Role of Pancreatic Stellate Cell-Derived Exosomes in Pancreatic Cancer-Related Diabetes: A Novel Hypothesis.

Pancreatic ductal adenocarcinoma (PDAC) is a devastating condition characterised by vague symptomatology and delayed diagnosis. About 30% of PDAC patients report a history of new onset diabetes, usually diagnosed within 3 years prior to the diagnosis of cancer. Thus, new onset diabetes, which is also known as pancreatic cancer-related diabetes (PCRD), could be a harbinger of PDAC. Diabetes is driven by progressive ß cell loss/dysfunction and insulin resistance, two key features that are also found in PCRD. Experimental studies suggest that PDAC cell-derived exosomes carry factors that are detrimental to ß cell function and insulin sensitivity. However, the role of stromal cells, particularly pancreatic stellate cells (PSCs), in the pathogenesis of PCRD is not known. PSCs are present around the earliest neoplastic lesions and around islets. Given that PSCs interact closely with cancer cells to drive cancer progression, it is possible that exosomal cargo from both cancer cells and PSCs plays a role in modulating ß cell function and peripheral insulin resistance. Identification of such mediators may help elucidate the mechanisms of PCRD and aid early detection of PDAC. This paper discusses the concept of a novel role of PSCs in the pathogenesis of PCRD.

Circulating tumour cells in pancreatic cancer: A systematic review and meta-analysis of clinicopathological implications.

BACKGROUND: The detection and quantification of circulating tumour cells (CTCs) in pancreatic cancer (PC) has the potential to provide prognostic information. The aim of this review was to provide an overview of the literature surrounding CTCs in PC. METHODS: A systematic literature review on CTCs in PC between 2005-2020 was performed. Data based on peripheral vein samples were used to determine the positivity rate of CTCs, their prognostic significance and their relative numbers compared to portal vein (PV) samples. RESULTS: The overall CTC detection rate in forty-four articles was 65% (95%CI: 55-75%). Detection rate for CellSearch was 26% (95%CI: 14-38%), which was lower than for both filtration and microfluidic techniques. In nine studies with >50 patients, overall survival was worse with CTC positivity (HR 1.82; 95%CI: 1.61-2.05). Five of seven studies which described PV CTC collection provided patient-level data. PV CTC yield was 7.7-fold (95%CI 1.35-43.9) that of peripheral blood. CONCLUSIONS: CTCs were detected in the peripheral circulation of most patients with PC and may be related to prognosis and disease stage. PV blood contains more CTCs than peripheral blood sampling. This review points to the maturation of techniques of CTC enrichment, and its evidence base for eventual clinical deployment.

Targeting HGF/c-MET Axis in Pancreatic Cancer.

Pancreatic cancer (pancreatic ductal adenocarcinoma (PDAC/PC)) has been an aggressive disease that is associated with early metastases. It is characterized by dense and collagenous desmoplasia/stroma, predominantly produced by pancreatic stellate cells (PSCs). PSCs interact with cancer cells as well as other stromal cells, facilitating disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells and endothelial cells. The current review discusses the role of the MET/HGF axis in tumour progression and dissemination of pancreatic cancer. Therapeutic approaches that were developed targeting either the ligand (HGF) or the receptor (c-MET) have not been shown to translate well into clinical settings. We discuss a two-pronged approach of targeting both the components of this pathway to interrupt the stromal-tumour interactions, which may represent a potential therapeutic strategy to improve outcomes in PC.

An Orthotopic Resectional Mouse Model of Pancreatic Cancer.

