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

Unveiling the significance of inducible nitric oxide synthase: Its impact on cancer progression and clinical implications

The intricate role of inducible nitric oxide synthase (iNOS) in cancer pathophysiology has garnered significant attention, highlighting the complex interplay between tumorigenesis, immune response, and cellular metabolism. As an enzyme responsible for producing nitric oxide (NO) in response to inflammatory stimuli. iNOS is implicated in various aspects of cancer development, including DNA damage, angiogenesis, and evasion of apoptosis. This review synthesizes the current findings from both preclinical and clinical studies on iNOS across different cancer types, reflecting the variability depending on cellular context and tumor microenvironment. We explore the molecular mechanisms by which iNOS modulates cancer cell growth, survival, and metastasis, emphasizing its impact on immune surveillance and response to treatment. Additionally, the potential of targeting iNOS as a therapeutic strategy in cancer treatment is examined. By integrating insights from recent advances, this review aims to elucidate the significant role of iNOS in cancer and pave the way for novel diagnostic and therapeutic approaches.

Research update for ferroptosis and cholangiocarcinoma

Cholangiocarcinoma (CCA) is the second most common hepatobiliary malignancy after hepatocellular carcinoma. Due to the poor treatment effect and high mortality rate of CCA, it is of great significance to explore new therapeutic targets. Ferroptosis is a type of cell death caused by iron-dependent cell oxidative injury, which is closely related to the occurrence and development of numerous diseases. Novel ideas for the prevention and treatment of related diseases have been provided by ferroptosis, which has become a focus of research in recent years. This review introduces the underlying mechanisms related to ferroptosis, as well as a research update for ferroptosis in the occurrence and development of CCA. The clinical value of ferroptosis-related regulatory mechanisms in CCA will be elucidated.

Replacement of nitrates and nitrites in meat-derived foods through the utilization of coagulase-negative staphylococci: A review

Nitrates and nitrites, which are synthetic additives, are traditionally used as curing agents in meat-based products. These synthetic additives are employed in the preparation of fermented meat foods to improve quality characteristics and microbiological safety, develop distinct flavours and red-colour stability, and counteract lipid oxidation. Nitrites also display significant bacteriostatic and bactericidal action against spoilage microorganisms and foodborne pathogens (such as Clostridium botulinum and Listeria monocytogenes). However, meat curing is currently under scrutiny because of its links to cardiovascular diseases and colorectal cancer. Based on the current literature, this review provides recent scientific evidence on the potential utilisation of coagulase-negative staphylococci (CNS) as nitrate and nitrite substitutes in meat-based foods. Indeed, CNS are reported to reproduce the characteristic red pigmentation and maintain the typical high-quality traits of cured-meats, thanks to their arginine degradation pathway, thus providing the nitrite-related desirable attributes in cured meat. The alternative strategy, still based on the NOS pathway, consisting of supplementing meat with arginine to release nitric oxide (NO) and obtain a meat characterised by the desired pinkish-red colour, is also reviewed. Exploiting NOS-positive CNS strains seems particularly challenging because of CNS technological adaptation and the oxygen dependency of the NOS reaction; however, this exploitation could represent a turning point in replacing nitrates and nitrites in meat foods.

Extrahepatic Outcomes of Nonalcoholic Fatty Liver Disease: Nonhepatocellular Cancers

Nonalcoholic fatty liver disease (NAFLD) encompasses the entire spectrum of fatty liver disease in individuals without significant alcohol consumption, including isolated steatosis, steatohepatitis, and cirrhosis. The overall global prevalence of NAFLD is estimated to be 30%, and the associated clinical and economic burden will continue to increase. NAFLD is a multisystemic disease with established links to cardiovascular disease, type 2 diabetes, metabolic syndrome, chronic kidney disease, polycystic ovarian syndrome, and intra- and extrahepatic malignancies. In this article the authors review the potential mechanisms and current evidence for the association between NAFLD and extrahepatic cancers and the resultant impact on clinical outcomes.

Epigenetic Silencing of 15-Hydroxyprostaglandin Dehydrogenase by Histone Methyltransferase EHMT2/G9a in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a lethal malignancy with few therapeutic options. NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) has been shown to inhibit CCA cell growth in vitro and in xenograft models. However, the role of 15-PGDH in CCA development has not been investigated and the mechanism for 15-PGDH gene regulation remains unclear. Here, we evaluated the role of 15-PGDH in CCA development by using a mouse model with hydrodynamic tail vein injection of transposase-based plasmids expressing Notch1 intracellular domain and myr-Akt, with or without co-injection of 15-PGDH expression plasmids. Our results reveal that 15-PGDH overexpression effectively prevents CCA development. Through patient data mining and experimental approaches, we provide novel evidences that 15-PGDH is epigenetically silenced by histone methyltransferase G9a. We observe that 15-PGDH and G9a expressions are inversely correlated in both human and mouse CCAs. By using CCA cells and mouse models, we show that G9a inhibition restores 15-PGDH expression and inhibited CCA in vitro and in vivo. Mechanistically, our data indicate that G9a is recruited to 15-PGDH gene promoter via protein-protein interaction with the E-box binding Myc/Max heterodimer. The recruited G9a then silences 15-PGDH gene through enhanced methylation of H3K9. Our further experiments have led to the identification of STAT4 as a key transcription factor involved in the regulation of 15-PGDH by G9a. Collectively, our findings disclose a novel G9a-15PGDH signaling axis which is importantly implicated in CCA development and progression. Implications: The current study describes a novel G9a-15PGDH signaling axis which is importantly implicated in cholangiocarcinoma (CCA) development and progression.

