaction”. The dense stroma surrounding carcinoma cells is composed of fibroblasts, activated stellate cells (myofibroblast-like cells), various inflammatory cells, proliferating vascular structures, collagens and fibronectin. In particular the cellular components of the stroma produce the tumor microenvironment, which plays a critical role in tumor growth, invasion, spreading, metastasis, angiogenesis, inhibition of anoikis, and chemoresistance. Fibroblasts, myofibroblasts and activated stellate cells produce the extracellular matrix components and are thought to interact actively with tumor cells, thereby promoting cancer progression. In this review, we discuss our current understanding of the role of pancreatic stellate cells (PSC) in the desmoplastic response of pancreas cancer and the effects of PSC on tumor progression, metastasis and drug resistance. Finally we present some novel ideas for tumor therapy by interfering with the cancer cell-host interaction.

Roles of pancreatic stellate cells in pancreatic inflammation and fibrosis

Over a decade, there is accumulating evidence that activated pancreatic stellate cells (PSCs) play a pivotal role in the development of pancreatic fibrosis. In response to pancreatic injury or inflammation, quiescent PSCs are transformed (activated) to myofibroblast-like cells, which express alpha-smooth muscle actin. Activated PSCs proliferate, migrate, produce extracellular matrix components, such as type I collagen, and express cytokines and chemokines. Recent studies have suggested novel roles of PSCs in local immune functions and angiogenesis in the pancreas. If the pancreatic inflammation and injury are sustained or repeated, PSC activation is perpetuated, leading to the development of pancreatic fibrosis. In this context, pancreatic fibrosis can be defined as pathologic changes of extracellular matrix composition in both quantity and quality, resulting from perpetuated activation of PSCs. Because PSCs are very similar to hepatic stellate cells, PSC research should develop in directions more relevant to the pathophysiology of the pancreas, for example, issues related to trypsin, non-oxidative alcohol metabolites, and pancreatic cancer. Indeed, in addition to their roles in chronic pancreatitis, it has been increasingly recognized that PSCs contribute to the progression of pancreatic cancer. Very recently, contribution of bone marrow-derived cells to PSCs was reported. Further elucidation of the roles of PSCs in pancreatic fibrosis should promote development of rational approaches for the treatment of chronic pancreatitis and pancreatic cancer.

Desmoplasia of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and is characterized by remarkable desmoplasia. The desmoplasia is composed of extracellular matrix (ECM) proteins, myofibroblastic pancreatic stellate cells, and immune cells associated with a multitude of cytokines, growth factors, and ECM metabolizing enzymes. The mechanisms of participation of this complex matrix process in carcinogenesis are only starting to be appreciated. Recent studies showed key roles for stellate cells in the production of ECM proteins as well as cytokines and growth factors that promote the growth of the cancer cells all present in the desmoplastic parts of PDAC. In addition, interactions of ECM proteins and desmoplastic secreted growth factors with the cancer cells of PDAC activate intracellular signals including reactive oxygen species that act to make the cancer cells resistant to dying. These findings suggest that the desmoplasia of PDAC is a key factor in regulating carcinogenesis of PDAC as well as responses to therapies. A better understanding of the biology of desmoplasia in the mechanism of PDAC will likely provide significant opportunities for better treatments for this devastating cancer.

Organotypic culture model of pancreatic cancer demonstrates that stromal cells modulate E-cadherin, beta-catenin, and Ezrin expression in tumor cells

