Expression of epidermal growth factor receptor, apomucins, matrix metalloproteinases, and p53 in rat and human cholangiocarcinoma: appraisal of an animal model of cholangiocarcinoma

Comprehensive Evaluation of Immune-Checkpoint DNA Cancer Vaccines in a Rat Cholangiocarcinoma Model

Cholangiocarcinoma (CCA) is a malignant tumor with aggressive biological behavior. Immune checkpoints such as cytotoxic T-lymphocyte antigen 4 (CTLA4) and antiprogrammed death 1 (PD-1) are critical immune-checkpoint molecules that repress T-cell activation. The DNA vaccine potential against CTLA4 and PD-1 in CCA is unknown. We used a thioacetamide (TAA)-induced intrahepatic cholangiocarcinoma (iCCA) rat model to investigate the DNA vaccine potential against CTLA4, PD-1, and PD-L1. We detected PD-L1 expression in CCA and CD8⁺ T-cell infiltration during CCA progression in rats. We validated antibody production, carcinogenesis, and CD8⁺ T-cell infiltration in rats receiving DNA vaccination against PD-1, PD-L1, or CTLA4. In our TAA-induced iCCA rat model, the expression of PD-L1 and the infiltration of CD8⁺ T cells increased as in rat CCA tumorigenesis. PD-1 antibodies in rats were not increased after receiving PD-1 DNA vaccination, and CCA tumor growth was not suppressed. However, in rats receiving PD-L1–CTLA4 DNA vaccination, CCA tumor growth was inhibited, and the antibodies of PD-L1 and CTLA4 were produced. Furthermore, the number of CD8⁺ T cells was enhanced after PD-L1–CTLA4 DNA vaccination. DNA vaccination targeting CTLA4–PD-L1 triggered the production of specific antibodies and suppressed tumor growth in TAA-induced iCCA rats.

Animal models of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary tract malignancy with a poor overall prognosis. There is a critical need to develop effective targeted therapies for the treatment of this lethal disease. In an effort to address this challenge, preclinical in vivo studies have become paramount in understanding CCA carcinogenesis, progression, and therapy. Various CCA animal models exist including carcinogen-based models in which animals develop CCA after exposure to a carcinogen, genetically engineered mouse models in which genetic changes are induced in mice leading to CCA, murine syngeneic orthotopic models, as well as xenograft tumors derived from xenotransplantation of CCA cells, organoids, and patient-derived tissue. Each type has distinct advantages as well as shortcomings. In the ideal animal model of CCA, the tumor arises from the biliary tract in an immunocompetent host with a species-matched tumor microenvironment. Such a model would also be time-efficient, recapitulate the genetic and histopathological features of human CCA, and predict therapeutic response in humans. Recently developed biliary tract transduction and orthotopic syngeneic transplant mouse models encompass several of these elements. Herein, we review the different animal models of CCA, their advantages and deficiencies, as well as features which mimic human CCA.

Evaluation of positive ductal margins of biliary tract cancer in intraoperative histological examination

At present the only method available to confirm microscopic infiltration of cancer into ductal margins during surgery, is intraoperative histological examination. In the present study, the status of the surgical margins and postoperative course were evaluated to determine any correlation between remnant carcinoma and postoperative survival. All consecutive patients who underwent resection for biliary tract cancer between January 2004 and May 2012 were identified from a database. Positive margin cases were divided into two groups, invasive carcinoma and carcinoma in situ (CIS). Immunohistochemical staining targeting Ki67 and p53 for positive margins was performed. Cases of major vessel invasion were significantly increased in the positive group compared with the negative group. The recurrence rate was significantly lower in the CIS group compared with the invasive group. The survival rate was significantly increased in the CIS group compared with the invasive group. The expression levels of p53 and Ki67 were significantly increased in the invasive group compared with the CIS group. No statistical correlations were observed between the expression of p53 or Ki67 and the survival or recurrence of disease. In the positive group, resected margin status was the principal factor associated with recurrence-free survival according to Cox-regression analysis. In conclusion, the status of the resected margins in the positive group was the most important factor for postoperative survival and recurrence in cholangiocarcinoma, not immunohistochemical staining targeting Ki67 and p53.

