Aberrant cyclooxygenase isozyme expression in human intrahepatic cholangiocarcinoma

Inhibition of T-cell-mediated immune response via the PD-1/ PD-L1 axis in cholangiocarcinoma cells

Cholangiocarcinoma (CCA) is a malignant biliary tract epithelium tumor. The programmed death-1 (PD-1)/programmed receptor-ligand 1 (PD-L1) signaling pathway has been implicated as an immune escape mechanism in several cancers. The present study aimed to assess the expression of PD-L1 on human CCA cell lines and its potential role in suppressing CD8⁺ T- cell function. A panel of intrahepatic CCA cell lines was evaluated for immune regulatory checkpoint ligands and inflammation markers. Effects of pro-inflammatory cytokine, interferon gamma (IFN-γ), on the expression of immune regulatory checkpoint ligands and inflammation markers were determined. The PD-L1 function was measured by co-culturing CCA cells with lymphocytes. Most of the selected Thai CCA cell lines, including HuCCA-1, RMCCA-1, KKU-100, and KKU-213, expressed higher PD-L1 than normal cholangiocyte MMNK-1 and ANK-1 cells. Both PD-L1 and cyclooxygenase-2 (COX-2) expressions were highest in HuCCA-1 cells. A 48 h treatment with IFN-γ increased the expression of PD-L1 and COX-2 in CCA cells. The expression of CTLA-4 ligands, including H7-1 and H7-2, did not change after IFN-γ treatment. Rofecoxib, a specific COX-2 inhibitor, mitigated IFN-γ-induced PD-L1 expression. After 48 h co-incubation, CD8⁺ T-cell apoptosis was increased as compared to the control group. Pretreatment of CCA cells with IFN-γ further increased CD8⁺ T-cell apoptosis. Pembrolizumab, an anti-PD-1 antibody, mitigated CCA cell escape phenomenon. The inhibition of T-cell-mediated immune response via the PD-L1/PD-1 axis are evidenced in intrahepatic CCA. Immunotherapy with checkpoint inhibitor offers a potentially therapeutic strategy for CCA patients; however, further in vivo and clinical studies are required.

Intrahepatic cholangiocarcinoma: Morpho-molecular pathology, tumor reactive microenvironment, and malignant progression

Intrahepatic cholangiocarcinoma (iCCA) is a relatively rare, but highly lethal and biologically complex primary biliary epithelial cancer arising within liver. After hepatocellular carcinoma, iCCA is the second most common primary liver cancer, accounting for approximately 10-20% of all primary hepatic malignancies. Over the last 10-20 years, iCCA has become the focus of increasing concern largely due to its rising incidence and high mortality rates in various parts of the world, including the United States. The challenges posed by iCCA are daunting and despite recent progress in the standard of care and management options for iCCA, the prognosis for this cancer continues to be dismal. In an effort to provide a framework for advancing our understanding of iCCA malignant aggressiveness and therapy resistance, this review will highlight key etiological, biological, molecular, and microenvironmental factors hindering more effective management of this hepatobiliary cancer. Particular focus will be on critically reviewing the cell origins and morpho-molecular heterogeneity of iCCAs, providing mechanistic insights into high risk fibroinflammatory cholangiopathies associated with iCCA development, and notably discussing the deleterious role played by the tumor reactive desmoplastic stroma in regulating iCCA malignant progression, lymphangiogenesis, and tumor immunobiology.

Multifaceted Aspects of Metabolic Plasticity in Human Cholangiocarcinoma: An Overview of Current Perspectives

Cholangiocarcinoma (CCA) is a deadly tumor without an effective therapy. Unique metabolic and bioenergetics features are important hallmarks of tumor cells. Metabolic plasticity allows cancer cells to survive in poor nutrient environments and maximize cell growth by sustaining survival, proliferation, and metastasis. In recent years, an increasing number of studies have shown that specific signaling networks contribute to malignant tumor onset by reprogramming metabolic traits. Several evidences demonstrate that numerous metabolic mediators represent key-players of CCA progression by regulating many signaling pathways. Besides the well-known Warburg effect, several other different pathways involving carbohydrates, proteins, lipids, and nucleic acids metabolism are altered in CCA. The goal of this review is to highlight the main metabolic processes involved in the cholangio-carcinogeneis that might be considered as potential novel druggable candidates for this disease.

ROS Generation and Antioxidant Defense Systems in Normal and Malignant Cells

Reactive oxygen species (ROS) are by-products of normal cell activity. They are produced in many cellular compartments and play a major role in signaling pathways. Overproduction of ROS is associated with the development of various human diseases (including cancer, cardiovascular, neurodegenerative, and metabolic disorders), inflammation, and aging. Tumors continuously generate ROS at increased levels that have a dual role in their development. Oxidative stress can promote tumor initiation, progression, and resistance to therapy through DNA damage, leading to the accumulation of mutations and genome instability, as well as reprogramming cell metabolism and signaling. On the contrary, elevated ROS levels can induce tumor cell death. This review covers the current data on the mechanisms of ROS generation and existing antioxidant systems balancing the redox state in mammalian cells that can also be related to tumors.

Potential candidate treatment agents for targeting of cholangiocarcinoma identified by gene expression profile analysis

Cholangiocarcinoma (CCA) remains to be a major health problem in several Asian countries including Thailand. The molecular mechanism of CCA is poorly understood. Early diagnosis is difficult, and at present, no effective therapeutic drug is available. The present study aimed to identify the molecular mechanism of CCA by gene expression profile analysis and to search for current approved drugs which may interact with the upregulated genes in CCA. Gene Expression Omnibus (GEO) was used to analyze the gene expression profiles of CCA patients and normal subjects. Using the Kyoto Encyclopedia of Genes and Genomes (KEGG), gene ontology enrichment analysis was also performed, with the KEGG pathway analysis indicating that pancreatic secretion, protein digestion and absorption, fat digestion and absorption, and glycerolipid metabolism may serve important roles in CCA oncogenesis. The drug signature database (DsigDB) was used to search for US Food and Drug Administration (FDA)-approved drugs potentially capable of reversing the effects of the upregulated gene expression in CCA. A total of 61 antineoplastic and 86 non-antineoplastic drugs were identified. Checkpoint kinase 1 was the most interacting with drug signatures. Many of the targeted protein inhibitors that were identified have been approved by the US-FDA as therapeutic agents for non-antineoplastic diseases, including cimetidine, valproic acid and lovastatin. The current study demonstrated an application for bioinformatics analysis in assessing the potential efficacy of currently approved drugs for novel use. The present results suggest novel indications regarding existing drugs useful for CCA treatment. However, further in vitro and in vivo studies are required to support the current predictions.

Arterial stiffness induces remodeling phenotypes in pulmonary artery smooth muscle cells via YAP/TAZ-mediated repression of cyclooxygenase-2

Pulmonary arterial stiffness is an independent risk factor for mortality in pulmonary hypertension (PH) and plays a critical role in PH pathophysiology. Our laboratory has recently demonstrated arterial stiffening early in experimental PH, along with evidence for a mechanobiological feedback loop by which arterial stiffening promotes further cellular remodeling behaviors (Liu F, Haeger CM, Dieffenbach PB, Sicard D, Chrobak I, Coronata AM, Suárez Velandia MM, Vitali S, Colas RA, Norris PC, Marinković A, Liu X, Ma J, Rose CD, Lee SJ, Comhair SA, Erzurum SC, McDonald JD, Serhan CN, Walsh SR, Tschumperlin DJ, Fredenburgh LE. JCI Insight 1: e86987, 2016). Cyclooxygenase-2 (COX-2) and prostaglandin signaling have been implicated in stiffness-mediated regulation, with prostaglandin activity inversely correlated to matrix stiffness and remodeling behaviors in vitro, as well as to disease progression in rodent PH models. The mechanism by which mechanical signaling translates to reduced COX-2 activity in pulmonary vascular cells is unknown. The present work investigated the transcriptional regulators Yes-associated protein (YAP) and WW domain-containing transcription regulator 1 (WWTR1, a.k.a., TAZ), which are known drivers of downstream mechanical signaling, in mediating stiffness-induced changes in COX-2 and prostaglandin activity in pulmonary artery smooth muscle cells (PASMCs). We found that YAP/TAZ activity is increased in PAH PASMCs and experimental PH and is necessary for the development of stiffness-dependent remodeling phenotypes. Knockdown of YAP and TAZ markedly induces COX-2 expression and downstream prostaglandin production by approximately threefold, whereas overexpression of YAP or TAZ reduces COX-2 expression and prostaglandin production to near undetectable levels. Together, our findings demonstrate a stiffness-dependent YAP/TAZ-mediated positive feedback loop that drives remodeling phenotypes in PASMCs via reduced COX-2 and prostaglandin activity. The ability to interrupt this critical mechanobiological feedback loop and enhance local prostaglandin activity via manipulation of YAP/TAZ signaling presents a highly attractive novel strategy for the treatment of PH.