A potential role for aspirin in the prevention and treatment of cholangiocarcinoma

Cholangiocarcinoma is the second most common primary hepatic cancer, with a rising incidence worldwide. Owing to late diagnosis and limited treatment options, the prognosis for cholangiocarcinoma remains dismal, compelling a search for new treatments. As aspirin exhibits a well-supported chemopreventive effect on common cancers, researchers have proposed using aspirin as a potential preventive and adjuvant agent for cholangiocarcinoma. In the present review of the literature, we provide a background on cholangiocarcinoma and potential mechanisms of action underlying the anticancer effect of aspirin. Although the exact mode of action remains unclear, multiple downstream effects of aspirin may interfere with cholangiocarcinogenesis, tumour growth and metastasis-including inhibiting the COX-2 pathway, preventing platelet aggregation and modulating certain proteins and signalling. This review also summarises evidence to support the chemopreventive effects of aspirin on common cancers, particularly colorectal cancer and discusses studies that report a positive outcome of aspirin in cholangiocarcinoma. Regular use of aspirin is associated with a reduced incidence of colorectal cancers as well as cholangiocarcinomas, and improved survival. Aspirin thus appears to play a role in the primary prevention and treatment of cholangiocarcinoma. However, further studies are needed to confirm these benefits and to establish a cause-and-effect relationship.

iNOS is associated with tumorigenicity as an independent prognosticator in human intrahepatic cholangiocarcinoma

BACKGROUND

Inducible nitric oxide synthase (iNOS) has supposed to implicate in inflammation, infection, liver cirrhosis, and neoplastic diseases. This study was designed to explore the biological and clinical function of iNOS in intrahepatic cholangiocarcinoma (ICC).

METHODS

RT-PCR (Real-time quantitative PCR) and immunohistochemical staining were used to analyze the expression of iNOS in ICC and adjacent tissues. CCK8, transwell assays, flow cytometry were conducted to detect the proliferation, apoptosis, cell cycle. Western blotting was performed to detect the expression of target proteins. Multivariate analyses were conducted to analysis associates between clinicopathological values and survival.

RESULTS

We found that levels of iNOS mRNA and protein were dramatically increased in ICC samples and positively correlated with complicated bile duct stone, differentiation, pathology T, pathology M, Wip1, MMP-2, and MMP-9. iNOS expression was significantly correlated with the poor survival of ICC patients. Furthermore, iNOS was high expression in ICC cell lines (QBC-939, ICC-9810, SSP-25) compare with human normal biliary epithelium cell line (HIBEpic); both iNOS knockdown and iNOS inhibitor (1400 W) suppressed cell proliferation, invasion, and migration though nitric oxide production in ICC cells. Down-regulation of iNOS also induced G0/G1 cell cycle arrest and ICC cell apoptosis. Moreover, iNOS knockdown treatment significantly decreased Wip1, MMP-9, and MMP-2 gene expression.

CONCLUSION

Lowly expressed iNOS-inhibited proliferation yet promoted apoptosis of ICC cells. Our data show targeted inhibition of iNOS in ICC may have therapeutic value.

Effects of aspirin and non-steroidal anti-inflammatory drugs on the risk of cholangiocarcinoma: a meta-analysis

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) can suppress the proliferation of cholangiocarcinoma (CCA) cells in vitro through inhibition of cyclooxygenase-2. However, the effects of aspirin and NSAIDs on the risk of CCA remain unclear. We performed this meta-analysis to assess the risk of biliary tract cancers in patients who take aspirin and/or NSAIDs.

METHODS

A systematic review was conducted utilizing MEDLINE, EMBASE, Cochrane databases from inception through October 2017 to identify studies that assessed the association of aspirin and/or NSAIDs use with risk of biliary tract cancers including CCA, gallbladder cancer and ampulla of Vater cancer. Effect estimates from the studies were extracted and combined using the random-effect, generic inverse variance method of DerSimonian and Laird.

RESULTS

Five observational studies with a total of 9 200 653 patients were enrolled. The pooled OR of CCA in patients with aspirin use was 0.56 (95% CI, 0.32-0.96). Egger's regression asymmetry test was performed and showed no publication bias for the association between aspirin use and CCA with P = 0.42. There was no significant association between NSAIDs use and CCA, with a pooled OR of 0.79 (95% CI, 0.28-2.21). One study showed a significant association between aspirin use and reduced risk of gallbladder cancer with OR of 0.37 (0.17-0.80). However, there was no significant association between aspirin and ampulla of Vater cancer with OR of 0.22 (0.03-1.65).

CONCLUSIONS

Our study demonstrates a significant association between aspirin use and a 0.56-fold decreased risk of CCA. However, there is no association between the use of NSAIDs and CCA.

Fibroinflammatory Liver Injuries as Preneoplastic Condition in Cholangiopathies

The cholangipathies are a class of liver diseases that specifically affects the biliary tree. These pathologies may have different etiologies (genetic, autoimmune, viral, or toxic) but all of them are characterized by a stark inflammatory infiltrate, increasing overtime, accompanied by an excess of periportal fibrosis. The cellular types that mount the regenerative/reparative hepatic response to the damage belong to different lineages, including cholagiocytes, mesenchymal and inflammatory cells, which dynamically interact with each other, exchanging different signals acting in autocrine and paracrine fashion. Those messengers may be proinflammatory cytokines and profibrotic chemokines (IL-1, and 6; CXCL1, 10 and 12, or MCP-1), morphogens (Notch, Hedgehog, and WNT/β-catenin signal pathways) and finally growth factors (VEGF, PDGF, and TGFβ, among others). In this review we will focus on the main molecular mechanisms mediating the establishment of a fibroinflammatory liver response that, if perpetuated, can lead not only to organ dysfunction but also to neoplastic transformation. Primary Sclerosing Cholangitis and Congenital Hepatic Fibrosis/Caroli’s disease, two chronic cholangiopathies, known to be prodrome of cholangiocarcinoma, for which several murine models are also available, were also used to further dissect the mechanisms of fibroinflammation leading to tumor development.

Non-alcoholic fatty liver disease as a risk factor for cholangiocarcinoma: a systematic review and meta-analysis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has been recently identified as a risk factor of gastrointestinal tract cancers, especially hepatocellular carcinoma, and colorectal cancer. Whether NAFLD is a risk factor for cholangiocarcinoma (CCA) remains inconclusive. The aim of this study is to determine a potential association between NAFLD and CCA, stratifying by its subtypes; intrahepatic CCA (iCCA), and extrahepatic CCA (eCCA).

METHODS

A search was conducted for relevant studies published up to April 2017 using MEDLINE, EMBASE, Scopus and Cochrane databases. Odds ratio (OR) and adjusted OR with 95% confidence interval (CI) were estimated using a random-effects model. Subgroup analyses were conducted with study characteristics.