Animal models of cholangiocarcinoma: What they teach us about the human disease

Despite recent advances, pathogenesis of cholangiocarcinoma, a highly lethal cancer, remains enigmatic. Furthermore, treatment options are still limited and often disappointing. For this reason, in the last few years there has been a mounting interest towards the generation of experimental models able to reproduce the main features associated with this aggressive behavior. Toxic and infestation-induced, genetically engineered and cell implantation rodent models have been generated, contributing to a deeper understanding of the complex cell biology of the tumor, sustained by multiple cell interactions and driven by a huge variety of molecular perturbations. Herein, we will overview the most relevant animal models of biliary carcinogenesis, highlighting the methodological strategy, the molecular, histological and clinical phenotypes consistent with the human condition, their particular strengths and weaknesses and the novel therapeutic approaches that have been developed.

Synergistic antiproliferative effects of an mTOR inhibitor (rad001) plus gemcitabine on cholangiocarcinoma by decreasing choline kinase activity

Although gemcitabine plus cisplatin is the gold standard chemotherapy regimen for advanced cholangiocarcinoma, the response rate has been disappointing. This study aims to investigate a novel therapeutic regimen [gemcitabine plus everolimus (rad001), an mTOR inhibitor] for cholangiocarcinoma. Gemcitabine, oxaliplatin, cetuximab and rad001 in various combinations were first evaluated in vitro using six cholangiocarcinoma cell lines. In vivo therapeutic efficacies of gemcitabine and rad001 alone and their combination were further evaluated using a xenograft mouse model and a chemically induced orthotopic cholangiocarcinoma rat model. In the in vitro study, gemcitabine plus rad001 exerted a synergistic therapeutic effect on the cholangiocarcinoma cells, irrespective of the KRAS mutation status. In the xenograft study, gemcitabine plus rad001 showed the best therapeutic effect on tumor volume change, and was associated with increased caspase-3 expression, decreased eIF4E expression, as well as overexpression of both death receptor- and mitochondrial apoptotic pathway-related genes. In a chemically induced cholangiocarcinoma-afflicted rat model, the gemcitabine plus rad001 treatment suppressed tumor glycolysis as measured by ¹⁸F-fludeoxyglucose micro-positron emission tomography. Also, increased intratumoral free choline, decreased glycerophosphocholine and nearly undetectable phosphocholine levels were demonstrated by proton nuclear magnetic resonance, supported by results of decreased choline kinase expression in western blotting. We concluded that gemcitabine plus rad001 has a synergistic antiproliferative effect on cholangiocarcinoma, irrespective of the KRAS mutation status. The antitumor effect is associated with activation of both death receptor and mitochondrial pathways, as well as the downregulation of choline kinase activity, resulting in a characteristic change in choline metabolism.

Summary: Rad001 plus gemcitabine exerts a synergistic antitumor effect on cholangiocarcinoma irrespective of KRAS mutation status, with underlying mechanisms involving activation of the death receptor, mitochondrial pathways and downregulated choline kinase activity.

EGFR Signaling in Liver Diseases

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase that is activated by several ligands leading to the activation of diverse signaling pathways controlling mainly proliferation, differentiation, and survival. The EGFR signaling axis has been shown to play a key role during liver regeneration following acute and chronic liver damage, as well as in cirrhosis and hepatocellular carcinoma (HCC) highlighting the importance of the EGFR in the development of liver diseases. Despite the frequent overexpression of EGFR in human HCC, clinical studies with EGFR inhibitors have so far shown only modest results. Interestingly, a recent study has shown that in human HCC and in mouse HCC models the EGFR is upregulated in liver macrophages where it plays a tumor-promoting function. Thus, the role of EGFR in liver diseases appears to be more complex than what anticipated. Further studies are needed to improve the molecular understanding of the cell-specific signaling pathways that control disease development and progression to be able to develop better therapies targeting major components of the EGFR signaling network in selected cell types. In this review, we compiled the current knowledge of EGFR signaling in different models of liver damage and diseases, mainly derived from the analysis of HCC cell lines and genetically engineered mouse models (GEMMs).

Clinicopathological and prognostic significances of EGFR, KRAS and BRAF mutations in biliary tract carcinomas in Taiwan

BACKGROUND AND AIM

Biliary tract carcinomas (BTCs) are difficult to diagnose and treat. Epidermal growth factor receptor (EGFR) represents a therapeutic target for the BTCs. Mutations of the EGFR gene and the activation of its downstream pathways, including KRAS and BRAF, predict the sensitivity to anti-EGFR treatment. The aims of this study were to analyze the EGFR, KRAS and BRAF mutations in BTCs and their association with clinical outcomes.