Hepatolithiasis and intrahepatic cholangiocarcinoma: A review

Although the incidence of hepatolithiasis is decreasing as the pattern of gallstone disease changes in Asia, the prevalence of hepatolithiasis is persistently high, especially in Far Eastern countries. Hepatolithiasis is an established risk factor for cholangiocarcinoma (CCA), and chronic proliferative inflammation may be involved in biliary carcinogenesis and in inducing the upregulation of cell-proliferating factors. With the use of advanced imaging modalities, there has been much improvement in the management of hepatolithiasis and the diagnosis of hepatolithiasis-associated CCA (HL-CCA). However, there are many problems in managing the strictures in hepatolithiasis and differentiating them from infiltrating types of CCA. Surgical resection is recommended in cases of single lobe hepatolithiasis with atrophy, uncontrolled stricture, symptom duration of more than 10 years, and long history of biliary-enteric anastomosis. Even after resection, patients should be followed with caution for development of HL-CCA, because HL-CCA is an independent prognostic factor for survival. It is not yet clear whether hepatic resection can reduce the occurrence of subsequent HL-CCA. Furthermore, there are no consistent findings regarding prediction of subsequent HL-CCA in patients with hepatolithiasis. In the management of hepatolithiasis, important factors are the reduction of recurrence of cholangitis and suspicion of unrecognized HL-CCA.

Omega-3 Polyunsaturated Fatty Acids Upregulate 15-PGDH Expression in Cholangiocarcinoma Cells by Inhibiting miR-26a/b Expression

Prostaglandin E2 (PGE2) is a proinflammatory lipid mediator that promotes cancer growth. The 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes oxidation of the 15(S)-hydroxyl group of PGE2, leading to its inactivation. Therefore, 15-PGDH induction may offer a strategy to treat cancers that are driven by PGE2, such as human cholangiocarcinoma. Here, we report that omega-3 polyunsaturated fatty acids (ω-3 PUFA) upregulate 15-PGDH expression by inhibiting miR-26a and miR-26b, thereby contributing to ω-3 PUFA-induced inhibition of human cholangiocarcinoma cell growth. Treatment of human cholangiocarcinoma cells (CCLP1 and TFK-1) with ω-3 PUFA (DHA) or transfection of these cells with the Fat-1 gene (encoding Caenorhabditis elegans desaturase, which converts ω-6 PUFA to ω-3 PUFA) significantly increased 15-PGDH enzymes levels, but with little effect on the activity of the 15-PGDH gene promoter. Mechanistic investigations revealed that this increase in 15-PGDH levels in cells was mediated by a reduction in the expression of miR-26a and miR-26b, which target 15-PGDH mRNA and inhibit 15-PGDH translation. These findings were extended by the demonstration that overexpressing miR-26a or miR-26b decreased 15-PGDH protein levels, reversed ω-3 PUFA-induced accumulation of 15-PGDH protein, and prevented ω-3 PUFA-induced inhibition of cholangiocarcinoma cell growth. We further observed that ω-3 PUFA suppressed miR-26a and miR-26b by inhibiting c-myc, a transcription factor that regulates miR-26a/b. Accordingly, c-myc overexpression enhanced expression of miR-26a/b and ablated the ability of ω-3 PUFA to inhibit cell growth. Taken together, our results reveal a novel mechanism for ω-3 PUFA-induced expression of 15-PGDH in human cholangiocarcinoma and provide a preclinical rationale for the evaluation of ω-3 PUFA in treatment of this malignancy.

Interleukin-6 and cyclooxygenase-2 in hilar cholangiocarcinoma

The pathogenesis of hilar cholangiocarcinoma is a complex process involving progressive abnormalities of cell proliferation, apoptosis and differentiation. The progress of molecular biology techniques and the advances in research of malignant tumor cell receptors and proliferation regulation at the molecular level have led to the development of molecular targeted therapy. In recent years, many studies suggest that interleukin-6 (IL-6) and cyclooxygenase-2 (COX-2) levels are correlated with the development and prognosis of cholangiocarcinoma. A more detailed understanding of the roles of cytokines may provide new therapeutic targets for hilar cholangiocarcinoma. In this paper, we review the progress in research of IL-6 and COX in hilar cholangiocarcinoma.

miR-21 targets 15-PGDH and promotes cholangiocarcinoma growth

miRNAs are a group of small, noncoding RNAs that modulate the translation of genes by binding to specific target sites in the target mRNA. This study investigated the biologic function and molecular mechanism of miR-21 in human cholangiocarcinoma. In situ hybridization analysis of human cholangiocarcinoma specimens showed increased miR-21 in cholangiocarcinoma tissue compared with the noncancerous biliary epithelium. Lentiviral transduction of miR-21 enhanced human cholangiocarcinoma cell growth and clonogenic efficiency in vitro, whereas inhibition of miR-21 decreased these parameters. Overexpression of miR-21 also promoted cholangiocarcinoma growth using an in vivo xenograft model system. The NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase (15-PGDH/HPGD), a key enzyme that converts the protumorigenic prostaglandin E2 (PGE2) to its biologically inactive metabolite, was identified as a direct target of miR-21 in cholangiocarcinoma cells. In parallel, cyclooxygenase-2 (COX2) overexpression and PGE2 treatment increased miR-21 levels and enhanced miR-21 promoter activity in human cholangiocarcinoma cells.

IMPLICATIONS

Cholangiocarcinogenesis and tumor progression are regulated by a novel interplay between COX-2/PGE2 and miR-21 signaling, which converges at 15-PGDH.

miR-101 inhibits cholangiocarcinoma angiogenesis through targeting vascular endothelial growth factor (VEGF)

Recent evidence has suggested an important role of miRNAs in liver biology and diseases, although the implication of miRNAs in cholangiocarcinoma remains to be defined further. This study was designed to examine the biological function and molecular mechanism of miR-101 in cholangiocarcinogenesis and tumor progression. In situ hybridization and quantitative RT-PCR were performed to determine the expression of miR-101 in human cholangiocarcinoma tissues and cell lines. Compared with noncancerous biliary epithelial cells, the expression of miR-101 is decreased in 43.5% of human cholangiocarcinoma specimens and in all three cholangiocarcinoma cell lines used in this study. Forced overexpression of miR-101 significantly inhibited cholangiocarcinoma growth in severe combined immunodeficiency mice. miR-101-overexpressed xenograft tumor tissues showed decreased capillary densities and decreased levels of vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2). The VEGF and COX-2 mRNAs were identified as the bona fide targets of miR-101 in cholangiocarcinoma cells by both computational analysis and experimental assays. miR-101 inhibits cholangiocarcinoma angiogenesis by direct targeting of VEGF mRNA 3'untranslated region and by repression of VEGF gene transcription through inhibition of COX-2. This study established a novel tumor-suppressor role of miR-101 in cholangiocarcinoma and it suggests the possibility of targeting miR-101 and related signaling pathways for future therapy.

Reappraisal of the therapeutic role of celecoxib in cholangiocarcinoma

Cholangiocarcinoma (CCA), a lethal disease, affects many thousands worldwide yearly. Surgical resection provides the best chance for a cure; however, only one-third of CCA patients present with a resectable tumour at the time of diagnosis. Currently, no effective chemotherapy is available for advanced CCA. Cyclooxygenase-2 (COX-2) is a potential oncogene expressing in human CCA tissues and represents a candidate target for treatment; however, COX-2 inhibitors increase the risk of negative cardiovascular events as application for chemoprevention aim. Here, we re-evaluated the effectiveness and safety of celecoxib, one widely used COX-2 inhibitor, in treating CCA. We demonstrated that celecoxib exhibited an anti-proliferative effect on CGCCA cells via cell cycle arrest at G2 phase and apoptosis induction. Treatment for 5 weeks high dose celecoxib (160 mg/kg) significantly repressed thioacetamide-induced CCA tumour growth in rats as monitored by animal positron emission tomography through apoptosis induction. No obviously observable side effects were noted during the therapeutic period. As retrospectively reviewing 78 intrahepatic mass-forming CCA patients, their survival was strongly and negatively associated with a positive resection margin and high COX-2 expression. Based on our result, we concluded that short-term high dose celecoxib may be a promising therapeutic regimen for CCA. Yet its clinical application still needs more studies to prove its safety.