RESULTS

Seven case-control studies were included in the analysis, with a total of 9,102 CCA patients (5,067 iCCA and 4,035 eCCA) and 129,111 controls. Overall, NAFLD was associated with an increased risk for CCA, with pooled OR of 1.95 (95%CI: 1.36-2.79, I 2 =76%). When classified by subtypes, NAFLD was associated with both iCCA and eCCA, with ORs of 2.22 (95%CI: 1.52-3.24, I 2 =67%) and 1.55 (95%CI: 1.03-2.33, I 2 =69%), respectively. The overall pooled adjusted ORs were 1.97 (95%CI: 1.41-2.75, I 2 =71%), 2.09 (95%CI, 1.49-2.91, I 2 =42%) and 2.05 (95%CI, 1.59-2.64, I 2 =0%) for all CCAs, iCCA, and eCCA, respectively.

CONCLUSIONS

This meta-analysis suggests that NAFLD may potentially increase the risk of CCA development. The magnitude of NAFLD on CCA risk is greater for iCCA than eCCA subtype, suggestive of a common pathogenesis of iCCA and hepatocellular carcinoma. Further studies to confirm this association are warranted.

TRIAL REGISTRATION

The protocol for this study was registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42016046573).

Intrahepatic cholangiocarcinoma: Role of metabolism in pathogenesis, clinical diagnosis, and treatment

Recent studies demonstrated that metabolism plays an important role in the pathogenesis, clinical diagnosis, and treatment of intrahepatic cholangiocarcinoma (ICC). The mechanisms of several metabolic enzymes associated with ICC, including pyruvate kinase M2 (PKM2), thymidine synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), isocitric acid dehydrogenase 1/2 (IDH1/2), and cyclo-oxygenase-2 (COX-2), have been gradually clarified and hopefully transformed into clinical application in the future. Besides, ICC patients always have concomitant abnormal lipid metabolism, which has attracted the attention of clinicians and researchers. Metabolites in serum and bile have potential diagnostic utility, which has yet to be verified by prospective clinical research. ¹⁸F-FDG PET/CT based on metabolism presents application value in many aspects of ICC, such as diagnosis, staging, evaluation of therapeutic effect, and monitoring prognosis. In this article, we review the recent progress in the understanding of the role of metabolism in ICC from both basic and clinical perspectives, with an aim to highlight the further research directions and accelerate the clinical transformation.

New insights into cholangiocarcinoma: multiple stems and related cell lineages of origin

Cholangiocarcinoma (CCA) is a heterogeneous group of malignancies that may develop at any level of the biliary tree. CCA is currently classified into intrahepatic (iCCA), perihilar (pCCA) and distal (dCCA) on the basis of its anatomical location. Notably, although these three CCA subtypes have common features, they also have important inter- and intra-tumor differences that can affect their pathogenesis and outcome. A unique feature of CCA is that it manifests in the hepatic parenchyma or large intrahepatic and extrahepatic bile ducts, furnished by two distinct stem cell niches: the canals of Hering and the peribiliary glands, respectively. The complexity of CCA pathogenesis highlights the need for a multidisciplinary, translational, and systemic approach to this malignancy. This review focuses on advances in the knowledge of CCA histomorphology, risk factors, molecular pathogenesis, and subsets of CCA.

Butanol extracts of Asparagus cochinchinensis fermented with Weissella cibaria inhibit iNOS-mediated COX-2 induction pathway and inflammatory cytokines in LPS-stimulated RAW264.7 macrophage cells

Roots of Asparagus cochinchinesis have been widely used to treat fever, cough, kidney disease, breast cancer, inflammatory and brain disease, although the effects of their fermented products have not been assessed until now. To investigate the anti-inflammatory effects on macrophages of a butanol extract from A. cochinchinensis roots fermented with Weissella cibaria (BAW), alterations in the inducible nitric oxide synthase (iNOS)-mediated cyclooxygenase-2 (COX-2) induction pathway and inflammatory cytokine expression were measured in lipopolysaccharide (LPS)-activated RAW264.7 cells following pretreatment with BAW. Briefly, W. cibaria was selected from two bacterial strains for the fermentation of A. cochinchinensis roots based on its hyaluronidase inhibition and NO suppression rates. Following fermentation with W. cibaria, the level of various key components including total phenols and protodioscin were significantly enhanced in BAW. In addition, BAW exhibited high free radical scavenging activity (IC₅₀=31.62 µg/ml) and induced a decrease of intracellular ROS production in RAW264.7 cells following DCFH-DA staining. Significant suppressions in the expression level of important members of the iNOS-mediated COX-2 induction pathway and the phosphorylation of mitogen-activated protein kinase members were detected. The expressions of pro-inflammatory and anti-inflammatory cytokines were recovered in BAW pretreated RAW264.7 cells. Overall, these results suggest that BAW may suppress inflammatory responses through differential regulation of the iNOS-mediated COX-2 induction pathway and inflammatory cytokine expressions in LPS-activated RAW264.7 cells.

Allogeneic Adipose-Derived Mesenchymal Stromal Cells Ameliorate Experimental Autoimmune Encephalomyelitis by Regulating Self-Reactive T Cell Responses and Dendritic Cell Function

Multipotent mesenchymal stromal cells (MSCs) have emerged as a promising therapy for autoimmune diseases, including multiple sclerosis (MS). Administration of MSCs to MS patients has proven safe with signs of immunomodulation but their therapeutic efficacy remains low. The aim of the current study has been to further characterize the immunomodulatory mechanisms of adipose tissue-derived MSCs (ASCs) in vitro and in vivo using the EAE model of chronic brain inflammation in mice. We found that murine ASCs (mASCs) suppress T cell proliferation in vitro via inducible nitric oxide synthase (iNOS) and cyclooxygenase- (COX-) 1/2 activities. mASCs also prevented the lipopolysaccharide- (LPS-) induced maturation of dendritic cells (DCs) in vitro. The addition of the COX-1/2 inhibitor indomethacin, but not the iNOS inhibitor L-NAME, reversed the block in DC maturation implicating prostaglandin (PG) E₂ in this process. In vivo, early administration of murine and human ASCs (hASCs) ameliorated myelin oligodendrocyte protein- (MOG_35-55-) induced EAE in C57Bl/6 mice. Mechanistic studies showed that mASCs suppressed the function of autoantigen-specific T cells and also decreased the frequency of activated (CD11c⁺CD40^high and CD11c⁺TNF-α⁺) DCs in draining lymph nodes (DLNs). In summary, these data suggest that mASCs reduce EAE severity, in part, through the impairment of DC and T cell function.