Pancreatic cancer is characterized by an intense stromal reaction. Reproducible three-dimensional in vitro systems for exploring interactions of the stroma with pancreatic cancer cells have not previously been available, prompting us to develop such a model. Cancer cells were grown on collagen/Matrigel and embedded with or without stromal cells (hTERT-immortalized human PS-1 stellate cells or MRC-5 fibroblasts) for 7 days. Proliferation and apoptosis, as well as important cell-cell adhesion and cytoskeleton-regulating proteins, were studied. PS-1 cells were confirmed as stellate based on the expression of key cytoskeletal proteins and lipid vesicles. Capan-1, and to a lesser extent PaCa-3, cells differentiated into luminal structures, exhibiting a central apoptotic core with a proliferating peripheral rim and an apico-basal polarity. Presence of either stromal cell type translocated Ezrin from apical (when stromal cells were absent) to basal aspects of cancer cells, where it was associated with invasive activity. Interestingly, the presence of 'normal' (not tumor-derived) stromal cells induced total tumor cell number reduction (P < 0.005) associated with a significant decrease in E-cadherin expression (P < 0.005). Conversely, beta-catenin expression was up-regulated (P < 0.01) in the presence of stromal cells with predominant cytoplasmic expression. Moreover, patient samples confirmed that these data recapitulated the clinical situation. In conclusion, pancreatic organotypic culture offers a reproducible, bio-mimetic, three-dimensional in vitro model that allows examination of the interactions between stromal elements and pancreatic cancer cells.

Cancer-stellate cell interactions perpetuate the hypoxia-fibrosis cycle in pancreatic ductal adenocarcinoma

BACKGROUND AND AIMS

Although both cancer and stellate cells (PSCs) secrete proangiogenic factors, pancreatic cancer is a scirrhous and hypoxic tumor. The impact of cancer-PSCs interactions on angiogenesis was analyzed.

METHODS

Expression of periostin, CD31, and alpha-smooth muscle actin was assessed by immunohistochemistry. Human PSCs and cancer cells were cultivated under normoxia and hypoxia alone, or in coculture, to analyze the changes in their angiogenic and fibrogenic attributes, using enzyme-linked immunosorbent assay, immunoblot, and quantitative polymerase chain reaction analyses and growth of cultured endothelial cells in vitro.

RESULTS

On the invasive front of the activated stroma, PSCs deposited a periostin-rich matrix around the capillaries in the periacinar spaces. Compared with the normal pancreas, there was a significant reduction in the microvessel density in chronic pancreatitis (five-fold, P < .001) and pancreatic cancer (four-fold, P < .01) tissues. In vitro, hypoxia increased PSCs' activity and doubled the secretion of periostin, type I collagen, fibronectin, and vascular endothelial growth factor (VEGF). Cancer cells induced VEGF secretion of PSCs (390 +/- 60%, P < .001), whereas PSCs increased the endostatin production of cancer cells (210 +/- 14%, P < .001) by matrix metalloproteinase-dependent cleavage. In vitro, PSCs increased the endothelial cell growth, whereas cancer cells alone, or their coculture with PSCs, suppressed it.

CONCLUSIONS

Although PSCs are the dominant producers of VEGF and increase endothelial cell growth in vitro, in the peritumoral stroma, they contribute to the fibrotic/hypoxic milieu through abnormal extracellular matrix deposition and by amplifying endostatin production of cancer cells.

Signal transduction in pancreatic stellate cells

Pancreatic fibrosis is a characteristic feature of chronic pancreatitis and of desmoplastic reaction associated with pancreatic cancer. For over a decade, there has been accumulating evidence that activated pancreatic stellate cells (PSCs) play a pivotal role in the development of pancreatic fibrosis in these pathological settings. In response to pancreatic injury or inflammation, quiescent PSCs undergo morphological and functional changes to become myofibroblast-like cells, which express alpha-smooth muscle actin (alpha-SMA). Activated PSCs actively proliferate, migrate, produce extracellular matrix (ECM) components, such as type I collagen, and express cytokines and chemokines. In addition, PSCs might play roles in local immune functions and angiogenesis in the pancreas. Following the initiation of activation, if the inflammation and injury are sustained or repeated, PSCs activation is perpetuated, leading to the development of pancreatic fibrosis. From this point of view, pancreatic fibrosis can be defined as pathological changes of ECM composition in the pancreas both in quantity and quality, resulting from perpetuated activation of PSCs. Because the activation and cell functions in PSCs are regulated by the dynamic but coordinated activation of intracellular signaling pathways, identification of signaling molecules that play a crucial role in PSCs activation is important for the development of anti-fibrosis therapy. Recent studies have identified key mediators of stimulatory and inhibitory signals. Signaling molecules, such as peroxisome proliferator-activated receptor-gamma (PPAR-gamma), Rho/Rho kinase, nuclear factor-kappaB (NF-kappaB), mitogen-activated protein (MAP) kinases, phosphatidylinositol 3 kinase (PI3K), Sma- and Mad-related proteins, and reactive oxygen species (ROS) might be candidates for the development of anti-fibrosis therapy targeting PSCs.