Elevated expression of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 in primary sclerosing cholangitis: ιmplications for cholangiocarcinogenesis

Cholangiocarcinoma (CCA) occurs frequently in primary sclerosing cholangitis (PSC). Cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) induced by inflammation are believed to mediate prostaglandin E2 (PGE2) production thereby promoting carcinogenesis. Their expression in PSC-associated CCA tissues and non-neoplastic bile duct epithelial cells (BDECs) in PSC was investigated. COX-2 and mPGES-1 levels in 15 PSC patients (7 with CCA) were scored using immunohistochemical staining. The results were compared with those obtained in CCA tissues and non-neoplastic BDECs (controls) of 15 sporadic CCA patients. Non-neoplastic BDECs from large and small bile ducts were investigated separately. The mRNA expression levels of COX-2 and mPGES-1 in CCA tissues were analyzed by quantitative polymerase chain reaction. Ki-67 immunostaining was performed to evaluate cell proliferation. COX-2 was strongly expressed in PSC-associated CCA tissues and non-neoplastic BDECs in PSC. This expression was significantly upregulated in both compared with sporadic CCA tissues and non-neoplastic BDECs in sporadic CCA (both P<0.01). mPGES-1 was expressed at moderate to strong levels in PSC. Compared with controls, the expression was significantly higher in non-neoplastic small BDECs (P<0.01). COX-2 mRNA levels were significantly higher in PSC-associated tissues than in sporadic CCA tissues (P<0.01). Conversely, no differences were observed in mPGES-1 mRNA levels. Ki-67 labeling indices were higher in PSC-associated CCA tissues and non-neoplastic BDECs in PSC than in controls. In conclusion, COX-2 and mPGES-1 were highly expressed in PSC-associated CCA tissues and non-neoplastic BDECs in PSC, suggesting the involvement of COX-2 and mPGES-1 in cholangiocarcinogenesis.

Different roles of inducible nitric oxide synthase and cyclooxygenase-2 in carcinogenesis and metastasis of intrahepatic cholangiocarcinoma

Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) have been implicated in chronic inflammatory conditions and carcinogenesis. However, little is known about the biological significance of iNOS and COX-2 in cholangiocarcinoma or its precursors or metastatic lesions. We examined iNOS and COX-2 immunohisotochemical expression in 40 biliary intraepithelial neoplasias, 134 primary intrahepatic cholangiocarcinoma cases, and 27 metastatic lymph nodes and analyzed the correlations with grade of atypia of biliary intraepithelial neoplasia, clinicopathological factors and outcomes of intrahepatic cholangiocarcinoma. iNOS and COX-2 expression was highly expressed in reactive epithelium and biliary intraepithelial neoplasia. In intrahepatic cholangiocarcinoma, lymphatic invasion and lymph node metastasis were significantly correlated with negative iNOS expression (P = .0002, P = .0324, respectively) and positive COX-2 expression (P = .0012, P = .0063, respectively). Vascular endothelial growth factor-C expression was associated with COX-2 expression (P = .0053), but not with iNOS expression. COX-2 expression in primary intrahepatic cholangiocarcinoma was higher than that in metastatic lymph nodes (P < .0001). COX-2-positive expression indicated a poor intrahepatic cholangiocarcinoma outcome (P = .0273). This study indicates that iNOS and COX-2 may play roles in carcinogenesis via biliary intraepithelial neoplasia, but play different roles in metastasis of intrahepatic cholangiocarcinoma. COX-2 may participate in a higher lymphatic invasion and metastasis via the vascular endothelial growth factor-C pathway.

Down-regulation of miR-214 contributes to intrahepatic cholangiocarcinoma metastasis by targeting Twist

miRNAs play an important role in many human diseases, including cancer metastasis. However, the mechanisms by which miRNAs regulate intrahepatic cholangiocarcinoma metastasis remain poorly understood. In the present study, we assayed the expression level of miR-214 in intrahepatic cholangiocarcinoma tissues by real-time PCR, and defined the target gene and biological function by luciferase reporter assay and Western blot analysis. We found that the miR-214 levels were remarkably decreased in metastatic intrahepatic cholangiocarcinoma tissues compared to non-metastatic tissues. Inhibition of miR-214 levels by its inhibitor promoted metastasis of human intrahepatic cholangiocarcinoma cell. We further demonstrated that down-regulation of miR-214 increased the transcript levels of the epithelial-mesenchymal transition-associated gene Twist, and then decreased E-cadherin levels. We confirmed that down-regulation of miR-214 promoted the epithelial-mesenchymal transition by directly targeting the Twist gene. These results suggest an important role for miR-214 in regulating metastasis of intrahepatic cholangiocarcinoma, and potential application of miR-214 in intrahepatic cholangiocarcinoma therapy.

MicroRNA-26a promotes cholangiocarcinoma growth by activating β-catenin

BACKGROUND & AIMS

MicroRNAs (miRNAs) have been implicated in the development and progression of human cancers. We investigated the roles and mechanisms of miR-26a in human cholangiocarcinoma.

METHODS

We used in situ hybridization and quantitative reverse transcriptase polymerase chain reaction to measure expression of miR-26a in human cholangiocarcinoma tissues and cell lines (eg, CCLP1, SG231, HuCCT1, TFK1). Human cholangiocarcinoma cell lines were transduced with lentiviruses that expressed miR-26a1 or a scrambled sequence (control); proliferation and colony formation were analyzed. We analyzed growth of human cholangiocarcinoma cells that overexpress miR-26a or its inhibitor in severe combined immune-deficient mice. Immunoblot, immunoprecipitation, DNA pull-down, immunofluorescence, and luciferase reporter assays were used to measure expression and activity of glycogen synthase kinase (GSK)-3β, β-catenin, and related signaling molecules.

RESULTS

Human cholangiocarcinoma tissues and cell lines had increased levels of miR-26a compared with the noncancerous biliary epithelial cells. Overexpression of miR-26a increased proliferation of cholangiocarcinoma cells and colony formation in vitro, whereas miR-26 depletion reduced these parameters. In severe combined immune-deficient mice, overexpression of miR-26a by cholangiocarcinoma cells increased tumor growth and overexpression of the miR-26a inhibitor reduced it. GSK-3β messenger RNA was identified as a direct target of miR-26a by computational analysis and experimental assays. miR-26a-mediated reduction of GSK-3β resulted in activation of β-catenin and induction of several downstream genes including c-Myc, cyclinD1, and peroxisome proliferator-activated receptor δ. Depletion of β-catenin partially prevented miR-26a-induced tumor cell proliferation and colony formation.

CONCLUSIONS

miR-26a promotes cholangiocarcinoma growth by inhibition of GSK-3β and subsequent activation of β-catenin. These signaling molecules might be targets for prevention or treatment of cholangiocarcinoma.

Immunodetection of cyclooxygenase-2 (COX-2) is restricted to tissue macrophages in normal rat liver and to recruited mononuclear phagocytes in liver injury and cholangiocarcinoma

It has been suggested that cyclooxygenase-2 (COX-2)-mediated prostaglandin synthesis is associated with liver inflammation and carcinogenesis. The aim of this study is to identify the cellular source of COX-2 expression in different stages, from acute liver injury through liver fibrosis to cholangiocarcinoma (CC). We induced in rats acute and "chronic" liver injury (thioacetamide (TAA) or carbon tetrachloride (CCl(4))) and CC development (TAA) and assessed COX-2 gene expression in normal and damaged liver tissue by RT-PCR of total RNA. The cellular localization of COX-2 protein in liver tissue was analyzed by immunohistochemistry as well as in isolated rat liver cells by Western blotting. The findings were compared with those obtained in human cirrhotic liver tissue. The specificity of the antibodies was tested by 2-DE Western blot and mass spectrometric identification of the positive protein spots. RT-PCR analysis of total RNA revealed an increase of hepatic COX-2 gene expression in acutely as well as "chronically" damaged liver. COX-2-protein was detected in those ED1(+)/ED2(+) cells located in the non-damaged tissue (resident tissue macrophages). In addition COX-2 positivity in inflammatory mononuclear phagocytes (ED1(+)/ED2(-)), which were also present within the tumoral tissue was detected. COX-2 protein was clearly detectable in isolated Kupffer cells as well as (at lower level) in isolated "inflammatory" macrophages. Similar results were obtained in human cirrhotic liver. COX-2 protein is constitutively detectable in liver tissue macrophages. Inflammatory mononuclear phagocytes contribute to the increase of COX-2 gene expression in acute and chronic liver damage induced by different toxins and in the CC microenvironment.