Clonorchis sinensis, an oriental liver fluke, as a human biological agent of cholangiocarcinoma: a brief review

Parasitic diseases remain an unarguable public health problem worldwide. Liver fluke Clonorchis sinensis is a high risk pathogenic parasitic helminth which is endemic predominantly in Asian countries, including Korea, China, Taiwan, Vietnam, and the far eastern parts of Russia, and is still actively transmitted. According to the earlier 8^th National Survey on the Prevalence of Intestinal Parasitic Infections in 2012, C. sinensis was revealed as the parasite with highest prevalence of 1.86% in general population among all parasite species surveyed in Korea. This fluke is now classified under one of the definite Group 1 human biological agents (carcinogens) by International Agency of Research on Cancer (IARC) along with two other parasites, Opisthorchis viverrini and Schistosoma haematobium. C. sinensis infestation is mainly linked to liver and biliary disorders, especially cholangiocarcinoma (CCA). For the purposes of this mini-review, we will only focus on C. sinensis and review pathogenesis and carcinogenesis of clonorchiasis, disease condition by C. sinensis infestation, and association between C. sinensis infestation and CCA. In this presentation, we briefly consider the current scientific status for progression of CCA by heavy C. sinensis infestation from the food-borne trematode and development of CCA.

Expert consensus document: Cholangiocarcinoma: current knowledge and future perspectives consensus statement from the European Network for the Study of Cholangiocarcinoma (ENS-CCA)

Cholangiocarcinoma (CCA) is a heterogeneous group of malignancies with features of biliary tract differentiation. CCA is the second most common primary liver tumour and the incidence is increasing worldwide. CCA has high mortality owing to its aggressiveness, late diagnosis and refractory nature. In May 2015, the "European Network for the Study of Cholangiocarcinoma" (ENS-CCA: www.enscca.org or www.cholangiocarcinoma.eu) was created to promote and boost international research collaboration on the study of CCA at basic, translational and clinical level. In this Consensus Statement, we aim to provide valuable information on classifications, pathological features, risk factors, cells of origin, genetic and epigenetic modifications and current therapies available for this cancer. Moreover, future directions on basic and clinical investigations and plans for the ENS-CCA are highlighted.

Prognostic molecular markers in resected extrahepatic biliary tract cancers; a systematic review and meta-analysis of immunohistochemically detected biomarkers

Better prognostic information for resected extrahepatic cholangiocarcinoma could guide treatment strategies and potentially improve outcome. This study performed a systematic review and meta-analysis to identify prognostic biomarkers for further investigation.

METHODS

Relevant literature was identified using Medline, EMBASE and Web of Science. Primary end point was overall survival assessed on univariate analysis. Log hazard ratio and variance were calculated and pooled using a random effects inverse variance approach. Hazard ratio and 95% confidence intervals were calculated.

RESULTS

Thirty-seven studies, including 2371 patients, met the inclusion criteria. Subsequently nine biomarkers predictive of OS were identified (HR, 95% CI): VEGF (2.32, 1.57-3.44), COX-2 (1.94, 1.01-3.71), GLUT-1 (2.09, 1.52-2.89), Cyclin D1 (1.96, 1.02-3.76), p16 (0.68, 0.47-0.98), p27 (0.48, 0.3-0.78), E-Cadherin (0.47, 0.35-0.63), Fascin (2.19, 1.35-3.55), and Ki-67 (1.69, 1.02-2.79).

CONCLUSION

Meta-analysis has identified a number of prognostic biomarkers for resected extrahepatic cholangiocarcinoma. These markers warrant further investigation as potential therapeutic targets and validation in a prospective setting.

IL-33 facilitates oncogene-induced cholangiocarcinoma in mice by an interleukin-6-sensitive mechanism

Cholangiocarcinoma (CCA) is a lethal hepatobiliary neoplasm originating from the biliary apparatus. In humans, CCA risk factors include hepatobiliary inflammation and fibrosis. The recently identified interleukin (IL)-1 family member, IL-33, has been shown to be a biliary mitogen which also promotes liver inflammation and fibrosis. Our aim was to generate a mouse model of CCA mimicking the human disease. Ectopic oncogene expression in the biliary tract was accomplished by the Sleeping Beauty transposon transfection system with transduction of constitutively active AKT (myr-AKT) and Yes-associated protein. Intrabiliary instillation of the transposon-transposase complex was coupled with lobar bile duct ligation in C57BL/6 mice, followed by administration of IL-33 for 3 consecutive days. Tumors developed in 72% of the male mice receiving both oncogenes plus IL-33 by 10 weeks but in only 20% of the male mice transduced with the oncogenes alone. Tumors expressed SOX9 and pancytokeratin (features of CCA) but were negative for HepPar1 (a marker of hepatocellular carcinoma). Substantive overlap with human CCA specimens was revealed by RNA profiling. Not only did IL-33 induce IL-6 expression by human cholangiocytes but it likely facilitated tumor development in vivo by an IL-6-sensitive process as tumor development was significantly attenuated in Il-6(-/-) male animals. Furthermore, tumor formation occurred at a similar rate when IL-6 was substituted for IL-33 in this model.

CONCLUSION

The transposase-mediated transduction of constitutively active AKT and Yes-associated protein in the biliary epithelium coupled with lobar obstruction and IL-33 administration results in the development of CCA with morphological and biochemical features of the human disease; this model highlights the role of inflammatory cytokines in CCA oncogenesis.

The challenge of cholangiocarcinoma: dissecting the molecular mechanisms of an insidious cancer

Cholangiocarcinoma is a fatal cancer of the biliary epithelium and has an incidence that is increasing worldwide. Survival beyond a year of diagnosis is less than 5%, and therapeutic options are few. Known risk factors include biliary diseases such as primary sclerosing cholangitis and parasitic infestation of the biliary tree, but most cases are not associated with any of these underlying diseases. Numerous in vitro and in vivo models, as well as novel analytical techniques for human samples, are helping to delineate the many pathways implicated in this disease, albeit at a frustratingly slow pace. As yet, however, none of these studies has been translated into improved patient outcome and, overall, the pathophysiology of cholangiocarcinoma is still poorly understood. There remains an urgent need for new approaches and models to improve management of this insidious and devastating disease. In this review, we take a bedside-to-bench approach to discussing cholangiocarcinoma and outline research opportunities for the future in this field.