There is a lack of satisfactory animal models to study adjuvant and/or neoadjuvant therapy in patients being considered for surgery of pancreatic cancer (PC). To address this deficiency, we describe a mouse model involving orthotopic implantation of PC followed by distal pancreatectomy and splenectomy. The model has been demonstrated to be safe and suitably flexible for the study of various therapeutic approaches in adjuvant and neo adjuvant settings. In this model, a pancreatic tumor is first generated by implanting a mixture of human pancreatic cancer cells (luciferase-tagged AsPC-1) and human cancer associated pancreatic stellate cells into the distal pancreas of Balb/c athymic nude mice. After three weeks, the cancer is resected by re-laparotomy, distal pancreatectomy and splenectomy. In this model, bioluminescence imaging can be used to follow the progress of cancer development and effects of resection/treatments. Following resection, adjuvant therapy can be given. Alternatively, neoadjuvant treatment can be given prior to resection. Representative data from 45 mice are presented. All mice underwent successful distal pancreatectomy/splenectomy with no issues of hemostasis. A macroscopic proximal pancreatic margin greater than 5 mm was achieved in 43 (96%) mice. The technical success rate of pancreatic resection was 100%, with 0% early mortality and morbidity. None of the animals died during the week after resection. In summary, we describe a robust and reproducible technique for a surgical resection model of pancreatic cancer in mice which mimics the clinical scenario. The model may be useful for the testing of both adjuvant and neoadjuvant treatments.

Targeting the HGF/c-MET pathway in advanced pancreatic cancer: a key element of treatment that limits primary tumour growth and eliminates metastasis.

BACKGROUND: Stromal-tumour interactions facilitate pancreatic cancer (PC) progression. The hepatocyte growth factor (HGF)/c-MET pathway is upregulated in PC and mediates the interaction between cancer cells and stromal pancreatic stellate cells (PSCs). This study assessed the effect of HGF/c-MET inhibition plus gemcitabine (G) on the progression of advanced PC. METHODS: Orthotopic PC was produced by implantation of luciferase-tagged human cancer cells + human PSCs into mouse pancreas. Tumours were allowed to develop without treatment for 4 weeks. Mice were then treated for 6 weeks with one of the following: IgG, G, HGF inhibitor (Hi), c-MET inhibitor (Ci), Hi + Ci, Hi + G, Ci + G, or Hi + Ci + G. RESULTS: Bioluminescence imaging showed similar tumour sizes in all mice at the initiation of treatments. Triple therapy (Hi + Ci + G): (1) completely eliminated metastasis; (2) significantly reduced tumour size as assessed by bioluminescence and at necropsy; (3) significantly reduced proliferating cancer cell density and stem cell marker DCLK1 expression in tumours. In vitro 3D culture studies supported our in vivo findings. CONCLUSION: Even at an advanced disease stage, a two-pronged approach, targeting (a) HGF/c-MET with relevant inhibitors and (b) cancer cells with chemotherapy, completely eliminated metastasis and significantly decreased tumour growth, suggesting that this is a promising treatment approach for PC.

Pancreatic stellate cells: Aiding and abetting pancreatic cancer progression.

Tumour-stromal interactions have now been acknowledged to play a major role in pancreatic cancer (PC) progression. The abundant collagenous stroma is produced by a specific cell type in the pancreas-the pancreatic stellate cell (PSC). Pancreatic stellate cells (PSCs) are a unique resident cell type of pancreas and with a critical role in both healthy and diseased pancreas. Accumulating evidence indicates that PSCs interact closely with cancer cells as well as with other cell types of the stroma such as immune cells, endothelial cells and neuronal cells, to set up a growth permissive microenvironment for pancreatic tumours, which facilitates local tumour growth as well as distant metastasis. Consequently, recent work in the field has focused on the development of novel therapeutic approaches targeting the stroma to inhibit PC progression. Such a multi-pronged approach targeting both tumour and stromal elements of PC has been successfully applied in pre-clinical settings. The challenge now is to translate the pre-clinical findings into the clinical setting to achieve better outcomes for pancreatic cancer patients.

Targeting the HGF/c-MET pathway: stromal remodelling in pancreatic cancer.

Stromal-tumor interactions in pancreatic cancer (PC) impact on treatment outcomes. Pancreatic stellate cells (PSCs) produce the collagenous stroma of PC and interact with cancer cells to facilitate disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells. We studied the effects on PC progression of inhibiting the HGF/c-MET pathway in the presence and absence of a representative chemotherapeutic agent, gemcitabine. Using an orthotopic model of PC we have shown that "triple therapy" (inhibition of both HGF and c-MET combined with gemcitabine) resulted in the greatest reduction in tumor volume compared to each of the treatments alone or in dual combinations. Importantly, metastasis was virtually eliminated in mice receiving triple therapy. Our in vivo findings were supported by in vitro studies showing that the increase in cancer cell proliferation and migration in response to PSC secretions was significantly inhibited by the triple regimen. Our studies suggest that a combined approach, that targets tumor cells by chemotherapy while inhibiting specific pathways that mediate stromal-tumor interactions, may represent a novel therapeutic strategy to improve outcomes in PC.