Microsomal prostaglandin E synthase-1 inhibits PTEN and promotes experimental cholangiocarcinogenesis and tumor progression

BACKGROUND & AIMS

Microsomal prostaglandin E synthase-1 (mPGES-1) is a rate-limiting enzyme that is coupled with cyclooxygenase (COX)-2 in the synthesis of prostaglandin E2. Although COX-2 is involved in the development and progression of various human cancers, the role of mPGES-1 in carcinogenesis has not been determined. We investigated the role of mPGES-1 in human cholangiocarcinoma growth.

METHODS

We used immunohistochemical analyses to examine the expression of mPGES-1 in formalin-fixed, paraffin-embedded human cholangiocarcinoma tissues. The effects of mPGES-1 on human cholangiocarcinoma cells were determined in vitro and in SCID mice. Immunoblotting and immunoprecipitation assays were performed to determine the levels of PTEN and related signaling molecules in human cholangiocarcinoma cells with overexpression or knockdown of mPGES-1.

RESULTS

mPGES-1 is overexpressed in human cholangiocarcinoma tissues. Overexpression of mPGES-1 in human cholangiocarcinoma cells increased tumor cell proliferation, migration, invasion, and colony formation; in contrast, RNA interference knockdown of mPGES-1 inhibited tumor growth parameters. In SCID mice with tumor xenografts, mPGES-1 overexpression accelerated tumor formation and increased tumor weight (P<.01), whereas mPGES-1 knockdown delayed tumor formation and reduced tumor weight (P<.01). mPGES-1 inhibited the expression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), leading to activation of the epidermal growth factor/phosphoinositide 3-kinase/AKT/mammalian target of rapamycin signaling pathways in cholangiocarcinoma cells. mPGES-1-mediated inhibition of PTEN is regulated through blocking of early growth response-1 sumoylation and binding to the 5'-untranslated region of the PTEN gene.

CONCLUSIONS

mPGES-1 promotes experimental cholangiocarcinogenesis and tumor progression by inhibiting PTEN.

Role of ErbB family receptor tyrosine kinases in intrahepatic cholangiocarcinoma

Aberrant expression and signaling of epidermal growth factor receptor (ErbB) family receptor tyrosine kinases, most notably that of ErbB2 and ErbB1, have been implicated in the molecular pathogenesis of intrahepatic cholangiocarcinoma. Constitutive overexpression of ErbB2 and/or ErbB1 in malignant cholangiocytes has raised interest in the possibility that agents which selectively target these receptors could potentially be effective in cholangiocarcinoma therapy. However, current experience with such ErbB-directed therapies have at best produced only modest responses in patients with biliary tract cancers. This review provides a comprehensive and critical analysis of both preclinical and clinical studies aimed at assessing the role of altered ErbB2 and/or ErbB1 expression, genetic modifications, and dysregulated signaling on cholangiocarcinoma development and progression. Specific limitations in experimental approaches that have been used to assess human cholangiocarcinoma specimens for ErbB2 and/or ErbB1 overexpression and gene amplification are discussed. In addition, current rodent models of intrahepatic cholangiocarcinogenesis associated with constitutive ErbB2 overexpression are reviewed. Select interactive relationships between ErbB2 or ErbB1 with other relevant molecular signaling pathways associated with intrahepatic cholangiocarcinoma development and progression are also detailed, including those linking ErbB receptors to bile acid, cyclooxygenase-2, interleukin-6/gp130, transmembrane mucins, hepatocyte growth factor/Met, and vascular endothelial growth factor signaling. Lastly, various factors that can limit therapeutic efficacy of ErbB-targeted agents against cholangiocarcinoma are considered.

Resistance of cholangiocarcinoma cells to parthenolide-induced apoptosis by the excretory-secretory products of Clonorchis sinensis

Infection by Clonorchis sinensis, the Chinese or oriental liver fluke, is a significant risk factor for the development of cholangiocarcinoma, a human epithelial carcinoma of the intrahepatic bile duct. Parthenolide is a sesquiterpene lactone that has strong anticancer properties and is also known to induce apoptosis in cholangiocarcinoma cells. Many investigators have reported that excretory-secretory (ES) products of C. sinensis as well as Opisthorchis viverrini promote the development of cholangiocarcinomas. However, the intrinsic mechanism is not clearly understood. Therefore, we investigated the biological roles of the ES products in a cholangiocarcinoma cell line, HuCCT1. The ES products of C. sinensis increased proliferation of HuCCT1 cells and augmented the expression of cyclooxygenase (COX)-2. To determine whether cells treated with ES products would respond differently to parthenolide, HuCCT1 cells were treated with parthenolide alone or parthenolide after pretreatment with ES products. Cells pretreated with ES products were resistant to parthenolide-induced apoptosis. Because parthenolide has been reported to be a COX-2 inhibitor, we hypothesize that COX-2 might be a key factor that promotes resistance of cholangiocarcinoma cancer cells to parthenolide-induced apoptosis. These results suggest that chemotherapy treatment regimens in cholangiocarcinoma patients with C. sinensis infection should be modulated to account for ES products excreted by the liver fluke.

Cholangiocarcinoma arising in von Meyenburg complexes: report of four cases

Although von Meyenburg complexes (VMC) are largely considered to be innocuous, neoplastic transformations have been described. The present report describes four cases of cholangiocarcinoma (CC) occurring on a background of VMC. The patients were all male and aged 69, 59, 68 and 75 years, respectively. While two patients were asymptomatic, the other two had a history of colon cancer. Radiologically the tumors measured 3, 4, 4.5 and 10 cm and were well enhanced from the arterial to delayed portal phase. Microscopically, the tumor consisted of multiple foci of characteristic VMC, and had a gradual transition from VMC to hyperplasia or dysplasia and well- to moderately differentiated adenocarcinomas. One patient had combined hepatocellular carcinoma (HCC) and CC, occurring in the high grade dysplastic nodule and VMC. On immunohistochemistry the epithelial cells of the VMC and CC were immunopositive for cytokeratin (CK) 7 in three patients, with another patient being focally positive only for CK19. The Ki-67 labeling indices increased from the VMC to the dysplastic areas and then to the carcinomas. As a potentially precancerous lesion, VMC should be carefully followed up in terms of any size increases. Thus, biopsies are essential to determine any proliferative epithelial changes including dysplasia and malignant transformation.

Cyclooxygenase in normal human tissues--is COX-1 really a constitutive isoform, and COX-2 an inducible isoform?

Cyclooxygenase (COX) is a key enzyme in prostanoid synthesis. It exists in two isoforms, COX-1 and COX-2. COX-1 is referred to as a ‘constitutive isoform’, and is considered to be expressed in most tissues under basal conditions. In contrast, COX-2 is referred to as an ‘inducible isoform’, which is believed to be undetectable in most normal tissues, but can be up-regulated during various conditions, many of them pathological. Even though the role of COX in homeostasis and disease in now well appreciated, controversial information is available concerning the distribution of COX isoforms in normal human tissues. There is mounting evidence that it is much more complex than generally believed. Our aim was therefore to analyse the expression and distribution of COX isoforms in normal human tissues, using immunohistochemistry, Western blotting and real-time RT-PCR. Autopsy samples from 20 healthy trauma victims and samples from 48 biopsy surgical specimens were included. COX-1 was found in blood vessels, interstitial cells, smooth muscle cells, platelets and mesothelial cells. In contrast, COX-2 was found predominantly in the parenchymal cells of many tissues, with few exceptions, for example the heart. Our results confirm the hypothesis that the distribution of COX isoforms in healthy tissues is much more complex than generally believed. This and previous studies indicate that both isoforms, not only COX-1, are present in many normal human tissues, and that both isoforms, not only COX-2, are up-regulated in various pathological conditions. We may have to revise the concept of ‘constitutive’ and ‘inducible’ COX isoforms.

Akt1/protein kinase B alpha is involved in gastric cancer progression and cell proliferation

Akt (also known as protein kinase B, PKB) is involved in a variety of biological processes, for example cell development, proliferation, and angiogenesis. Clinical studies in support of the idea that increased activity of Akt could contribute directly to gastric carcinogenesis are rare, however. In this study we discovered that phospho-Akt1 was overexpressed in human gastric cancers and its levels correlated with tumor differentiation and pTNM. Akt1 activation promoted cell survival, because the phosphatidylinositol 3-kinase(PI3K) inhibitor LY294002 inhibited Akt1 phosphorylation and inhibited cell growth, especially in cells with active Akt1. Dominant negative Akt inhibited proliferation of gastric cancer cells and induced G1 cell-cycle arrest whereas constitutively active Akt increased cell proliferation. We have therefore identified Akt1 as an active kinase that contributes to gastric cancer progression and promotes proliferation of gastric cancer cells.