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.

Advances in research of signaling pathways in cholangiocarcinoma

Epidemiological data indicate that the incidence and mortality of cholangiocarcinoma (CC) show an increasing trend worldwide over the past several years. Many pathophysiologic aspects of this neoplasia are still unknown and need to be fully discovered. However, progress has been recently made in understanding molecular mechanisms involved in the transformation and growth of malignant cholangiocytes. It is found that cholangiocarcinogenesis is a multistep cellular process evolving from a normal condition of the epithelial biliary cells and ending with malignant transformation through a chronic inflammation status. The bad prognosis related to CC justifies why a better identification of the molecular mechanisms involved in the growth and progression of this cancer is required for the development of effective preventive measures and valid treatment regimens. Signaling pathways can regulate substance and energy metabolism in organisms and are closely related to biological growth and development. This paper mainly introduces signaling pathways which occur in cholangiocarcinoma and their roles in cholangiocarcinoma cells.

Molecular pathogenesis of cholangiocarcinoma

Epidemiological data from the last years show an increasing trend of incidence and mortality of cholangiocarcinoma (CC) worldwide. Many pathophysiologic aspects of this neoplasia are still unknown and need to be fully discovered. However, several progresses were recently made in order to establish the molecular mechanisms involved in the transformation and growth of malignant cholangiocytes. The principal concept that at least seems to be established is that cholangiocarcinogenesis is a multistep cellular process evolving from a normal condition of the epithelial biliary cells through a chronic inflammation status ending with malignant transformation. The bad prognosis related to CC justifies why a better identification of the molecular mechanisms involved in the growth and progression of this cancer is required for the development of effective preventive measures and valid treatment regimens. This Paper describes the scientific progresses made in the last years in defining the molecular pathways implicated in the generation of this devastating disease.

Molecular mechanisms of cholangiocarcinoma

Cholangiocarcinoma (CC), the malignant tumor of the epithelial cells lining the biliary ducts, has undergone a worldwide increase in incidence and mortality. The malignant transformation of the biliary cells originates from a multistep process evolving through chronic inflammation of the biliary tract to CC. In the last few years several advances have been towards understanding and clarifying the molecular mechanisms implicated in the cholangiocarcinogenesis process. However, many pathophysiologic aspects governing the growth of CC are still undefined. The poor prognosis of this tumor underlines the urgent need to codify the underlying molecular mechanisms involved in the growth and progression of CC in order to design effective preventive measures and valid treatment regimens. This review reports on progresses made in the last few years in clarifying the molecular pathways involved in the process of cholangiocarcinogenesis.

Cholangiocarcinoma: update and future perspectives

Cholangiocarcinoma is commonly considered a rare cancer. However, if we consider the hepato-biliary system a single entity, cancers of the gallbladder, intra-hepatic and extra-hepatic biliary tree altogether represent approximately 30% of the total with incidence rates close to that of hepatocellular carcinoma, which is the third most common cause of cancer-related death worldwide. In addition, cholangiocarcinoma is characterized by a very poor prognosis and virtually no response to chemotherapeutics; radical surgery, the only effective treatment, is not frequently applicable because late diagnosis. Biomarkers for screening programs and for follow-up of categories at risk are under investigation, however, currently none of the proposed markers has reached clinical application. For all these considerations, cancers of the biliary tree system should merit much more scientific attention also because a progressive increase in incidence and mortality for these cancers has been reported worldwide. This manuscript deals with the most recent advances in the epidemiology, biology and clinical presentation of cholangiocarcinoma.

New insights on cholangiocarcinoma

Cholangiocarcinoma (CCA) is a devastating cancer arising from the neoplastic transformation of the biliary epithelium. It is characterized by a progressive increase in incidence and prevalence. The only curative therapy is radical surgery or liver transplantation but, unfortunately, the majority of patients present with advanced stage disease, which is not amenable to surgical therapies. Recently, proposed serum and bile biomarkers could help in the screening and surveillance of categories at risk and in diagnosing CCA at an early stage. The molecular mechanisms triggering neoplastic transformation and growth of biliary epithelium are still undefined, but significant progress has been achieved in the last few years. This review deals with the most recent advances on epidemiology, biology, and clinical management of CCA.

Inhibition of nitric oxide synthesis during induced cholestasis ameliorates hepatocellular injury by facilitating S-nitrosothiol homeostasis

Cholestatic liver injury following extra- or intrahepatic bile duct obstruction causes nonparenchymal cell proliferation and matrix deposition leading to end-stage liver disease and cirrhosis. In cholestatic conditions, nitric oxide (NO) is mainly produced by a hepatocyte-inducible NO synthase (iNOS) as a result of enhanced inflow of endotoxins to the liver and also by accumulation of bile salts in hepatocytes and subsequent hepatocellular injury. This study was aimed to investigate the role of NO and S-nitrosothiol (SNO) homeostasis in the development of hepatocellular injury during cholestasis induced by bile duct ligation (BDL) in rats. Male Wistar rats (200-250 g) were divided into four groups (n=10 each), including sham-operated (SO), bile duct-ligated (BDL), tauroursodeoxycholic acid (TUDCA, 50 mg/kg) and S-methylisothiourea (SMT, 25 mg/kg) treated. After 7 days, BDL rats showed elevated serum levels of gamma-glutamiltranspeptidase, aspartate aminotransferase, alanine aminotransferase, LDH, and bilirubin, bile duct proliferation and fibrosis, compared with the SO group. TUDCA treatment did not significantly alter these parameters, but the iNOS inhibitor SMT ameliorated hepatocellular injury, as shown by lower levels of circulating hepatic enzymes and bilirubin, and a decreased grade of bile duct proliferation and fibrosis. Both TUDCA and SMT treatments reversed Mrp2 canalicular pump expression to control levels. However, only SMT treatment significantly lowered the increased levels of plasma NO and S-nitrosation (S-nitrosylation) of liver proteins in BDL rats. Moreover, BDL resulted in a reduction of the S-nitrosoglutathione reductase (GSNOR/Adh5) enzymatic activity and a downregulation of the GSNOR/Adh5 mRNA expression that was reverted by SMT, but not TUDCA, treatment. A total of 25 liver proteins, including S-adenosyl methionine synthetase, betaine-homocysteine S-methyltransferase, Hsp90 and protein disulfide isomerase, were found to be S-nitrosated in BDL rats. In conclusion, the inhibition of NO production during induced cholestasis ameliorates hepatocellular injury. This effect is in part mediated by the improvement of cell proficiency in maintaining SNO homeostasis.

