Desmoplastic reaction in pancreatic cancer: role of pancreatic stellate cells

Pancreatic stellate cells enhance stem cell-like phenotypes in pancreatic cancer cells

The interaction between pancreatic cancer cells and pancreatic stellate cells (PSCs), a major profibrogenic cell type in the pancreas, is receiving increasing attention. There is accumulating evidence that PSCs promote the progression of pancreatic cancer by increasing cancer cell proliferation and invasion as well as by protecting them from radiation- and gemcitabine-induced apoptosis. Recent studies have identified that a portion of cancer cells, called "cancer stem cells", within the entire cancer tissue harbor highly tumorigenic and chemo-resistant phenotypes, which lead to the recurrence after surgery or re-growth of the tumor. The mechanisms that maintain the "stemness" of these cells remain largely unknown. We hypothesized that PSCs might enhance the cancer stem cell-like phenotypes in pancreatic cancer cells. Indirect co-culture of pancreatic cancer cells with PSCs enhanced the spheroid-forming ability of cancer cells and induced the expression of cancer stem cell-related genes ABCG2, Nestin and LIN28. In addition, co-injection of PSCs enhanced tumorigenicity of pancreatic cancer cells in vivo. These results suggested a novel role of PSCs as a part of the cancer stem cell niche.

Pancreatic stellate cells form a niche for cancer stem cells and promote their self-renewal and invasiveness

Chronic pancreatitis and pancreatic ductal adenocarcinoma (PDAC) are characterized by extensive fibrosis. Importantly, in PDAC, this results in poor vascularization and impaired drug delivery to the cancer cells. Therefore, the combined targeting of pancreatic tumor stroma and chemotherapy should enhance response rates, but the negative outcome of a recent phase III clinical trial for the combination of chemotherapy and hedgehog pathway inhibition suggests that other means also need to be considered. Emerging data indicate that elimination of cancer stem cells as the root of the cancer is of pivotal importance for efficient treatment of pancreatic cancer. Recently, we demonstrated in a highly relevant preclinical mouse model for primary pancreatic cancers that the combination of cancer stem cell-targeting strategies in combination with a stroma-targeting agent, such as a hedgehog pathway inhibitor and chemotherapy, results in significantly enhanced long-term and progression-free survival. In the present study, we demonstrate mechanistically that Nodal-expressing pancreatic stellate cells are an important component of the tumor stroma for creating a paracrine niche for pancreatic cancer stem cells. Secretion of the embryonic morphogens Nodal/Activin by pancreatic stellate cells promoted in vitro sphere formation and invasiveness of pancreatic cancer stem cells in an Alk4-dependent manner. These data imply that the pancreatic cancer stem cell phenotype is promoted by paracrine Nodal/Activin signaling at the tumor-stroma interface. Therefore, targeting the tumor microenvironment is not only able to improve drug delivery but, even more importantly, destroys the cancer stem cell niche and, therefore, should be an integral part of cancer stem cell-based treatment strategies.

PDGFRβ expression in tumor stroma of pancreatic adenocarcinoma as a reliable prognostic marker

Pancreatic adenocarcinoma is a lethal disease that often develops a desmoplastic reaction in tumor stroma. In general, desmoplasia is thought to promote tumor growth. However, its molecular pathology and prognostic potential have not been fully investigated. Here, we investigate 26 cases of pancreatic ductal adenocarcinoma and examine the clinicopathological association between survival and expression levels of several molecular markers for stromal cells. These include alpha-smooth muscle actin (SMA) and platelet-derived growth factor (PDGF) receptor β (PDGFRβ). Both are markers of activated fibroblasts or pancreatic stellate cells (PSCs) that play an important role in desmoplasia. The staining patterns of both molecular markers were not uniform, so we categorized them into 3 grades (high, middle, and low) according to intensity. Interestingly, Kaplan-Meier analysis revealed that higher expression of PDGFRβ matched shorter prognosis (p=0.0287, log-rank test) as well as lymphatic invasion and lymph node metastasis, whereas SMA did not (p=0.6122). Our results suggest the prognostic potential of cancer stroma via PDGF-B signaling. Regulation of PDGF-B-associated signaling crosstalk between cancer cells and stroma cells, therefore, may indicate a possible therapeutic target for desmoplastic malignant tumors such as pancreatic adenocarcinoma.

Bone marrow-derived proangiogenic cells in pancreatic cancer

Tumor-derived signals systemically induce an angiogenic switch that allows cancer cells to survive and grow. However, the vascular network in tumors is not well organized and fails to meet metabolic needs to maintain tissue homeostasis, resulting in significant hypoxia. Among various tumors, pancreatic ductal adenocarcinoma (PDAC) typically develops in an unusually disordered microenvironment, which contributes to its highly aggressive behavior. Since anti-vascular endothelial growth factor (VEGF) (Avastin) has failed to demonstrate a survival benefit in PDAC, we need to re-visit the basic biology of this disease and understand what makes it so refractory to the anti-angiogenic approaches that are clinically effective in other neoplasms. To address this issue, we specifically focused on the process of neovascularization where bone marrow-derived cells (BMDCs) play a role during pancreatic tumorigenesis. We have identified subsets of BMDCs that regulate key processes during development of the neovessels through paracrine Hedgehog signaling. Considering the importance of systemic responses occurring in tumor bearing hosts, we are currently using genetically engineered mice, which spontaneously develop PDAC, Pdx1-Cre;LSL-Kras(G12D);p53(lox/+) strain, to clarify critical events that can trigger aberrant angiogenesis in pancreatic cancer. These studies allow us to provide insights into the cellular and molecular mechanisms of pancreatic tumorigenesis and have an implication for the design of therapies against this difficult disease.

Epidemiology, risk factors, and the promotion of pancreatic cancer: role of the stellate cell

There are approximately 277,000 new cases of pancreatic cancer and 266,000 deaths from pancreatic cancer annually, indicating a mortality rate of 96% of the cases diagnosed. Because of the ineffectiveness of therapies, a major emphasis needs to be placed on prevention. This paper reviews the epidemiology and risk factors for pancreatic cancer, and uses this information to propose plausible research directions for determining the biological mechanisms mediating the effects of risk factors on the promotion of pancreatic cancer, with a focus on the pancreatic stellate cell.

Dangerous liaisons: pancreatic stellate cells and pancreatic cancer cells

One of the characteristic features of the majority of pancreatic ductal adenocarcinomas is an abundant desmoplastic/stromal reaction. Until recently, this stroma had received little attention from researchers studying the pathogenesis of pancreatic cancer, with most of the research focus resting on the biology of tumor cells themselves. However, evidence is now accumulating that the stroma plays a critical role in pancreatic cancer progression. The cells responsible for producing the stromal reaction in pancreatic cancer are activated pancreatic stellate cells (PSCs, the key effector cells in pancreatic fibrogenesis). In vitro and in vivo studies have convincingly demonstrated a close bi-directional interaction between PSCs and pancreatic cancer cells, which facilitates local tumor growth as well as distant metastasis. PSCs also interact closely with endothelial cells to stimulate angiogenesis and are possibly involved in the known resistance of pancreatic cancer to chemotherapy and radiation. Most interestingly, it has recently been shown that PSCs from the primary tumor can travel to distant metastatic sites where they likely facilitate the seeding, survival, and proliferation of cancer cells. Thus, it is now recognized that the stroma is an important alternative therapeutic target in this disease and concerted pre-clinical research is underway to develop strategies to modulate/deplete the stromal reaction to inhibit cancer progression. The challenge is to translate these developments into clinically applicable treatments for patients.

