Myofibroblasts are responsible for the desmoplastic reaction surrounding human pancreatic carcinomas

Dynamic mast cell-stromal cell interactions promote growth of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) exists in a complex desmoplastic microenvironment, which includes cancer-associated fibroblasts [also known as pancreatic stellate cells (PSC)] and immune cells that provide a fibrotic niche that impedes successful cancer therapy. We have found that mast cells are essential for PDAC tumorigenesis. Whether mast cells contribute to the growth of PDAC and/or PSCs is unknown. Here, we tested the hypothesis that mast cells contribute to the growth of PSCs and tumor cells, thus contributing to PDAC development. Tumor cells promoted mast cell migration. Both tumor cells and PSCs stimulated mast cell activation. Conversely, mast cell-derived interleukin (IL)-13 and tryptase stimulated PSC proliferation. Treating tumor-bearing mice with agents that block mast cell migration and function depressed PDAC growth. Our findings suggest that mast cells exacerbate the cellular and extracellular dynamics of the tumor microenvironment found in PDAC. Therefore, targeting mast cells may inhibit stromal formation and improve therapy.

Triggering the landslide: The tumor-promotional effects of myofibroblasts

Cancers become significantly more dangerous when the tumor progresses from in situ, or contained, to an invasive state, in which the cancer cells acquire the ability to pass through the surrounding basement membrane (BM), a specialized extracellular matrix (ECM) that provides structure and contextual information to the underlying tissue. While the majority of tumors are carcinomas, derived from epithelial cells, it is the stromal cells surrounding the epithelial-derived tumor cells, including fibroblasts and myofibroblasts, vasculature, and immune cells, that are largely responsible for the production and remodeling of the ECM. Here, we will discuss myofibroblasts as key effectors of tumor progression, focusing on recent advances in breast and pancreatic carcinoma, showing how myofibroblasts may function properly in normal tissue remodeling and wound-healing processes, how in the tumor context they can drive cancer invasion and metastasis, and how the pathogenic functions of myofibroblasts may be targeted therapeutically.

Therapeutic potential of perineural invasion, hypoxia and desmoplasia in pancreatic cancer

Pancreatic cancer is one of the most fatal human malignancies. Though a relatively rare malignancy, it remains one of the deadliest tumors, with an extremely high mortality rate. The prognosis of patients with pancreatic cancer remains poor; only patients with small tumors and complete resection have a chance of a complete cure. Pancreatic cancer responds poorly to conventional therapies, including chemotherapy and irradiation. Tumor-specific targeted therapy is a relatively recent addition to the arsenal of anti-cancer therapies. It is important to find novel targets to distinguish tumor cells from their normal counterparts in therapeutic approaches. In the past few decades, studies have revealed the molecular mechanisms of pancreatic tumorigenesis, growth, invasion and metastasis. The proteins that participate in the pathophysiological processes of pancreatic cancer might be potential targets for therapy. This review describes the main players in perineural invasion, hypoxia and desmoplasia and the molecular mechanisms of these pathophysiological processes.

Peritumoral stromal remodeling, pattern of invasion and expression of c-met/HGF in advanced squamous cell carcinoma of the cervix uteri, FIGO stages III and IV

OBJECTIVE

Different patterns of invasion (PIs) have prognostic impact in several types of cancer and are associated with different grades of peritumoral stromal remodeling, characterized by the desmoplastic stromal response (DSR). One key regulator influencing cellular motility and peritumoral stromal response is c-met/HGF. This study evaluates the association between different PI, peritumoral DSR and its correlation to the expression of c-met/HGF in squamous cell carcinomas of the uterine cervix (CX).

STUDY DESIGN

131 advanced stage CX (FIGO III/IV) were re-evaluated histologically regarding PI, using a two-level scoring system. The tumor grows in solid cords/trabeculae in finger-like PI and in very small groups or single cells in spray-like PI. DSR was categorized as none/weak and moderate/strong. The tumors were stained with antibodies against c-met and HGF. The staining of >30% of tumor cells was defined as overexpression. The PI was correlated to the prognostic outcome, different categories of DSR and expression status of c-met and HGF.

RESULTS

66.4% of the tumors showed a finger-like, and 33.6% a spray-like PI. The spray-like PI showed a reduced two-year overall survival when compared to the finger-like PI (14.0% vs. 29.1%, respectively; p=0.012), and was associated with moderate/strong DSR. The majority of the tumors showed overexpression of c-met (85.4%) and HGF (74.8%). There was no correlation between the expression status of c-met/HGF and the FIGO stage, peritumoral DSR or the prognostic outcome.

CONCLUSIONS

Spray-like PI is of prognostic impact in cervical carcinoma FIGO III/IV and is associated with strong peritumoral stromal remodeling. There is no prognostic impact of the immunohistochemical expression of c-met/HGF in advanced stage cervical carcinomas.

Biochemical role of the collagen-rich tumour microenvironment in pancreatic cancer progression

PDAC (pancreatic ductal adenocarcinoma) is among the most deadly of human malignances. A hallmark of the disease is a pronounced collagen-rich fibrotic extracellular matrix known as the desmoplastic reaction. Intriguingly, it is precisely these areas of fibrosis in which human PDAC tumours demonstrate increased expression of a key collagenase, MT1-MMP [membrane-type 1 MMP (matrix metalloproteinase); also known as MMP-14]. Furthermore, a cytokine known to mediate fibrosis in vivo, TGF-β1 (transforming growth factor-β1), is up-regulated in human PDAC tumours and can promote MT1-MMP expression. In the present review, we examine the regulation of PDAC progression through the interplay between type I collagen (the most common extracellular matrix present in human PDAC tumours), MT1-MMP and TGF-β1. Specifically, we examine the way in which signalling events through these pathways mediates invasion, regulates microRNAs and contributes to chemoresistance.

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.

Emerging pathways and future targets for the molecular therapy of pancreatic cancer

INTRODUCTION

Pancreatic cancer treatment remains a challenge for clinicians and researchers. Despite undisputable advances in the comprehension of the molecular mechanisms underlying cancer development and progression, early disease detection and clinical management of patients has made little, if any, progress in the past 20 years. Clinical development of targeted agents directed against validated pathways, such as the EGF/EGF receptor axis, the mutant KRAS protein, MMPs, and VEGF-mediated angiogenesis, alone or in combination with gemcitabine-based standard chemotherapy, has been disappointing.

AREAS COVERED

This review explores the preclinical rationale for clinical approaches aimed at targeting the TGF-β, IGF, Hedgehog, Notch and NF-κB signaling pathways, to develop innovative therapeutic strategies for pancreatic cancer.

