Bile acids induce cyclooxygenase-2 expression via the epidermal growth factor receptor in a human cholangiocarcinoma cell line

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.

Predictive factors for intrahepatic cholangiocarcinoma recurrence in the liver following surgery

BACKGROUND

We performed hepatectomy without lymph node (LN) dissection for intrahepatic cholangiocarcinoma (ICC) limited to the peripheral region of the liver, and hepatectomy with extrahepatic bile duct resection and regional LN dissection for any types of ICC extending to the hepatic hilum. Surgical outcomes were evaluated to elucidate the prognostic factors that influence patient survival with respect to intrahepatic recurrence.

METHODS

Forty-one patients underwent resection of ICC with no macroscopic evidence of residual cancer.

RESULTS

Significant risk factors for poorer survival included preoperative jaundice (P = 0.0115), serum CA19-9 levels >37 U/ml (P = 0.0089), tumor diameter >4.5 cm (P = 0.017), ICC extending to the hepatic hilum (P = 0.0065), mass-forming with periductal-infiltrating type (P = 0.003), poorly differentiated adenocarcinoma, portal vein involvement (P = 0.0785), LN metastasis at initial hepatectomy (P < 0.0001), and positive surgical margin (P = 0.023). Intrahepatic recurrence, which was the predominant manner of recurrence, was detected in 20 patients (74.1%). Patients with intrahepatic recurrence had a significantly high incidence of high serum CA19-9 levels (>37 U/ml; P = 0.0006), preoperative jaundice (P = 0.0262), ICC extended to the hepatic hilum (P = 0.0349), large tumors (>4.5 cm; P = 0.0351), portal vein involvement (P = 0.0423), and LN metastasis at initial hepatectomy (P = 0.009) compared with disease-free patients. The multiple logistic regression analysis revealed that preoperative CA19-9 elevation and obstructive jaundice influenced intrahepatic recurrence of ICC.

CONCLUSIONS

Although LN metastasis is a significant prognostic factor, the most obvious recurrence pattern after surgery was intrahepatic recurrence, which could be predicted preoperatively by a combination of elevated serum CA19-9 levels and manifestation of obstructive jaundice.

Chenodeoxycholic acid stimulates the progression of human esophageal cancer cells: A possible mechanism of angiogenesis in patients with esophageal cancer

Bile acids are known to promote the growth of gastrointestinal cancer. However, the underlying mechanism remains unclear. We examined whether bile acids induce tumor growth via the cyclooxygenase (COX)-2 angiogenic pathway. In vitro, esophageal squamous cell carcinoma (ESCC) cells and esophageal adenocarcinoma cells were studied. Production of prostaglandin E2 (PGE2) and vascular endothelial growth factor (VEGF) in response to treatment with chenodeoxycholic acid (CDCA) was assessed by enzyme-linked immunosorbent assay (ELISA). COX-2 protein and VEGF protein were measured by immunoblot analysis, and COX-2 activity was measured by ELISA. In vivo, CDCA was administered to ESCC cell-bearing mice. Tumor tissues were analyzed immunohistochemically, and microvessel density was evaluated. Clinically, 134 patients with ESCC who underwent esophagectomy were studied. In vitro, CDCA induced the production of PGE2 and VEGF in dose- and time-dependent manners, and these effects were attenuated by a selective COX-2 inhibitor, mitogen-activated protein kinases inhibitor, or epidermal growth factor receptor inhibitor. CDCA-induced COX-2 in the cell lysate increased the secretion of VEGF into the culture medium. In vivo, CDCA markedly enhanced tumor growth and increased vascularization. Clinically, patients whose tumors expressed both COX-2 and VEGF had poor outcomes. Our results suggest that bile acids, important constituents of duodenal fluid, stimulate the development of human esophageal cancer by promoting angiogenesis via the COX-2 pathway.

Lysophosphatidylcholine suppresses apoptotic cell death by inducing cyclooxygenase-2 expression via a Raf-1 dependent mechanism in human cholangiocytes

PURPOSE

The high incidence of biliary tract carcinoma in patients with anomalous pancreaticobiliary ductal junction (APBDJ) implicates that a compositional alteration in bile may contribute to the genesis of this cancer. Lysophosphatidylcholine (LPC) is generated in the bile of these patients. Given the role of cyclooxygenase-2 (COX-2) in biliary tract carcinogenesis, we postulated that LPC induces COX-2 in cholangiocytes.

METHODS

The effect of LPC on COX-2 expression in cholangiocytes was evaluated by immunoblot analysis, real-time PCR and reporter gene assay. Apoptosis was induced by TRAIL treatment, and quantified using DAPI staining.

RESULTS

Lysophosphatidylcholine increased COX-2 protein expression in cholangiocytes in a concentration- and time-dependent manner. LPC-induced Raf-1 activation was responsible for this COX-2 induction. Accordingly, LPC increased COX-2 mRNA levels in a Raf-1 dependent manner by stabilizing COX-2 mRNA. Finally, LPC attenuated TRAIL-mediated apoptosis through a COX-2/PgE2 dependent mechanism.

CONCLUSIONS

Collectively, these results implicate that LPC inhibits cholangiocyte apoptosis by inducing COX-2 expression via a Raf-1 dependent mechanism. This anti-apoptotic signaling may participate in biliary tract carcinogenesis in APBDJ patients, and therefore, its interruption may be a viable chemopreventative strategy.