Conophylline suppresses pancreatic stellate cells and improves islet fibrosis in Goto-Kakizaki rats

Activin A is a differentiation factor for β-cells and is effective to promote β-cell neogenesis. Activin A is also an autocrine activator of pancreatic stellate cells, which play a critical role in fibrogenesis of the pancreas. Conophylline (CnP) is a natural compound, which reproduces the effect of activin on β-cell differentiation and promotes β-cell neogenesis when administered in vivo. However, its effect on stellate cells is not known. We therefore investigated the effect of CnP on stellate cells both in vitro and in vivo. Unlike activin A, CnP inhibited activation of cultured stellate cells and reduced the production of collagen. We then analyzed the involvement of stellate cells in islet fibrosis in Goto-Kakizaki (GK) rats, a model of type 2 diabetes mellitus. In pancreatic sections obtained from 6-wk-old GK rats, CD68-positive macrophages and glial fibrillary acidic protein- and α-smooth muscle actin-positive stellate cells infiltrated into islets. Later, the number of macrophages was increased, and the α-smooth muscle actin staining of stellate cells became stronger, indicating the involvement of stellate cells in islet fibrosis in GK rats. When CnP was administered orally for 4 wk, starting from 6 wk of age, invasion of stellate cells and macrophages was markedly reduced and islet fibrosis was significantly improved. The insulin content was twice as high in CnP-treated rats. These results indicate that CnP exerts antifibrotic actions both in vitro and in vivo and improves islet fibrosis in Goto-Kakizaki rats.

Aberrant signaling pathways in pancreatic cancer: a two compartment view

Pancreatic cancer is a devastating disease with historically limited success in treatment and a poor prognosis. Pancreatic cancer appears to have a progressive pathway of development, initiating from well-described pancreatic intraepithelial neoplasia lesions and concluding with invasive carcinoma. These early lesions have been shown to harbor-specific alterations in signaling pathways that remain throughout this tumorigenesis process. Meanwhile, new alterations occur during this process of disease progression to have a cumulative effect. This series of events not only impacts the epithelial cells comprising the tumor, but they may also affect the surrounding stromal cells. The result is the formation of complex signaling networks of communication between the tumor epithelial cell and the stromal cell compartments to promote a permissive and cooperative environment. This article highlights some of the most common pathway aberrations involved with this disease, and how these may subsequently affect one or both cellular compartments. Consequently, furthering our understanding of these pathways in terms of their function on the tumoral epithelial and stromal compartments may prove to be crucial to the development of targeted and more successful therapies in the future.

Recruitment and activation of pancreatic stellate cells from the bone marrow in pancreatic cancer: a model of tumor-host interaction

Background and Aims

Chronic pancreatitis and pancreatic cancer are characterised by extensive stellate cell mediated fibrosis, and current therapeutic development includes targeting pancreatic cancer stroma and tumor-host interactions. Recent evidence has suggested that circulating bone marrow derived stem cells (BMDC) contribute to solid organs. We aimed to define the role of circulating haematopoietic cells in the normal and diseased pancreas.

Methods

Whole bone marrow was harvested from male β-actin-EGFP donor mice and transplanted into irradiated female recipient C57/BL6 mice. Chronic pancreatitis was induced with repeat injections of caerulein, while carcinogenesis was induced with an intrapancreatic injection of dimethylbenzanthracene (DMBA). Phenotype of engrafted donor-derived cells within the pancreas was assessed by immunohistochemistry, immunofluorescence and in situ hybridisation.

Results

GFP positive cells were visible in the exocrine pancreatic epithelia from 3 months post transplantation. These exhibited acinar morphology and were positive for amylase and peanut agglutinin. Mice administered caerulein developed chronic pancreatitis while DMBA mice exhibited precursor lesions and pancreatic cancer. No acinar cells were identified to be donor-derived upon cessation of cerulein treatment, however rare occurrences of bone marrow-derived acinar cells were observed during pancreatic regeneration. Increased recruitment of BMDC was observed within the desmoplastic stroma, contributing to the activated pancreatic stellate cell (PaSC) population in both diseases. Expression of stellate cell markers CELSR3, PBX1 and GFAP was observed in BMD cancer-associated PaSCs, however cancer-associated, but not pancreatitis-associated BMD PaSCs, expressed the cancer PaSC specific marker CELSR3.

Conclusions

This study demonstrates that BMDC can incorporate into the pancreas and adopt the differentiated state of the exocrine compartment. BMDC that contribute to the activated PaSC population in chronic pancreatitis and pancreatic cancer have different phenotypes, and may play important roles in these diseases. Further, bone marrow transplantation may provide a useful model for the study of tumor-host interactions in cancer and pancreatitis.

Ion channels and transporters in cancer. 3. Ion channels in the tumor cell-microenvironment cross talk

The traditional view of cancer as a collection of proliferating cells must be reconsidered, and cancer must be viewed as a “tissue” constituted by both transformed cells and a heterogeneous microenvironment, that tumor cells construct and remodel during multistep tumorigenesis. The “tumor microenvironment” (TM) is formed by mesenchymal, endothelial, and immune cells immersed in a network of extracellular matrix (ECM) proteins and soluble factors. The TM strongly contributes to tumor progression, through long distance, cell-to-cell or cell-to-matrix signals, which influence different aspects of tumor cell behavior. Understanding the relationships among the different components of the cancer tissue is crucial to design and develop new therapeutic strategies. Ion channels are emerging as relevant players in the cross talk between tumor cells and their TM. Ion channels are expressed on tumor cells, as well as in the different cellular components of the TM. In all these cells, ion channels are in a strategic position to sense and transmit extracellular signals into the intracellular machinery. Often, this transmission is mediated by integrin adhesion receptors, which can be functional partners of ion channels since they form molecular complexes with the channel protein in the context of the plasma membrane. The same relevant role is exerted by ion transporters, which also contribute to determine two facets of the cancer tissue: hypoxia and the acidic extracellular pH. On the whole, it is conceivable to prospect the targeting of ion channels for new therapeutic strategies aimed at better controlling the malignant progression of the cancer tissue.