Cyclooxygenase-2-derived prostaglandin E2 activates beta-catenin in human cholangiocarcinoma cells: evidence for inhibition of these signaling pathways by omega 3 polyunsaturated fatty acids

Cholangiocarcinoma is a highly malignant neoplasm of the biliary tree. It has a high rate of mortality, and currently, there is no effective chemoprevention and treatment. This study was designed to investigate the potential effect of omega 3 polyunsaturated fatty acids (omega 3-PUFA) on human cholangiocarcinoma cell growth and to determine their mechanisms of actions. Treatment of three human cholangiocarcinoma cells (CCLP1, HuCCT1, SG231) with two omega 3-PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for 12 to 72 h resulted in a dose- and time-dependent inhibition of cell growth; in contrast, arachidonic acid, a omega 6-PUFA, had no significant effect. The omega 3-PUFA effect is due to the induction of apoptosis, given that DHA induced the cleaved form of PARP, caspase-3, and caspase-9. DHA and EPA treatment caused dephosphorylation (and hence, the activation) of glycogen synthase kinase-3beta (GSK-3beta) with a decline of beta-catenin protein. Accordingly, DHA treatment also decreased the beta-catenin-mediated T cell factor/lymphoid enhancer factor (TCF/LEF) reporter activity, and inhibited the expression of c-Met, a beta-catenin-controlled downstream gene implicated in cholangiocarcinogenesis. The GSK-3beta inhibitor, SB216763, partially prevented DHA-induced reduction of beta-catenin protein and TCF/LEF reporter activity, and restored cell growth, suggesting the involvement of GSK-3beta dephosphorylation in omega 3-PUFA-induced beta-catenin degradation. In parallel, DHA treatment also induced the formation of the beta-catenin/Axin/GSK-3beta binding complex, further leading to beta-catenin degradation. Moreover, DHA inhibited the expression of cyclooxygenase-2 (COX-2) and enhanced the expression of 15-hydroxyprostaglandin dehydrogenase, a physiologic COX-2 antagonist, in human cholangiocarcinoma cells. These findings suggest that omega 3-PUFAs block cholangiocarcinoma cell growth at least in part through inhibition of Wnt/beta-catenin and COX-2 signaling pathways. Thus, utilization of omega 3-PUFAs may represent an effective and safe therapeutic approach for the chemoprevention and treatment of human cholangiocarcinoma.

Elevated expression of cyclooxygenase-2 is a negative prognostic factor for overall survival in intrahepatic cholangiocarcinoma

The production of prostaglandins is regulated by cyclooxygenases (COXs), which also have a role in tumour development and progression in various human malignancies, including cholangiocarcinoma. Limited information is available of the correlation of COX-2 protein expression and prognosis in intrahepatic cholangiocarcinoma (ICC). The aim of the present study was to determine the clinical significance of COX-2 expression in ICC. In addition the correlation of COX-2 expression and apoptosis/proliferation was analysed. COX-2 expression was determined immunohistochemically in 62 resected ICCs. Proliferation was assessed using Ki67-immunohistochemistry, and apoptosis was measured with the TdT-mediated dUTP nick-end-labelling technique. COX-2 was identified as an independent prognostic factor (P = 0.028) in resected ICC by survival analysis. High levels of COX-2 expression were found to be associated both with reduced apoptosis and increased proliferation of tumour cells. This study demonstrates the independent prognostic value of the COX-2 expression in resected ICC, thus, offering a potential additional adjuvant therapeutic approach with COX-2 inhibitors.

Therapeutic effect of CS-706, a specific cyclooxygenase-2 inhibitor, on gallbladder carcinoma in BK5.ErbB-2 mice

Biliary tract cancer is still challenging to treat and manage due to its poor sensitivity to conventional therapies and the inability to prevent or detect the early tumor formation. The most well known risk factor for gallbladder cancer is the presence of chronic inflammation, usually related to gallstones. It has been suggested that cyclooxygenase-2 (COX-2) plays a variety of roles in the gastrointestinal tract, including pathogenic processes such as neoplasia. Recently, we have generated transgenic mice that overexpress rat ErbB-2 under the control of bovine keratin 5 promoter (BK5.ErbB-2 mice). Homozygous BK5.ErbB-2 mice develop adenocarcinoma of gallbladder with an approximately 90% incidence. In addition to the activation of ErbB-2 and epidermal growth factor receptor, mRNA and protein levels of COX-2 were up-regulated in the gallbladder carcinomas that developed in these transgenic mice. The aim of this study was to examine the effects of a COX-2 inhibitor, CS-706, on the development of gallbladder carcinomas using the BK5.ErbB-2 mouse model. Ultrasound image analysis as well as histologic evaluation revealed a significant therapeutic effect of CS-706 on the gallbladder tumors, either as reversion to a milder phenotype or inhibition of tumor progression. The antitumor effect was associated with inhibition of prostaglandin E(2) synthesis. CS-706 treatment also down-regulated the activation of ErbB-2 and epidermal growth factor receptor, resulting in decreased levels of phosphorylated Akt and COX-2 in gallbladder cancers of BK5.ErbB-2 mice. Based on our results, targeting COX-2 could provide a potentially new and effective therapy alone or in combination with other therapeutic agents for patients with biliary tract cancer.

Biological characteristics of cancers in the gallbladder and biliary tract and targeted therapy

Adenocarcinomas of the gallbladder (GBC) and bile ducts (cholangiocarcinoma) (combined as biliary tract cancers, BTC) are uncommon tumors in the United States, but are endemic in parts of South America and Asia. BTC are aggressive tumors with poor survival. Published response rates to chemotherapy are less than 30% and no survival benefit has been demonstrated from palliative systemic therapy. Improved understanding of the biological characteristics and molecular carcinogenic mechanisms of these malignancies may lead to improved therapeutic regimens for patients.

A novel positive feedback loop between peroxisome proliferator-activated receptor-delta and prostaglandin E2 signaling pathways for human cholangiocarcinoma cell growth

Peroxisome proliferator-activated receptor-delta (PPARdelta) is a nuclear receptor implicated in lipid oxidation and the pathogenesis of obesity and diabetes. This study was designed to examine the potential effect of PPARdelta on human cholangiocarcinoma cell growth and its mechanism of actions. Overexpression of PPARdelta or activation of PPARdelta by its pharmacological ligand, GW501516, at low doses (0.5-50 nM) promoted the growth of three human cholangiocarcinoma cell lines (CCLP1, HuCCT1, and SG231). This effect was mediated by induction of cyclooxygenase-2 (COX-2) gene expression and production of prostaglandin E2 (PGE2) that in turn transactivated epidermal growth factor receptor (EGFR) and Akt. In support of this, inhibition of COX-2, EGFR, and Akt prevented the PPARdelta-induced cell growth. Furthermore, PPARdelta activation or PGE2 treatment induced the phosphorylation of cytosolic phospholipase A2alpha (cPLA2alpha), a key enzyme that releases arachidonic acid (AA) substrate for PG production via COX. Overexpression or activation of cPLA2alpha enhanced PPARdelta binding to PPARdelta response element (DRE) and increased PPARdelta reporter activity, indicating a novel role of cPLA2alpha for PPARdelta activation. Consistent with this, AA enhanced the binding of PPARdelta to DRE, in vitro, suggesting a direct role of AA for PPARdelta activation. In contrast, although PGE2 treatment increased the DRE reporter activity in intact cells, it failed to induce PPARdelta binding to DRE in cell-free system, suggesting that cPLA2alpha-mediated AA release is required for PGE2-induced PPARdelta activation. Taken together, these observations reveal that PPARdelta induces COX-2 expression in human cholangiocarcinoma cells and that the COX-2-derived PGE2 further activates PPARdelta through phosphorylation of cPLA2alpha. This positive feedback loop plays an important role for cholangiocarcinoma cell growth and may be targeted for chemoprevention and treatment.

What are cyclooxygenases and lipoxygenases doing in the driver's seat of carcinogenesis?

Substantial evidence supports a functional role for cyclooxygenase- and lipoxygenase-catalyzed arachidonic and linoleic acid metabolism in cancer development. Genetic intervention studies firmly established cause-effect relations for cyclooxygenase-2, but cyclooxygenase-1 may also be involved. In addition, pharmacologic cyclooxygenase inhibition was found to suppress carcinogenesis in both experimental mouse models and several cancers in humans. Arachidonic acid-derived eicosanoid or linoleic acid-derived hydro[peroxy]fatty acid signaling are likely to be involved impacting fundamental biologic phenomena as diverse as cell growth, cell survival, angiogenesis, cell invasion, metastatic potential and immunomodulation. However, long chain unsaturated fatty acid oxidation reactions indicate antipodal functions of distinct lipoxygenase isoforms in carcinogenesis, i.e., the 5- and platelet-type 12-lipoxygenase exhibit procarcinogenic activities, while 15-lipoxygenase-1 and 15-lipoxygenase-2 may suppress carcinogenesis.