Targeting liver fibrosis: strategies for development and validation of antifibrotic therapies

We have made striking progress in our understanding of the biochemistry and cell biology that underlies liver fibrosis and cirrhosis, including the development of strategies and agents to prevent and reverse fibrosis. However, translation of this knowledge into clinical practice has been hampered by (1) the limitation of many in vitro and in vivo models to confirm mechanisms and to test antifibrotic agents, and (2) the lack of sensitive methodologies to quantify the degree of liver fibrosis and the dynamics of fibrosis progression or reversal in patients. Furthermore, whereas cirrhosis and subsequent decompensation are accepted hard clinical endpoints, fibrosis and fibrosis progression alone are merely plausible surrogates for future clinical deterioration. In this review we focus on an optimized strategy for preclinical antifibrotic drug development and highlight the current and future techniques that permit noninvasive assessment and quantification of liver fibrosis and fibrogenesis. The availability of such noninvasive methodologies will serve as the pacemaker for the clinical development and validation of potent antifibrotic agents.

Minocycline in the treatment of patients with primary sclerosing cholangitis: results of a pilot study

OBJECTIVES

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of young adults that is associated with significant morbidity and mortality. No effective medical therapy is available. Minocycline has been found to exert biological effects independent of its antimicrobial properties, including anti-inflammatory activities such as inhibition of inducible nitric oxide synthase, upregulation of interleukin 10, and direct suppressive effect on B- and T-cell function. Minocycline may also inhibit cell death pathways by reducing both proapoptotic and proinflammatory enzyme activation. We sought to investigate the safety and efficacy of minocycline among patients with PSC.

METHODS

We evaluated the efficacy of minocycline in patients with PSC in a pilot study. Sixteen patients with PSC were enrolled. Minocycline, 100 mg orally twice daily, was given for 1 year.

RESULTS

A statistically significant improvement in serum alkaline phosphatase activity (330 U/l vs. 265 U/l, P=0.04) and Mayo risk score (0.55 vs. 0.02, P=0.05) occurred with treatment. Serum bilirubin and albumin remained essentially unchanged while on treatment.

CONCLUSIONS

The results of this pilot study indicate that minocycline is reasonably well tolerated and potentially effective in patients with PSC. These findings might be explained by the anti-inflammatory and antiapoptotic properties of minocycline. Though the data presented are too preliminary to support the clinical use of minocycline in the treatment of PSC at this time, its use should be further investigated.

Cholangiocarcinoma: A compact review of the literature

Cholangiocarcinoma (CC) is a devastating cancer arising from biliary epithelia. Unfortunately, the incidence of this disease is increasing in Western countries. These tumors progress insidiously, and liver failure, biliary sepsis, malnutrition and cancer cachexia are general modes of death associated with this disease. To date, no established therapy for advanced disease has been established or validated. However, our knowledge in tumor biology is increasing dramatically and new drugs are under investigation for treatment of this notorious tumor. In clinical practice, there are better diagnostic tools in use to facilitate an earlier diagnosis of CC, at least in those patients with known risk factors. CC is resectable for cure in only a small percentage of patients. Preoperative staging for vascular and biliary extension of CC is very important in this tumor. Laparoscopy and recently endosonography seem to protect against unnecessary laparotomies in these patients. During the last 15 years, aggressive surgical approaches, including combined liver resections and vascular reconstructive surgical expertise, have improved survival in patients with CC. Surgery is contraindicated in CC cases having primary sclerosing cholangitis (PSC). Although CC was previously considered a contraindication to liver transplantation, new cautious protocols, including neo-adjuvant chemoradiation therapies and staging procedures before the transplantation, have made it possible to achieve long-term survival after liver transplantation in this disease. New ablative therapies with photodynamic therapy, intraductal high-intensity ultrasonography and chemotherapy-impregnated plastic biliary endoprosthesis are important steps in the palliative management of extra-hepatic CCs. Radiofrequency and chemo-embolization methods are also applicable for intra-hepatic CCs as palliative modes of treatment. We need more prospective randomized controlled trials to evaluate the role of the new emerging therapies for CC patients.

Mechanisms of biliary carcinogenesis and growth

Cholangiocarcinoma is a rare cancer originating from the neoplastic transformation of the epithelial cells (i.e. cholangiocytes) that line the biliary tract. The prognosis for patients with cholangiocarcinoma is grim due to lack of viable treatment options. The increase in world-wide incidence and mortality from cholangiocarcinoma highlights the importance of understanding the intracellular mechanisms that trigger the neoplastic transformation of cholangiocytes and the growth of biliary cancers. The purpose of the following review is to address what has been learned over the past decade concerning the molecular basis of cholangiocarcinogenesis. The material presented is divided into two sections: (1) mechanisms regulating neoplastic transformation of cholangiocytes; and (2) factors regulating cholangiocarcinoma growth. An understanding of the growth regulatory mechanisms of cholangiocarcinoma will lead to the identification of therapeutic targets for this devastating cancer.

The multidisciplinary management of gastrointestinal cancer. Biliary tract cancers: from pathogenesis to endoscopic treatment

Cholangiocarcinoma is the second most common hepatobiliary tumour. Even if it is a rare tumour, its incidence is increasing over these last decades, probably due in part to a better knowledge of the disease and to an improvement of the diagnosis. Accurate diagnosis and staging are key steps to determine the appropriate treatment. The only curative treatment of this cancer is surgical resection. To date, no neoadjuvant or adjuvant treatments have ever proved any survival benefit, and are not recommended outside clinical trials. Liver transplantation (with or without neoadjuvant treatment) can be an option for highly selected cases. Unfortunately, these tumours are generally diagnosed at an advanced stage or are unresectable. For most of these patients, palliative therapeutic options exist and are in further development, based on multimodal promising combinations including chemotherapy, targeted agents, radiation, endoscopic stenting and photodynamic treatment.