MT1-MMP cooperates with Kras(G12D) to promote pancreatic fibrosis through increased TGF-β signaling

Pancreatic cancer is associated with a pronounced fibrotic reaction that was recently shown to limit delivery of chemotherapy. To identify potential therapeutic targets to overcome this fibrosis, we examined the interplay between fibrosis and the key proteinase membrane type 1-matrix metalloproteinase (MT1-MMP, MMP-14), which is required for growth and invasion in the collagen-rich microenvironment. In this article, we show that compared with control mice (Kras(+)/MT1-MMP(-)) that express an activating Kras(G12D) mutation necessary for pancreatic cancer development, littermate mice that express both MT1-MMP and Kras(G12D) (Kras(+)/MT1-MMP(+)) developed a greater number of large, dysplastic mucin-containing papillary lesions. These lesions were associated with a significant amount of surrounding fibrosis, increased α-smooth muscle actin (+) cells in the stroma, indicative of activated myofibroblasts, and increased Smad2 phosphorylation. To further understand how MT1-MMP promotes fibrosis, we established an in vitro model to examine the effect of expressing MT1-MMP in pancreatic ductal adenocarcinoma (PDAC) cells on stellate cell collagen deposition. Conditioned media from MT1-MMP-expressing PDAC cells grown in three-dimensional collagen enhanced Smad2 nuclear translocation, promoted Smad2 phosphorylation, and increased collagen production by stellate cells. Inhibiting the activity or expression of the TGF-β type I receptor in stellate cells attenuated MT1-MMP conditioned medium-induced collagen expression by stellate cells. In addition, a function-blocking anti-TGF-β antibody also inhibited MT1-MMP conditioned medium-induced collagen expression in stellate cells. Overall, we show that the bona fide collagenase MT1-MMP paradoxically contributes to fibrosis by increasing TGF-β signaling and that targeting MT1-MMP may thus help to mitigate fibrosis.

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.

Phenotypic changes in mouse pancreatic stellate cell Ca2+ signaling events following activation in culture and in a disease model of pancreatitis

The specific characteristics of intracellular Ca 2+ signaling and the downstream consequences of these events were investigated in mouse pancreatic stellate cells (PSC) in culture and in situ using multiphoton microscopy in pancreatic lobules. PSC undergo a phenotypic transformation from a quiescent state to a myofibroblast-like phenotype in culture. This is believed to parallel the induction of an activated state observed in pancreatic disease such as chronic pancreatitis and pancreatic cancer. By day 7 in culture, the complement of cell surface receptors coupled to intracellular Ca 2+ signaling was shown to be markedly altered. Specifically, protease-activated receptors (PAR) 1 and 2, responsive to thrombin and trypsin, respectively, and platelet-derived growth factor (PDGF) receptors were expressed only in activated PSC (aPSC). PAR-1, ATP, and PDGF receptor activation resulted in prominent nuclear Ca 2+ signals. Nuclear Ca 2+ signals and aPSC proliferation were abolished by expression of parvalbumin targeted to the nucleus. In pancreatic lobules, PSC responded to agonists consistent with the presence of only quiescent PSC. aPSC were observed following induction of experimental pancreatitis. In contrast, in a mouse model of pancreatic disease harboring elevated K-Ras activity in acinar cells, aPSC were present under control conditions and their number greatly increased following induction of pancreatitis. These data are consistent with nuclear Ca 2+ signaling generated by agents such as trypsin and thrombin, likely present in the pancreas in disease states, resulting in proliferation of "primed" aPSC to contribute to the severity of pancreatic disease.

Pancreatic stellate cells radioprotect pancreatic cancer cells through β1-integrin signaling

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a strong desmoplastic reaction where the stromal compartment often accounts for more than half of the tumor volume. Pancreatic stellate cells (PSC) are a central mediator of desmoplasia. There is increasing evidence that desmoplasia is contributing to the poor therapeutic response of PDAC. We show that PSCs promote radioprotection and stimulate proliferation in pancreatic cancer cells (PCC) in direct coculture. Our in vivo studies show PSC-dependent radioprotection in response to a single dose and to fractionated radiation. Abrogating β1-integrin signaling abolishes the PSC-mediated radioprotection in PCCs. Furthermore, this effect is independent of PI3K (phosphoinositide 3-kinase) but dependent on FAK. Taken together, we show for the first time that PSCs promote radioprotection of PCCs in a β1-integrin-dependent manner.

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.

Studies on mechanisms of interferon-gamma action in pancreatic cancer using a data-driven and model-based approach

Background

Interferon-gamma (IFNγ) is a multifunctional cytokine with antifibrotic and antiproliferative efficiency. We previously found that pancreatic stellate cells (PSC), the main effector cells in cancer-associated fibrosis, are targets of IFNγ action in the pancreas. Applying a combined experimental and computational approach, we have demonstrated a pivotal role of STAT1 in IFNγ signaling in PSC. Using in vivo and in vitro models of pancreatic cancer, we have now studied IFNγ effects on the tumor cells themselves. We hypothesize that IFNγ inhibits tumor progression through two mechanisms, reduction of fibrogenesis and antiproliferative effects on the tumor cells. To elucidate the molecular action of IFNγ, we have established a mathematical model of STAT1 activation and combined experimental studies with computer simulations.

Results

In BALB/c-nu/nu mice, flank tumors composed of DSL-6A/C1 pancreatic cancer cells and PSC grew faster than pure DSL-6A/C1 cell tumors. IFNγ inhibited the growth of both types of tumors to a similar degree. Since the stroma reaction typically reduces the efficiency of therapeutic agents, these data suggested that IFNγ may retain its antitumor efficiency in PSC-containing tumors by targeting the stellate cells. Studies with cocultures of DSL-6A/C1 cells and PSC revealed a modest antiproliferative effect of IFNγ under serum-free conditions. Immunoblot analysis of STAT1 phosphorylation and confocal microscopy studies on the nuclear translocation of STAT1 in DSL-6A/C1 cells suggested that IFNγ-induced activation of the transcription factor was weaker than in PSC. The mathematical model not only reproduced the experimental data, but also underscored the conclusions drawn from the experiments by indicating that a maximum of 1/500 of total STAT1 is located as phosphorylated STAT1 in the nucleus upon IFNγ treatment of the tumor cells.

Conclusions

IFNγ is equally effective in DSL-6A/C1 tumors with and without stellate cells. While its action in the presence of PSC may be explained by inhibition of fibrogenesis, its efficiency in PSC-free tumors is unlikely to be caused by direct effects on the tumor cells alone but may involve inhibitory effects on local stroma cells as well. To gain further insights, we also plan to apply computer simulations to the analysis of tumor growth in vivo.

Hypoxia induced tumor metabolic switch contributes to pancreatic cancer aggressiveness

Pancreatic ductal adenocarcinoma remains one of the most lethal of all solid tumors with an overall five-year survival rate of only 3-5%. Its aggressive biology and resistance to conventional and targeted therapeutic agents lead to a typical clinical presentation of incurable disease once diagnosed. The disease is characterized by the presence of a dense stroma of fibroblasts and inflammatory cells, termed desmoplasia, which limits the oxygen diffusion in the organ, creating a strong hypoxic environment within the tumor. In this review, we argue that hypoxia is responsible for the highly aggressive and metastatic characteristics of this tumor and drives pancreatic cancer cells to oncogenic and metabolic changes facilitating their proliferation. However, the molecular changes leading to metabolic adaptations of pancreatic cancer cells remain unclear. Cachexia is a hallmark of this disease and illustrates that this cancer is a real metabolic disease. Hence, this tumor must harbor metabolic pathways which are probably tied in a complex inter-organ dialog during the development of this cancer. Such a hypothesis would better explain how under fuel source limitation, pancreatic cancer cells are maintained, show a growth advantage, and develop metastasis.