METHODS

Paraffin-embedded specimens containing 137 BTCs resected at the National Taiwan University Hospital between 1995 and 2004 were analyzed. The exons 18-21 of EGFR gene, the codon 12, 13 and 61 of KRAS gene, and BRAF V600E mutation were analyzed. We examined the correlation between these mutations and the overall survival, tumor location, stage, and differentiation in BTCs.

RESULTS

Thirteen (9.5%) BTC patients had EGFR mutations while 23 (16.8%) patients had KRAS mutations. Only one patient had BRAF mutation. Factors influencing survival on univariate analysis were tumor stage, tumor differentiation, and EGFR mutation. On multivariate analysis, EGFR mutation and tumor stage were independent prognostic factors. A correlation between KRAS or BRAF mutations and prognosis was not observed.

CONCLUSIONS

EGFR and KRAS mutations are not uncommon in BTCs. BRAF mutation is rare in BTCs. EGFR mutation was an independent prognostic marker in BTCs in addition to tumor stage and differentiation. No simultaneous EGFR and KRAS mutations in extrahepatic cholangiocarcinoma and gallbladder carcinoma were found. EGFR and KRAS mutations should be evaluated when tailoring molecular-targeted therapy to patients with BTCs.

Mycoepoxydiene induces apoptosis and inhibits TPA-induced invasion in human cholangiocarcinoma cells via blocking NF-κB pathway

Human cholangiocarcinoma (CCA) is a chemoresistant bile duct carcinoma with a poor prognosis. Conventional chemotherapy and radiotherapy have not been reported to be effective in improving long-term survival. Mycoepoxydiene (MED), a polyketide isolated from the marine fungal strain Diaporthe sp. HLY-1 associated with mangroves, has been shown to be an agent capable of inducing apoptosis in MCF-7 and Hela cell lines. However, little is known about the effect of MED in CCA. Herein, we investigated the effect of MED on CCA cells proliferation and invasion. The results demonstrated that MED induced apoptosis in CCA cells such as SK-ChA-1 and Mz-ChA-1 through inhibiting the expression of anti-apoptotic proteins such as Bcl-XL and Bcl-2, two targets of NF-κB. In addition, MED significantly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced CCA cells invasion in a dose-dependent manner by reducing the expression of matrix metalloelastase 9 (MMP-9). Moreover, MED inhibited TPA-induced NF-κB activation via blocking phosphorylation and degradation of IκBα and phosphorylation of IκB kinase (IKK). MED had no effect on the activation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK) and p38, which are also involved in regulating the MMP-9 expression. Collectively, MED significantly suppressed proliferation and invasion of CCA cells such as SK-ChA-1 and Mz-ChA-1, suggesting that MED is a potential lead compound for the development of novel drugs for therapy of CCA.

Systemic and targeted therapy for biliary tract tumors and primary liver tumors

Tumors of the biliary tract and hepatocellular carcinoma (HCC) are complex tumors with heterogeneous carcinogenic mechanisms. Patients with hepatobiliary cancer have advances disease and need systematic therapy to palliate symptoms and extend survival. Development of effective systematic therapy is a significant unmet medical need. It is hoped that current and future clinical trials will identify additional effective systemic agents, combination systemic therapies, and combined modality options. The HCC community needs validated biomarkers to help identify the patients who will benefit most from emerging treatment options.

Liver carcinogenesis: rodent models of hepatocarcinoma and cholangiocarcinoma

Hepatocellular carcinoma and cholangiocarcinoma are primary liver cancers, both represent a growing challenge for clinicians due to their increasing morbidity and mortality. In the last few years a number of in vivo models of hepatocellular carcinoma and cholangiocarcinoma have been developed. The study of these models is providing a significant contribution in unveiling the pathophysiology of primary liver malignancies. They are also fundamental tools to evaluate newly designed molecules to be tested as new potential therapeutic agents in a pre-clinical set. Technical aspects of each model are critical steps, and they should always be considered in order to appropriately interpret the findings of a study or its planning. The purpose of this review is to describe the technical and experimental features of the most significant rodent models, highlighting similarities or differences between the corresponding human diseases. The first part is dedicated to the discussion of models of hepatocellular carcinoma, developed using toxic agents, or through dietary or genetic manipulations. In the second we will address models of cholangiocarcinoma developed in rats or mice by toxin administration, genetic manipulation and/or bile duct incannulation or surgery. Xenograft or syngenic models are also proposed.