Characterization of tumor-derived pancreatic stellate cells

BACKGROUND

Pancreatic stellate cells (PSCs) are key mediators of the desmoplastic reaction that characterizes pancreatic adenocarcinoma. We sought to isolate and characterize tumor-derived pancreatic stellate (TDPS) cells to further understand how these stromal cells influence pancreatic cancer behavior.

METHODS

We established a stable line of non-immortalized PSCs from a patient with pancreatic adenocarcinoma using a modified prolonged outgrowth method. Cell staining for cytokeratin, vimentin, and alpha smooth muscle actin (alphaSMA) was performed. Total RNA was harvested from TDPS and panc-1 cells and gene expression determined by microarray analysis.

RESULTS

TDPS cells contain lipid droplets in the cytoplasm, and later stain positive for both vimentin and alphaSMA, indicative of activated myofibroblasts. Microarray analysis revealed a distinct gene expression profile compared with pancreatic cancer cells, including expression of proteases that facilitate cancer cell invasion and growth factors known to activate pancreatic cancer cells. Additionally, TDPS cells expressed many of the key components of the pancreatic tumor stroma, including collagen, fibronectin, and S100A4, confirming their importance in the tumor microenvironment.

CONCLUSIONS

Characterization of tumor-derived PSCs will facilitate further studies to determine how the tumor microenvironment promotes the aggressive behavior of pancreatic cancer.

Tumor-derived pancreatic stellate cells promote pancreatic cancer cell invasion through release of thrombospondin-2

BACKGROUND

Tumor derived pancreatic stellate cells (TDPS) cells are key cellular components of the pancreatic tumor microenvironment. These stellate cells can release growth factors, proteases, and extracellular matrix proteins that may stimulate the spread of pancreatic cancer. We sought to determine whether TDPS cells promote the local invasion of pancreatic cancer cells and mechanisms involved.

METHODS

TDPS and panc-1 cells were grown in coculture to determine directional migration and panc-1 invasiveness was quantified using Matrigel invasion chambers, comparing TDPS cells to human foreskin fibroblasts (HFFs). ELISA was used to determine the secretion of growth factors, proteases, and extracellular matrix proteins from TDPS cells and HFFs, and then siRNAs used to knockdown expression of factors.

RESULTS

In coculture panc-1 cells migrate toward TDPS cells, creating nests of cancer cells within the stromal cells. TDPS cells promote the invasion of panc-1 cells and release thrombospondin 2 (TSP-2), whereas HFFs did not. When TSP-2 expression is reduced in TDPS cells using selective siRNAs, pancreatic cancer cell invasion was inhibited.

CONCLUSION

Tumor-derived pancreatic stellate cells stimulate pancreatic cancer cell invasion, likely through release of TSP-2. Targeting pro-invasive elements, such as TSP-2, within the tumor microenvironment may inhibit local invasion, thus permitting more patients to undergo curative resection of pancreatic cancer.

In vitro models of pancreatic cancer for translational oncology research

BACKGROUND: Pancreatic cancer is a disease of near uniform fatality and the overwhelming majority of patients succumb to their advanced malignancy within a few months of diagnosis. Despite considerable advances in our understanding of molecular mechanisms underlying pancreatic carcinogenesis, this knowledge has not yet been fully translated into clinically available treatment strategies that yield significant improvements in disease free or overall survival. OBJECTIVE: Cell line-based in vitro model systems provide powerful tools to identify potential molecular targets for therapeutic intervention as well as for initial pre-clinical evaluation of novel drug candidates. Here we provide a brief overview of recent literature on cell line-based model systems of pancreatic cancer and their application in the search for novel therapeutics against this vicious disease. CONCLUSION: While in vitro models of pancreatic cancer are of tremendous value for genetic studies and initial functional screenings in drug discovery, they carry several imanent drawbacks and are often poor in predicting therapeutic response in humans. Therefore, in most instances they are successfully exploited to generate hypothesis and identify molecular targets for novel therapeutics, which are subsequently subject to further in-depth characterization using more advanced in vivo model systems and clinical trials.