Contribution of epithelial-mesenchymal transition to pancreatic cancer progression

Pancreatic adenocarcinoma (PDAC) is one of the most lethal human malignancies, with median survival of less than one year and overall five-year survival of less than 5%. There is increasing evidence demonstrating that epithelial-mesenchymal transition (EMT) contributes to pancreatic cancer metastasis and to treatment resistance. In this review, we will examine the data demonstrating the role and regulation of EMT in pancreatic cancer progression, focusing particularly on the transcription factors and microRNAs involved in EMT. We will examine how EMT is involved in the generation and maintenance of stem cells, and the role of EMT in modulating resistance of PDAC cells to drug therapies. We will also identify putative EMT-targeting agents that may help to reduce the morbidity and mortality associated with pancreatic cancer.

Pancreatic stellate cells promote epithelial-mesenchymal transition in pancreatic cancer cells

The interaction between pancreatic cancer cells and pancreatic stellate cells (PSCs), a major profibrogenic cell type in the pancreas, is receiving increasing attention. There is accumulating evidence that PSCs promote the progression of pancreatic cancer by increasing cancer cell proliferation and invasion as well as by protecting them from radiation- and gemcitabine-induced apoptosis. Because epithelial-mesenchymal transition (EMT) plays a critical role in the progression of pancreatic cancer, we hypothesized that PSCs promote EMT in pancreatic cancer cells. Panc-1 and SUIT-2 pancreatic cancer cells were indirectly co-cultured with human PSCs isolated from patients undergoing operation for pancreatic cancer. The expression of epithelial and mesenchymal markers was examined by real-time PCR and immunofluorescent staining. The migration of pancreatic cancer cells was examined by scratch and two-chamber assays. Pancreatic cancer cells co-cultured with PSCs showed loose cell contacts and a scattered, fibroblast-like appearance. The expression of E-cadherin, cytokeratin 19, and membrane-associated β-catenin was decreased, whereas vimentin and Snail (Snai-1) expression was increased more in cancer cells co-cultured with PSCs than in mono-cultured cells. The migration of pancreatic cancer cells was increased by co-culture with PSCs. The PSC-induced decrease of E-cadherin expression was not altered by treatment with anti-TGF-β-neutralizing antibody, excluding a central role of TGF-β in this process. In conclusion, PSCs promoted EMT in pancreatic cancer cells suggesting a novel mechanism by which PSCs contribute to the aggressive behavior of pancreatic cancer cells.

Hepatic stellate cells accelerate the malignant behavior of cholangiocarcinoma cells

BACKGROUND

Although tumor-stromal interaction has been discussed, the role of hepatic stellate (HS) cells against cancer, especially cholangiocarcinoma (CC), has not been clarified. The aim of this study is to investigate the effect of HS cells on CC cell progression in vitro and in vivo.

METHODS

The effects of CC conditioned medium (CC-CM) on activation and proliferation of HS cells (LI90 and LX-2), the influences of HS cell CM (HS-CM) on proliferation and invasion of CC cells (HuCCT-1 and RBE), and the effects of their interaction on HUVEC tube formation were assessed using each CM. The effect of HS cells on tumor growth was examined in vivo by subcutaneous co-injection. Cytokine array was performed to assess the secreted proteins induced by their coculture.

RESULTS

CC-CM activated HS cells and increased their proliferation. HS-CM dose-dependently increased CC cell proliferation and invasion. Chemotherapy of CC cells was less effective when treated with HS-CM. HS-CM activated the mitogen-activated protein kinase and Akt pathways in tumor cells. The indirect interaction of CC and HS cells promotes tube formation of human umbilical venous endothelial cells. Subcutaneous co-injection of tumor cells with HS cells in nude mouse resulted in increased tumor size. Several proteins were found in the culture medium induced by their coculture, thought to be key proteins which regulated tumor-stromal interaction.

CONCLUSIONS

This study indicates that HS cells play an important role in accelerating cholangiocarcinoma progression and may be a therapeutic target in cholangiocarcinoma.

alpha-Smooth Muscle Actin Expressing Stroma Promotes an Aggressive Tumor Biology in Pancreatic Ductal Adenocarcinoma

OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is often characterized by a prominent desmoplastic stroma that is induced partially by alpha-smooth muscle actin (SMA)-expressing activated pancreatic stellate cells (PSCs). This study aimed to investigate the significance of alpha-SMA expression in PDAC and the correlation between alpha-SMA mRNA levels and the patient prognosis. METHODS: We obtained formalin-fixed, paraffin-embedded tissue samples from 109 patients with PDAC, who underwent pancreatectomy at our institution from 1992 to 2007. We measured alpha-SMA mRNA levels by quantitative real-time reverse transcription-polymerase chain reaction and investigated the association of alpha-SMA mRNA expression with clinicopathologic parameters and survival time. We also assessed the influence of activated PSCs on malignant behaviors of pancreatic cancer cells using in vitro experiments. RESULTS: alpha-SMA immunoreactivity was detected exclusively in the stroma of PDAC. The group with high alpha-SMA expression showed a significantly shorter survival, as shown by univariate analysis (P = 0.005) and multivariate analysis (P < 0.0001). alpha-SMA-expressing activated PSCs enhanced the invasiveness, proliferation, and colony formation of pancreatic cancer cells. CONCLUSIONS: Quantitative analysis of alpha-SMA mRNA expression using formalin-fixed, paraffin-embedded tissue samples was useful to predict the prognosis of patients with PDAC. Activated PSCs may regulate the malignant behavior of pancreatic cancer cells.

Role of pancreatic stellate cells in pancreatic cancer metastasis

Pancreatic stellate cells (PSCs) produce the stromal reaction in pancreatic cancer (PC), and their interaction with cancer cells facilitates cancer progression. This study investigated the role of human PSCs (hPSCs) in the metastatic process and tumor angiogenesis using both in vivo (orthotopic model) and in vitro (cultured PSC and PC cells) approaches. A sex mismatch study (injection of male hPSCs plus female PC cells into the pancreas of female mice) was conducted to determine whether hPSCs accompany cancer cells to metastatic sites. Metastatic nodules were examined by fluorescent in situ hybridization for the presence of the Y chromosome. Angiogenesis was assessed by i) immunostaining tumors for CD31, an endothelial cell marker; and ii) quantifying human microvascular endothelial cell (HMEC-1) tube formation in vitro on exposure to conditioned media from hPSCs. Transendothelial migration was assessed in vitro by examining the movement of fluorescently labeled hPSCs through an endothelial cell monolayer. Human PSCs i) were found in multiple metastatic sites in each mouse injected with male hPSCs plus female PC cells; ii) increased CD31 expression in primary tumors from mice injected with MiaPaCa-2 and hPSCs and stimulated tube formation by HMEC-1 in vitro; and iii) exhibited transendothelial migration that was stimulated by cancer cells. Human PSCs accompany cancer cells to metastatic sites, stimulate angiogenesis, and are able to intravasate/extravasate to and from blood vessels.