Modulation of Stat3 activation by the cytosolic phospholipase A2alpha and cyclooxygenase-2-controlled prostaglandin E2 signaling pathway

A variety of human cancers show constitutive activation of signal transducer and activator of transcription-3 (Stat3) and overexpression of cyclooxygenase-2 (COX-2). This study describes a novel cross-talk between the COX-2-controlled prostaglandin E(2) (PGE(2)) and Stat3 signaling pathways that coordinately regulate human cancer cell growth. COX-2-derived PGE(2) induces interleukin-6 production through activation of EP(4) receptor and subsequent phosphorylation of gp130/Stat3 in human cholangiocarcinoma cells. In parallel, activation of COX-2/PGE(2) signaling also enhances Stat3 phosphorylation and reporter activity through EP(1) receptor-induced activation of c-Src and EGFR in these cells. Moreover, the observations that EP(1) receptor is detected in the nucleus as well as in the Stat3.DNA binding complex and that activation of EP(1) receptor in the nuclei enhances Stat3 activation depicts a previously undescribed G protein-coupled receptor in the nucleus for Stat3 activation and tumor cell growth.

Bile acid interactions with cholangiocytes

Cholangiocytes are exposed to high concentrations of bile acids at their apical membrane. A selective transporter for bile acids, the Apical Sodium Bile Acid Cotransporter (ASBT) (also referred to as Ibat; gene name Slc10a2) is localized on the cholangiocyte apical membrane. On the basolateral membrane, four transport systems have been identified (t-ASBT, multidrug resistance (MDR)3, an unidentified anion exchanger system and organic solute transporter (Ost) heteromeric transporter, Ostα-Ostβ. Together, these transporters unidirectionally move bile acids from ductal bile to the circulation. Bile acids absorbed by cholangiocytes recycle via the peribiliary plexus back to hepatocytes for re-secretion into bile. This recycling of bile acids between hepatocytes and cholangiocytes is referred to as the cholehepatic shunt pathway. Recent studies suggest that the cholehepatic shunt pathway may contribute in overall hepatobiliary transport of bile acids and to the adaptation to chronic cholestasis due to extrahepatic obstruction. ASBT is acutely regulated by an adenosine 3', 5’-monophosphate (cAMP)-dependent translocation to the apical membrane and by phosphorylation-dependent ubiquitination and proteasome degradation. ASBT is chronically regulated by changes in gene expression in response to biliary bile acid concentration and inflammatory cytokines. Another potential function of cholangiocyte ASBT is to allow cholangiocytes to sample biliary bile acids in order to activate intracellular signaling pathways. Bile acids trigger changes in intracellular calcium, protein kinase C (PKC), phosphoinositide 3-kinase (PI3K), mitogen-activated protein (MAP) kinase and extracellular signal-regulated protein kinase (ERK) intracellular signals. Bile acids significantly alter cholangiocyte secretion, proliferation and survival. Different bile acids have differential effects on cholangiocyte intracellular signals, and in some instances trigger opposing effects on cholangiocyte secretion, proliferation and survival. Based upon these concepts and observations, the cholangiocyte has been proposed to be the principle target cell for bile acids in the liver.

Biliary wound healing, ductular reactions, and IL-6/gp130 signaling in the development of liver disease

Basic and translational wound healing research in the biliary tree lag significantly behind similar studies on the skin and gastrointestinal tract. This is at least partly attributable to lack of easy access to the biliary tract for study. But clinical relevance, more interest in biliary epithelial cell (BEC) pathophysiology, and widespread availability of BEC cultures are factors reversing this trend. In the extra-hepatic biliary tree, ineffectual wound healing, scarring and stricture development are pressing issues. In the smallest intra-hepatic bile ducts either impaired BEC proliferation or an exuberant response can contribute to liver disease. Chronic inflammation and persistent wound healing reactions in large and small bile ducts often lead to liver cancer. General concepts of wound healing as they apply to the biliary tract, importance of cellular processes dependent on IL-6/gp130/STAT3 signaling pathways, unanswered questions, and future directions are discussed.

Bile Acid Promotes the Proliferation of Squamous Cell Carcinoma of the Esophagus, Independent of its Inducing COX-2 Expression

BACKGROUND

We have reported G1 progression and cyclooxygenase-2 (COX-2) induction during carcinogenesis of the squamous epithelium of the esophagus. As bile acid induces COX-2 expression and promotes carcinogenesis in the digestive tract, we investigated the effect of bile acid on the proliferation of squamous cell carcinoma of the esophagus (ESCC).

MATERIALS AND METHODS

MTT assay, Western blot analysis of COX-2 and cell cycle-related molecules in the G1 phase (Rb, CDC25A, cyclin D1), and CDK2 kinase assay were performed on chenodeoxycholic acid (CDCA) exposure to ESCC cell lines (TE2R, TE3, TE13, TE15).

RESULTS

In the presence of gradient bile acid concentration (up to 100 microm), growth of ESCC cell lines was stimulated at a low concentration (maximally at 20-30 microm), but suppressed at a higher concentration. Only a low dose of bile acid induced the expression of cyclin D1 and CDC25A and showed high Rb phosphorylation and high CDK2 kinase activity. In contrast, bile acid progressively induced COX-2 expression in a dose-dependent manner, regardless of its biphasic effects on cell proliferation, and a COX-2 specific inhibitor (JTE-522) did not suppress growth stimulation by a low dose of bile acid.

CONCLUSIONS

Bile acid at a low dose stimulates the proliferation of ESCC by inducing G1-regulating molecules. However, COX-2 expression, which is also induced by bile acid, does not affect cell proliferation. Further work is needed to elucidate its role in carcinogenesis.

Bile acid-mediated induction of cyclooxygenase-2 and Mcl-1 in hepatic stellate cells

In cholestatic liver diseases, bile acids induce hepatocyte apoptosis and thus cause liver injury, but hepatic stellate cells (HSCs) survive in the presence of bile acids. We attempted to analyze anti-apoptotic signaling pathways in HSCs against bile acid-induced apoptosis. In immortalized human HSCs and primarily cultured rat HSCs, bile acid treatment increased the expression levels of cyclooxygenase-2 (COX-2) and Mcl-1. COX-2 induction was found to be due to transcriptional enhancement dependent on p42/44, p38 MAPK, and JNK activation, whereas Mcl-1 induction resulted from bile acid-mediated protein stabilization in a Raf-1-dependent manner. Moreover, the inhibitions of either COX-2 activity by celecoxib or Mcl-1 induction by siRNA transfection rendered HSCs susceptible to bile acid-induced apoptosis. These results imply that the bile acid-mediated inductions of COX-2 and Mcl-1 may lead to HSC survival in cholestatic liver diseases.