HER3 overexpression is a prognostic indicator of extrahepatic cholangiocarcinoma

Members of the HER (ERBB) receptor protein tyrosine kinase family play an important role in regulating cellular division, proliferation, differentiation, and migration and have prognostic significance in a number of cancers. Here, we sought to define their role in extrahepatic cholangiocarcinoma (EHCC). HER2 and HER3 protein expression was studied in 230 EHCC cases using a tissue microarray and compared with clinicopathological variables, including the survival of EHCC patients. HER3 was predominantly localized to the cytoplasm, whereas HER2 exhibited a membranous expression pattern. Overexpression of HER2 and HER3 was observed in 6 % (13/224) and 39 % (90/230) of EHCCs, respectively. Membranous HER2 overexpression occurred more frequently in intraductal papillary neoplasms with an associated invasive carcinoma than in tubular adenocarcinomas (P = 0.02). HER3 protein was more commonly overexpressed in nodular and infiltrative than in papillary tumors (P = 0.03). HER3 overexpression was associated with decreased survival in both univariate (P = 0.01) and multivariate (P = 0.008) analyses, whereas HER2 overexpression was not associated with survival. HER2 and HER3 are overexpressed in subsets of EHCC patients. Notably, HER3 overexpression is correlated with decreased patient survival, suggesting that HER3 constitutes a prognostic factor as well as a potential candidate for targeted therapy.

The role of the myofibroblast in tumor stroma remodeling

Since its first description in wound granulation tissue, the myofibroblast has been recognized to be a key actor in the epithelial-mesenchymal cross-talk that plays a crucial role in many physiological and pathological situations, such as regulation of prostate development, ventilation-perfusion in lung alveoli or organ fibrosis. The presence of myofibroblasts in the stroma reaction to epithelial tumors is well established and many data are accumulating which suggest that the stroma compartment is an active participant in tumor onset and/or evolution. In this review we summarize the evidence in favor of this concept, the main mechanisms that regulate myofibroblast differentiation and function, as well as the biophysical and biochemical factors possibly involved in epithelial-stroma interactions, using liver carcinoma as main model, in view of achieving a better understanding of tumor progression mechanisms and of tools directed toward stroma as eventual therapeutic target.

Characterization of a novel rat cholangiocarcinoma cell culture model-CGCCA

AIM: To characterize a culture model of rat CCA cells, which were derived from a transplantable TTA-induced CCA and designated as Chang Gung CCA (CGCCA).

METHODS: The CGCCA cells were cultured at in vitro passage 12 times on a culture dish in DMEM medium. To measure the doubling time, 10³ cells were plated in a 96-well plate containing the growth medium. The cells were harvested 4 to 10 d after seeding, and a standard MTT assay was used to measure the growth. The phenotype of CACCA cell and xenograft was determined by immunohistochemical study. We also determine the chromosomal alterations of CGCCA, G-banding and spectral karyotyping studies were performed. The CGCCA cell line was transplanted into the nude mice for examining its tumorigenicity. 2-Deoxy-2-(¹⁸F)fluoro-D-glucose (FDG) autoradiography was also performed to evaluate the FDG uptake of the tumor xenograft.

RESULTS: The doubling time for the CGCCA cell line was 32 h. After transplantation into nude mice, FDG autoradiography showed that the tumors formed at the cell transplantation site had a latency period of 4-6 wk with high FDG uptake excluding necrosis tissue. Moreover, immunohistochemical staining revealed prominent cytoplasmic expression of c-erb-B2, CK19, c-Met, COX-II, EGFR, MUC4, and a negative expression of K-ras. All data confirmed the phenotypic features of the CGCCA cell line coincide with the xenograft mice tumors, indicating cells containing the tumorigenicity of CCA originated from CCA. In addition, karyotypic banding analysis showed that the diploid (2n) cell status combines with ring and giant rod marker chromosomes in these clones; either both types simultaneously appeared or only one type of marker chromosome in a pair appeared in a cell. The major materials contained in the marker chromosome were primarily identified from chromosome 4.