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.

CD10+ pancreatic stellate cells enhance the progression of pancreatic cancer

BACKGROUND & AIMS

Pancreatic stellate cells (PSCs) promote the progression of pancreatic cancer by producing extracellular matrix and soluble factors. However, the functional heterogeneity of PSCs has not been identified until now. Detailed characterization of the PSCs in human pancreatic cancer would provide a set of potential targets for stroma-directed therapy.

METHODS

We isolated PSCs from fresh pancreatic ductal adenocarcinoma tissue and sorted them by flow cytometry according to cell surface expression of CD10, which is a stromal prognostic marker for various tumors. We analyzed the functional differences between CD10(+) PSCs and CD10(-) PSCs.

RESULTS

Immunohistochemical analysis showed that the frequency of CD10 expression by PSCs was markedly higher in tumor tissue than in normal tissue (33.7% vs 0%, respectively, P = .028). In pancreatic ductal adenocarcinoma, CD10 expression by PSCs was associated with positive nodal metastases (P = .011) and a shorter survival time (P < .001). In vitro coculture experiments showed that CD10(+) PSCs promoted the invasiveness of pancreatic cancer cell lines, SUIT-2 and Panc-1 cells more intensively than CD10(-) PSCs. CD10(+) PSCs significantly increased the tumor growth and invasiveness of SUIT-2 cells in a murine cotransplantation model. CD10(+) PSCs secreted higher levels of matrix metalloproteinase 3 than CD10(-) PSCs, and knockdown of matrix metalloproteinase 3 in cocultured PSCs reduced the invasion of SUIT-2 and Panc-1 cells.

CONCLUSIONS

CD10(+) PSCs enhance the progression of pancreatic cancer cells. CD10(+) PSCs may be a candidate for selective therapeutic targeting in the treatment of pancreatic cancer.

Isolation of quiescent human pancreatic stellate cells: a promising in vitro tool for studies of human pancreatic stellate cell biology

BACKGROUND

Pancreatic stellate cells (PSCs) play a critical role in pancreatic fibrosis. To date, human PSC biology has been studied using cancer- or inflammation-associated (pre-activated) PSCs, but an in vitro model of quiescent normal human PSCs (NhPSCs) has been lacking.

AIMS

To (i) isolate and characterize quiescent NhPSCs, and (ii) evaluate the response of culture-activated NhPSCs to cytokines and LPS.

METHODS

Quiescent NhPSCs were isolated from normal pancreatic tissue using density gradient centrifugation. PSC markers, glial fibrillary acidic protein (GFAP), desmin, α-smooth muscle actin (αSMA) and the lipopolysaccharide (LPS) receptors TLR4 and CD14 were identified by immunoblotting and immunocytochemistry. The effect of platelet-derived growth factor (PDGF), transforming growth factor β (TGFβ) and LPS on NhPSC activation was also assessed.

RESULTS

Freshly isolated NhPSCs displayed a polygonal appearance with refringent cytoplasmic lipid droplets. Culture-activated NhPSCs expressed GFAP, desmin, αSMA, TLR4 and CD14, and were responsive to PDGF, TGFβ and LPS.

CONCLUSION

Isolated NhPSCs expressed the same markers as rat PSCs and human cancer-associated PSCs and responded to PDGF and TGFβ similarly to rat PSCs. NhPSC preparations provide a useful in vitro tool to study the biology of PSCs in their physiological, non-activated state. and IAP.

Prognostic significance of PINCH signalling in human pancreatic ductal adenocarcinoma

OBJECTIVE

Prognostic markers for pancreatic ductal adenocarcinoma (PDA) have failed to accurately predict patient prognosis. Recently, interest has developed in the accuracy of integrin-associated PINCH protein expression in human cancers as a predictive marker of tumour status. The goal of this study was to define the expression of PINCH protein in PDA.

METHODS

Human PDA samples and orthotopic tumours from a murine model were analysed by immunohistochemistry for PINCH expression. In the animal model, PINCH expression was compared between primary and metastatic tumours. In the human samples, PINCH expression was correlated with stage, nodal involvement, margin status and overall survival.

RESULTS

In the murine model, there was greater PINCH expression in metastatic tumours than in primary tumours. In the human PDA samples, greater staining for PINCH in the tumour cells was correlated with higher T status. Additionally, high PINCH expression in the stroma was associated with decreased overall survival.

CONCLUSIONS

Findings of increased PINCH protein in more advanced stages of human PDA, as well as in metastatic tumours in the animal model, support the hypothesis that PINCH is an important controller of cell survival and migration. Additionally, the importance of the differential expression of PINCH in the human tumour and stroma warrants further evaluation.

Pancreatic stellate cells increase the invasion of human pancreatic cancer cells through the stromal cell-derived factor-1/CXCR4 axis

AIM

Both pancreatic stellate cells (PSCs) and the stromal cell-derived factor-1(SDF-1)/CXCR4 receptor ligand system have important roles in pancreatic cancer progression. This study set out to detect if PSCs express SDF-1 and promote the invasion of pancreatic cancer through the SDF-1/CXCR4 receptor ligand axis.

METHODS

RT-PCR was performed to detect the expression of SDF-1 and CXCR4 in PSCs, pancreatic cancer lines and cancer tissue samples. ELISA was used to investigate the concentration of SDF-1 in PSC supernatants. An MTT assay was applied to detect the proliferation of pancreatic cancer cells. A transwell chamber migration assay was employed to detect the migration of AsPC-1 cells. An in vitro invasion assay was used to detect the invasion of AsPC-1 cells.

RESULTS

CXCR4 expression was detected in PSCs; AsPC-1, SW1990 and BxPC-3 cancer cells; and cancer tissues. SDF-1 was detected in PSCs and cancer tissues, but not in AsPC-1, SW1990 and BxPC-3 cells. SDF-1alpha protein was found in PSC supernatants. PSC-conditioned media can promote the proliferation, migration and invasion of pancreatic cancer cells. SDF-1 neutralizing antibody or AMD3100 can significantly inhibit these promotive and IAP.

Pancreatic cancer: pathobiology, treatment options, and drug delivery

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the USA. The high mortality rate is partly due to lack of effective treatments. This review summarizes the pathobiology and current treatment options for pancreatic cancer. Moreover, the review discusses the opportunities of developing novel therapies for pancreatic cancer provided by the progress in understanding the genetic mutations, tumor microenvironment, cancer stem cells, and drug delivery.

Pancreatic stellate cells promote the invasion and migration of human pancreatic cancer Patu8988 cells

AIM: To investigate the effects of immortalized pancreatic stellate cells (IPSCs) on the invasion and migration of human pancreatic cancer Patu8988 cells.