ATP-binding cassette C transporters in human pancreatic carcinoma cell lines. Upregulation in 5-fluorouracil-resistant cells

BACKGROUND

Pancreatic cancer is characterized by high resistance to chemotherapy. Such chemoresistance can be mediated by multidrug resistance proteins (MRPs), breast cancer resistance protein (BCRP), and MDR1 P-glycoprotein. However, the contribution of individual MRP isoforms to chemoresistance in pancreatic carcinoma is unclear. We studied ATP-binding cassette (ABC) transporter expression in human pancreatic carcinoma cell lines as compared to primary pancreatic duct cells, and analyzed the MRP expression profile in 5-fluorouracil-resistant cells.

METHODS

Transporter expression was analyzed by quantitative and qualitative RT-PCR, by immunoblot, and chemoresistance by cytotoxicity assay.

RESULTS

Primary pancreatic duct cells expressed MRP1, MRP3, MRP4, and MRP5, but not MRP2 mRNA. The established carcinoma cell lines expressed MRP1, MRP4, and MRP5, most of them also MRP2, MRP3, MRP7, and BCRP, but none contained detectable amounts of MRP6, MRP8, or MRP9 mRNA. Immunoblot analyses demonstrated presence of MRP1, MRP4, and MRP5 protein in all, but MRP3 and BCRP protein only in some of these cells. Compared to parental Capan-1 cells, Capan-1 cells with acquired chemoresistance towards 5-fluorouracil showed an upregulated mRNA and protein expression of MRP3, MRP4, and MRP5. In addition, silencing of MRP5 by RNA interference resulted in enhanced sensitivity of parental Capan-1 cells towards 5-fluorouracil cytotoxicity.

CONCLUSION

MRP3, MRP4, and MRP5 are upregulated in 5-fluorouracil-resistant cells, and MRP5 contributes to 5-FU resistance in pancreatic carcinoma cells.

Pancreatic islet and stellate cells are the main sources of endocrine gland-derived vascular endothelial growth factor/prokineticin-1 in pancreatic cancer

AIMS

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF)/prokineticins have been identified as tissue-specific angiogenic factors. This study investigates the expression and localization of EG-VEGF and its receptors in pancreatic tissues and pancreatic stellate cells (PSCs).

METHODS

mRNA levels of EG-VEGF/prokineticin 1 (PK1), prokineticin 2 (PK2) and their receptors 1 (PKR1) and 2 (PKR2) were measured in pancreatic tissues, pancreatic cancer cell lines and PSCs by quantitative reverse-transcriptase polymerase chain reaction (QRT-PCR). Protein expression of PK1, PKR1 and PKR2 was assessed in pancreatic tissues by immunohistochemistry. Growth factor-induced secretion of EG-VEGF was measured by ELISA.

RESULTS

QRT-PCR analysis in bulk tissues of normal pancreas, chronic pancreatitis and pancreatic ductal adenocarcinoma showed no significant difference of PK1 mRNA levels, whereas PK2 mRNA was barely detectable. High PK1 mRNA levels were observed only in cultured PSCs and microdissected islet cells, but not in cancer cells, and PK1 protein was localized mainly in islets and cancer-associated stromal cells. PKR1 and PKR2 proteins were present in endothelial cells of small blood vessels. TGF-beta(1) and PDGF-BB specifically stimulated PK1 secretion in PSCs.

CONCLUSIONS

Islet and/or PSC-derived PK1 might act through its receptors on endothelial cells to increase angiogenesis in pancreatic diseases.