EXPERT OPINION

Although some of the already clinically explored approaches (particularly EGFR and KRAS targeting) deserve further clinical consideration, by employing more innovative and creative clinical trial designs than the gemcitabine-targeted agent paradigm that has thus far invariably failed, the targeting of emerging and relatively unexplored signaling pathways holds great promise to increase our understanding of the complex molecular biology and to advance the clinical management of pancreatic cancer.

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.

Membrane drug transporters and chemoresistance in human pancreatic carcinoma

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

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 stromal myofibroblasts in invasive breast cancer: stromal expression of alpha-smooth muscle actin correlates with worse clinical outcome

BACKGROUND

Recently, the desmoplastic reaction has been implicated as having an important function in epithelial solid tumor biology. There have been no reports showing the relativity of invasive breast cancer and the desmoplastic reaction by a quantitative analysis of the myofibroblasts that were an important player in the desmoplastic reaction. The purpose of this study was to immunohistochemically investigate the correlation between the desmoplastic reaction and the clinicopathology of invasive breast cancer.

METHODS

The study included 60 patients with a known prognosis of invasive breast cancer. We quantified the expression of α-SMA as a marker of myofibroblasts in the invasive breast cancer. After staining samples for α-SMA, their expression was extracted and quantified as a relative percentage by computer-assisted image analysis.

RESULTS

There was relatively wide variation in the expression of α-SMA with the percentage of the area from 0.68 to 28.15% (mean 8.48 ± 5.40%). The metastasis group showed significantly higher α-SMA expression compared with the no metastasis group (p < 0.001). When the patients were divided into two groups according to their α-SMA expression using a cutoff point at the mean value of 8.48%, the high α-SMA group had a significantly poorer overall survival rate (p < 0.001). Multivariate analysis demonstrated that α-SMA and lymph node metastasis were identified as independent predictive factors of metastasis.

CONCLUSION

Myofibroblasts represent an important prognostic factor for invasive growth that is translated into a poor clinical prognosis for patients with invasive breast cancer.

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.

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.

Significance of stromal desmoplasia and myofibroblast appearance at the invasive front in squamous cell carcinoma of the oral cavity

BACKGROUND

Tumor invasion involves complex interactions between tumor and stromal cells. We examined the extent of connective tissue in the tumor stroma and whether myofibroblasts play a role in assisting cancer invasion and metastasis.

METHODS

Biopsy materials from 84 patients with oral squamous cell carcinoma (SCC) were used. We compared data from intrastromal collagen fibers using Azan staining, immunohistochemical identification of myofibroblasts by cytoskeletal markers, alpha-smooth muscle actin, vimentin, desmin, and clinicopathological parameters. Clinical outcome was compared by 5-year survival rate.

RESULTS

There were high levels of stromal collagen fibers in invasive tumors. Myofibroblast appearance increased with increasing tumor invasiveness. Lymph node metastasis occurred more frequently in the myofibroblast-positive group, and the survival rate was significantly poorer in this group.

CONCLUSIONS

Fibrous stroma in SCC appeared to have a desmoplastic response. However, an independent invasive mechanism may regulate the stroma, with tumor desmoplasia occurring in highly developed, invasive tumors.

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.

Bone marrow-derived progenitor cells could modulate pancreatic cancer tumorigenesis via peritumoral microenvironment in a rat model

Metaplastic tubular complexes (MTC) have been proposed as precursor lesions for pancreatic adenocarcinoma (PDAC). In this study, we investigated the potential role of bone marrow-derived progenitor cells (BMPC) in the formation of MTC and PDAC in a rat model. F344 rats defective for CD26 (dipeptidyl peptidase IV, DPPIV) expression were sublethally irradiated and received rescue bone marrow cells from wild-type F344 rats that express CD26. After confirming engraftment, recipient animals received dimethylbenzanthracene (DMBA) implantation in their pancreas. Animals were sacrificed monthly from 3 to 7 months. We observed both MTC and tumors in animals that received DMBA. These MTC were ductal complexes because they stained positive for cytokeratin but were negative for chymotrypsin and chromogranin A. Cells that expressed both CD26 and cytokeratin were rarely observed in the MTC. Cells expressing either both CD26 and CD45 or CD26 and smooth muscle actin were also found near the MTC. However, no CD26 signal was detected in the tumors. Within this model, there appeared to be no evidence supporting that BMPC turned into tumor cells directly. BMPC could modulate pancreatic cancer growth through tumor microenvironment.

Bone marrow-derived progenitor cells could modulate pancreatic cancer tumorigenesis via peritumoral microenvironment in a rat model

Metaplastic tubular complexes (MTC) have been proposed as precursor lesions for pancreatic adenocarcinoma (PDAC). In this study, we investigated the potential role of bone marrow-derived progenitor cells (BMPC) in the formation of MTC and PDAC in a rat model. F344 rats defective for CD26 (dipeptidyl peptidase IV, DPPIV) expression were sublethally irradiated and received rescue bone marrow cells from wild-type F344 rats that express CD26. After confirming engraftment, recipient animals received dimethylbenzanthracene (DMBA) implantation in their pancreas. Animals were sacrificed monthly from 3 to 7 months. We observed both MTC and tumors in animals that received DMBA. These MTC were ductal complexes because they stained positive for cytokeratin but were negative for chymotrypsin and chromogranin A. Cells that expressed both CD26 and cytokeratin were rarely observed in the MTC. Cells expressing either both CD26 and CD45 or CD26 and smooth muscle actin were also found near the MTC. However, no CD26 signal was detected in the tumors. Within this model, there appeared to be no evidence supporting that BMPC turned into tumor cells directly. BMPC could modulate pancreatic cancer growth through tumor microenvironment.

Expression of CD34, alpha-smooth muscle actin and transforming growth factor-beta1 in squamous intraepithelial lesions and squamous cell carcinoma of the cervix

This retrospective study investigated CD34, alpha-smooth muscle actin (alpha-SMA), and transforming growth factor-beta1 (TGF-beta1) expression in stromal cells of cervical intraepithelial neoplasias (CINs; n = 30), invasive cervical squamous cell carcinomas (SCCs; n = 38) and adjacent normal cervix. Normal cervix and CINs contained diffuse CD34-positive stromal cells but no alpha-SMA-positive myofibroblasts. In contrast, 34 of 38 SCCs were free of CD34-positive stromal cells and all contained alpha-SMA-positive stromal myofibroblasts; adjacent normal tissue contained CD34-positive stromal cells and no alpha-SMA-positive myofibroblasts. More intense TGF-beta1 expression was observed in SCC cells than in normal cervical epithelium or CINs. This study shows that the disappearance of CD34-positive stromal cells and appearance of alpha-SMA-positive stromal myofibroblasts may be associated with transformation of cervical CIN to SCC. These findings support the suggestion that over-production of TGF-beta1 in SCC cells is one potential mechanism mediating the transformation of stromal cells to myofibroblasts in cervical carcinogenesis.