METHODS: After Patu8988 cells were incubated with the culture supernatant of IPSCs, their growth, adherence, invasion, migration, clonogenicity and resistance to hydrogen peroxide (H2O2)-induced apoptosis were measured.

RESULTS: Compared with untreated Patu8988 cells, cell growth, adherence, invasion, migration and clonogenicity were promoted (all P < 0.05), and H2O2-induced apoptosis (P < 0.05) was inhibited in Patu8988 cells incubated with the supernatant of IPSCs.

CONCLUSION: Pancreatic stellate cells may exert an important role in the progression and metastasis of pancreatic cancer by promoting the growth, adherence, invasion, migration and clonogenicity of Patu8988 cells and inhibiting their apoptosis.

Pancreatic cancer organotypic cultures

Pancreatic cancer, the fourth most common cause of cancer-related death, is a devastating disease with poor prognosis. Over the last four decades, no effective new treatments have been developed for this cancer. As a result, its prognosis has remained unchanged. Appropriate cancer models, representing all aspects of pancreatic cancer, will enhance our understanding of its biology. In this review we discuss the evolution and merit of organotypic culture models. These co-culture in vitro systems of cancer and stromal cells grown within, or on top of, reconstituted extracellular matrix gels model pancreatic cancer more realistically than 2D systems. Different methodologies are discussed which enable interrogation of various hypotheses examining the tumour-stroma cross-talk. Thus this validated organotypic culture model provides a system, which can be easily manipulated and used to test (novel) treatment options targeting the cancer, the stromal compartment or both, in a physiologically relevant environment. The big challenge for future research is to expand this model further so that its mimicry of the human tumour is more robust. This will increase our understanding of the biology of this aggressive tumour; ultimately resulting in improved therapies and, therefore, a better prognosis.

Alcohol, signaling, and ECM turnover

Alcohol is recognized as a direct hepatotoxin, but the precise molecular pathways that are important for the initiation and progression of alcohol-induced tissue injury are not completely understood. The current understanding of alcohol toxicity to organs suggests that alcohol initiates injury by generation of oxidative and nonoxidative ethanol metabolites and via translocation of gut-derived endotoxin. These processes lead to cellular injury and stimulation of the inflammatory responses mediated through a variety of molecules. With continuing alcohol abuse, the injury progresses through impairment of tissue regeneration and extracellular matrix (ECM) turnover, leading to fibrogenesis and cirrhosis. Several cell types are involved in this process, the predominant being stellate cells, macrophages, and parenchymal cells. In response to alcohol, growth factors and cytokines activate many signaling cascades that regulate fibrogenesis. This mini-review brings together research focusing on the underlying mechanisms of alcohol-mediated injury in a number of organs. It highlights the various processes and molecules that are likely involved in inflammation, immune modulation, susceptibility to infection, ECM turnover and fibrogenesis in the liver, pancreas, and lung triggered by alcohol abuse.

Tumor-stromal interactions with direct cell contacts enhance proliferation of human pancreatic carcinoma cells

Pancreatic ductal adenocarcinoma is often characterized by an abundant desmoplastic stroma that is partially induced by activated pancreatic stellate cells (PSCs). Indirect co-culture has often been used to investigate the effects of cancer-stromal interactions on the proliferation of cancer cells, but the effects of cell-cell adhesion and juxtacrine signaling between cancer and stromal cells cannot be evaluated using this method. This study aimed to establish a simplified direct co-culture system that could be used to quantify populations of cancer cells in co-culture with PSCs, and to evaluate the effects of direct cell contact on the proliferation of cancer cells. We established three green fluorescent protein (GFP)-expressing pancreatic cancer cell lines and were able to quantify them with high reliability and reproducibility, even when co-cultured directly with PSCs, using a color plate reader. We assessed the differential effects of direct and indirect co-culture with PSCs on the proliferation of cancer cells, and found that the proliferation of GFP-expressing pancreatic cancer cell lines was dramatically enhanced by direct co-culture with PSCs, compared with the indirect co-culture system. We also found that direct co-culture of cancer cells and PSCs activated the Notch signaling pathway in both cell types. Direct cell contact between cancer cells and PSCs plays an important role in the control of cancer cell proliferation, and is essential to the understanding of tumor-stromal interactions.

Translational advances and novel therapies for pancreatic ductal adenocarcinoma: hope or hype?

Biological complexity, inaccessible anatomical location, nonspecific symptoms, lack of a screening biomarker, advanced disease at presentation and drug resistance epitomise pancreatic ductal adenocarcinoma (PDA) as a poor-prognosis, lethal disease. Twenty-five years of research (basic, translational and clinical) have barely made strides to improve survival, mainly because of a fundamental lack of knowledge of the biological processes initiating and propagating PDA. However, isolation of pancreas cancer stem cells or progenitors, whole-genome sequencing for driver mutations, advances in functional imaging, mechanistic dissection of the desmoplastic reaction and novel targeted therapies are likely to shed light on how best to treat PDA. Here we summarise current knowledge and areas where the field is advancing, and give our opinion on the research direction the field should be focusing on to better deliver promising therapies for our patients.

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.

New insights into alcoholic pancreatitis and pancreatic cancer

Pancreatitis and pancreatic cancer represent two major diseases of the exocrine pancreas. Pancreatitis exhibits both acute and chronic manifestations. The commonest causes of acute pancreatitis are gallstones and alcohol abuse; the latter is also the predominant cause of chronic pancreatitis. Recent evidence indicates that endotoxinemia, which occurs in alcoholics due to increased gut permeability, may trigger overt necroinflammation of the pancreas in alcoholics and one that may also play a critical role in progression to chronic pancreatitis (acinar atrophy and fibrosis) via activation of pancreatic stellate cells (PSCs). Chronic pancreatitis is a major risk factor for the development of pancreatic cancer, which is the fourth leading cause of cancer-related deaths in humans. Increasing attention has been paid in recent years to the role of the stroma in pancreatic cancer progression. It is now well established that PSCs play a key role in the production of cancer stroma and that they interact closely with cancer cells to create a tumor facilitatory environment that stimulates local tumor growth and distant metastasis. This review summarizes recent advances in our understanding of the pathogenesis of alcoholic pancreatitis and pancreatic cancer, with particular reference to the central role played by PSCs in both diseases. An improved knowledge of PSC biology has the potential to provide an insight into pathways that may be therapeutically targeted to inhibit PSC activation, thereby inhibiting the development of fibrosis in chronic pancreatitis and interrupting stellate cell-cancer cell interactions so as to retard cancer progression.