Molecular pathology of biliary tract cancers

The molecular mechanisms underlying the development, growth and metastatic diffusion of biliary tract cancers are still undefined. The increase in worldwide incidence and mortality of cholangiocarcinoma justifies the impellent need to clarify the intracellular mechanisms triggering the malignant transformation of the biliary epithelium and growth of biliary malignancies. A more complete characterization of the molecular pathology of bile duct cancers could lead to the identification of valid targets for the diagnosis and therapy of these devastating malignancies. This review describes the scientific progress made over the past decades with regard to the understanding of the molecular processes of cholangiocarcinogenesis.

Cholangiocarcinoma: modern advances in understanding a deadly old disease

Cholangiocarcinomas are tumors that arise anywhere in the biliary tract, presumably of cholangiocyte origin. The global incidence of this rare disease is on the rise. Several known risk factors exist, and link chronic biliary inflammation to the pathogenesis of cholangiocarcinoma. Among these, amplification of the epidermal growth factor receptor, the interleukin-6 signaling pathway, inducible nitric oxide, erb-2, and cyclooxygenase-2 are well defined. Most patients present late, with a median survival of months. Although, imaging studies and clinical context often indicate cholangiocarcinoma, pathologic and cytologic diagnosis is difficult to obtain. Advanced cytologic tests with fluorescence in situ hybridization or digital image analysis can increase diagnostic sensitivity. Surgical resection is the current therapy of choice for both intrahepatic and ductal cholangiocarcinomas. However, the 5-year survival is poor, with 60 to greater than 90% recurrence rates. In a single center experience, liver transplantation with neoadjuvant chemoirradiation, for highly selected patients, has a 5-year disease free survival of greater than 80%. Future targeted therapies will depend on a better understanding of the cellular and molecular biology of cholangiocarcinomas.

Chronic bile duct injury associated with fibrotic matrix microenvironment provokes cholangiocarcinoma in p53-deficient mice

Intrahepatic cholangiocarcinoma (CCA) is a lethal malignancy of the biliary epithelium associated with p53 mutations, bile duct injury, inflammation, and fibrosis. Here, to validate these processes in CCA, we developed a liver cirrhosis model driven by chronic intermittent toxin exposure, which provokes bile duct injury/necrosis and proliferation, fibroblast recruitment, and progressive extracellular matrix (ECM) changes. Fibrotic changes in the matrix microenvironment, typified by increased type I and III collagens and fibroblast recruitment, were shown to stimulate biliary epithelium hyperplasia with subsequent progression to malignant intrahepatic CCA only in mice harboring a p53 mutant allele. These murine CCAs bear histologic and genetic features of human intrahepatic CCA, including dense peritumoral fibrosis, increased inducible nitric oxide synthase, nitrotyrosine, and cyclooxygenase-2 expression, c-Met activation, cErbB2 overexpression, down-regulation of membrane-associated E-cadherin, and p53 codon 248 mutation. Thus, p53 deficiency, chronic bile duct injury/proliferation, and the fibrotic matrix microenvironment cooperate to induce intrahepatic CCA, highlighting the key role of the ECM microenvironment in this common liver cancer.

Estrogen regulation of nitric oxide and inducible nitric oxide synthase (iNOS) in immune cells: implications for immunity, autoimmune diseases, and apoptosis

Nitric oxide plays a central role in the physiology and pathology of diverse tissues including the immune system. It is clear that the levels of nitric oxide must be carefully regulated to maintain homeostasis. Appropriate levels of nitric oxide derived from iNOS assist in mounting an effective defense against invading microbes. Conversely, inability to generate nitric oxide results in serious, even fatal, susceptibility to infections. Further, dysregulation or overproduction of nitric oxide has been implicated in the pathogenesis of many disorders, including atherosclerosis, neurodegenerative diseases, inflammatory autoimmune diseases, and cancer. Therefore, depending upon the levels of nitric oxide generated, the potential exists for nitric oxide to behave like a "double-edged" biological sword. Taking these issues into consideration, it is thus pivotal to understand the regulation of nitric oxide. Nitric oxide is regulated by many endogenous factors including hormones such as estrogens. While the effects of estrogen on the generation of nitric oxide in non-immune tissues are relatively well documented, the effect of estrogen on iNOS/nitric oxide in immune cells is only now becoming apparent. Our laboratory has recently shown that estrogen treatment of mice markedly upregulates the levels of iNOS mRNA, iNOS protein, and nitric oxide in activated splenocytes. This upregulation of nitric oxide is in part mediated through interferon-gamma (IFN-gamma), a pro-inflammatory cytokine that is enhanced by estrogen. These findings are important considering that estrogens are not only involved in regulation of normal immune responses, but also are implicated in many autoimmune and inflammatory diseases. To date, there are no reviews on the effects of estrogen on immune tissue-derived nitric oxide and therefore this review will address this critical gap in the literature. Given the increasing importance of immune-tissue-derived iNOS in health and disease, studies on estrogen-induced regulation of iNOS may offer a better understanding of diseases and aid in devising new therapeutic interventions.

Ibuprofen Inhibits Skeletal Muscle Hypertrophy in Rats

PURPOSE

We sought to determine whether cyclooxygenase (COX) activity is necessary for overload-induced growth of adult rat skeletal muscle, and whether nitric oxide synthase (NOS) activity is involved in upregulation of COX messenger RNA (mRNA) expression in skeletal muscle.

METHODS

Unilateral surgical removal of the gastrocnemius and soleus was performed on the right hindlimb of 16 female Sprague-Dawley rats (approximately 230 g) to induce chronic overload (OL) of the plantaris for 14 d, with sham surgeries performed on the contralateral leg as a normally loaded (NL) control. Half of the rats were treated with the nonspecific COX inhibitor, ibuprofen (0.2 mg.mL(-1) in drinking water; approximately 20 mg.kg(-1).d(-1)). In a second experiment, the plantaris was unilaterally overloaded for 5 or 14 d in male rats (approximately 350 g; N = 16 rats per time point) and half of the animals were treated with the NOS inhibitor, L-NAME (0.75 mg.mL(-1) in drinking water; approximately 90 mg.kg(-1).d(-1)).