Bile salt exposure increases proliferation through p38 and ERK MAPK pathways in a non-neoplastic Barrett's cell line

Bile reflux has been implicated in the neoplastic progression of Barrett's esophagus (BE). Bile salts increase proliferation in a Barrett's-associated adenocarcinoma cell line (SEG-1 cells) by activating ERK and p38 MAPK pathways. However, it is not clear that these findings in cancer cells are applicable to non-neoplastic cells of benign BE. We examined the effect of bile salts on three human cell lines: normal esophageal squamous (NES) cells, non-neoplastic Barrett's cells (BAR cells), and SEG-1 cells. We hypothesized that bile salt exposure activates proproliferative and antiapoptotic pathways to promote increased growth in BE. NES, BAR, and SEG-1 cells were exposed to glycochenodeoxycholic acid (GCDA) at a neutral pH for 5 min. Proliferation was measured by Coulter counter cell counts and a 5-bromo-2'-deoxyuridine (BrdU) incorporation assay. GCDA-induced MAPK activation was examined by Western blot analysis for phosphorylated ERK and p38. Apoptosis was measured by TdT-mediated dUTP nick-end labeling and annexin V staining after GCDA and UV-B exposure. Statistical significance was determined by ANOVA. NES cells exposed to 5 min of GCDA did not increase cell number. In BAR cells, GCDA exposure increased cell number by 31%, increased phosphorylated p38 and ERK levels by two- to three-fold, increased BrdU incorporation by 30%, and decreased UV-induced apoptosis by 15-20%. In conclusion, in a non-neoplastic Barrett's cell line, GCDA exposure induces proliferation by activation of both ERK and p38 MAPK pathways. These findings suggest a potential mechanism whereby bile reflux may facilitate the neoplastic progression of BE.

Ligand-dependent activation of the epidermal growth factor receptor by secondary bile acids in polarizing colon cancer cells

BACKGROUND

Secondary bile acids such as deoxycholic acid (DCA) are known to promote colorectal cancer (CRC). Increasing evidence suggests that DCA-induced signaling is mediated by activation of the epidermal growth factor receptor (EGFR). We have shown that activation of the EGFR induces up-regulation of cyclooxygenase 2, basolateral release of prostaglandins (PGs), and mitogenesis in a polarizing human colon cancer cell line, HCA-7. The purpose of this study was to determine the mechanism by which DCA activates EGFR in human polarizing CRC cell lines HCA-7 and HCT-8.

METHODS

A primary, non-tumor-promoting bile acid (cholic acid [CA]) and a secondary, tumor-promoting bile acid, DCA, were added to the apical and basolateral compartment of polarized HCA-7 and HCT-8 cells. These cells were pretreated with monoclonal antibody 528, a monoclonal antibody that inhibits ligand binding to EGFR, or with WAY-022, a selective inhibitor of tumor necrosis factor-alpha converting enzyme/a disintegrin and metalloprotease-17 (TACE/ADAM-17), which cleaves amphiregulin (AR) to its mature, soluble form from the basolateral cell membrane. AR levels were measured in the apical and basolateral medium and cell lysates by radioimmunoassay. PGs were measured in the apical and basolateral medium by gas chromatography/mass spectrometry.

RESULTS

Basolateral delivery of DCA, but not CA, preferentially stimulated release of AR into the basolateral medium compared with cell lysates of polarized HCA-7 and HCT-8 cells. Basolateral delivery of DCA resulted in increased basolateral PGE2 levels (P < .05), and this effect was attenuated by pretreatment with monoclonal antibody 528 (P < .05). Inhibiting cell surface cleavage of AR with WAY-022 before DCA treatment reduced AR (P < .05) and PGE2 (P < .05) levels in the basolateral medium.

CONCLUSION

DCA, but not CA, results in compartment-specific, ligand-dependent activation of EGFR and subsequent increased basolateral PGE2 levels. The mechanism of DCA-induced EGFR activation is ligand-dependent and is controlled, at least in part, at the level of AR release from the basolateral cell membrane.

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.

Chemopreventive and Therapeutic Efficacy of Orally Active Tyrosine Kinase Inhibitors in a Transgenic Mouse Model of Gallbladder Carcinoma

Biliary tract cancer (BTC) is the second most common primary hepatobiliary cancer after hepatocellular cancer. At the time of diagnosis, most BTC are at an advanced stage and are unresectable. There is presently no effective curative treatment of the advanced disease nor is there any effective clinical therapy that will prevent the development of BTC. All of these factors render gallbladder cancer nearly incurable with a poor survival rate. The aim of our study was to provide a better understanding of the mechanisms involved in the development of gallbladder carcinoma as the advancement of more effective treatment options would significantly improve prognosis. In the present study, we examined the effect of gefitinib, a selective epidermal growth factor receptor/tyrosine kinase inhibitor (EGFR/TKI), on the development of gallbladder carcinoma in BK5.erbB2 mice. In addition, we examined the effect of another quinazoline derivative, GW2974, which is able to block the activation of both the EGFR and erbB2, in this model. Animals were treated with either 400 ppm gefitinib or 200 ppm GW2974 as a supplement in the diet using either a chemopreventive or therapeutic protocol. The results show that both compounds were potent chemopreventive and therapeutic agents in this mouse model of human BTC. The results also suggest that activation of the EGFR plays an important role in development of BTC in this model and that targeting both the EGFR and erbB2 may be an effective strategy for treatment of this disease.