Selection of tumour specific promoters for adenoviral gene therapy of cholangiocarcinoma

BACKGROUND/AIMS

The majority of cholangiocarcinoma patients present with advanced incurable disease. Therefore development of new therapeutic modalities including adenoviral gene therapy is of paramount importance. We set out to identify tumour specific promoters which have low activity in human liver cells and retain their specificity in an adenoviral vector.

METHODS

mRNA levels of cyclo-oxygenase-2, cytokeratin-19, mucin-1, midkine and telomerase reverse transcriptase (TERT) were determined in human liver, cholangiocarcinoma (resection specimens and cell lines), primary human hepatocytes, cholangiocytes and endothelial cells by Reverse Transcriptase-quantitative PCR. The activity of candidate promoters in adenoviral vectors was then determined in cholangiocarcinoma cell lines, primary human hepatocytes and cholangiocytes.

RESULTS

mRNA levels of all tested tumour markers were significantly higher in cholangiocarcinoma than in normal liver. Based on low expression in hepatocytes, either in combination with low expression in primary cholangiocytes or endothelial cells, the cytokeratin-19, mucin-1 and TERT promoters were selected for further analyses. In an adenoviral vector, the activity of the TERT or cytokeratin-19 promoters were low in normal human hepatocytes and cholangiocytes, and high in cholangiocarcinoma cell lines.

CONCLUSIONS

The TERT and Cytokeratin-19 promoters are highly expressed in cholangiocarcinoma and seem suitable to restrict adenoviral gene therapy to these intra-hepatic tumours.

Cyclooxygenase-2 and prostaglandin signaling in cholangiocarcinoma

Cholangiocarcinoma is a highly malignant epithelial neoplasm arising within the biliary tract and its incidence and mortality is rising. Early diagnosis is difficult and there is presently no effective treatment. Significant progress has been made over the past several years in defining the link between COX-2 and cholangiocarcinogenesis. Selective COX-2 inhibitors have been shown to inhibit cholangiocarcinoma cell growth in vitro and in animal models. However, recently, concerns have been raised about the cardiovascular side effect associated with some COX-2 inhibitors utilized at relatively high dose for antitumor chemoprevention, despite that these inhibitors have a proven safety profile when given as monotherapy to arthritis patients. Therefore, there is an urgent and practical need to develop novel chemopreventive strategy that simultaneously targets COX-2 signaling and other related key molecules in cholangiocarcinogenesis, such as EGFR or utilization of agents inhibiting COX-2 signaling in conjunction with other standard chemotherapy or radiation therapy; these approaches are expected to provide synergistic anti-tumor effect with lesser side effect. In this context, the recently delineated interplay between COX-2-derived PG signaling and other growth-regulatory pathways, such as EGFR, ErbB2, IL-6/GP130, HGF/Met, TGF-beta/Smad, and iNOS is expected to provide important therapeutic implications. This review will summarize the recent advances in understanding the mechanisms for COX-2-derived PG signaling in cholangiocarcinogenesis and focus on the newly unveiled interactions between PG cascade and other key signaling pathways that coordinately regulate cholangiocarcinoma growth. Knowledge on these aspects will help develop more effective therapeutic strategy targeting COX-2 and related key signaling molecules.

Cyclooxygenase-2 and prostaglandin signaling in cholangiocarcinoma

Cholangiocarcinoma is a highly malignant epithelial neoplasm arising within the biliary tract and its incidence and mortality is rising. Early diagnosis is difficult and there is presently no effective treatment. Significant progress has been made over the past several years in defining the link between COX-2 and cholangiocarcinogenesis. Selective COX-2 inhibitors have been shown to inhibit cholangiocarcinoma cell growth in vitro and in animal models. However, recently, concerns have been raised about the cardiovascular side effect associated with some COX-2 inhibitors utilized at relatively high dose for antitumor chemoprevention, despite that these inhibitors have a proven safety profile when given as monotherapy to arthritis patients. Therefore, there is an urgent and practical need to develop novel chemopreventive strategy that simultaneously targets COX-2 signaling and other related key molecules in cholangiocarcinogenesis, such as EGFR or utilization of agents inhibiting COX-2 signaling in conjunction with other standard chemotherapy or radiation therapy; these approaches are expected to provide synergistic anti-tumor effect with lesser side effect. In this context, the recently delineated interplay between COX-2-derived PG signaling and other growth-regulatory pathways, such as EGFR, ErbB2, IL-6/GP130, HGF/Met, TGF-beta/Smad, and iNOS is expected to provide important therapeutic implications. This review will summarize the recent advances in understanding the mechanisms for COX-2-derived PG signaling in cholangiocarcinogenesis and focus on the newly unveiled interactions between PG cascade and other key signaling pathways that coordinately regulate cholangiocarcinoma growth. Knowledge on these aspects will help develop more effective therapeutic strategy targeting COX-2 and related key signaling molecules.

Cyclooxygenase-2-derived prostaglandin E2 promotes human cholangiocarcinoma cell growth and invasion through EP1 receptor-mediated activation of the epidermal growth factor receptor and Akt

Cyclooxygenase-2 (COX-2)-mediated prostaglandin synthesis has recently been implicated in human cholangiocarcinogenesis. This study was designed to examine the mechanisms by which COX-2-derived prostaglandin E2 (PGE2) regulates cholangiocarcinoma cell growth and invasion. Immunohistochemical analysis revealed elevated expression of COX-2 and the epidermal growth factor (EGF) receptor (EGFR) in human cholangiocarcinoma tissues. Overexpression of COX-2 in a human cholangiocarcinoma cell line (CCLP1) increased tumor cell growth and invasion in vitro and in severe combined immunodeficient mice. Overexpression of COX-2 or treatment with PGE2 or the EP1 receptor agonist ONO-DI-004 induced phosphorylation of EGFR and enhanced tumor cell proliferation and invasion, which were inhibited by the EP1 receptor small interfering RNA or antagonist ONO-8711. Treatment of CCLP1 cells with PGE2 or ONO-DI-004 enhanced binding of EGFR to the EP1 receptor and c-Src. Furthermore, PGE2 or ONO-DI-004 treatment also increased Akt phosphorylation, which was blocked by the EGFR tyrosine kinase inhibitors AG 1478 and PD 153035. These findings reveal that the EP1 receptor transactivated EGFR, thus activating Akt. On the other hand, activation of EGFR by its cognate ligand (EGF) increased COX-2 expression and PGE2 production, whereas blocking PGE2 synthesis or the EP1 receptor inhibited EGF-induced EGFR phosphorylation. This study reveals a novel cross-talk between the EP1 receptor and EGFR signaling that synergistically promotes cancer cell growth and invasion.

A review and update on cholangiocarcinoma

Cholangiocarcinoma is a malignant neoplasm arising from the biliary epithelium that was first described by Durand-Fardel in 1840. Today, it continues to defy diagnosis and treatment. It is difficult to diagnose in part because of its relative rarity, and because it is clinically silent until it becomes advanced disease with obstructive symptoms. The worldwide incidence of cholangiocarcinoma has risen over the past three decades. There is marked geographic variability in the prevalence of this disease, due in large part to regional environmental risk factors. Surgical resection remains the only curative treatment, and high priorities are improving diagnostic methods, and clinical staging for resection once the disease is suspected. A recent trend towards aggressive surgical management has improved outcomes. Chemotherapy, palliative stenting, and radiation are reserved for patients who are not resectable, those with recurrence after surgery, and those who decline surgical intervention. Recent trials using combination systemic chemotherapy and neoadjuvant chemoradiation are promising, but require further study. Over the past five years, several important studies have yielded new insights into the molecular mechanisms of cholangiocarcinoma tumorigenesis. In this review we discuss epidemiology, etiologic factors, molecular pathogenesis, diagnosis, staging, and treatment of cholangiocarcinoma. Particular focus is on recent studies into the cellular and molecular pathogenesis of the disease, recent chemotherapy trials, and newer methods of staging and screening for this devastating malignancy.