Circulating pancreatic stellate (stromal) cells in pancreatic cancer-a fertile area for novel research.

Pancreatic stellate cells (PSCs) are known to play an important role in facilitating pancreatic cancer progression-both in terms of local tumour growth as well as the establishment of metastases. We have previously demonstrated that PSCs from the primary cancer seed to distant metastatic sites. We therefore hypothesise that PSCs circulate along with pancreatic cancer cells (circulating tumour cells-CTCs) to help create a growth permissive microenvironment at distant metastatic sites. This review aims to explore the concept of circulating PSCs in pancreatic cancer and suggests future directions for research in this area.

Hepatocyte growth factor inhibition: a novel therapeutic approach in pancreatic cancer.

BACKGROUND: Pancreatic stellate cells (PSCs, which produce the stroma of pancreatic cancer (PC)) interact with cancer cells to facilitate PC growth. A candidate growth factor pathway that may mediate this interaction is the HGF-c-MET pathway. METHODS: Effects of HGF inhibition (using a neutralising antibody AMG102) alone or in combination with gemcitabine were assessed (i) in vivo using an orthotopic model of PC, and (ii) in vitro using cultured PC cells (AsPC-1) and human PSCs. RESULTS: We have shown that human PSCs (hPSCs) secrete HGF but do not express the receptor c-MET, which is present predominantly on cancer cells. HGF inhibition was as effective as standard chemotherapy in inhibiting local tumour growth but was significantly more effective than gemcitabine in reducing tumour angiogenesis and metastasis. HGF inhibition has resulted in reduced metastasis; however, interestingly this antimetastatic effect was lost when combined with gemcitabine. This suggests that gemcitabine treatment selects out a subpopulation of cancer cells with increased epithelial-mesenchymal transition (EMT) and stem-cell characteristics, as supported by our findings of increased expression of EMT and stem-cell markers in tumour sections from our animal model. In vitro studies showed that hPSC secretions induced proliferation and migration, but inhibited apoptosis, of cancer cells. These effects were countered by pretreatment of hPSC secretions with a HGF-neutralising antibody but not by gemcitabine, indicating a key role for HGF in PSC-PC interactions. CONCLUSIONS: Our studies suggest that targeted therapy to inhibit stromal-tumour interactions mediated by the HGF-c-MET pathway may represent a novel therapeutic approach in PC that will require careful modelling for optimal integration with existing treatment modalities.

Key role of pancreatic stellate cells in pancreatic cancer.

Pancreatic stellate cells (PSCs) are responsible for producing the collagenous stroma in pancreatic cancer. Findings from the majority of in vitro and in vivo studies to date indicate that PSCs interact with cancer cells as well as with other cellular elements in the stroma including immune cells, endothelial cells and neuronal cells to set up a growth permissive microenvironment for pancreatic tumours. However, two recent studies reporting a protective effect of myofibroblasts in pancreatic cancer have served to remind researchers of the possibility that the role of PSCs in this disease may be context and time-dependent, such that any possible early protective role of PSCs is subverted in later stages by the ability of cancer cells to turn PSCs into cancer-promoting aides. This concept is supported by the development in recent years of several novel therapeutic approaches targeting the stroma that have been successfully applied in pre-clinical settings to inhibit disease progression. A multi-pronged approach aimed at tumour cells as well as stromal elements may be the key to achieving better clinical outcomes in patients with pancreatic cancer.

Alcohol and cigarette smoke components activate human pancreatic stellate cells: implications for the progression of chronic pancreatitis.