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

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

A nuclear receptor ligand down-regulates cytosolic phospholipase A2 expression to reduce bile acid-induced cyclooxygenase 2 activity in cholangiocytes: implications of anticarcinogenic action of farnesoid X receptor agonists

Bile acids are considered to be involved in the development of biliary tract carcinoma, although the underlying mechanisms are yet to be established. The aims of this study were (1) to investigate the carcinogenic role of bile acids in the biliary system based on the arachidonate-prostanoid pathway and (2) to clarify the therapeutic role of a farnesoid X receptor (FXR) ligand that modifies bile acid metabolism. Immortalized mouse cholangiocytes were incubated with glycochenodeoxycholate (GCDC), taurocholate, taurochenodeoxycholate, taurodeoxycholate, and tauroursodeoxycholate. GCDC induced cyclooxygenase 2 (COX-2) expression (Western blotting, 1.7-fold; RT-PCR, 2.3-fold) and prostaglandin (PG) production (PGE2, 6.3-fold; PGF2alpha, 8.5-fold), whereas cytosolic phospholipase A2 (cPLA2) expression and activity were reduced. In contrast, no marked changes were induced by the other bile acids. When the same experiment was performed in the presence of a synthetic FXR ligand (GW4064), cPLA2 expression and activity were reduced, although COX-2 expression was unchanged. GW4064 also suppressed PG generation by 40%. In conclusion, the present findings suggest a carcinogenic potential of GCDC. A synthetic FXR ligand (GW4064) inhibited the induction of COX-2 activity (detected as PG production) by GCDC, suggesting its anticarcinogenic potential. This effect seemed to be due to down-regulation of cPLA2. FXR ligands may have therapeutic potential against biliary carcinogenesis, but a delivery system for these agents is still to be developed.

Bile acid induced gene expression in LT97 colonic adenoma cells

LT97 human colonic adenoma cells reflecting early premalignant genotype and growth characteristics have been posed to tumor promoting bile acids in order to identify marker genes that permit identification of tumor promoters in vitro. Physiologically relevant concentrations of desoxycholate (DOC) and chenodesoxycholate (CDC) upregulated expression of c-fos and COX-2 in a concentration- and time-dependent manner. Transient induction of c-fos was seen with the non-promoting taurodesoxycholate (TDOC) as well as DOC, however extended induction at 3 h was only achieved by DOC and CDC reaching 3-6-fold as compared to the control. Stimulation of COX-2 expression was completely specific for the tumor promoting analogs DOC and CDC. It was about 4-fold in the 80 microM DOC and CDC groups after 3 h and increased to 12- and 7-fold respectively after 6 h. Expression of VEGF was stimulated 4-5-fold in the tumor promoter (DOC and CDC) groups and about 2-fold in the non-promoting controls TDOC and GCDC. At later times the tumor promoter specific difference was lost. Our results show that all three genes are modulated in a tumor promoter dependent way and that their upregulation in LT97 adenoma cells can be used for in vitro testing of colon tumor promoters and chemopreventive compounds.

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.

Deoxycholic acid inhibits pacemaker currents by activating ATP-dependent K+ channels through prostaglandin E2 in interstitial cells of Cajal from the murine small intestine

1. We investigated the role of deoxycholic acid in pacemaker currents using whole-cell patch-clamp techniques at 30 degrees C in cultured interstitial cells of Cajal (ICC) from murine small intestine. 2. The treatment of ICC with deoxycholic acid resulted in a decrease in the frequency and amplitude of pacemaker currents and increases in resting outward currents. Also, under current clamping, deoxycholic acid produced the hyperpolarization of membrane potential and decreased the amplitude of the pacemaker potentials. 3. These observed effects of deoxycholic acid on pacemaker currents and pacemaker potentials were completely suppressed by glibenclamide, an ATP-sensitive K(+) channel blocker. 4. NS-398, a specific cyclooxygenase-2 (COX-2) inhibitor, significantly inhibited the deoxycholic acid-induced effects. The treatment with prostaglandin E(2) (PGE(2)) led to a decrease in the amplitude and frequency of pacemaker currents and to an increase in resting outward currents, and these observed effects of PGE(2) were blocked by glibenclamide. 5. We next examined the role of deoxycholic acid in the production of PGE(2) in ICC, and found that deoxycholic acid increased PGE(2) production through the induction of COX-2 enzyme activity and its gene expression. 6. The results suggest that deoxycholic acid inhibits the pacemaker currents of ICC by activating ATP-sensitive K(+) channels through the production of PGE(2).

Selective inhibitors of MEK1/ERK44/42 and p38 mitogen-activated protein kinases potentiate apoptosis induction by sulindac sulfide in human colon carcinoma cells

The nonsteroidal anti-inflammatory drug (NSAID) sulindac prevents experimental colon cancer and can regress precancerous polyps in humans. Sulindac sulfide inhibits cyclooxygenase (COX)-mediated prostaglandin synthesis and retards the growth of cultured colon cell lines primarily by inducing apoptosis. Given the known role of mitogen-activated protein kinase (MAPK) in signal transduction and the regulation of cell survival and death, we determined the effect of sulindac sulfide on MAPK activation, COX-2 expression, and apoptosis induction in HCA-7 human colon cancer cells. Sulindac sulfide treatment was associated with activation of ERKp44/42 and p38 MAPK in a dosage- and time-dependent manner, and also activated upstream MEK. Similar results were seen in HCT-15 cells and also with the selective COX-2 inhibitor NS398. ERKp44/42 and p38 activation were accompanied by an induction of COX-2 protein expression. Selective inhibitors of sulindac sulfide–induced ERKp44/42 (PD98059) and p38 MAPK (SB203580) activation also suppressed the induction of COX-2 by this NSAID. Furthermore, both MAPK inhibitors significantly augmented sulindac sulfide–induced apoptosis, as did suppression of constitutive COX-2 using antisense oligonucleotides. In conclusion, MEK/ERK and p38 MAPK activation mediate COX-2 induction by sulindac sulfide. Selective inhibitors of these MAPKs potentiate apoptosis induction by this NSAID, suggesting a novel strategy for the prevention or treatment of colorectal cancer.