Inducible nitric oxide synthase upregulates cyclooxygenase-2 in mouse cholangiocytes promoting cell growth

Both inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2) have been implicated in the biliary tract carcinogenesis. However, it is not known whether these inflammatory mediators are induced by interdependent or parallel pathways. Because iNOS activity has been associated with diverse gene expression, the aim of this study was to determine whether iNOS induces COX-2. To address this objective, immortalized, but nonmalignant, murine cholangiocytes, 603B cells were employed for these studies. Both iNOS and COX-2 protein and mRNA were expressed in these cells. However, iNOS inhibition with either N-[3-(aminomethyl) benzyl]acetamidine or stable transfection with an iNOS antisense construct inhibited COX-2 mRNA and protein expression, an effect that was reversed by NO donors. COX-2 mRNA expression in 603B cells was reduced by pharmacological inhibitors of the p38 MAPK and JNK1/2 pathways. In contrast, neither inhibitors of the soluble guanylyl cyclase inhibitor/protein kinase G nor p42/44 MAPK pathways attenuated COX-2 mRNA expression. Finally, 603B cells grew at a rate threefold greater than 603B-iNOS antisense cells. The low growth rate of 603B-iNOS antisense cells could be restored to near that of the parent cell line with exogenous PGE(2.) In conclusion, iNOS induces COX-2 expression in cholangiocytes, which promotes cell growth. COX-2 induction may contribute to iNOS-associated carcinogenesis.

Expression of cyclooxygenase-2 in cholangiocarcinoma: correlation with clinicopathological features and prognosis

BACKGROUND AND AIMS

No information is available on the nature of the correlation between cyclooxygenase-2 (COX-2) expression and the clinicopathological features and prognosis of cholangiocarcinoma (CC). The goal of the present study was to determine the possible roles and clinical significance of COX-2 expression in CC.

METHODS

We investigated the immunohistochemical expression of COX-2 in 102 patients with CC with respect to clinicopathological characteristics, namely evidence of Clonorchis sinensis infection, proliferation index (PI, assessed by Ki-67 expression), apoptotic index (AI, assessed by TUNEL stain), and microvessel density (MVD, assessed by CD34 expression). Evidence of C. sinensis infection was assessed by the microscopic examination of stools for C. sinensis ova, serological testing (ELISA), and the detection of peripheral bile duct dilations by imaging studies.

RESULTS

An immunohistochemical investigation demonstrated the immunolabeling of tumor cells, mainly in the cytoplasmic and perinuclear regions, in 53 (52%) of the 102 patients with CC. No significant differences were found in terms of age, sex, tumor differentiation, involvement of the resection margin, presence of lymph nodes or liver metastases, or in pTNM stage between COX-2 positive and COX-2 negative patients. However, evidence of C. sinensis infection was more common in COX-2 positive patients (P < 0.05). No significant differences were found for PI, AI, MVD, or cumulative survival between COX-2 positive and COX-2 negative patients.

CONCLUSION

Clonorchis sinensis infection is related to aberrant COX-2 expression in patients with CC. However, COX-2 expression is not related to clinical outcome in CC patients.

Cyclooxygenase-2 promotes human cholangiocarcinoma growth: evidence for cyclooxygenase-2-independent mechanism in celecoxib-mediated induction of p21waf1/cip1 and p27kip1 and cell cycle arrest

The expression of cyclooxygenase-2 (COX-2) is increased in human cholangiocarcinoma. However, the biologic function and molecular mechanisms of COX-2 in the control of cholangiocarcinoma cell growth have not been well established. This study was designed to examine the direct effect of COX-2 and its inhibitor celecoxib on the growth of human intrahepatic cholangiocarcinoma cells. Overexpression of COX-2 or treatment with prostaglandin E(2) (PGE(2)) enhanced human cholangiocarcinoma cell growth, whereas antisense depletion of COX-2 in these cells decreased PGE(2) production and inhibited growth. These findings demonstrate a direct role of COX-2-mediated PGE(2) in the growth regulation of human cholangiocarcinoma cells. Furthermore, the COX-2 inhibitor celecoxib induced a dose-dependent inhibition of cell growth, cell cycle arrest at the G(1)-S checkpoint, and induction of cyclin-dependent kinase inhibitors p21(waf1/cip1) and p27(kip1). However, the high concentration of celecoxib (50 micro M) required for inhibition of growth, the incomplete protection of celecoxib-induced inhibition of cell growth by PGE(2) or COX-2 overexpression, and the fact that overexpression or antisense depletion of COX-2 failed to alter the level of p21(waf1/cip1) and p27(kip1) indicate the existence of a COX-2-independent mechanism in celecoxib-induced inhibition of cholangiocarcinoma cell growth.

Celecoxib-induced apoptosis in rat cholangiocarcinoma cells mediated by Akt inactivation and Bax translocation

Recently, we demonstrated that the cyclooxygenase-2 (COX-2) inhibitor celecoxib acts to significantly suppress the growth of rat C611B cholangiocarcinoma (ChC) cells in vitro. To establish a molecular mechanism for this growth suppression, we investigated the effects of celecoxib on apoptotic signaling pathways in cultured rat C611B ChC cells. Celecoxib and another COX-2 inhibitor, rofecoxib, at 5 microM were almost equally effective in inhibiting prostaglandin E(2) (PGE(2)) production by these cells, but at this low concentration, neither inhibitor suppressed growth or induced apoptosis. Celecoxib at 50 microM induced prominent apoptosis in these cells, whereas rofecoxib at 50 microM was without effect in either suppressing growth or inducing apoptosis. Celecoxib (50 microM) did not alter Bcl-2, Bcl-x(L), or COX-2 protein levels, nor did it inhibit p42/44 mitogen-activated protein kinase (MAPK) phosphorylation; however, it significantly suppressed serine/threonine kinase Akt/PKB (Akt) phosphorylation and kinase activity in cultured C611B cells. This effect, in turn, directly correlated with Bax translocation to mitochondria, cytochrome c release into cytosol, activation of caspase-9 and caspase-3, and cleavage of poly (ADP-ribose) polymerase (PARP). Addition of 25 microM PGE(2) to C611B cell cultures blocked the apoptotic actions of celecoxib. Rofecoxib (50 microM) was without effect in suppressing Akt phosphorylation and caspase-3 activation. In vivo, celecoxib partially suppressed tumorigenic growth of C611B ChC cells. In conclusion, our results indicate that celecoxib preferentially acts in vitro to induce apoptosis in ChC cells through a mechanism involving Akt inactivation, Bax translocation, and cytochrome c release. Our in vivo results further suggest celecoxib might have potential therapeutic or chemopreventive value against ChC.

[Role of cyclooxygenase-2 in the pathogenesis of chronic liver diseases]

Cyclooxygenase (COX) is a crucial enzyme in the biosynthesis of prostaglandins. There are two COX isoforms: COX-1 is constitutively expressed in a number of cell types and is involved in the homeostatic functions of prostaglandins, whereas COX-2 is inducible by a variety of proinflammatory stimuli, such as cytokines and lipopolysaccharide. In the liver, COX-2 and prostaglandins production has been implicated in hepatic regeneration, liver matrix remodeling and portal hypertension. In animal models of alcoholic-induced liver disease has been demonstrated its relation with necro-inflammatory activity. In viral hepatitis, hepatocellular COX-2 expression was observed and associated with fibrosis progression. More interestingly it has been the demonstration of COX-2 role in the development of hepatocellular carcinoma and cholangiocarcinoma, such in experimental models as in human samples. It has also been demonstrated that COX-2 was implicated in carcinogenesis through apoptosis inhibition and increased proliferation of human tumor cells. Experimental evidences show that selective pharmacologic inhibition of COX-2 could be useful in chemoprevention of primary liver tumors.

The cyclooxygenase-2 inhibitor celecoxib blocks phosphorylation of Akt and induces apoptosis in human cholangiocarcinoma cells

The expression of cyclooxygenase (COX)-2 is increased in human cancers including cholangiocarcinoma. This study was designed to evaluate the effect and mechanisms of the selective COX-2 inhibitor celecoxib in the growth control of human cholangiocarcinoma cells. Immunohistochemical analysis using human cholangiocarcinoma tissues showed increased levels of COX-2 as well as phospho-Akt (Thr 308), a protein kinase activated by COX-2-mediated prostaglandins, in human cholangiocarcinoma cells. Treatment of cultured human cholangiocarcinoma cells (HuCCT1, SG231, and CCLP1) with celecoxib resulted in a dose- and time-dependent reduction of cell viability. Fluorescence microscopy, Western blot, and caspase activity assays demonstrated that celecoxib induced morphological features of apoptosis, activation of caspase-9 and caspase-3, and release of cytochrome c. The celecoxib-induced cell death was significantly blocked by N-benzyloxy-carbonyl-Val-Ala-Asp-fluoromethylketone, a wide-spectrum caspase inhibitor. Furthermore, cholangiocarcinoma cells treated with celecoxib showed significant reduction of Akt phosphorylation, whereas the levels of Bcl-2 and Bax were not altered. Inhibition of Akt activation by LY294002 significantly decreased the viability of human cholangiocarcinoma cells. These findings suggest that celecoxib inhibits cholangiocarcinoma growth partly through induction of apoptosis and inhibition of Akt phosphorylation.