Transforming growth factor-beta induces nerve growth factor expression in pancreatic stellate cells by activation of the ALK-5 pathway

Nerve growth factor (NGF), a survival factor for neurons enforces pain by sensitizing nociceptors. Also in the pancreas, NGF was associated with pain and it can stimulate the proliferation of pancreatic cancer cells. Hepatic stellate cells (HSC) respond to NGF with apoptosis. Transforming growth factor (TGF)-beta, one of the strongest pro-fibrogenic activators of pancreatic stellate cells (PSC) induced NGF and its two receptors in an immortalized human cell line (ihPSC) and primary rat PSC (prPSC) as determined by RT-PCR, western blot, and immunofluorescence. In contrast to HSC, PSC expressed both NGF receptors, although p75(NTR) expression was weak in prPSC. In contrast to ihPSC TGF-beta activated both Smad signaling cascades in prPSC. NGF secretion was diminished by the activin-like kinase (ALK)-5 inhibitor SB431542, indicating the predominant role of ALK5 in activating the NGF system in PSC. While NGF did not affect proliferation or survival of PSC it induced expression of Inhibitor of Differentiation-1. We conclude that under conditions of upregulated TGF-beta, like fibrosis, NGF levels will also increase in PSC which might contribute to pancreatic wound healing responses.

Mathematical modelling of interferon-gamma signalling in pancreatic stellate cells reflects and predicts the dynamics of STAT1 pathway activity

Signal transducer and activator of transcription (STAT) 1 is essentially involved in the mediation of antifibrotic interferon-gamma (IFN gamma) effects in pancreatic stellate cells (PSC). Here, we have further analysed the activation of the STAT1 pathway in a PSC line by combining quantitative data generation with mathematical modelling. At saturating concentrations of IFN gamma, a triphasic pattern of STAT1 activation was observed. An initial, rapid induction of phospho-STAT1 was followed by a plateau phase and another, long-lasting phase of further increase. The late increase occurred despite enhanced expression of the feedback inhibitor (SOCS1), and corresponded to increased levels of total STAT1 protein. If IFN gamma was applied at non-saturating concentrations, phospho-STAT1 and SOCS1 levels peaked and declined again over a 12 hour period, while STAT1 protein levels remained high. The mathematical model, based on a system of ordinary differential equations, describes temporal changes of the network components as a function of interactions and transport processes. The model reproduced activation profiles of all components of the STAT1 pathway that were experimentally analysed. Furthermore, it successfully predicted the dynamics of network components in additional experimental studies. Based on experimental findings and the results obtained from modelling, we suggest exhaustion of applied IFN gamma and STAT1 dephosphorylation by tyrosine phosphatases as limiting factors of STAT1 activation in PSC. In contrast, we did not obtain compelling evidence that SOCS1 acts as an efficient feedback inhibitor in our experimental system. We believe that further investigations into mathematical modelling of the STAT1 pathway will improve the understanding of the antifibrotic interferon action.

Epidermal growth factor receptor regulates pancreatic fibrosis

The development of pancreatic fibrosis has been shown to be a major component in several diseases of the pancreas including pancreatic cancer, chronic pancreatitis, and type 2 diabetes mellitus, but its actual role in the progression of these disorders is still unknown. This fibrosis is characterized by stromal expansion and the excessive deposition of extracellular matrix (ECM) that replaces pancreatic tissue. This eventually leads to dysregulation of ECM turnover, production of cytokines, restriction of blood flow, and often exocrine and endocrine insufficiencies. Activated pancreatic stellate cells (PSCs) have been identified as key mediators in the progression of pancreatic fibrosis, serving as the predominant source of excess ECM proteins. Previously, we found that overexpression of the growth factor heparin-binding epidermal growth factor-like growth factor (HB-EGF) in pancreatic islets led to intraislet fibrosis. HB-EGF binds to and activates two receptors, epidermal growth factor receptor (EGFR) and ErbB4, as well as heparin moieties and CD9/DRAP27. To understand the mechanism underlying the induction of fibrogenesis by HB-EGF, we utilized a hypomorphic allele of Egfr, the Waved-2 allele, to demonstrate that EGFR signaling regulates fibrogenesis in vivo. Using an in vitro cell migration assay, we show that HB-EGF regulates both chemoattraction and stimulation of proliferation of PSCs via EGFR activation.

Hepatic stellate cells may relate to progression of intrahepatic cholangiocarcinoma

BACKGROUND

Although cumulative evidence supports the fact that stromal myofibroblasts promote tumor progression, the influence of myofibroblasts on intrahepatic cholangiocarcinoma (ICC) is unclear. We hypothesized that hepatic stellate (HS) cells can differentiate into myofibroblasts in ICC stroma and that they promote cancer progression. This study aims to: (1) assess the influence of myofibroblasts on the prognosis of ICC, (2) identify HS cells in ICC stroma, and (3) investigate the interaction between HS cells (LI90 and LX-2) and ICC cells (HuCCT-1 and MEC) in vitro.

METHODS

The association between alpha-smooth muscle actin (alpha-SMA) expression and the prognoses of 46 ICC patients after hepatic resection was evaluated by immunohistochemical analysis. The HS cells in myofibroblasts of ICC were identified (double immunostaining) using antibodies for alpha-SMA, glial fibrillary acidic protein (GFAP), and desmin. The influence of HS cells on the invasion and growth of ICC cells was examined in vitro using a coculture system.

RESULTS

Patients with high alpha-SMA expression exhibited the worse outcomes. Multivariate analyses revealed that high alpha-SMA expression (P = 0.0045) and positivity for lymph-node metastasis were independent prognostic factors. Because desmin- or GFAP-positive cells coexpressing alpha-SMA were observed in the ICC samples, they were considered to be derived from the HS cells. On coculturing with HS cells, a remarkable increase was observed in the invasion and growth of the two ICC cell lines.

CONCLUSIONS

Stromal myofibroblasts may relate to the poor prognoses in ICC patients. HS cells appear to be involved in the progression of ICC.

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.

Histopathological examination of the pancreas of the Koala (Phascolarctos cinereus)

This retrospective study, which was based on koala pancreatic specimens taken 2, 24, 48 and 72h after death, showed that the degree of autolysis did not necessarily exclude histopathological examination. Disorders not previously reported in the pancreas of koalas included the following: inflammation and necrosis; atrophy and fibrosis of exocrine pancreatic tissue; lymphosarcoma; pancreatic heterotopy; and ductal adenocarcinoma.

Establishment and characterization of 4 new human pancreatic cancer cell lines: evidences of different tumor phenotypes

OBJECTIVES

Pancreatic cancer still remains a challenge for its biological complexity and lack of effective therapeutic strategies. Establishing new pancreatic cancer cell lines is therefore of paramount importance to clarify its biology.

METHODS

We established and characterized 4 new pancreatic cancer cell lines (PP78, PP109, PP117, and PP161) according to their genetic (K-Ras, TP53, CDKN2A, and MADH4; DNA fingerprinting; karyotype), cytostructural (cytokeratins 7, 8, 18, and 19 vimentin, and ezrin), and functional profiles (doubling time; migration assay).