Up-regulation of L1CAM in pancreatic duct cells is transforming growth factor beta1- and slug-dependent: role in malignant transformation of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is thought to originate from ductal structures, exhibiting strong desmoplastic reaction with stromal pancreatic myofibroblasts (PMF), which are supposed to drive PDAC tumorigenesis. Previously, we observed high expression of the adhesion molecule L1CAM (CD171) in PDAC cells accounting for chemoresistance. Thus, this study aimed to investigate whether PMFs are involved in the induction of tumoral L1CAM and whether this contributes to malignant transformation of pancreatic ductal cells and PDAC tumorigenesis. Immunohistochemistry of tissues from chronic pancreatitis specimens revealed considerable L1CAM expression in ductal structures surrounded by dense fibrotic tissue, whereas no L1CAM staining was seen in normal pancreatic tissues. Using the human pancreatic duct cell line H6c7, we show that coculture with PMFs led to a transforming growth factor-beta1 (TGF-beta1)-dependent up-regulation of L1CAM expression. Similarly, L1CAM expression increased in monocultured H6c7 cells after administration of exogenous TGF-beta1. Both TGF-beta1- and PMF-induced L1CAM expression were independent of Smad proteins but required c-Jun NH(2)-terminal kinase activation leading to the induction of the transcription factor Slug. Moreover, Slug interacted with the L1CAM promoter, and its knockdown abrogated the TGF-beta1- and PMF-induced L1CAM expression. As a result of L1CAM expression, H6c7 cells acquired a chemoresistant and migratory phenotype. This mechanism of TGF-beta1-induced L1CAM expression and the resulting phenotype could be verified in the TGF-beta1-responsive PDAC cell lines Colo357 and Panc1. Our data provide new insights into the mechanisms of tumoral L1CAM induction and how PMFs contribute to malignant transformation of pancreatic duct cells early in PDAC tumorigenesis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Relationship between pancreatic stellate cells and pancreatic cancer

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

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LY2109761, a novel transforming growth factor beta receptor type I and type II dual inhibitor, as a therapeutic approach to suppressing pancreatic cancer metastasis

Most pancreatic cancer patients present with inoperable disease or develop metastases after surgery. Conventional therapies are usually ineffective in treating metastatic disease. It is evident that novel therapies remain to be developed. Transforming growth factor beta (TGF-beta) plays a key role in cancer metastasis, signaling through the TGF-beta type I/II receptors (TbetaRI/II). We hypothesized that targeting TbetaRI/II kinase activity with the novel inhibitor LY2109761 would suppress pancreatic cancer metastatic processes. The effect of LY2109761 has been evaluated on soft agar growth, migration, invasion using a fibroblast coculture model, and detachment-induced apoptosis (anoikis) by Annexin V flow cytometric analysis. The efficacy of LY2109761 on tumor growth, survival, and reduction of spontaneous metastasis have been evaluated in an orthotopic murine model of metastatic pancreatic cancer expressing both luciferase and green fluorescence proteins (L3.6pl/GLT). To determine whether pancreatic cancer cells or the cells in the liver microenvironment were involved in LY2109761-mediated reduction of liver metastasis, we used a model of experimental liver metastasis. LY2109761 significantly inhibited the L3.6pl/GLT soft agar growth, suppressed both basal and TGF-beta1-induced cell migration and invasion, and induced anoikis. In vivo, LY2109761, in combination with gemcitabine, significantly reduced the tumor burden, prolonged survival, and reduced spontaneous abdominal metastases. Results from the experimental liver metastasis models indicate an important role for targeting TbetaRI/II kinase activity on tumor and liver microenvironment cells in suppressing liver metastasis. Targeting TbetaRI/II kinase activity on pancreatic cancer cells or the cells of the liver microenvironment represents a novel therapeutic approach to prevent pancreatic cancer metastasis.

Pancreatic stellate cells: partners in crime with pancreatic cancer cells

Pancreatic stellate cells (PSC) produce the stromal reaction in pancreatic cancer, but their role in cancer progression is not fully elucidated. We examined the influence of PSCs on pancreatic cancer growth using (a) an orthotopic model of pancreatic cancer and (b) cultured human PSCs (hPSC) and human pancreatic cancer cell lines MiaPaCa-2 and Panc-1. Athymic mice received an intrapancreatic injection of saline, hPSCs, MiaPaCa-2 cells, or hPSCs + MiaPaCa-2. After 7 weeks, tumor size, metastases, and tumor histology were assessed. In vitro studies assessed the effect of cancer cell secretions on PSC migration and the effect of hPSC secretions on cancer cell proliferation, apoptosis, and migration. Possible mediators of the effects of hPSC secretions on cancer cell proliferation were examined using neutralizing antibodies. Compared with mice receiving MiaPaCa-2 cells alone, mice injected with hPSCs + MiaPaCa-2 exhibited (a) increased tumor size and regional and distant metastasis, (b) fibrotic bands (desmoplasia) containing activated PSCs within tumors, and (c) increased tumor cell numbers. In vitro studies showed that, in the presence of pancreatic cancer cells, PSC migration was significantly increased. Furthermore, hPSC secretions induced the proliferation and migration, but inhibited the apoptosis, of MiaPaCa-2 and Panc-1 cells. The proliferative effect of hPSC secretions on pancreatic cancer cells was inhibited in the presence of neutralizing antibody to platelet-derived growth factor. Our studies indicate a significant interaction between pancreatic cancer cells and stromal cells (PSCs) and imply that pancreatic cancer cells recruit stromal cells to establish an environment that promotes cancer progression.

Pancreatic stellate cells--role in pancreas cancer

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Stromal biology of pancreatic cancer

The genetic paradigm of cancer, focused largely on sequential molecular aberrations and associated biological impact in the neoplastic cell compartment of malignant tumors, has dominated our view of cancer pathogenesis. For the most part, this conceptualization has overlooked the dynamic and complex contributions of the surrounding microenvironment comprised of non-tumor cells (stroma) that may resist, react to, and/or foster tumor development. Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease in which a prominent tumor stroma compartment is a defining characteristic. Indeed, the bulk of PDAC tumor volume consists of non-neoplastic fibroblastic, vascular, and inflammatory cells surrounded by immense quantities of extracellular matrix, far exceeding that found in most other tumor types. Remarkably, little is known about the composition and physiology of the PDAC tumor microenvironment, in particular, the role of stroma in tumor initiation and progression. This review attempts to define key challenges, opportunities and state-of-knowledge relating to the PDAC microenvironment research with an emphasis on how inflammatory processes and key cancer pathways may shape the ontogeny of the tumor stroma. Such knowledge may be used to understand the evolution and biology of this lethal cancer and may convert these insights into new points of therapeutic intervention.