CONCLUSION: The current CGCCA cell line may be used as a non-K-ras effect CCA model and to obtain information and reveal novel pathways for CCA. Further applications regarding tumor markers or therapeutic targeting of CCA should be addressed accordingly.

Epidermal growth factor receptor and HER-2/neu status by immunohistochemistry and fluorescence in situ hybridization in adenocarcinomas of the biliary tree and gallbladder

Adenocarcinomas of the biliary tract and gallbladder are aggressive tumors with a poor prognosis. Standard chemotherapy often offers minimal benefit. Because epidermal growth factor receptor and HER-2/neu antagonists have been successfully used in adenocarcinomas from other sites, their use in cholangiocarcinoma can be potentially beneficial. This study examines the epidermal growth factor receptor and HER-2/neu expression and the epidermal growth factor receptor gene copy number in biliary tract adenocarcinomas. Fifty-one formalin-fixed, paraffin-embedded cases of adenocarcinomas (26 intrahepatic, 19 extrahepatic, 6 gallbladder) were stained with monoclonal antibodies against epidermal growth factor receptor and HER-2/neu. Fluorescence in situ hybridization analysis was performed in 37 cases using probes directed against epidermal growth factor receptor and centromeric region of chromosome 7. Epidermal growth factor receptor expression was present in 41 (80%) cases, with moderate or strong epidermal growth factor receptor staining in 30 (59%) cases. HER-2/neu was positive in 2 (4%) cases. Fluorescence in situ hybridization analysis showed gain in epidermal growth factor receptor gene copy number in 17 (46%) tumors. Of the latter, 1 showed gene amplification, whereas all others showed gain in chromosome 7, indicating balanced polysomy. Epidermal growth factor receptor overexpression by immunohistochemistry correlated significantly with epidermal growth factor receptor copy number by fluorescence in situ hybridization (P = .02). HER2/neu expression is uncommon in these tumors.

Intrahepatic cholangiocarcinoma progression: prognostic factors and basic mechanisms

In this review, we will examine various molecular biomarkers for their potential to serve as independent prognostic factors for predicting survival outcome in postoperative patients with progressive intrahepatic cholangiocarcinoma. Specific rodent models of intrahepatic cholangiocarcinoma that mimic relevant cellular, molecular, and clinical features of the human disease are also described, not only in terms of their usefulness in identifying molecular pathways and mechanisms linked to cholangiocarcinoma development and progression, but also for their potential value as preclinical platforms for suggesting and testing novel molecular strategies for cholangiocarcinoma therapy. Last, recent studies aimed at addressing the role of desmoplastic stroma in promoting intrahepatic cholangiocarcinoma progression are highlighted in an effort to underline the potential value of targeting tumor stromal components together with that of cholangiocarcinoma cells as a novel therapeutic option for this devastating cancer.

Molecular Markers in the Pathogenesis of Cholangiocarcinoma: Potential for Early Detection and Selection of Appropriate Treatment

Cholangiocarcinoma (CC) is a primary malignancy that arises from cholangiocytes, the epithelial cells lining the bile duct livers. The worldwide incidence of CC is increasing and despite of combined therapeutic strategies, its prognosis remains poor. Till now surgery remains the only curative treatment modality. Over the past years, several important studies have yielded new insights into the molecular mechanisms of cholangiocarcinoma. This review focused on critical molecular player during the development from inflammation and cellular and molecular pathogenesis of this disease. The novel prophylactic and therapeutic approach deals especially the molecules involved in inflammation of cholangiocite or those related to promotion and progression of CC. The elucidation of their specific effects and interaction of this complex mechanism will accelerate the development of new biomarker for early detection and predictor factors outcome in CC.