BACKGROUND: Chronic pancreatitis, a known complication of alcohol abuse, is characterized histopathologically by prominent fibrosis. Pancreatic stellate cells (PSCs) are responsible for producing this fibrous tissue in chronic pancreatitis and are activated by alcohol. Progression of alcoholic chronic pancreatitis (as assessed by calcification and fibrosis) is thought to be facilitated by concurrent smoking, but the mechanisms are unknown. This study aimed to (a) determine whether human PSCs (hPSCs) and rat PSCs express nicotinic acetylcholine receptors (nAChRs), which are known to bind 2 important components of cigarette smoke, namely nicotine and nicotine-derived nitrosamine ketone (NNK), and (b) examine the effects of cigarette smoke components in the presence and absence of alcohol on PSC activation in vitro. METHODS: Western blotting was used to detect the presence of nAChRs in primary cultures of PSCs. Clinically relevant concentrations of cigarette smoke components (either cigarette smoke extract [CSE], NNK, or nicotine) ± ethanol (EtOH) were used to treat primary cultures of PSCs, and stellate cell activation was assessed by cell migration, proliferation, collagen production, and apoptosis. RESULTS: We demonstrate, for the first time, that PSCs express nAChRs (isoforms α3, α7, ß, ε) and that the expression of the α7 isoform in hPSCs is induced by CSE + EtOH. We also provide novel findings that PSCs are activated by CSE and NNK (both alone and in combination with EtOH) as evidenced by an increase in cell migration and/or proliferation. Further, we demonstrate that activation of PSCs by CSE + EtOH and NNK + EtOH may be mediated via nAChRs on the cells. CONCLUSIONS: PSCs are activated by clinically relevant concentrations of cigarette smoke components (CSE and NNK), alone and in combination with EtOH. Thus, in alcoholics who smoke, progression of pancreatic fibrosis may be facilitated by the combined effects of alcohol and cigarette smoke components on hPSC behavior.

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

PURPOSE OF REVIEW: Ever since the first descriptions of methods to isolate pancreatic stellate cells (PSCs) from rodent and human pancreas 17 years ago, rapid advances have been made in our understanding of the biology of these cells and their functions in health and disease. This review updates recent literature in the field, which indicates an increasingly complex role for the cells in normal pancreas, pancreatitis and pancreatic cancer. RECENT FINDINGS: Work reported over the past 12 months includes improved methods of PSC immortalization, a role for PSCs in islet fibrosis, novel factors causing PSC activation as well as those inducing quiescence, and translational research aimed at inhibiting the facilitatory effects of PSCs on disease progression in chronic pancreatitis as well as pancreatic cancer. SUMMARY: Improved understanding of the role of PSCs in pancreatic pathophysiology has prompted a focus on translational studies aimed at developing novel approaches to modulate PSC function in a bid to improve clinical outcomes of two major fibrotic diseases of the pancreas: chronic pancreatitis and pancreatic cancer.

The role of the hepatocyte growth factor/c-MET pathway in pancreatic stellate cell-endothelial cell interactions: antiangiogenic implications in pancreatic cancer.

Activated cancer-associated human pancreatic stellate cells (CAhPSCs, which produce the collagenous stroma of pancreatic cancer [PC]) are known to play a major role in PC progression. Apart from inducing cancer cell proliferation and migration, CAhPSCs have also been implicated in neoangiogenesis in PC. However, the mechanisms mediating the observed angiogenic effects of CAhPSCs are unknown. A candidate pathway that may be involved in this process is the hepatocyte growth factor (HGF)/c-MET pathway and its helper molecule, urokinase-type plasminogen activator (uPA). This study investigated the effects of CAhPSC secretions on endothelial cell function in the presence and absence of HGF, c-MET and uPA inhibitors. HGF levels in CAhPSC secretions were quantified using ELISA. CAhPSC secretions were then incubated with human microvascular endothelial cells (HMEC-1) and angiogenesis assessed by quantifying HMEC-1 tube formation and proliferation. CAhPSC-secreted HGF significantly increased HMEC-1 tube formation and proliferation; notably, these effects were downregulated by inhibition of HGF, its receptor c-MET and uPA. Phosphorylation of p38 mitogen-activated protein kinase was downregulated during inhibition of the HGF/c-MET pathway, whereas phosphatidylinositol-3 kinase and ERK1/2 remained unaffected. Our studies have shown for the first time that CAhPSCs induce proliferation and tube formation of HMEC-1 and that the HGF/c-MET pathway plays a major role in this induction. Given that standard antiangiogenic treatment targeting vascular endothelial growth factor has had limited success in the clinical setting, the findings of the current study provide strong support for a novel, alternative antiangiogenic approach targeting the HGF/c-MET and uPA pathways in PC.