Stromal myofibroblasts predict disease recurrence for colorectal cancer

PURPOSE

Myofibroblasts, which are specifically differentiated fibroblasts, are thought to play a central role in the desmoplastic reaction, a dynamic stromal change closely associated with cancer development. Although fundamental studies suggest that myofibroblasts may either facilitate or inhibit cancer progression, cumulative evidence supports their role in promoting tumor progression. The aim of this study was to assess the value of myofibroblasts in the cancer stroma as an indicator of disease recurrence after colorectal cancer surgery.

EXPERIMENTAL DESIGN

Using computer-assisted image analysis, we quantified myofibroblasts in the cancer-associated stroma of 192 colorectal cancers using alpha-smooth muscle actin as a marker.

RESULTS

The cancer-associated stroma contained various numbers of myofibroblasts (0.35-19.0%; mean, 5.55 +/- 3.85%). Tumors with abundant myofibroblasts were associated with shorter disease-free survival rate (P = 0.001) for stage II and III colorectal cancer. Multivariate analysis indicated that alpha-smooth muscle actin was a significant prognostic factor comparable with lymph node metastasis and superior to other tumor and stromal components, including histology of the tumor invasive front, peritumoral lymphocytic infiltration, and Crohn's-like lymphoid reaction. Moreover, colorectal cancers with synchronous liver metastasis generally displayed an active desmoplastic reaction, which was retained in the metastatic lesion to a similar extent.

CONCLUSIONS

The results suggest that the abundance of myofibroblasts in cancer-associated stroma may be a useful indicator of disease recurrence after curative colorectal cancer surgery.

Periostin creates a tumor-supportive microenvironment in the pancreas by sustaining fibrogenic stellate cell activity

BACKGROUND & AIMS

Pancreatic cancer creates desmoplasia by stimulating stellate cells (PSCs), thereby influencing tumor aggressiveness. The aim of this study was to analyze the impact of the PSC-specific matrix protein periostin on tumor responses to radiochemotherapy.

METHODS

PSCs and cancer cells in primary and metastatic lesions of patients treated with or without neoadjuvant radiochemotherapy were evaluated by immunohistochemistry. Periostin messenger-RNA levels determined by quantitative reverse-transcription polymerase chain reaction were correlated to patient survival. Interactions between PSCs and cancer cells and the effects of periostin in modulating cellular responses under conditions of hypoxia, starvation, and radiochemotherapy were assessed by immunoblotting and by growth, clonogenicity, and invasion assays.

RESULTS

Periostin messenger-RNA levels were elevated 42-fold in cancer, and patients with increased expression had a tendency toward shorter survival (19 vs 12 months; P = .14). Stromal cells were the only source of periostin in the pancreas and in metastatic sites. Cancer cell supernatants stimulated periostin secretion from PSCs. Recombinant periostin increased alpha-smooth muscle actin, periostin, collagen-1, fibronectin, and transforming growth factor-beta1 expression while decreasing PSC invasiveness. These effects were reversed by silencing periostin expression and secretion by small interfering RNA transfection. In cancer cells, periostin stimulated growth and conferred resistance to starvation and hypoxia. In addition, the periostin downstream target collagen-1 significantly increased chemoresistance.

CONCLUSIONS

Once stimulated by cancer cells, PSCs remain active via an autocrine periostin loop even under radiotherapy and produce excessive extracellular matrix proteins, creating a tumor-supportive microenvironment. Increased periostin expression may therefore reflect a more aggressive tumor phenotype.

High glucose activates rat pancreatic stellate cells through protein kinase C and p38 mitogen-activated protein kinase pathway

OBJECTIVE

Hyperglycemia is implicated in fibrosis in many organs. Exocrine and endocrine pancreas are closely linked both anatomically and physiologically, and pathological conditions in the exocrine gland can cause impairment of endocrine function and vice versa. Chronic pancreatitis causes pancreatic fibrosis and sometimes results in diabetes mellitus. Pancreatic stellate cells (PSCs) play a pivotal role in pancreatic fibrogenesis. However, the effects of high glucose concentrations on PSC activation have not been fully elucidated.

METHODS

Cultured PSCs were incubated in the presence of various concentrations of glucose. Pancreatic stellate cell proliferation, alpha-smooth muscle actin (alpha-SMA) expression, and collagen production were determined by colorimetric conversion assay, Western blot analysis, and Sirius red dye binding assay, respectively.

RESULTS

High glucose concentrations significantly increased PSC proliferation, alpha-SMA expression, and collagen type I production in PSCs. High glucose concentrations activated protein kinase C (PKC) in PSCs, and PKC inhibitor GF109203X inhibited glucose-stimulated PSC proliferation, alpha-SMA expression, and collagen secretion. High glucose also activated p38 mitogen-activated protein kinase (MAPK) in PSCs, and p38 MAPK inhibitor SB203580 inhibited glucose-stimulated collagen secretion.

CONCLUSIONS

Our results indicate that high glucose concentrations stimulate PSC activation via PKC-p38 MAP kinase pathway and suggest that high glucose may aggravate pancreatic fibrosis.

The pancreatic stellate cell: a star on the rise in pancreatic diseases

Pancreatic stellate cells (PaSCs) are myofibroblast-like cells found in the areas of the pancreas that have exocrine function. PaSCs are regulated by autocrine and paracrine stimuli and share many features with their hepatic counterparts, studies of which have helped further our understanding of PaSC biology. Activation of PaSCs induces them to proliferate, to migrate to sites of tissue damage, to contract and possibly phagocytose, and to synthesize ECM components to promote tissue repair. Sustained activation of PaSCs has an increasingly appreciated role in the fibrosis that is associated with chronic pancreatitis and with pancreatic cancer. Therefore, understanding the biology of PaSCs offers potential therapeutic targets for the treatment and prevention of these diseases.

Fibroblast activation protein is expressed by rheumatoid myofibroblast-like synoviocytes

Fibroblast activation protein (FAP), as described so far, is a type II cell surface serine protease expressed by fibroblastic cells in areas of active tissue remodelling such as tumour stroma or healing wounds. We investigated the expression of FAP by fibroblast-like synoviocytes (FLSs) and compared the synovial expression pattern in rheumatoid arthritis (RA) and osteoarthritis (OA) patients. Synovial tissue from diseased joints of 20 patients, 10 patients with refractory RA and 10 patients with end-stage OA, was collected during routine surgery. As a result, FLSs from intensively inflamed synovial tissues of refractory RA expressed FAP at high density. Moreover, FAP expression was co-localised with matrix metalloproteinases (MMP-1 and MMP-13) and CD44 splice variants v3 and v7/8 known to play a major role in the concert of extracellular matrix degradation. The pattern of signals appeared to constitute a characteristic feature of FLSs involved in rheumatoid arthritic joint-destructive processes. These FAP-expressing FLSs with a phenotype of smooth muscle actin-positive myofibroblasts were located in the lining layer of the synovium and differ distinctly from Thy-1-expressing and non-proliferating fibroblasts of the articular matrix. The intensity of FAP-specific staining in synovial tissue from patients with RA was found to be different when compared with end-stage OA. Because expression of FAP by RA FLSs has not been described before, the findings of this study highlight a novel element in cartilage and bone destruction of arthritic joints. Moreover, the specific expression pattern qualifies FAP as a therapeutic target for inhibiting the destructive potential of fibroblast-like synovial cells.