Pancreatitis-associated protein inhibits human pancreatic stellate cell MMP-1 and -2, TIMP-1 and -2 secretion and RECK expression

BACKGROUND/AIMS

Pancreatic stellate cells (PSCs) play a key role in fibrogenesis associated with acute and chronic pancreatitis. Pancreatitis-associated protein (PAP), an acute-phase protein, is dramatically upregulated during acute and chronic pancreatitis. Assuming a protective role of PAP, we investigated its effects on human PSCs.

METHODS

PSCs were obtained by outgrowth from fibrotic human pancreas tissue. PAP was expressed in the yeast Pichia pastoris. PAP was added at 10 ng/ml to cultured PSCs. Cell proliferation was determined by bromodeoxyuridine incorporation. PSC migration was assessed by a wound healing assay. Collagen types I and III, fibronectin, matrix metalloproteinases (MMPs), tissue inhibitors of MMPs (TIMPs) and reversion-inducing cysteine-rich protein with Kazal motifs (RECK) were demonstrated on protein and mRNA level.

RESULTS

PAP had no significant effect on PSC proliferation and migration. Cell-associated fibrillar collagen types I and III and fibronectin increased after addition of PAP to PSCs. PAP diminished the expression of MMP-1 and -2 and TIMP-1 and -2 and their concentrations in PSC supernatants. RECK was detected on the surface of PSCs and its expression was reduced after PAP application.

CONCLUSIONS

Our data offer new insights into the biological functions of PAP, which may play an important role in wound healing response and cell-matrix interactions.

Relationship between pancreatic stellate cells and pancreatic cancer

Pancreatic carcinoma is a highly malignant tumor in digestive tract, characterized by rapid progression, early metastasis, limited response to chemotherapy and radiotherapy, and an intense fibrotic reaction known as tumor desmoplasia. Carcinoma cells are surrounded by dense stroma consisting of myofibroblast-like cells, collagens, and fibronectin. Recent studies suggest that pancreatic stellate cells play an important role in this reaction and can stimulate pancreatic tumor cell proliferation, progression and metastasis. This review describes the discovery, activation pathway, interaction between pancreatic stellate cells and pancreatic tumor cells, and the role of pancreatic stellate cells in the process of pancreatic cancer initiation, progression, and metastasis.

The activated stroma index is a novel and independent prognostic marker in pancreatic ductal adenocarcinoma

BACKGROUND AND AIMS

Pancreatic ductal adenocarcinoma (PDAC) is a highly desmoplastic tumor with an innate resistance to therapy. Pancreatic stellate cells (PSCs) produce this excessively desmoplastic microenvironment. The impact of PSC activity on PDAC behavior in vivo is analyzed.

METHODS

233 patients who underwent surgery for PDAC were evaluated by immunohistochemistry using antibodies against alpha-smooth muscle actin as a marker of PSC activity. Aniline was used to stain collagen deposition. The ratio of alpha-smooth muscle actin-stained area to collagen-stained area was defined as the activated stroma index (ASI). Survival analysis was performed using the Kaplan-Meier method. Prognostic factors were determined in a multivariable analysis using a Cox proportional hazards model.

RESULTS

Four major patterns of collagen deposition were defined with regard to PSC activity. The combination of high stromal activity and low collagen deposition was associated with a worse prognosis, whereas the combination of high collagen deposition and low stromal activity indicated a better prognosis. Patients with the lowest ASI had the best median survival rate (25.7 mo). The highest ASI was found in patients with the worst median survival rate (16.1 mo; P = .007; lowest vs highest ASI: hazard ratio, 1.61; 95% confidence interval, 1.014-2.562). ASI was an independent prognostic marker in multivariable survival analysis comparable with the nodal status of cancer.

CONCLUSIONS

The activated stroma index is a novel independent prognostic marker in PDAC in cases undergoing surgery. This finding highlights the impact of the microenvironment in cancer progression and on patient survival.