Stars and stripes in pancreatic cancer: role of stellate cells and stroma in cancer progression.

Pancreatic cancer is a devastating disease with an unacceptably high mortality to incidence ratio. Traditional therapeutic approaches such as surgery in combination with chemo- or radiotherapy have had limited efficacy in improving the outcome of this disease. Up until just under a decade ago, the prominent desmoplastic reaction which is a characteristic of the majority of pancreatic ductal adenocarcinomas (PDAC) had been largely ignored. However, since the identification of the pancreatic stellate cell (PSC) as the key cell responsible for the production of the collagenous stroma in PDAC, increasing attention has been paid to the role of the stromal reaction in pancreatic cancer pathobiology. There is now compelling evidence that PSCs interact not only with cancer cells themselves, but with several other cell types in the stroma (endothelial cells, immune cells, and possibly neuronal cells) to promote cancer progression. This review summarizes current knowledge in the field about the influence of PSCs and the stromal microenvironment on cancer behavior and discusses novel therapeutic approaches which reflect an increasing awareness amongst clinicians and researchers that targeting cancer cells alone is no longer sufficient to improve patient outcome and that combinatorial treatments targeting the stroma as well as the cancer cells will be required to change the clinical course of this disease.

Extracellular matrix composition significantly influences pancreatic stellate cell gene expression pattern: role of transgelin in PSC function.

Activated pancreatic stellate cells (PSCs) are responsible for the fibrotic matrix of chronic pancreatitis and pancreatic cancer. In vitro protocols examining PSC biology have usually involved PSCs cultured on plastic, a nonphysiological surface. However, PSCs cultured on physiological matrices, e.g., Matrigel (normal basement membrane) and collagen (fibrotic pancreas), may have distinctly different behaviors compared with cells cultured on plastic. Therefore, we aimed to 1) compare PSC gene expression after culture on plastic, Matrigel, and collagen I; 2) validate the gene array data for transgelin, the most highly dysregulated gene in PSCs grown on activating vs. nonactivating matrices, at mRNA and protein levels; 3) examine the role of transgelin in PSC function; and 4) assess transgelin expression in human chronic pancreatitis sections. Culture of PSCs on different matrices significantly affected their gene expression pattern. 146, 619, and 432 genes, respectively, were differentially expressed (P < 0.001) in PSCs cultured on collagen I vs. Matrigel, Matrigel vs. plastic, and collagen I vs. plastic. The highest fold change (12.5-fold upregulation) in gene expression in cells on collagen I vs. Matrigel was observed for transgelin (an actin stress fiber-associated protein). Transgelin was significantly increased in activated PSCs vs. quiescent PSCs. Silencing transgelin expression decreased PSC proliferation and also reduced platelet-derived growth factor-induced PSC migration. Notably, transgelin was highly expressed in chronic pancreatitis in stromal areas and periacinar spaces but was absent in acinar cells. These findings suggest that transgelin is a potentially useful target protein to modulate PSC function so as to ameliorate pancreatic fibrosis.

Pancreatic stellate cells: a starring role in normal and diseased pancreas.

While the morphology and function of cells of the exocrine and endocrine pancreas have been studied over several centuries, one important cell type in the gland, the pancreatic stellate cell (PSC), had remained undiscovered until as recently as 20 years ago. Even after its first description in 1982, it was to be another 16 years before its biology could begin to be studied, because it was only in 1998 that methods were developed to isolate and culture PSCs from rodent and human pancreas. PSCs are now known to play a critical role in pancreatic fibrosis, a consistent histological feature of two major diseases of the pancreas-chronic pancreatitis and pancreatic cancer. In health, PSCs maintain normal tissue architecture via regulation of the synthesis and degradation of extracellular matrix (ECM) proteins. Recent studies have also implied other functions for PSCs as progenitor cells, immune cells or intermediaries in exocrine pancreatic secretion in humans. During pancreatic injury, PSCs transform from their quiescent phase into an activated, myofibroblast-like phenotype that secretes excessive amounts of ECM proteins leading to the fibrosis of chronic pancreatitis and pancreatic cancer. An ever increasing number of factors that stimulate and/or inhibit PSC activation via paracrine and autocrine pathways are being identified and characterized. It is also now established that PSCs interact closely with pancreatic cancer cells to facilitate cancer progression. Based on these findings, several therapeutic strategies have been examined in experimental models of chronic pancreatitis as well as pancreatic cancer, in a bid to inhibit/retard PSC activation and thereby alleviate chronic pancreatitis or reduce tumor growth in pancreatic cancer. The challenge that remains is to translate these pre-clinical developments into clinically applicable treatments for patients with chronic pancreatitis and pancreatic cancer.