Differential expression of insulin-like growth factor binding protein-5 in pancreatic adenocarcinomas: identification using DNA microarray

Pancreatic ductal adenocarcinoma (PDAC) is characterized by its aggressiveness and resistance to both radiation and chemotherapeutic treatment. To better understand the molecular pathogenesis of pancreatic cancer, DNA array technology was employed to identify genes differentially expressed in pancreatic tumors when compared to non-malignant pancreatic tissues. RNA isolated from 11 PDACs and 14 non-malignant bulk pancreatic duct specimens was used to probe Affymetrix U95A DNA arrays. Genes that displayed at least a fourfold differential expression were identified and real-time quantitative PCR was used to verify the differential expression of selected upregulated genes. Interrogation of the DNA array revealed that 73 genes were upregulated in PDACs and 77 genes were downregulated. The majority of the 150 genes identified have not been previously reported to be differentially expressed in pancreatic tumors, although a number of the upregulated transcripts have been reported previously. Immunohistochemistry was used to correlate calponin and insulin-like growth factor binding protein-5 (IGFBP-5) RNA levels with protein expression in PDACs and revealed peritumoral calponin staining in the reactive stroma and intense focal staining of islets cells expressing IGFBP-5 at the edge of tumors; thus implicating the interplay of various cell types to promote neoplastic cell growth within pancreatic carcinomas. As a potential modulator of cell proliferation, the overexpression of IGFBP-5 may, therefore, play a significant role in the malignant transformation of normal pancreatic epithelial cells.

Coordinate cell-surface expression of matrix metalloproteinases and their inhibitors on cancer-associated myofibroblasts from malignant ascites in patients with gastric carcinoma

PURPOSE

The crucial role of tumor stroma in cancer cell invasion has been described in human carcinoma tissues. However, myofibroblastic invasion remains largely unexplored in malignant ascites. Purpose of this study is to investigate the spatial localization or regulation of matrix metalloproteinases (MMP-2, -7 -9, MT1-MMP) and their inhibitors (TIMP-2 and -4) on myofibroblasts from malignant ascites in 20 patients with gastric carcinoma.

METHODS

The quantitative flow cytometric analysis of MMPs or TIMPs on myofibroblasts was based on the percentage of double positive cells defined by anti MMPs or anti TIMPs, and anti alpha-smooth muscle actin (alpha-SMA) antibodies.

RESULT

The results clearly showed that the coordination of the high level of cell-surface expression of secreted MMPs and TIMPs was noted on the alpha-SMA+ myofibroblasts. The finding suggests the possible formation of ternary complex, MT1-MMP/TIMPs/MMPs on the cells. The events might be a cause and result of activation processing of MMPs on the cells.

CONCLUSION

This study provides the presence of invasive myofibroblasts with activated MMPs in close association with MMPs+ and TIMPs+ cancer cells and tumor-infiltrating lymphocytes from malignant ascites, emphasizing the importance of molecular cross-talk in tumor-host microenvironment for cancer invasion, metastasis and progression.

Extracellular matrix stimulates reactive oxygen species production and increases pancreatic cancer cell survival through 5-lipoxygenase and NADPH oxidase

The extracellular matrix (ECM) facilitates pancreatic cancer cells survival, which is of central importance for pancreatic adenocarcinoma that is highly fibrotic. Here, we show that reactive oxygen species (ROS) mediate the prosurvival effect of ECM in human pancreatic cancer cells. Fibronectin and laminin stimulated ROS production and NADPH oxidase activation in pancreatic cancer cells. Both pharmacological and molecular approaches show that fibronectin stimulated ROS production through activation of NADPH oxidase and NADPH oxidase-independent pathways and that 5-lipoxygenase (5-LO) mediates both these pathways. Analyses of the mechanisms of ROS production by ECM proteins and growth factors indicate that activation of NADPH oxidase (Nox4) is a common mechanism employed both by ECM proteins and growth factors to increase ROS in pancreatic cancer cells. We also found that Nox4 is present in human pancreatic adenocarcinoma tissues and that these tissues display membrane NADPH oxidase activity. ECM proteins and growth factors activate NADPH oxidase through different mechanisms; in contrast to ECM proteins, growth factors activate NADPH oxidase through 5-LO-independent mechanisms. Inhibition of 5-LO or NADPH oxidase with pharmacological inhibitors of these enzymes and with Nox4 or 5-LO antisense oligonucleotides markedly stimulated apoptosis in cancer cells cultured on fibronectin. Our results indicate that ROS generation via 5-LO and downstream NADPH oxidase mediates the prosurvival effect of ECM in pancreatic cancer cells. These mechanisms may play an important role in pancreatic cancer resistance to treatments and thus represent novel therapeutic targets.

Proteomic analysis of chronic pancreatitis and pancreatic adenocarcinoma

BACKGROUND & AIMS

Markers to differentiate among pancreatic adenocarcinoma, chronic pancreatitis, and normal pancreas would be of significant clinical utility. This study was therefore designed to analyze the proteome of such specimens and identify new candidate proteins for differential diagnosis.

METHODS

A PowerBlot analysis with more than 900 well-characterized antibodies was performed with tissue specimens from patients with chronic pancreatitis, pancreatic adenocarcinoma, and normal pancreas. Differential expression of selected proteins was confirmed on a larger scale by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry using tissue arrays.

RESULTS

A total of 30 and 102 proteins showed significant deregulation between normal pancreas when compared with chronic pancreatitis and pancreatic adenocarcinoma, respectively, and although a substantial proportion were found similarly dysregulated in both chronic pancreatitis and pancreatic adenocarcinoma, several proteins were identified as potential disease-specific markers.

CONCLUSIONS

A large number of proteins are differentially expressed in chronic pancreatitis and pancreatic adenocarcinoma compared with normal pancreas. Among these, expression analysis of UHRF1, ATP7A, and aldehyde oxidase 1 in combination could potentially provide a useful additional diagnostic tool for fine-needle aspirated or cytological specimens obtained during endoscopic investigations.