Nuclear overexpression of mitotic regulatory proteins in biliary tract cancer: correlation with clinicopathologic features and patient survival

Mitosis dysregulation is common in cancers. This study explored the nuclear expression patterns and prognostic significance of mitotic regulatory proteins, including Aurora kinases, survivin, and p53, in biliary tract cancer (BTC). Archival tumor samples from 161 BTC patients who underwent surgery were tested for the expression of Aurora-A, Aurora-B, survivin, and p53 by immunohistochemistry. The potential endogeneity among the clinicopathologic variables and survival outcome was assessed by a generalized simultaneous equations model. Nuclear overexpression of Aurora-A, Aurora-B, survivin, and p53 was found in 79 (49.1%), 45 (28.0%), 55 (34.2%), and 55 (34.2%) patients, respectively. Intrahepatic cholangiocarcinoma, compared with the other two subtypes, had significantly higher proportions of nuclear overexpression of Aurora-B and survivin (37.8% and 47.3%, respectively). Simultaneous overexpression of Aurora-A and Aurora-B was correlated with that of p53. Overexpression of Aurora-B was also correlated with that of survivin and tumor grade. Our data indicate that simultaneous overexpression of Aurora-A and Aurora-B, suggesting dysregulated mitosis is associated with worse survival in patients with BTC. Independent prognostic factors for poor overall survival included simultaneous overexpression of Aurora-A and Aurora-B (hazard ratio, 1.997; 95% confidence interval, 1.239-3.219; P = 0.0045) and tumor grade (hazard ratio, 2.117; 95% confidence interval, 1.339-3.348; P = 0.0013) assessed by a multivariate analysis stratified by American Joint Committee on Cancer stage and p53 overexpression. Endogeneity testing suggested that nuclear overexpression of p53 and tumor type may influence patient survival through their interactions with Aurora-A/Aurora-B expression and tumor grade.

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.

[Physiologic and pathologic experimental models for studying cholangiocytes]

Cholangiocytes (epithelial cells lining the intra- and extrahepatic bile ducts) and hepatocytes are two major components of liver epithelia. Although cholangiocytes are less numerous than hepatocytes, they are involved in both bile secretion and diverse cellular processes such as cell-cycle phenomena, cell signaling, and interactions with other cells, matrix components, foreign organisms, and xenobiotics. Cholangiocytes are also targets in several human diseases including cholangiocarcinoma, primary sclerosing cholangitis, autoimmune cholangitis, and vanishing bile-duct syndrome. The rapid advances in experimental biology technologies are greatly expanding interest in and knowledge of the physiology and pathophysiology of cholangiocytes. This review focuses on the progress of in vivo and in vitro experimental models in elucidating the physiologic functions of cholangiocytes and the pathophysiology of various cholangiopathies. The following aspects are reviewed: isolation of cholangiocytes from the liver and their heterogeneity, various culture systems, establishment of cholangiocyte cell lines, isolation and usage of intrahepatic bile-duct units, three-dimensional modeling of the bile duct, experimental models for inducing cholangiocyte proliferation, and various cholangiopathies such as cholangiocarcinoma, primary sclerosing cholangitis, and autoimmune cholangitis.

Animal PET for thioacetamide-induced rat cholangiocarcinoma: a novel and reliable platform

PURPOSE

Cholangiocarcinoma (CCA) is a lethal disease afflicting many thousands of patients worldwide. We have previously developed an oral thioacetamide (TAA)-induced model of rat CCA that recapitulates the histologic progression of human CCA. Our objective was to evaluate the feasibility of animal PET in detecting CCA in the setting of the TAA rat model.

PROCEDURES

Male Sprague-Dawley rats (n = 30) were used in this study. Drinking water with TAA 300 mg/l was administered orally in 26 rats, and animal PET was performed at 20 weeks after initiation of TAA. A total of four rats served as controls. Animal PET images were acquired sequentially using both C-11 acetate and 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) to determine the optimal tracer. Dynamic animal PET images were collected to assess the optimal scan time based on the highest tumor-to-liver (T/L) ratio using time-activity curves. Animal PET findings were compared lesion by lesion with the results of autoradiography and the histological data.

RESULTS

FDG animal PET images had a higher T/L ratio compared to images obtained with C-11 acetate as a marker. The optimal scan time for FDG animal PET was determined as 90 min postinjection of the tracer. This was when the T/L ratio reached its peak. Necropsy and histology confirmed the presence of TAA-induced CCA in 22 rats (84.6 %). Static animal PET images showed intense FDG uptake in 17 of the 22 tumor-bearing animals (77.3%). The average T/L ratio was 1.60 +/- 0.09. The sensitivity and specificity of animal PET in the detection of CCA were 77% (17/22) and 100% (4/4), respectively.

CONCLUSIONS

We conclude that animal PET in the setting of the TAA rat model seems to be feasible for the detection of CCA. Future translational studies are needed to confirm and expand our findings.