Imatinib mesylate induces apoptosis in human cholangiocarcinoma cells

BACKGROUND

Cholangiocarcinoma is a highly malignant, usually fatal cancer with limited therapeutic options. Receptor tyrosine kinases contribute to the development and progression of this cancer. The relatively selective tyrosine kinase inhibitor imatinib mesylate (STI-571 or Gleevec(R)) has recently been licensed. However, the ability of this drug to inhibit signal transduction and induce apoptosis in human cholangiocarcinoma cells is incompletely studied. Thus, our goal was to examine the ability of STI-571 to induce apoptosis in KMCH-1 cells, a human cholangiocarcinoma cell line.

METHODS

Apoptosis was assessed morphologically and also biochemically by measuring caspase activity and the mitochondrial membrane potential. STI-571 induced apoptosis and inhibited growth of KMCH-1 cells in a time- and concentration-dependent manner. The induction of apoptosis was accompanied by mitochondrial depolarization followed by a 4.5-fold increase in caspase activation and was abrogated by the pancaspase inhibitor z-VAD(OMe)-fmk. Interestingly, cholangiocarcinoma cells do not express detectable PDGFR, c-Abl or c-Kit, which are protein kinases known to be directly inhibited by STI-571. However, a significant decrease in epidermal growth factor receptor (EGFR) and focal adhesion kinase (FAK) phosphorylation was observed following treatment with STI-571. This decrease in EGFR and FAK phosphorylation was associated with a reduction in Akt activity resulting in loss of Mcl-1, a potent anti-apoptotic Bcl-2 family protein.

CONCLUSIONS

These results indicate that STI-571 induces caspase-dependent apoptosis in a human cholangiocarcinoma cell line and suggest that STI-571 might warrant further investigation as a possible agent for treatment of human cholangiocarcinoma.

Enhanced epidermal growth factor receptor activation in human cholangiocarcinoma cells

BACKGROUND/AIMS

Epidermal growth factor receptor (EGFR) signaling has been implicated in the genesis and progression of cholangiocarcinoma. However, the characteristics of EGFR signaling in cholangiocarcinoma cells have not been characterized. Thus, we attempted to more fully characterize EGF/EGFR signaling in human cholangiocarcinoma cells.

METHODS

EGFR phosphorylation and ubiquitination were evaluated using immunoblot techniques. EGFR internalization was analyzed by immunofluorescent staining of EGFR or by immunoblot analysis for biotinylated EGFR. Cell growth was assessed using the MTS assay.

RESULTS

EGFR activation was sustained following EGF stimulation in cholangiocarcinoma cells as compared to hepatoma cells. This prolonged EGFR activation resulted in extended p42/44 MAPK activation in cholangiocarcinoma cells. Despite ubiquitination, EGFR activation-dependent internalization was defective in cholangiocarcinoma cells. Cell growth was increased in cholangiocarcinoma cells following EGF stimulation as compared to hepatoma cells, and this was significantly attenuated by EGFR kinase inhibitors. The EGFR kinase inhibitors also significantly decreased COX-2 expression in cholangiocarcinoma cells, while this was not evident in hepatoma cells.

CONCLUSIONS

The results demonstrate that cholangiocarcinoma cells exhibit sustained EGFR activation due to defective receptor internalization. As EGFR kinase inhibitors effectively attenuated cellular growth, these agents may be therapeutically efficacious in human cholangiocarcinoma.

Tauroursodeoxycholic acid protects rat hepatocytes from bile acid-induced apoptosis via activation of survival pathways

Ursodeoxycholic acid (UDCA) is used in the treatment of cholestatic liver diseases, but its mechanism of action is not yet well defined. The aim of this study was to explore the protective mechanisms of the taurine-conjugate of UDCA (tauroursodeoxycholic acid [TUDCA]) against glycochenodeoxycholic acid (GCDCA)-induced apoptosis in primary cultures of rat hepatocytes. Hepatocytes were exposed to GCDCA, TUDCA, the glyco-conjugate of UDCA (GUDCA), and TCDCA. The phosphatidylinositol-3 kinase pathway (PI3K) and nuclear factor-kappaB were inhibited using LY 294002 and adenoviral overexpression of dominant-negative IkappaB, respectively. The role of p38 and extracellular signal-regulated protein kinase mitogen-activated protein kinase (MAPK) pathways were investigated using the inhibitors SB 203580 and U0 126 and Western blot analysis. Transcription was blocked by actinomycin-D. Apoptosis was determined by measuring caspase-3, -9, and -8 activity using fluorimetric enzyme detection, Western blot analysis, immunocytochemistry, and nuclear morphological analysis. Our results demonstrated that uptake of GCDCA is needed for apoptosis induction. TUDCA, but not TCDCA and GUDCA, rapidly inhibited, but did not delay, apoptosis at all time points tested. However, the protective effect of TUDCA was independent of its inhibition of caspase-8. Up to 6 hours of preincubation with TUDCA before addition of GCDCA clearly decreased GCDCA-induced apoptosis. At up to 1.5 hours after exposure with GCDCA, the addition of TUDCA was still protective. This protection was dependent on activation of p38, ERK MAPK, and PI3K pathways, but independent of competition on the cell membrane, NF-kappaB activation, and transcription. In conclusion, TUDCA contributes to the protection against GCDCA-induced mitochondria-controlled apoptosis by activating survival pathways.

Ursodeoxycholate further increases bile-duct cell proliferative response induced by partial bile-duct ligation in rats

BACKGROUND

Bile salts (BSs) stimulate cholangiocyte proliferation in vitro and in vivo in normal rats. In this study, we evaluated the effects of BS-enriched diets on cholangiocyte proliferative activity already triggered by partial bile-duct ligation (pBDL), a surgical model that induces mild cholestatic conditions, focusing our attention on ursodeoxycholate (UDC).