Immortalization of pancreatic stellate cells as an in vitro model of pancreatic fibrosis: deactivation is induced by matrigel and N-acetylcysteine

Tissue fibrosis is one of the characteristics of chronic pancreatitis and pancreatic adenocarcinoma. Activated pancreatic stellate cells (PSC) play a central role in this process. However, analysis of the molecular mechanisms leading to PSC activation is hampered by the lack of an established human PSC line. To overcome this problem, we immortalized and characterized primary human PSC. The cells were isolated by the outgrowth method and were immortalized by transfection with SV40 large T antigen and human telomerase (hTERT). Primary human PSC served as controls. An immortalized line, RLT-PSC, was analyzed for the expression of stellate cell markers. Moreover, the effects of transforming growth factor beta 1(TGFbeta1) or platelet-derived growth factor stimulation and of cultivation on basement membrane components or N-acetylcysteine (NAC) treatment on gene and protein expression and proliferation were analyzed. Immortal RLT-PSC cells retained the phenotype of activated PSC proven by the expression of alpha-smooth muscle actin (alphaSMA), vimentin, desmin and glial fibrillary acidic protein (GFAP). TGFbeta1 treatment upregulated the expression of alphaSMA, collagen type I (Col I), fibronectin and TGFbeta1. Incubation of RLT-PSC cells and primary human activated PSC on Matrigel plus NAC treatment resulted in a deactivated phenotype as evidenced by a decrease of alphaSMA, connective tissue growth factor and Col I expression and by a decreased proliferation of the cells. Moreover, this treatment restored the ability of the cells to store vitamin A in cytoplasmic vesicles. In conclusion, we have established an immortal pancreatic stellate cell line, without changing the characteristic phenotype. Importantly, we were able to demonstrate that besides soluble factors, the matrix surrounding PSC plays a pivotal role in the maintenance of the activation process of PSC. Cultivation of activated PSC on a reconstituted basement membrane plus treatment with NAC was able to deactivate the cells, thus pointing to the possibility of an antifibrosis therapy in chronic pancreatitis.

Pancreatic stellate cells (PSCs) express cyclooxygenase-2 (COX-2) and pancreatic cancer stimulates COX-2 in PSCs

Background

Cyclooxygenase 2 (COX-2), the inducible form of prostaglandin G/H synthase, is associated with several human cancers including pancreatic adenocarcinoma. Pancreatic stellate cells (PSCs) play a central role in the intense desmoplasia that surrounds pancreatic adenocarcinoma. The present study examined COX-2 expression in PSCs. PSCs isolated from normal rats, were cultured and exposed to conditioned medium (CM) from the human pancreatic cell line, PANC-1.

Methods

COX-2 expression was evaluated by immunostaining and western blotting. Proliferation of PSCs was determined by thymidine incorporation and cell counting.

Results

COX-2 was found to be constitutively expressed in PSCs, and COX-2 protein was up-regulated by PANC-1 CM. Moreover, the induction of COX-2 by PANC-1 CM was prevented by U0126, an extracellular signal-regulated kinase (ERK) 1/2 inhibitor suggesting that activation of ERK 1/2 is needed for stimulation of COX-2. Finally, NS398, a selective COX-2 inhibitor, reduced the growth of PSCs by PANC-1 CM, indicating that activation of COX-2 is required for cancer stimulated PSC proliferation.

Conclusion

The results suggest that COX-2 may play an important role in the regulation of PSC proliferation in response to pancreatic cancer.

Pancreatic carcinoma cells induce fibrosis by stimulating proliferation and matrix synthesis of stellate cells

BACKGROUND & AIMS

Tumor desmoplasia is one of the representative histopathologic findings in ductal pancreatic adenocarcinoma. The aims of this study were to examine the cellular and molecular mechanisms of fibrogenesis associated with pancreatic adenocarcinomas.

METHODS

Immunostainings were performed with human pancreatic adenocarcinomas (n = 27) and tumors induced in nude mice (n = 36) by subcutaneously injecting MiaPaCa2, Panc1, and SW850 with and without pancreatic stellate cells. Matrix-producing cells were isolated from pancreatic adenocarcinomas and compared with pancreatic stellate cells isolated from tissue of chronic pancreatitis. Paracrine stimulation of pancreatic stellate cells by carcinoma cells was studied regarding matrix synthesis (collagen and c-fibronectin on protein and messenger RNA level) and cell proliferation (bromodeoxyuridine incorporation).

RESULTS

High numbers of desmin and alpha-smooth muscle actin-positive cells were detected in 26 of 27 pancreatic adenocarcinomas. Intense fibronectin and collagen stainings were associated with these cells. By using cytofilament stainings, gene expression profiling, and morphological examinations, the matrix-producing cells obtained by the outgrowth method from pancreatic adenocarcinomas were identified as pancreatic stellate cells. Supernatants of MiaPaCa2, Panc1, and SW850 cells stimulated proliferation and collagen type I and c-fibronectin synthesis of cultured pancreatic stellate cells. Preincubation of the carcinoma cell supernatants with neutralizing antibodies against fibroblast growth factor 2, transforming growth factor beta 1, and platelet-derived growth factor significantly reduced the stimulatory effects. Subcutaneous injection of carcinoma cells and pancreatic stellate cells induced fast-growing subcutaneous fibrotic tumors in nude mice. Morphometric analysis of carcinoma cells (cytokeratin stainings) showed a high density of carcinoma cells in these tumors.

CONCLUSIONS

Pancreatic stellate cells strongly support tumor growth in the nude mouse model. The increased deposition of connective tissue in pancreatic carcinoma is the result of a paracrine stimulation of pancreatic stellate cells by carcinoma cells.

Significance of histological response to preoperative chemoradiotherapy for pancreatic cancer

BACKGROUND

Neoadjuvant (preoperative) chemoradiotherapy (CRT) for pancreatic cancer offers theoretical advantages over the standard approach of surgery followed by adjuvant CRT. We hypothesized that histological responses to CRT would be significant prognostic factors in patients undergoing neoadjuvant CRT followed by resection.

METHODS

Since 1994, 193 patients with biopsy-proven pancreatic adenocarcinoma have completed neoadjuvant CRT, and 70 patients have undergone resection. Specimens were retrospectively examined by an individual pathologist for histological responses (tumor necrosis, tumor fibrosis, and residual tumor load) and immunohistochemical staining for p53 and epidermal growth factor receptor. Factors influencing overall survival were analyzed with the Kaplan-Meier (univariate) and Cox proportional hazards (multivariate) methods.

RESULTS

The estimated overall survival (median +/- SE) in the entire group of patients undergoing resection was 23 +/- 4.2 months, with an estimated 3-year survival of 37% +/- 6.6% and a median follow-up of 28 months. Complete histological responses occurred in 6% of patients. Overexpression of p53 was more common in patients with large residual tumor loads. Tumor necrosis was an independent negative prognostic factor, as were positive lymph nodes, a large residual tumor load, and poor tumor differentiation.