Thalidomide attenuates tumor growth and preserves fast-twitch skeletal muscle fibers in cholangiocarcinoma rats

BACKGROUND

The prognosis for cholangiocarcinoma remains dismal due to a low resection rate and early recurrence. Cancer cachexia is associated with decreased survival and poor quality of life. Herein, we present a rat model of cholangiocarcinoma and demonstrate that thalidomide attenuates tumor growth and improves cachexia.

METHODS

A cholangiocarcinoma model was established using Sprague-Dawley rats that were fed thioacetamide for 40 weeks. Cholangiocarcinoma rats were treated using either thalidomide or saline for 8 weeks. Tumor growth and body weight were recorded for all animals. The expression of CD31, VEGF, and eIF4E of cholangiocarcinoma were determined using immunohistochemistry. Level of apoptosis and Fas-mediated apoptosis genes of cholangiocarcinoma were determined using TUNEL assay and ribonuclease protection assay, respectively. The distribution of fast-twitch soleus skeletal muscle fibers was determined as was the expression of TNFalpha and TGFbeta1 within soleus muscle.

RESULTS

After an 8-week treatment, the mean weight of saline- and thalidomide-treated rats was 24% and 19%, respectively, less than that of control (ANOVA, P < .05). The tumor volume (x +/-SD) of thalidomide-treated rats was less than saline-treated rats (1.9 +/- 0.4 vs 4.6 +/- 1.3 cm3, P < .01). The expression of CD31, eIF4E, and VEGF of cholangiocarcinoma was less than thalidomide-treated rats than for saline-treated rats, while the level of apoptosis of tumor cells was greater for thalidomide- treated rats than for saline-treated rats. The expression of mRNA for Fas, caspase-3, and Bax of cholangiocarcinoma in the thalidomide-treated rats was greater than for saline-treated rats. The number of fast-twitch skeletal muscle fibers per 500 mm2 of control, saline-, and thalidomide-treated rats was 43 +/- 6, 14 +/- 3, and 41 +/- 8 (ANOVA, P < .001). The expression of TNFalpha and TGFbeta1 of soleus muscles for thalidomide-treated rats was less than for saline-treated rats.

CONCLUSIONS

Using our rat cholangiocarcinoma model, we demonstrated that thalidomide inhibited tumor growth and was associated with a decrease in expression of reduced eIF4E and VEGF expression; in addition, thalidomide preserved fast-twitch skeletal muscle fibers and was associated with decreased expression of TNFalpha and TGFbeta1.

Effects of the anti-epidermal growth factor receptor antibody cetuximab on cholangiocarcinoma of the liver

BACKGROUND

Cholangiocarcinoma is a malignant neoplasm arising from the biliary epithelium. The disease is notoriously difficult to diagnose and is usually fatal because of its late clinical presentation and the lack of effective nonsurgical therapeutic modalities. The overall survival rate, including in patients who underwent tumor resections, is poor, with less than 5% surviving more than 5 years. Over the past 5 years, several important studies have yielded new insight into the molecular mechanisms involved in the development and growth of these tumors. The tumor cells of the cholangiocarcinoma express an epidermal growth factor receptor which plays an important role in the pathogenesis of these tumors.

CASE REPORT

A 49-year-old woman with cholangiocarcinoma of the liver developed spinal metastases. The antiepidermal growth factor receptor (anti-EGFR) antibody was used successfully in combination with radiotherapy. The response to treatment was assessed by magnetic resonance imaging and positron-emission tomography.

CONCLUSION

The patient with cholangiocarcinoma had a response to cetuximab-based therapies. This may lead to another option for the treatment of hepatic cholangiocarcinoma.

[(18)F]FDG accumulation in an experimental model of multistage progression of cholangiocarcinoma

AIM

The diagnosis of cholangiocarcinoma (CCA) is difficult, and due to the insidious course of the disease, most cases present at a relatively late stage. Positron emission tomography (PET), using [(18)F]fluoro-2-deoxyglucose ([(18)F]FDG) as a tracer is one the most powerful molecular imaging techniques available. We hypothesized that [(18)F]FDG accumulates at sites of early CCA development and that FDG-PET may be of value for the early diagnosis of CCA.