METHODS

Animals (n=45) were fed either a standard diet, or a 0.2% deoxycholate- or 0.2% UDC-enriched diet for 4 weeks. Then, in each group, ten animals underwent pBDL and five underwent sham operation. Serum and biliary BS levels, serum cholestasis and cytolysis indexes, as well as liver conventional histology, apoptosis and proliferative activity were evaluated 48 h after the operation.

RESULTS

Animals that underwent pBDL showed sustained proliferative response compared with sham-operated rats. BS-enriched diets did not influence cholangiocyte proliferation in sham-operated rats. However, significantly increased proliferation was observed in pBDL rats fed a UDC-enriched diet. The evaluation of humoral and histological parameters excluded the possibility that the increased proliferation induced by UDC-enriched diet could be related to concomitant liver cell damage.

CONCLUSION

A UDC-enriched diet is able to amplify the magnitude of the cholangiocyte hyperplastic process, which occurs by a stimulatory mechanism after partial bile-duct ligation.

Differential effects of deoxycholic acid and taurodeoxycholic acid on NF-kappa B signal transduction and IL-8 gene expression in colonic epithelial cells

Several effects of bile acids (BAs) on colonic epithelial cells (CECs) have been described, including induction of proliferation and apoptosis. Some of these effects are mediated through activation of the NF-kappa B transcriptional system. In this study, we investigated the molecular mechanisms underlying the BA-induced gene expression in CECs. The human CEC line HT-29 and primary human CECs were treated with dilutions of salts of deoxycholic acid (DCA) and taurodeoxycholic acid (TDCA). NF-kappa B binding activity was analyzed with EMSA, RelA translocation with immunofluorescence, and I kappa B alpha- and RelA-phosphorylation with Western blot analysis. IL-8 mRNA and protein expression were assessed by quantitative PCR and ELISA. Functional impact of NF-kappa B activation was determined by blocking the proteasome activity with MG132 or by preventing IKK activity with a dominant-negative IKK beta delivered by adenoviral dominant-negative (dn) IKK beta (Ad5dnIKK beta). DCA and TDCA induced IL-8 expression in a dose- and time-dependent manner. It is interesting that DCA but not TDCA induced I kappa B alpha-phosphorylation, RelA translocation, and NF-kappa B binding activity. Accordingly, the proteasome inhibitor MG132 blocked DCA- but not TDCA-induced IL-8 gene expression. In contrast, TDCA-induced IL-8 gene expression correlated with enhanced RelA phosphorylation, which was blocked by Ad5dnIKK beta. Our data suggest that DCA-induced signal transduction mainly utilized the I kappa B degradation and RelA nuclear translocation pathway, whereas TDCA primarily induced IL-8 gene expression through RelA phosphorylation. These differences may have implications for the understanding of the pathophysiology of inflammation and carcinogenesis in the gut.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Deoxycholic acid activates beta-catenin signaling pathway and increases colon cell cancer growth and invasiveness

Colorectal cancer is often lethal when invasion and/or metastasis occur. Tumor progression to the metastatic phenotype is mainly dependent on tumor cell invasiveness. Secondary bile acids, particularly deoxycholic acid (DCA), are implicated in promoting colon cancer growth and progression. Whether DCA modulates beta-catenin and promotes colon cancer cell growth and invasiveness remains unknown. Because beta-catenin and its target genes urokinase-type plasminogen activator receptor (uPAR) and cyclin D1 are overexpressed in colon cancers, and are linked to cancer growth, invasion, and metastasis, we investigated whether DCA activates beta-catenin signaling and promotes colon cancer cell growth and invasiveness. Our results show that low concentrations of DCA (5 and 50 microM) significantly increase tyrosine phosphorylation of beta-catenin, induce urokinase-type plasminogen activator, uPAR, and cyclin D1 expression and enhance colon cancer cell proliferation and invasiveness. These events are associated with a substantial loss of E-cadherin binding to beta-catenin. Inhibition of beta-catenin with small interfering RNA significantly reduced DCA-induced uPAR and cyclin D1 expression. Blocking uPAR with a neutralizing antibody significantly suppressed DCA-induced colon cancer cell proliferation and invasiveness. These findings provide evidence for a novel mechanism underlying the oncogenic effects of secondary bile acids.

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

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

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

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

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

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

Bile acids enhance the activity of the insulin receptor and glycogen synthase in primary rodent hepatocytes

Previously, we demonstrated that deoxycholic acid (DCA)-induced ERK1/2 and AKT signaling in primary hepatocytes is a protective response. In the present study, we examined the regulation of the phosphatidylinositol 3 (PI3) kinase/AKT/glycogen synthase (kinase) 3 (GSK3)/glycogen synthase (GS) pathway by bile acids. In primary hepatocytes, DCA activated ERBB1 (the epidermal growth factor receptor), ERBB2, and the insulin receptor, but not the insulin-like growth factor 1 (IGF-1) receptor. DCA-induced activation of the insulin receptor correlated with enhanced phosphorylation of insulin receptor substrate 1, effects that were both blocked by the insulin receptor inhibitor AG1024 and by expression of the dominant negative IGF-1 receptor (K1003R), which inhibited in trans. Expression of the dominant negative IGF-1 receptor (K1003R) also abolished DCA-induced AKT activation. Bile acid-induced activation of AKT and phosphorylation of GSK3 were blunted by the ERBB1 inhibitor AG1478 and abolished by AG1024. Bile acids caused activation of GS to a similar level induced by insulin (50 nM); both were blocked by inhibition of insulin receptor function and the PI3 kinase/AKT/GSK3 pathway. In conclusion, these findings suggest that bile acids and insulin may cooperate to regulate glucose storage in hepatocytes.