CONCLUSIONS

Histological response to neoadjuvant CRT--as measured by residual tumor load--may be useful as a surrogate marker for treatment efficacy. Characterization of the tumor cells that survive neoadjuvant CRT may help us to identify new or more appropriate targets for systemic therapy.

Pancreatic cancer stimulates pancreatic stellate cell proliferation and TIMP-1 production through the MAP kinase pathway

Pancreatic adenocarcinoma is characterized by an intense desmoplastic reaction that surrounds the tumor. Pancreatic stellate cells (PSCs) are thought to be responsible for production of this extracellular matrix. When activated, PSCs have a myofibroblast phenotype and produce not only components of the extracellular matrix including collagen, fibronectin, and laminin, but also matrix metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). Since PSCs are found in the stroma surrounding human pancreatic adenocarcinoma, we postulate that pancreatic cancer could impact PSC proliferation and TIMP-1 production. Rat PSCs were isolated and cultured. Isolated PSCs were exposed to PANC-1 conditioned medium (CM) and proliferation, activation of the mitogen-activated protein (MAP) kinase pathway, and TIMP-1 gene induction were determined. Exposure to PANC-1 CM increased PSC DNA synthesis, cell number, and TIMP-1 mRNA (real-time PCR) as well as activating the extracellular-regulated kinase (ERK) 1/2. Inhibition of ERK 1/2 phosphorylation (U0126) prevented the increases in growth and TIMP-1 expression. PANC-1 CM stimulates PSC proliferation and TIMP-1 through the MAP kinase (ERK 1/2) pathway.

Cell death pathways in pancreatitis and pancreatic cancer

The understanding of the regulation of apoptosis and necrosis, the two principal cell death pathways, is becoming exceedingly important in investigations of the pathogenesis and treatment of pancreatitis and pancreatic cancer. For example, in acute pancreatitis significant amounts of pancreatic necrosis are associated with increased morbidity and mortality. Thus, determining the key steps regulating necrosis should provide insights into potential therapeutic strategies for improving outcome in these patients. On the other hand, in pancreatic cancer various survival mechanisms act to prevent cell death, resulting in promotion of tumor growth and metastasis. Resistance of pancreatic cancer to apoptosis is the key factor preventing responses to therapies. Investigations of the regulation of cell death mechanisms specific to pancreatic cancer should lead to improvements in our current therapies for this disease. The present review is designed to provide information about cell death pathways in pancreatitis and pancreatic cancer with reference to areas that need further investigation, as well as to provide measurement techniques adapted to pancreatic tissue and cells.

Type I Collagen Promotes the Malignant Phenotype of Pancreatic Ductal Adenocarcinoma

PURPOSE

The purpose of this study was to determine the role of functional interactions between pancreatic cancer cells and pancreatic stellate cells (PSCs) in the formation of the desmoplastic reaction (DR) in pancreatic cancer and to characterize the effect of type I collagen (the predominant component of the DR) on pancreatic cancer cell phenotype.

EXPERIMENTAL DESIGN

PSCs and type I collagen were identified in sections of pancreatic cancer using immunohistochemistry, and their anatomic relationship was studied. Interactions among pancreatic cancer cell lines (MIA PaCa-2, Panc-1, and AsPC-1), primary cultures of human PSCs, and type I collagen were investigated in a series of tissue culture models.

RESULTS

In vivo, the DR causes gross distortion of normal pancreas, bringing cancer cells into close contact with numerous PSCs and abundant type I collagen. In tissue culture models of pancreatic cancer, conditioned media from each cell line increased PSC [3H]thymidine incorporation up to 6.3-fold that of controls, and AsPC-1 cells also increased PSC collagen synthesis 1.3-fold. Type I collagen was observed to increase long-term survival of pancreatic cancer cells treated with 5-fluorouracil, by up to 62% in clonogenic assays. This was because type I collagen increased the proliferation of cancer cells ([3H]thymidine incorporation was up to 2.8-fold that of cells cultured on tissue culture plastic) and reduced apoptosis of AsPC-1 cells in response to 5-fluorouracil (by regulating mcl-1).

CONCLUSIONS

These experiments elucidate a mechanism by which the DR in pancreatic cancer may form and, via the collagen within it, promote the malignant phenotype of pancreatic cancer cells, suggesting significant detriment to the host.

The molecular basis of pancreatic fibrosis: common stromal gene expression in chronic pancreatitis and pancreatic adenocarcinoma

OBJECTIVES

Tissue desmoplasia occurs in a number of disease states, but its molecular basis is poorly understood. To determine which genes are overexpressed in cells contained within the desmoplastic stroma of pancreatic adenocarcinoma and chronic pancreatitis, we undertook genetic profiling of microdissected tissue samples of pancreatic adenocarcinoma, chronic pancreatitis, normal pancreas, and pancreatic cancer cell lines. We observed that samples of both pancreatic adenocarcinoma and chronic pancreatitis showed elevated expression of many shared genes compared with the normal pancreas. We hypothesized that these common genes likely important in stromal production and/or function could be identified using a strategy that involved comparisons between pancreatic adenocarcinoma, chronic pancreatitis, normal pancreas, and pancreatic cancer cell lines.

METHODS

We performed oligonucleotide microarray analysis of 6800 different genes expressed in 10 samples of pancreatic adenocarcinoma, 5 samples of normal pancreas, 5 samples of chronic pancreatitis, and 7 pancreatic cancer cell lines. Microarray findings were validated with RT-PCR, and immunohistochemistry was used to verify protein localization to the stromal compartment of both pancreatic cancer and chronic pancreatitis.

RESULTS

We employed a deductive comparison whereby genes expressed in the normal pancreas and pancreatic cancer cell lines were selectively eliminated from those expressed in common by pancreatic adenocarcinoma and chronic pancreatitis. This strategy identified 107 genes predicted to be expressed within cells of the stromal compartment of both pancreatic adenocarcinoma and chronic pancreatitis.

CONCLUSIONS

These genes are likely important factors in epithelial-stromal signaling in pancreatic desmoplasia and may serve as diagnostic or therapeutic targets.