Oxysterols induce cyclooxygenase-2 expression in cholangiocytes: implications for biliary tract carcinogenesis

Cyclooxygenase-2 (COX-2), which is expressed by cholangiocytes in biliary tract disorders, has recently been implicated in biliary tract carcinogenesis. The mechanisms responsible for this COX-2 expression remain unclear. In human diseases, bile contains oxygenated derivatives of cholesterol (oxysterols) which possess diverse biological properties. Therefore, we determined if oxysterols modulate COX-2 expression. The effect of an oxysterol (22(R)-hydroxycholesterol, 22-HC) on COX-2 expression in KMBC cells, a human cholangiocarcinoma cell line, was examined. 22-HC enhanced COX-2 protein expression. This oxysterol activated p42/44 and p38 MAPK, but not JNK 1/2. A p42/44 MAPK inhibitor did not block COX-2 induction, while p38 MAPK inhibitor effectively attenuated COX-2 induction. Although COX-2 mRNA levels were increased by 22-HC, this increase was not transcriptionally regulated, as 22-OH did not increase activity in a COX-2 promoter gene assay. In contrast, COX-2 mRNA stability was augmented by 22-HC treatment, and this effect was reversed by a p38 MAPK inhibitor. In conclusion, the results demonstrate that the oxysterol 22-HC stabilizes COX-2 mRNA via a p38 MAPK-dependent mechanism. This enhanced COX-2 protein expression by oxysterols may participate in the genesis and progression of cholangiocarcinoma.

Development of a therapeutic adenoviral vector for cholangiocarcinoma combining tumor-restricted gene expression and infectivity enhancement

Cholangiocarcinoma is an invasive malignancy that is most often unresectable upon diagnosis and unresponsive to chemotherapy and radiation. While adenoviral gene therapy has shown promise in treating many tumors, systemic toxicity and low tumor transduction efficiency have hampered its application in many gastrointestinal cancers. To overcome these difficulties, we have constructed an adenoviral vector utilizing a tumor-specific promoter (TSP) for selective transgene expression and a vector with an RGD-motif in the fiber-knob region for infectivity enhancement. In seeking a TSP for cholangiocarcinoma, Secretory Leukoprotease Inhibitor, Midkine, Gastrin Releasing Peptide, VEGF, Cox-2M, and Cox-2L promoters were configures in adenoviral vectors, and evaluated in cholangiocarcinoma cells lines (Oz and SkChA-1). Luciferase assays demonstrated that Cox-2 promoters (M and L) showed the highest promoter activity, with Cox-2M appearing slightly stronger than Cox-2L. Infectivity enhanced vectors with RGD-motif in the fiber-knob region were also constructed with the luciferase transgene driven by a CMV control and the Cox-2M and Cox-2L promoters. Subsequent luciferase assays comparing the unmodified vectors to the RGD-modified versions demonstrated higher levels of luciferase activity than the RGD-infected cells. This paradigm was then applied to a therapeutic HSV-TK/GCV model by constructing RGD-enhanced HSV-TK vectors driven by Cox-2M and Cox-2L promoters. In vitro cytocidal effect analysis confirmed that the RGD-modified, cox-2 (M and L) driven vectors showed a stronger cytocidal effect upon gancyclovir administration than the vectors with wild-type fiber. The Cox-2 promoter demonstrates a favorable selectivity profile for cholangiocarcinoma, and RGD-modification further enhances transduction efficiency. This combination has potential to overcome the obstacles to clinical application of adenoviral gene therapy in cholangiocarcinoma.

Proliferative activity of bile from congenital choledochal cyst patients

AIM: To explore the potential carcinogenicity of bile from congenital choledochal cyst (CCC) patients and the mechanism of the carcinogenesis in congenital choledochal cyst patients.

METHODS: 20 bile samples from congenital choledochal cyst patients and 10 normal control bile samples were used for this study. The proliferative effect of bile was measured by using Methabenzthiazuron (MTT) assay; Cell cycle and apoptosis were analyzed by using flow cytometry (FCM), and the PGE₂ levels in the supernatant of cultured cholangiocarcinoma cells were quantitated by enzyme-linked immunoabsordent assay (ELISA).

RESULTS: CCC bile could significantly promote the proliferation of human cholangiocarcinoma QBC939 cells compared with normal bile (P = 0.001) and negative control group (P = 0.002), and the proliferative effect of CCC bile could be abolished by addition of cyclooxygenase-2 specific inhibitor celecoxib (20 µM). The QBC939 cells proliferative index was increased significantly after treated with 1% bile from CCC patient (P = 0.008) for 24 h, the percentage of S phase (29.48 ± 3.27)% was increased remarkably (P < 0.001) compared with normal bile (11.72 ± 2.70)%, and the percentage of G0/G1 phase (54.19 ± 9.46)% was decreased remarkably (P = 0.042) compared with normal bile (69.16 ± 10.88)%, however, bile from CCC patient had no significant influence on apoptosis of QBC939 cells (P = 0.719).

CONCLUSION: Bile from congenital choledochal cyst patients can promote the proliferation of human cholangiocarcinoma QBC939 cells via COX-2 and PGE₂ pathway.

Mouse skin as a model for cancer chemoprevention by nonsteroidal anti-inflammatory drugs

The mouse skin model of multistage carcinogenesis has demonstrated that cancer results from a synergism between genotoxic and nongenotoxic factors. The former induce irreversible genetic alterations, whereas the latter promote tumor development by favoring the clonal outgrowth of the genetically altered cells. While therapeutic gene repair is a still unrealized dream, tumor promotion provides an attractive target for cancer prevention. A key event in epithelial tumor development is an aberrant constitutive overexpression of cyclooxygenase-2 (COX-2), being detectable already in premalignant lesions and leading to an overproduction of prostaglandins. In the mouse skin model, prostaglandin F2alpha has been identified as an endogenous tumor promoter. The well-established chemopreventive effect of nonsteroidal anti-inflammatory drugs seems to be mainly due to COX-2 inhibition. Targeted transgenic overexpression of COX-2 in mouse epidermis induces a preneoplastic phenotype and renders the tissue extremely sensitive to genotoxic carcinogens; i.e., for the induction of skin tumor development, tumor promoter treatment can be omitted in those animals. It is concluded that COX-2 acts as an endogenous tumor promoter and that its overexpression represents a first order risk factor for cancer development. Conversely, specific COX-2 inhibitors rank among the most promising agents for cancer chemoprevention.

Involvement of 85-kd cytosolic phospholipase A(2) and cyclooxygenase-2 in the proliferation of human cholangiocarcinoma cells

Cyclooxygenase 2 (COX-2) and cytosolic phospholipase A(2) (cPLA(2)) are the crucial rate-limiting enzymes in prostaglandin (PG) metabolism that show increased expression in a number of human cancers, including cholangiocarcinomas; and treatment of cholangiocarcinoma cell lines with COX-2 inhibitors can decrease proliferation. Cholangiocarcinomas also produce and proliferate in response to nonneoplastic biliary epithelial cell mitogens, such as interleukin 6 (IL-6) and hepatocyte growth factor (HGF). This study was designed to determine whether there is any relationship between eicosanoid metabolism and growth stimulation by IL-6 and HGF, two important biliary epithelial cell and cholangiocarcinoma mitogens. Incubation of SG231, a well-characterized human cholangiocarcinoma cell line, with HGF, IL-6, PGE(2), or PGF(2)alpha resulted in significantly increased cell growth. HGF and IL-6 also induced a rapid release of arachidonic acid (AA) from SG231 and increased the synthesis of PGE(2) and PGF(2)alpha. The cPLA(2) inhibitor arachidonyl fluorophosphonate (MAFP) and the COX-2 inhibitor NS-398 significantly inhibited HGF- and IL-6-induced release of AA, PG synthesis, and proliferation in SG231 cells as well as two other human cholangiocarcinoma cell lines, HuCCT1 and CC-LP-1 cells. Thus, PGs alone can induce cholangiocarcinoma growth, and the HGF- and IL-6-induced proliferation is mediated, at least in part, by PGs. HGF and IL-6 also induced a rapid phosphorylation of cPLA(2) (within 1 minute) but did not alter cPLA(2) and COX-2 protein expression. The HGF- and IL-6-induced cPLA(2) phosphorylation was blocked by the inhibitors of p38 and p42/44 MAP kinases, protein kinase C, calmodulin kinase, and tyrosine kinase, showing that HGF- and IL-6-induced AA release and PG production are mediated by phosphorylation of cPLA(2). In conclusion, molecular pathways link classic biliary epithelial cell mitogens to PG metabolism constituents in cholangiocarcinoma growth, which may be exploited as potential therapeutic targets.