Gs protein-coupled receptor agonists induce transactivation of the epidermal growth factor receptor in T84 cells: implications for epithelial secretory responses

We have previously shown that Gq protein-coupled receptor (GqPCR) agonists stimulate epidermal growth factor receptor (EGFr) transactivation and activation of mitogen-activated protein kinases (MAPK) in colonic epithelial cells. This constitutes a mechanism by which Cl- secretory responses to GqPCR agonists are limited. In the present study we examined a possible role for the EGFr in regulating Cl- secretion stimulated by agonists that act through GsPCRs. All experiments were performed using monolayers of T84 colonic epithelial cells grown on permeable supports. Protein phosphorylation and protein-protein interactions were analyzed by immunoprecipitation and Western blotting. Cl- secretion was measured as changes in short-circuit current (DeltaIsc) across voltage-clamped T84 cells. The GsPCR agonist, vasoactive intestinal polypeptide (VIP; 100 nM), rapidly stimulated EGFr phosphorylation in T84 cells. This effect was mimicked by a cell-permeant analog of cAMP, Bt2cAMP/AM (3 microM), and was attenuated by the protein kinase A (PKA) inhibitor, H-89 (20 microM). The EGFr inhibitor, tyrphostin AG1478 (1 microM), inhibited both Bt2cAMP/AM-stimulated EGFr phosphorylation and Isc responses. VIP and Bt2cAMP/AM both stimulated ERK MAPK phosphorylation and recruitment of the p85 subunit of phosphatidylinositol 3-kinase (PI3K) to the EGFr in a tyrphostin AG1478-sensitive manner. The PI3K inhibitor, wortmannin (50 nM), but not the ERK inhibitor, PD 98059 (20 microM), attenuated Bt2cAMP/AM-stimulated secretory responses. We conclude that GsPCR agonists rapidly transactivate the EGFr in T84 cells by a signaling pathway involving cAMP and PKA. Through a mechanism that likely involves PI3K, transactivation of the EGFr is required for the full expression of cAMP-dependent Cl- secretory responses.

Selective abrogation of the proinvasive activity of the trefoil peptides pS2 and spasmolytic polypeptide by disruption of the EGF receptor signaling pathways in kidney and colonic cancer cells

Trefoil peptides (TFFs) are now considered as scatter factors, proinvasive and angiogenic agents acting through cyclooxygenase-2 (COX-2)- and thromboxane A2 receptor (TXA2-R)-dependent signaling pathways. As expression and activation levels of the epidermal growth factor receptor (EGFR) predict the metastatic potential of human colorectal cancers, the purpose of this study was to establish whether the EGF receptor tyrosine kinase (EGFR-TK) contributes to cellular invasion induced by TFFs in kidney and colonic cancer cells. Both the dominant negative form of the EGFR (HER-CD533) and the EGFR-TK inhibitor ZD1839 (Iressa) abrogated cellular invasion induced by pS2, spasmolytic polypeptide (SP) and the src oncogene, but not by ITF and the TXA2-R. Similarly, EGFR-TK inhibition by ZD1839 reversed the invasive phenotype promoted by the constitutively activated form of the EGFR (EGFRvIII) and the EGFR agonists transforming growth factor alpha (TGFalpha), amphiregulin and EGF. We also provide evidence that TFFs, EGFRvIII, and TGFalpha trigger common proinvasive pathways using the PI3'-kinase and Rho/Rho- kinase cascades. These findings identify the EGFR-TK as a key signaling element for pS2- and SP-mediated cellular invasion. It is concluded that although pS2, SP and ITF belong to the same family of inflammation- and cancer-associated regulatory peptides, they do not control identical signaling networks.

Identification of novel cellular targets in biliary tract cancers using global gene expression technology

Biliary tract carcinoma carries a poor prognosis, and difficulties with clinical management in patients with advanced disease are often due to frequent late-stage diagnosis, lack of serum markers, and limited information regarding biliary tumor pathogenesis. RNA-based global analyses of gene expression have led to the identification of a large number of up-regulated genes in several cancer types. We have used the recently developed Affymetrix U133A gene expression microarrays containing nearly 22,000 unique transcripts to obtain global gene expression profiles from normal biliary epithelial scrapings (n = 5), surgically resected biliary carcinomas (n = 11), and biliary cancer cell lines (n = 9). Microarray hybridization data were normalized using dCHIP (http://www.dCHIP.org) to identify differentially up-regulated genes in primary biliary cancers and biliary cancer cell lines and their expression profiles was compared to that of normal epithelial scrapings using the dCHIP software as well as Significance Analysis of Microarrays or SAM (http://www-stat.stanford.edu/ approximately tibs/SAM/). Comparison of the dCHIP and SAM datasets revealed an overlapping list of 282 genes expressed at greater than threefold levels in the cancers compared to normal epithelium (t-test P <0.1 in dCHIP, and median false discovery rate <10 in SAM). Several pathways integral to tumorigenesis were up-regulated in the biliary cancers, including proliferation and cell cycle antigens (eg, cyclins D2 and E2, cdc2/p34, and geminin), transcription factors (eg, homeobox B7 and islet-1), growth factors and growth factor receptors (eg, hepatocyte growth factor, amphiregulin, and insulin-like growth factor 1 receptor), and enzymes modulating sensitivity to chemotherapeutic agents (eg, cystathionine beta synthase, dCMP deaminase, and CTP synthase). In addition, we identified several "pathway" genes that are rapidly emerging as novel therapeutic targets in cancer (eg, cytosolic phospholipase A2, an upstream target of the cyclooxygenase pathway, and ribosomal protein S6 kinase and eukaryotic translation initiation factor 4E, two important downstream mediators of the mitogenic Akt/mTOR signaling pathway). Overexpression of selected up-regulated genes was confirmed in tissue microarrays of biliary cancers by immunohistochemical analysis (n = 4) or in situ hybridization (n = 1), and in biliary cancer cell lines by reverse transcriptase PCR (n = 2). The majority of genes identified in the present study has not been previously reported in biliary cancers, and represent novel potential screening and therapeutic targets of this cancer type.