Pancreatic tumor cells influence the composition of the extracellular matrix

The malignant behavior of cancers depends on the microenvironmental context. We investigated compositional alterations of the extracellular matrix (ECM) in pancreatic cancer, with special emphasis on the proteoglycans decorin, lumican, and versican. Compared with normal controls (n=18), marked overexpression of these proteoglycans was observed in pancreatic cancer tissues (n=30) by quantitative RT-PCR (p<0.0001). Immunohistochemistry revealed abundance of proteoglycans in the ECM of pancreatic cancer specimens, whereas tumor cells themselves were devoid of either decorin, lumican or versican. RT-PCR confirmed pancreatic stellate cells (PSCs) as the major source of these proteins. Interestingly, TGFbeta1 and conditioned medium derived from pancreatic cancer cell lines synergistically suppressed the expression of known anti-tumor factors decorin and lumican, but stimulated the expression of pro-metastatic factor versican in cultured PSCs. These findings indicate that malignant cells can actively influence the composition of the ECM through TGFbeta1 and other soluble factors, altering their microenvironment in a tumor-favorable way.

Desmoplastic reaction in pancreatic cancer: role of pancreatic stellate cells

OBJECTIVES

Pancreatic cancer has a very poor prognosis, largely due to its propensity for early local and distant spread. Histopathologically, most pancreatic cancers are characterized by a prominent stromal/fibrous reaction in and around tumor tissue. The aims of this study were to determine whether (1) the cells responsible for the formation of the stromal reaction in human pancreatic cancers are activated pancreatic stellate cells (PSCs) and (2) an interaction exists between pancreatic cancer cells and PSCs that may facilitate local and distant invasion of tumor.

METHODS

Serial sections of human pancreatic cancer tissue were stained for desmin and glial fibrillary acidic protein (stellate cell selective markers) and alpha-smooth muscle actin (alphaSMA), a marker of activated PSC activation, by immunohistochemistry, and for collagen using Sirius Red. Correlation between the extent of positive staining for collagen and alphaSMA was assessed by morphometry. The cellular source of collagen in stromal areas was identified using dual staining methodology, ie, immunostaining for alphaSMA and in situ hybridization for procollagen alpha1I mRNA. The possible interaction between pancreatic cancer cells and PSCs was assessed in vitro by exposing cultured rat PSCs to control medium or conditioned medium from 2 pancreatic cancer cell lines (PANC-1 and MiaPaCa-2) for 24 hours. PSC activation was assessed by cell proliferation and alphaSMA expression.

RESULTS

Stromal areas of human pancreatic cancer stained strongly positive for the stellate cell selective markers desmin and GFAP (indicating the presence of PSCs), for alphaSMA (suggesting that the PSCs were in their activated state) and for collagen. Morphometric analysis demonstrated a close correlation (r = 0.77; P < 0.04; 8 paired sections) between the extent of PSC activation and collagen deposition. Procollagen mRNA expression was localized to alphaSMA-positive cells in stromal areas indicating that activated PSCs were the predominant source of collagen in stromal areas. Exposure of PSCs to pancreatic cancer cell secretions in vitro resulted in PSC activation as indicated by significantly increased cell proliferation and alphaSMA expression.

CONCLUSIONS

Activated PSCs are present in the stromal reaction in pancreatic cancers and are responsible for the production of stromal collagen. PSC function is influenced by pancreatic cancer cells. Interactions between tumor cells and stromal cells (PSCs) may play an important role in the pathobiology of pancreatic cancer.

Generation and characterization of immortalized rat pancreatic stellate cells

Pancreatic stellate cells (PSCs) are involved in, among other things, the pathogenesis of pancreatic fibrosis. Here, we present the generation of immortalized PSCs 7 and 14 days after isolation by retroviral gene transfer of the SV40 large T antigen encoding region. Propagated cell lines [large T immortalized cells (LTC)-7, LTC-14] retained characteristics of primary cells in terms of morphology, responsiveness to mediators regulating cellular functions such as proliferation, and expression profile of a number of investigated genes. Whereas LTC-14 kept the morphological features of the differentiation status of the primary cells they were made of, LTC-7 appeared similar to an earlier stage. Thus the established cell lines represent a versatile tool to investigate various aspects of PSC biology.

Tumor-stroma interaction of human pancreatic cancer: acquired resistance to anticancer drugs and proliferation regulation is dependent on extracellular matrix proteins

INTRODUCTION

Pancreatic cancer is one of the major causes of cancer-related deaths in industrialized countries. It is known that pancreatic cancer is resistant to chemotherapy and that cancer cells are surrounded by extracellular matrix (ECM) proteins including collagen I, collagen IV, fibronectin, and laminin.

AIMS

To examine the role of ECM proteins in acquired resistance to anticancer drugs and proliferation regulation in pancreatic cancers.

METHODOLOGY AND RESULTS

We used an in vitro model of ECM-induced chemoresistance and cell proliferation of cancer cell lines (MIA PaCa-2, PANC-1, and Capan-1) with 3 different malignancy grades and found that resistance to cytotoxic drugs and proliferation regulation was dependent on ECM proteins. Pancreatic cancer cell lines, especially MIA PaCa-2 cells, adhering to any of the ECM proteins showed decreased cytotoxicity of anticancer drugs, except for gemcitabine. PANC-1 and Capan-1 cells adhering to fibronectin, collagen I, and collagen IV proliferated more than the controls.

CONCLUSION

ECM proteins have important roles in acquired resistance to anticancer drugs and cell proliferation regulation of pancreatic cancer cells. Therefore, the expression of ECM proteins in pancreatic cancer specimens could provide valuable information to aid anticancer drug cytotoxicity, and gemcitabine would be useful for treatment of patients with pancreatic cancer.

Image analysis can be used to detect spatial changes in the histopathology of pancreatic tumours

Pancreatic cancer is frequently associated with intense growth of fibrous tissue at the periphery of tumours, but the histopathological quantification of this stromal reaction has not yet been used as a prognostic factor because of the difficulty of obtaining quantitative measures using manual methods. Manual histological grading is a poor indicator of outcome in this type of cancer and there is a clinical need to establish a more sensitive indicator. Recent pancreatic tumour biology research has focused upon the stromal reaction and there is an indication that its histopathological quantification may lead to a new prognostic indicator. Histological samples from 21 cases of pancreatic carcinoma were stained using the sirius red, light-green method. Multiple images from the centre and periphery of each tumour were automatically segmented using colour cluster analysis to subdivide each image into representative colours. These were classified manually as stroma, cell cytoplasm or lumen in order to measure the area of each component in each image. Measured areas were analysed to determine whether the technique could detect spatial differences in the area of each tissue component over all samples, and within individual samples. Over all 21 cases, the area of stromal tissue at the periphery of the tumours exceeded that at the centre by an average of 10.0 percentage points (P < 0.001). Within individual tumours, the algorithm was able to detect significantly more stroma (P < 0.05) at the periphery than the centre in 11 cases, whilst none of the remaining cases had significantly more stromal tissue at the centre than the periphery. The results demonstrate that semi-automated analysis can be used to detect spatial differences in the area of fibrous tissue in routinely stained sections of pancreatic cancer.