RESULTS

K-Ras, TP53, and CDKN2A gene alterations were detected in all 4 of them. Each cell line had a unique DNA profile revealed by DNA fingerprinting. A complex karyotype with numerous structural and numeric chromosomal abnormalities was present in each cell line. All 4 cell lines showed positivity for cytokeratins 7, 8, and 18. All but PP78 expressed cytokeratin 19, whereas vimentin was expressed only in PP117 and PP78 cells. A different ezrin cellular distribution was noticed in PP78 and PP117, being mostly located at membrane ruffles. This peculiar distribution was associated with the strongest migratory capability.

CONCLUSIONS

Our results seem to confirm the pancreatic ductal adenocarcinoma heterogeneity; in fact, the same genetic abnormalities (K-Ras, TP53, and CDKN2A) may have different effects on tumor biology depending on cellular differentiation.

Synergistic growth inhibitory effects of the dual endothelin-1 receptor antagonist bosentan on pancreatic stellate and cancer cells

Pancreatic stellate cells (PSC) play a key role in pancreatic fibrosis. Activation of PSC occurs in response to pro-fibrogenic stimuli and is maintained by autocrine loops of mediators, such as endothelin (ET)-1. Here, we have evaluated effects of the dual ET receptor antagonist bosentan in models of pancreatic fibrogenesis and cancer. Cell culture studies revealed that PSC and DSL6A pancreatic cancer cells expressed both ET-1 and ET receptors. Bosentan efficiently inhibited proliferation of both cell types and collagen synthesis in PSC. Expression of the myofibroblastic marker alpha-smooth muscle actin, connective tissue growth factor, and ET-1 itself in PSC was reduced, while expression of matrix metalloproteinase-9 was enhanced. Like PSC, DSL6A cells secrete less ET-1 when cultured with bosentan. In a rat model of pancreatic fibrosis, chronic pancreatitis induced by dibutyltin dichloride, a tendency towards a diminished disease progression was observed in a subgroup of rats with less severe disease. Together, our results indicate that bosentan exerts antifibrotic and antitumor effects in vitro. Its efficiency in vivo warrants further investigation.

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.

Pancreatic stellate cells and pancreatic cancer cells: an unholy alliance

Pancreatic cancer--a tumor displaying a particularly abundant stromal reaction--is notorious for its poor prognosis. Recent studies, via newly developed orthotopic models, provide compelling evidence of an important role for pancreatic stellate cells (PSC) in pancreatic cancer progression. Characterization of the mechanisms mediating PSC-cancer interactions will lead to the development of much needed alternative therapeutic approaches to improve disease outcome.

Progressive metaplastic and dysplastic changes in mouse pancreas induced by cyclooxygenase-2 overexpression

Cyclooxygenase-2 (COX-2) overexpression is an established factor linking chronic inflammation with metaplastic and neoplastic change in various tissues. We generated transgenic mice (BK5.COX-2) in which elevation of COX-2 and its effectors trigger a metaplasia-dysplasia sequence in exocrine pancreas. Histologic evaluation revealed a chronic pancreatitis-like state characterized by acinar-to-ductal metaplasia and a well-vascularized fibroinflammatory stroma that develops by 3 months. By 6 to 8 months, strongly dysplastic features suggestive of pancreatic ductal adenocarcinoma emerge in the metaplastic ducts. Increased proliferation, cellular atypia, and loss of normal cell/tissue organization are typical features in transgenic pancreata. Alterations in biomarkers associated with human inflammatory and neoplastic pancreatic disease were detected using immunohistochemistry. The abnormal pancreatic phenotype can be completely prevented by maintaining mice on a diet containing celecoxib, a well-characterized COX-2 inhibitor. Despite the high degree of atypia, only limited evidence of invasion to adjacent tissues was observed, with no evidence of distant metastases. However, cell lines derived from spontaneous lesions are aggressively tumorigenic when injected into syngeneic or nude mice. The progressive nature of the metaplastic/dysplastic changes observed in this model make it a valuable tool for examining the transition from chronic inflammation to neoplasia.

Imaging of primary and metastatic pancreatic cancer using a fluorophore-conjugated anti-CA19-9 antibody for surgical navigation

BACKGROUND

Despite recent surgical advances, pancreatic cancer remains the fourth leading cause of cancer-related death in the United States. This is due to inaccurate staging and difficulty in achieving negative margins at the time of pancreaticoduodenectomy. CA19-9 is a carbohydrate tumor-associated antigen found in up to 94% of pancreatic adenocarcinomas. In this study we investigate the use of a fluorophore-labeled anti-CA19-9 monoclonal antibody to improve intraoperative visualization of both primary and metastatic tumors in a mouse model of pancreatic cancer.

METHODS

A monoclonal antibody specific for CA19-9 was conjugated to a green fluorophore and delivered to tumor-bearing mice as a single intravenous (IV) dose. Intravital fluorescence imaging was used to localize tumor implants 24 h after antibody administration.

RESULTS

Using fluorescence imaging, the primary tumor was clearly visible at laparotomy, as were small metastatic implants within the liver and spleen and on the peritoneum. These tumor implants, which were nearly impossible to see using standard bright-field imaging, demonstrated clear fluorescence under LED light excitation. The fluorescence signal within the tumor tissue was maintained for over 3 weeks after a single administration of the labeled antibody. Histologic evaluation of tissue from animals treated with the conjugated anti-CA19-9 antibody likewise revealed strong staining of the tumor cells with minimal background staining of the peritumoral stroma.

CONCLUSIONS

Fluorophore-labeled anti-CA19-9 offers a novel intraoperative imaging technique for enhanced visualization of primary and metastatic tumors in pancreatic cancer when CA19-9 expression is present and may improve intraoperative staging and efficacy of resection.

Color-coded imaging of splenocyte-pancreatic cancer cell interactions in the tumor microenvironment

In spite of advances in surgical and medical care, pancreatic cancer remains a leading cause of cancer-related death in the United States. An understanding of cancer-cell interactions with host cells is critical to our ability to develop effective antitumor therapeutics for pancreatic cancer. We report here a color-coded model system for imaging cancer cell interactions with host immune cells within the native pancreas. A human pancreatic cancer cell line engineered to express green fluorescent protein (GFP) in the nucleus and red fluorescent protein (RFP) (DsRed2) in the cytoplasm was orthotopically implanted into the pancreas of a nude mouse. After 10-14 days, red or green fluorescent splenocytes from immune-competent transgenic-mouse donors expressing RFP and GFP, respectively, were delivered systemically to the pancreatic cancer-bearing nude mice. Animals were imaged after splenocyte delivery using high-resolution intravital imaging systems. At 1 day after iv injection red- or green-fluorescent spleen cells were found distributed in lung, liver, spleen and pancreas. By 4 days after cell delivery, however, the immune cells could be clearly imaged surrounding the tumor cells within the pancreas as well as collecting within lymphatic tissues such as lymph nodes and spleen. With the high-resolution intravital imaging afforded by the Olympus IV100 and OV100 systems, the interactions of the dual-colored cancer cells and the red- or green-fluorescent spleen cells could be clearly imaged in this orthotopic pancreatic cancer model. This color-coded in vivo imaging technology offers a novel approach to imaging the interactions of cancer and immune cells in the tumor microenvironment (TME).