Cancer-associated stromal fibroblasts promote pancreatic tumor progression

Pancreatic adenocarcinoma is characterized by a dense background of tumor associated stroma originating from abundant pancreatic stellate cells. The aim of this study was to determine the effect of human pancreatic stellate cells (HPSC) on pancreatic tumor progression. HPSCs were isolated from resected pancreatic adenocarcinoma samples and immortalized with telomerase and SV40 large T antigen. Effects of HPSC conditioned medium (HPSC-CM) on in vitro proliferation, migration, invasion, soft-agar colony formation, and survival in the presence of gemcitabine or radiation therapy were measured in two pancreatic cancer cell lines. The effects of HPSCs on tumors were examined in an orthotopic murine model of pancreatic cancer by co-injecting them with cancer cells and analyzing growth and metastasis. HPSC-CM dose-dependently increased BxPC3 and Panc1 tumor cell proliferation, migration, invasion, and colony formation. Furthermore, gemcitabine and radiation therapy were less effective in tumor cells treated with HPSC-CM. HPSC-CM activated the mitogen-activated protein kinase and Akt pathways in tumor cells. Co-injection of tumor cells with HPSCs in an orthotopic model resulted in increased primary tumor incidence, size, and metastasis, which corresponded with the proportion of HPSCs. HPSCs produce soluble factors that stimulate signaling pathways related to proliferation and survival of pancreatic cancer cells, and the presence of HPSCs in tumors increases the growth and metastasis of these cells. These data indicate that stellate cells have an important role in supporting and promoting pancreatic cancer. Identification of HPSC-derived factors may lead to novel stroma-targeted therapies for pancreatic cancer.

Crucial role of fibrogenesis in pancreatic diseases

Chronic pancreatitis and pancreatic cancer are characterised by a progressive fibrosis. Accumulation of extracellular matrix not only accompanies both diseases but is directly involved in their progression, suggesting inhibition of fibrogenesis as a potential therapeutic strategy. Pancreatic stellate cells (PSC) are the main extracellular matrix-producing cell type in the diseased pancreas. In response to pro-fibrogenic mediators including cytokines and ethanol metabolites, PSC undergo phenotypic changes termed activation, resulting in the exhibition of a myofibroblast-like phenotype. In the perpetuation of PSC activation, autocrine loops of mediators such as transforming growth factor beta play an important role. Most recently signal transduction pathways in PSC that are associated with the process of activation were characterised, facilitating identification of potential intracellular targets for an anti-fibrotic therapy. While some putative inhibitors of fibrogenesis have been tested in animal models of pancreatic fibrosis for their in vivo efficiency, clinical studies still remain to be performed.

Pancreatic stellate cells--role in pancreas cancer

BACKGROUND

Adenocarcinomas of the pancreas are characterized by a rapid progression, an early metastasis, a limited response to chemo- and radiotherapy, and an intense fibrotic reaction known as tumor desmoplasia. Carcinoma cells are surrounded by a dense stroma consisting of myofibroblast-like cells, collagens, and fibronectin.

MATERIALS AND METHODS

This review describes the interaction of activated pancreatic stellate cells (myofibroblast-like cells) with tumor cells in pancreas adenocarcinomas. Our data were obtained in cell culture experiments and in in vivo investigations.

RESULTS

Carcinoma cells produce soluble mediators and stimulate motility, proliferation, matrix-, and MMP synthesis of stellate cells. Vice versa-activated stellate cells release mitogens, stimulating proliferation of cancer cells. Cancer cell proliferation and resistance to apoptosis might further be induced by the microenvironment (extracellular matrix), which is primarily provided by stellate cells. A very important aspect in the interaction of stellate cells with cancer cells is the expression of EMMPRIN (extracellular matrix metalloproteinase inducer) by cancer cells, the shedding of the extracellular part of EMMPRIN by matrix metalloproteinases (MMPs), and the induction of MMPs in stellate cells by soluble EMMPRIN. In particular, the stellate cells in close proximity to tumor cells therefore express MMPs and degrade connective tissue.

CONCLUSION

Through complex interactions between stellate cells and carcinoma cells, tumor progression and cancer cell invasion are accelerated. As we gain better understanding of these mechanisms, adequate therapies to reduce tumor cell invasion and cancer progression might be developed.