Withdrawal of alcohol promotes regression while continued alcohol intake promotes persistence of LPS-induced pancreatic injury in alcohol-fed rats.

BACKGROUND AND AIMS: Administration of repeated lipopolysaccharide (LPS) injections in alcohol-fed rats leads to significant pancreatic injury including fibrosis. However, it remains unknown whether alcoholic (chronic) pancreatitis has the potential to regress when alcohol is withdrawn. The aims of the study were (1) to compare the effect of alcohol withdrawal/continuation on pancreatic acute injury and fibrosis; and (2) to assess the effects of alcohol ± LPS on pancreatic stellate cell (PSC) apoptosis in vivo and in vitro. METHODS: Rats fed isocaloric Liebere-De-Carli liquid diets ± alcohol for 10 weeks were challenged with LPS (3 mg/kg/week for 3 weeks) and then either switched to control diet or maintained on an alcohol diet for 3 days, 7 days or 3 weeks. Pancreatic sections were assessed for acute tissue injury, fibrosis, PSC apoptosis and activation. Cultured rat PSCs were exposed to 10 mM ethanol 6 1 mg/ml LPS for 48 or 72 h and apoptosis was assessed (Annexin V, caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)). RESULTS: Withdrawal of alcohol led to resolution of pancreatic lesions including fibrosis and to increased PSC apoptosis. Continued alcohol administration perpetuated pancreatic injury and prevented PSC apoptosis. Alcohol and LPS significantly inhibited PSC apoptosis in vitro, and the effect of LPS on PSC apoptosis could be blocked by Toll-like receptor 4 small interfering RNA. CONCLUSIONS: Induction of PSC apoptosis upon alcohol withdrawal is a key mechanism mediating the resolution of pancreatic fibrosis. Conversely, continued alcohol intake perpetuates pancreatic injury by inhibiting apoptosis and promoting activation of PSCs. Characterisation of the pathways mediating PSC apoptosis has the potential to yield novel therapeutic strategies for chronic pancreatitis.

Mechanisms of alcoholic pancreatitis.

Alcoholic pancreatitis is a major complication of alcohol abuse. The risk of developing pancreatitis increases with increasing doses of alcohol, suggesting that alcohol exerts dose-related toxic effects on the pancreas. However, it is also clear that only a minority of alcoholics develop the disease, indicating that an additional trigger may be required to initiate clinically evident pancreatic injury. It is now well established that alcohol is metabolized by the pancreas via both oxidative and non-oxidative metabolites. Alcohol and its metabolites produce changes in the acinar cells, which may promote premature intracellular digestive enzyme activation thereby predisposing the gland to autodigestive injury. Pancreatic stellate cells (PSCs) are activated directly by alcohol and its metabolites and also by cytokines and growth factors released during alcohol-induced pancreatic necroinflammation. Activated PSCs are the key cells responsible for producing the fibrosis of alcoholic chronic pancreatitis. Efforts to identify clinically relevant factors that may explain the susceptibility of some alcoholics to pancreatitis have been underway for several years. An unequivocal, functionally characterized, association is yet to be identified in clinical studies, although in the experimental setting, endotoxin has been shown to trigger overt pancreatic injury and to promote disease progression in alcohol-fed animals. Thus, while the molecular effects of alcohol on the pancreas have been increasingly clarified in recent years, identification of predisposing or triggering factors remains a challenge.

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.