RESULTS

Ibuprofen treatment inhibited plantaris hypertrophy by approximately 50% (P < 0.05) following 14 d of OL, as did L-NAME treatment (P < 0.05). COX-1 and COX-2 mRNA did not differ between any groups at 5 d. At 14 d, however, L-NAME caused a 30-fold increase in plantaris COX-1 mRNA expression independent of loading condition. Additionally, OL induced a 20-fold increase in COX-2 mRNA expression compared with NL (P < 0.05) at 14 d, without affecting COX-1 mRNA level. L-NAME treatment significantly inhibited OL-induced expression of COX-2 mRNA.

CONCLUSION

COX activity is important for in vivo muscle hypertrophy, and plantaris overload is associated with NOS activity-dependent COX-2 expression.

Estrogen up-regulates inducible nitric oxide synthase, nitric oxide, and cyclooxygenase-2 in splenocytes activated with T cell stimulants: role of interferon-gamma

Estrogen is implicated in many autoimmune diseases and is a robust immunomodulator. For example, it regulates interferon (IFN)-gamma, a cytokine believed to up-regulate inducible nitric oxide synthase (iNOS). A notable gap in the literature is a lack of information on the regulation of nitric oxide in immune tissues by estrogen. We now show that activation of splenocytes with T cell stimulants [concanavalin-A (Con-A) or anti-CD3 antibodies] results in copious release of nitric oxide in splenocyte cultures from estrogen-treated but not placebo-treated mice. Moreover, even a low dose of T cell stimulants induced nitric oxide in splenocytes from estrogen-treated, but not placebo-treated, mice. Con-A-activated splenocytes from estrogen-treated mice also have up-regulated iNOS mRNA, iNOS protein, and cyclooxygenase-2 (a nitric oxide-regulated downstream proinflammatory protein) when compared with controls. Our studies suggest that the induction of nitric oxide by activated splenocytes from estrogen-treated mice is mediated in part by IFNgamma. First, blocking costimulatory signals mediated through interactions of CD28 and B7 molecules by CTLA-4Ig markedly decreased not only IFNgamma but also nitric oxide. Second, estrogen treatment of IFNgamma-knockout (IFNgamma(-)/(-)) mice did not induce iNOS protein or nitric oxide. Finally, in vitro addition of recombinant IFNgamma to Con-A-activated splenocytes from IFNgamma((-)/(-)) mice induced iNOS protein primarily in estrogen-treated mice. Overall, this is the first report to show that estrogen treatment up-regulates IFNgamma-inducible-iNOS gene expression, iNOS protein, nitric oxide, and cyclooxygenase-2 as an indirect consequence of activation of T cells. These findings may have wide implications to immunity and inflammatory disorders including female-predominant autoimmune diseases.

Antisense-mediated knockdown of iNOS expression in the presence of cytokines

The impact of nitric oxide (NO) synthesized after activation by proinflammatory cytokines and/or bacterial products by an inducible NO synthase (iNOS) is still contradictory. Various methods to inhibit iNOS expression or activity have been established. A relatively new approach to inhibit iNOS-derived NO production is the antisense (AS) technique, which theoretically provides a specific and efficient method for inhibiting gene expression and function. This chapter focuses on the application of iNOS-specific AS-oligodeoxynucleotide (ODN) and highlights some of the pitfalls that must be considered to use this technique effectively.

What sense lies in antisense inhibition of inducible nitric oxide synthase expression?

The impact of nitric oxide (NO) synthesized after activation by proinflammatory cytokines and/or bacterial products by an inducible NO synthase (iNOS) is still contradictory. Expression of iNOS in inflammatory reactions is often found predominantly in cells of epithelial origin, and in these cases NO may serve as a protective agent limiting pathogen spreading, downregulating local inflammatory reactions by inducing production of Th2-like responses in a classical feedback circle, or limiting tissue damage during stress conditions. However, an abundant amount of data on chronic human disorders with predominant proinflammatory Th1-like reactions points to a destructive role of iNOS activity calling for a specific inhibition. Various methods to inhibit iNOS have been established to elucidate a protective versus a destructive role of NO during various stresses. In this review, we focus on antisense (AS)-mediated gene knock-down as a relatively new method to inhibit NO production and summarize the techniques applied and their successes. At least in theory, it provides a specific, rapid, and potentially high-throughput method for inhibiting gene expression and function. We here discuss the opportunities of iNOS-directed AS-ODN, and extensively deal with limitations and experimental problems.

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.

Cholangiocarcinoma: molecular targeting strategies for chemoprevention and therapy

Cholangiocarcinomas are devastating cancers that are increasing in both their worldwide incidence and mortality rates. The challenges posed by these often lethal biliary tract cancers are daunting, with conventional treatment options being limited and the only hope for long-term survival being that of complete surgical resection of the tumor. Unfortunately, the vast majority of patients with cholangiocarcinoma typically seek treatment with advanced disease, and often these patients are deemed poor candidates for curative surgery. Moreover, conventional chemotherapy and radiation therapy have not been shown to be effective in prolonging long-term survival, and although photodynamic therapy combined with stenting has been reported to be effective as a palliative treatment, it is not curative. Thus, there is a real need to develop novel chemopreventive and adjuvant therapeutic strategies for cholangiocarcinoma based on exploiting select molecular targets that would impact in a significant way on clinical outcome. This review focuses on potential preventive targets in cholangiocarcinogenesis, such as inducible nitric oxide synthase, cyclooxygenase-2, and altered bile acid signaling pathways. In addition, molecular alterations related to dysregulation of cholangiocarcinoma cell growth and survival, aberrant gene expression, invasion and metastasis, and tumor microenvironment are described in the context of various clinical and pathological presentations. Moreover, an emphasis is placed on the importance of critical signaling pathways and postulated interactions, including those of ErbB-2, hepatocyte growth factor/Met, interleukin-6/glycoprotein130, cyclooxygenase-2, vascular endothelial growth factor, transforming growth factor-beta, MUC1 and MUC4, beta-catenin, telomerase, and Fas pathways as potential molecular therapeutic targets in cholangiocarcinoma.