Bile acids activate EGF receptor via a TGF-alpha-dependent mechanism in human cholangiocyte cell lines

Bile acids transactivate the EGF receptor (EGFR) in cholangiocytes. However, the mechanisms by which bile acids transactivate the EGFR remain unknown. Our aims were to examine the effects of bile acids on EGFR activation in human cholangiocyte cell lines KMBC and H-69. Bile acids stimulated cell growth and induced EGFR phosphorylation in a ligand-dependent manner. Although cells constitutively expressed several EGFR ligands, only transforming growth factor-alpha (TGF-alpha) antisera effectively blocked bile acid-induced EGFR phosphorylation. Consistent with the concept that matrix metalloproteinase (MMP) activity is requisite for TGF-alpha membrane release and ligand function, bile acid transactivation of EGFR and cell growth was blocked by an MMP inhibitor. In conclusion, bile acids activate EGFR via a TGF-alpha-dependent mechanism, and this EGFR activation promotes cellular growth.

Effects of cyclooxygenase-2 antisense vector on proliferation of human cholan-giocarcinoma cells

AIM

To transfect antisense vector of human COX-2 gene into COX-2 highly expressing cholangiocarcinoma cell line QBC939 and to explore its biological activities and role in carcinogenesis.

METHODS

QBC939 cells were transfected with antisense vector of human COX-2 gene using LipoVecTM transfecting technique. Transfected cells were selected with G418; COX-2 mRNA was examined by using reverse transcription polymerase chain reaction (RT-PCR) and COX-2 protein expression was detected by immunocytochemistry using isozyme selective antibodies. The proliferative status of transfected cells was measured by using methabenzthiazuron (MTT) assay; Cell cycle and apoptosis was analyzed by using flow cytometry (FCM).

RESULTS

RT-PCR showed a lower COX-2 mRNA level in transfected cells and immunocytochemistry showed weaker COX-2 protein expression in transfected cells. The proliferative index of the transfected cells decreased significantly(P<0.01), the percentage of S phase decreased remarkably in transfected cells(9.27±1.91%) compared with that in QBC939 cells without transfection (16.35±2.87%)(P<0.05), and the percentage of G0/G1 phase increased remarkably in transfected cells (75.16±4.13%) compared with that in QBC939 cells without transfection (57.31±10.16%)(P<0.05). Transfection with antisense vector of human COX-2 gene had no significant influence on the apoptosis in QBC939 cells (P>0.05).

CONCLUSION

Transfection with antisense vector of human COX-2 gene is able to inhibit the proliferation of human cholangiocarcinoma QBC939 cells.

Bile from a patient with anomalous pancreaticobiliary ductal union promotes the proliferation of human cholangiocarcinoma cells via COX-2 pathway

AIM: To explore the effects of COX-2 gene in the proliferative activity induced by bile from anomalous pancreaticobiliary ductal union (APBDU) on human cholangiocarcinoma cell line.

METHODS: Bile sample from APBDU and normal bile sample were used for this study. The proliferative effect of bile was measured by methabenzthiazuron (MTT) assay; COX-2 mRNA was examined by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Cell cycle was analyzed by flow cytometry (FCM), and the PGE₂ levels in the supernatant of cultured cholangiocarcinoma cells were quantitated by enzyme-linked immunoabsordent assay (ELISA).

RESULTS: Bile from APBDU can significantly promote the proliferation of human cholangiocarcinoma QBC939 cells compared with normal bile (P = 0.005) and up-regulated remarkably their COX-2 mRNA expression (P = 0.004). The proliferative activity of APBDU bile can be abolished by addition of cyclooxygenase-2 specific inhibitor celecoxib.

CONCLUSION: Bile from APBDU can promote the proliferation of human cholangiocarcinoma QBC939 cells via COX-2 pathway.

Cholestatic syndromes

Further insights into the cellular and molecular mechanisms underlying hepatobiliary transport function and its regulation now permit a better understanding of the pathogenesis and treatment options of cholestatic liver diseases. Identification of the molecular basis of hereditary cholestatic syndromes will result in an improved diagnosis and management of these conditions. New insights into the pathogenesis of extrahepatic manifestations of cholestasis (eg, pruritus) have facilitated new treatment strategies. Important new studies have been published about the pathogenesis, clinical features, diagnosis, and treatment of primary biliary cirrhosis, primary sclerosing cholangitis, cholestasis of pregnancy, total parenteral nutrition-induced cholestasis, drug-induced cholestasis, and viral cholestatic syndromes.

Influence of ursodeoxycholate-enriched diet on liver tumor growth in HBV transgenic mice

Hepatitis B virus (HBV) transgenic mice (official designation, Tg [Alb-1 HBV] Bri 44) invariably develop macroscopically evident tumors within the 20th month of life. Sustained proliferative activity seems to play an important role in the development of these lesions. We previously showed that ursodeoxycholate (UDC) stimulates hepatocyte proliferation in various experimental settings. Herein, we tested the assumption that biological factors able to further increase liver cell proliferation, such as UDC, could accelerate tumor development in this animal model. For this study, 22 eight-week-old male transgenic mice were divided into 2 groups; 11 animals received a standard diet, and 11 received a UDC-enriched diet. The 2 groups were further divided into 2 subgroups of 5 and 6 animals each and were sacrificed at 3 and 15 months of age, respectively. These different times were chosen to exclude diet-related toxicity (in 3-month-old mice) and evaluate tumor growth (in 15-month-old mice). In addition, hepatocyte proliferation was assessed in all animals. In 3-month-old mice receiving UDC, cholestatic and cytolytic indices as well as liver histology were comparable to those in controls. At 15 months, all UDC-treated mice showed large multinodular tumors whereas only 33% of controls developed smaller uninodular neoplasms. Hepatocyte proliferation was increased in all animals receiving UDC compared with controls. In conclusion, the increase in serum UDC (undetectable in mice fed a standard diet), in the absence of any toxic effect on the liver, suggests the involvement of this bile salt in the stimulation of hepatocyte proliferation and tumor growth.

Proliferative activity of bile from congenital choledochal cyst patients

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

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

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

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