METHODS

We added 300 mg/L thioacetamide to the drinking water of rats who went on to develop CCA within 20 weeks. From eight weeks onwards, groups of three rats were injected with [(18)F]FDG, subsequently the liver was perfused, dissected and subjected to quantitative autoradiography using a phosphor imaging system. The liver sections were stained for histology, and glutathione S-transferase (GST) enzyme activity was determined. We correlated [(18)F]FDG uptake with pathological liver changes.

RESULTS

The experiments demonstrate that thioacetamide causes atypical bile ducts and invasive CCA. Rat livers harvested early after the start of administration of thioacetamide contained only cirrhosis and/or atypical bile ducts, but CCA and FDG accumulation were absent. At 20 weeks, all rats had developed CCA and all, except two animals with a very small carcinoma, had strongly elevated focal FDG uptake. Quantitative autoradiography revealed tumor-to-normal-liver ratios as high as 5:4. In all rats with a carcinoma, there was a backdrop of cirrhosis, and interestingly cirrhotic areas did not show elevated FDG accumulation.

CONCLUSION

[(18)F]FDG accumulates in CCA, is able to distinguish CCA from liver cirrhosis, but is probably unsuitable to detect very early CCA lesions.

Cyclooxygenase-2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer related mortality worldwide. The incidence of HCC is rising worldwide, especially in the United States. The overall survival of patients with HCC is grim and currently no efficient secondary prevention or systemic treatments are available. Recent evidence suggests that COX-2 signaling is implicated in hepatocarcinogenesis and COX-2 inhibitors prevent HCC cell growth in vitro and in animal models. However, given the recently reported side effect associated with some of the COX-2 inhibitors, it is imperative to develop chemotherapeutic strategy that simultaneously targets COX-2 and other related key molecules in hepatocarcinogenesis or to utilize agents inhibiting COX-2 signaling in conjunction with other standard chemotherapy or radiation therapy. Such combinational therapeutic approaches are expected to provide synergistic anti-tumor effect with lesser side effect. In this regard, the recently delineated interplay between COX-2-derived PG signaling and other growth-regulatory pathways such as EGFR, Met, iNOS, VEGF and n-3 polyunsaturated fatty acids is expected to provide important therapeutic implications. This review summarizes the recent advances in understanding the mechanisms for COX-2-derived PG signaling in hepatocarcinogenesis and focuses on the newly unveiled interactions between PG cascade and other key signaling pathways that coordinately regulate HCC growth. Understanding these mechanisms and interplays will facilitate the development of more effective chemopreventive and therapeutic strategies.

erbB-2/neu transformed rat cholangiocytes recapitulate key cellular and molecular features of human bile duct cancer

BACKGROUND & AIMS

Cholangiocarcinomas appear to arise from the malignant transformation of cholangiocytes lining the biliary tract. Because the development of an in vitro model of malignant transformation can provide a powerful new tool for establishing critical events governing the molecular pathogenesis of cholangiocarcinoma, we investigated the potential of achieving malignant transformation of cultured rat cholangiocytes in relation to aberrant overexpression of mutationally activated erbB-2/neu.

METHODS

Malignant neoplastic transformation was achieved after infection of the rat cholangiocyte cell line, designated BDE1, with the retrovirus Glu664-neu, containing the transforming rat erbB-2/neu oncogene.

RESULTS

Compared with untransformed control cells, malignant transformants carrying the activating erbB-2/neu mutation prominently overexpressed p185neu receptor protein, which was phosphorylated strongly at its major autophosphorylation site at tyrosine 1248. Moreover, erbB-2/neu transformation of BDE1 cells resulted in increased telomerase activity, up-regulation of cyclooxygenase-2 with overproduction of prostaglandin E(2), enhanced phosphorylation of mitogen-activated protein kinase and of serine/threonine kinase Akt/PKB, overexpression of vascular endothelial growth factor, and increased mucin 1 messenger RNA expression. Only erbB-2/neu transformants were tumorigenic when transplanted into isogeneic rats, yielding a 100% incidence of tumors closely resembling human desmoplastic ductal cholangiocarcinomas in their morphology. Malignant cholangiocytes in the tumors were strongly immunoreactive for biliary cytokeratin 19, p185neu, and cyclooxygenase-2.

CONCLUSIONS

This unique malignant transformation model recapitulates key molecular features of the human disease and appears to be well suited for testing novel molecular therapeutic strategies against cholangiocarcinoma.

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.