Increased expression of matrix metalloproteinases-21 and -26 and TIMP-4 in pancreatic adenocarcinoma

Pancreatic adenocarcinoma is known for early aggressive local invasion, high metastatic potential, and a low 5-year survival rate. Matrix metalloproteinases (MMPs) play important roles in tumor growth and invasion. Earlier studies on pancreatic cancer have found increased expression of certain MMPs to correlate with poorer prognosis, short survival time or presence of metastases. We studied the expression of MMP-21, -26, and tissue inhibitor of matrix metalloproteinases (TIMP)-4 in 50 tissue samples, including 25 adenocarcinomas, seven other malignant pancreatic tumors, and 18 control samples of non-neoplastic pancreatic tissue with immunohistochemistry. The regulation of MMP-21, -26, and TIMP-4 mRNAs by cytokines was studied with RT-PCR in pancreatic cancer cell lines PANC-1, BxPC-3, and AsPC-1. MMP-21, -26, and TIMP-4 were detected in cancer cells in 64, 40, and 60% of tumors, respectively. MMP-21 expressed in well-differentiated cancer cells and occasional fibroblasts, like TIMP-4, tended to diminish in intensity from grade I to grade III tumors. Patients with metastatic lymph nodes had increased expression of MMP-26 in actual tumor samples. All cultured cancer cell lines expressed MMP-21 basally at low levels, and presence of the protein was confirmed immunohistochemically in cultured cells. MMP-21 expression was induced by epidermal growth factor (EGF) in PANC-1 cells. MMP-26 was neither expressed basally nor induced by tumor necrosis factor alpha, transforming growth factor beta-1 (TGFbeta1), EGF, or interferon gamma. Basal TIMP-4 expression was lowest in the poorly differentiated cancer cell line PANC-1 compared to better-differentiated BxPC-3 and AsPC-1 cells. TIMP-4 expression was induced by TGFbeta1 in PANC-1 cells and by EGF in BxPC-3 cells. Our findings suggest that MMP-21 is not a marker of invasiveness, but rather of differentiation, in pancreatic cancer and it may be upregulated by EGF. The putative role of MMP-26 as a marker of metastases warrants further studies. Unlike other TIMPs, TIMP-4 was not upregulated in relation to aggressiveness of pancreatic cancer.

Antifibrogenic effects of histone deacetylase inhibitors on pancreatic stellate cells

Pancreatic stellate cells (PSCs) are essentially involved in pancreatic fibrogenesis and considered as a target for antifibrotic therapies. Here, we have analyzed the effects of three histone deacetylase inhibitors (HDACIs), sodium butyrate, sodium valproate (VPA) and trichostatin A (TSA), on profibrogenic activities of PSC and elucidated molecular targets of HDACI action. Therefore, cultured PSCs were exposed to HDACI. Cell proliferation and viability were assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation and trypan blue staining assays. Exhibition of the myofibroblastic PSC phenotype was monitored by immunofluorescence analysis of alpha-smooth muscle actin (alpha-SMA) expression. [(3)H]-proline incorporation into acetic acid-soluble proteins was measured to quantify collagen synthesis. Levels of mRNA were determined by quantitative reverse transcriptase real-time PCR. Protein expression, phosphorylation and acetylation were analyzed by immunoblotting, and gel shift assays were performed to study DNA binding of nuclear proteins. HDACI enhanced histone H3 acetylation in a dose-dependent manner. In the same dose range, they strongly inhibited cell proliferation, alpha-SMA expression and collagen synthesis. A significantly increased rate of cell death was observed in response to TSA at 1 microM. While all three HDACI inhibited mRNA expression of endothelin-1, only VPA significantly reduced expression of transforming growth factor-beta1. Both mediators exert autocrine profibrogenic effects on PSC. Furthermore, HDACI-treated PSC displayed a diminished DNA binding of AP-1, a key transcription factor in profibrogenic signaling. Together, the results suggest that HDACI exert antifibrogenic effects on PSC. Interruption of AP-1 signaling and autocrine loops enhancing PSC activation might be key mechanisms of HDACI action.