Alphonse E. Sirica

Immunohistochemical demonstration of MET overexpression in human intrahepatic cholangiocarcinoma and in hepatolithiasis

Expression of MET, the c-met-encoded receptor for hepatocyte growth factor, has not been investigated in proliferative biliary diseases of human liver, including hepatolithiasis and cholangiocarcinoma. Comparatively, we analyzed by immunohistochemistry the expression of MET in normal adult human livers (n = 20), normal postnatal preadult livers (n = 21), fetal livers (n = 36), hepatolithiatic livers (n = 32), and intrahepatic cholangiocarcinomas (n = 26). In normal adult livers, obvious MET immunoreactivity was not found in any cell types. In fetal liver, MET was weakly expressed in primitive biliary cells (ductal plate and immature bile ducts) and immature hepatocytes during 8 to 30 gestational weeks but was essentially negative thereafter. In hepatolithiasis, a condition of risk for cholangiocarcinoma development, MET was overexpressed in proliferated biliary cells in 26 of 32 cases (81%). In this nonneoplastic proliferative biliary condition, MET immunoreactivity was observed to be most prominent in the hyperplastic septal and large bile ducts of liver, and in the proliferated peribiliary glands associated with intrahepatic large bile ducts. In intrahepatic cholangiocarcinoma, MET overexpression in neoplastic biliary epithelium was observed in 15 of 26 cases (58%) and correlated with the degree of tumor differentiation, being highest in well-differentiated tumors and relatively low in poorly differentiated tumors. These data show for the first time that overexpression of MET is a common feature of hyperplastic and neoplastic biliary epithelial cells in human liver and suggest that MET/hepatocyte growth factor may be playing an important role in human biliary hyperplasia and in cholangiocarcinogenesis in vivo.

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

Recently, we demonstrated that the cyclooxygenase‐2 (COX‐2) inhibitor celecoxib acts to significantly suppress the growth of rat C611B cholangiocarcinoma (ChC) cells in vitro. To establish a molecular mechanism for this growth suppression, we investigated the effects of celecoxib on apoptotic signaling pathways in cultured rat C611B ChC cells. Celecoxib and another COX‐2 inhibitor, rofecoxib, at 5 μM were almost equally effective in inhibiting prostaglandin E2 (PGE2) production by these cells, but at this low concentration, neither inhibitor suppressed growth or induced apoptosis. Celecoxib at 50 μM induced prominent apoptosis in these cells, whereas rofecoxib at 50 μM was without effect in either suppressing growth or inducing apoptosis. Celecoxib (50 μM) did not alter Bcl‐2, Bcl‐xL, or COX‐2 protein levels, nor did it inhibit p42/44 mitogen‐activated protein kinase (MAPK) phosphorylation; however, it significantly suppressed serine/threonine kinase Akt/PKB (Akt) phosphorylation and kinase activity in cultured C611B cells. This effect, in turn, directly correlated with Bax translocation to mitochondria, cytochrome c release into cytosol, activation of caspase‐9 and caspase‐3, and cleavage of poly (ADP‐ribose) polymerase (PARP). Addition of 25 μM PGE2 to C611B cell cultures blocked the apoptotic actions of celecoxib. Rofecoxib (50 μM) was without effect in suppressing Akt phosphorylation and caspase‐3 activation. In vivo, celecoxib partially suppressed tumorigenic growth of C611B ChC cells. In conclusion, our results indicate that celecoxib preferentially acts in vitro to induce apoptosis in ChC cells through a mechanism involving Akt inactivation, Bax translocation, and cytochrome c release. Our in vivo results further suggest celecoxib might have potential therapeutic or chemopreventive value against ChC. (HEPATOLOGY 2004;39:1028–1037.)

Expression of an intestine-specific transcription factor (CDX1) in intestinal metaplasia and in subsequently developed intestinal type of cholangiocarcinoma in rat liver.

CDX1 is a caudal-type homeobox intestine-specific transcription factor that has been shown to be selectively expressed in epithelial cells in intestinal metaplasia of the human stomach and esophagus and variably expressed in human gastric and esophageal adenocarcinomas (Silberg DG, Furth EE, Taylor JK, Schuck T, Chiou T, Traber PG: Gastroenterology 1997, 113: 478-486). Through the use of immunohistochemistry and Western blotting, we investigated whether CDX1 is also uniquely associated with the intestinal metaplasia associated with putative precancerous cholangiofibrosis induced in rat liver during furan cholangiocarcinogenesis, as well as expressed in neoplastic glands in a subsequently developed intestinal type of cholangiocarcinoma. In normal, control adult rat small intestine, specific nuclear immunoreactivity for CDX1 was most prominent in enterocytes lining the crypts. In comparison, epithelium from intestinal metaplastic glands within furan-induced hepatic cholangiofibrosis and neoplastic epithelium from later developed primary intestinal-type cholangiocarcinoma each demonstrated strong nuclear immunoreactivity for CDX1. CDX1-positive cells were detected in hepatic cholangiofibrotic tissue as early as 3 weeks after the start of chronic furan treatment. We further determined that the percentages of CDX1-positive neoplastic glands and glandular nuclei are significantly higher in primary tumors than in a derived, transplantable cholangiocarcinoma serially-propagated in vivo. Western blotting confirmed our immunohistochemical results, and no CDX1 immunoreactivity was detected in normal adult rat liver or in hyperplastic biliary epithelial cells. These findings indicate that CDX1 is specifically associated with early intestinal metaplasia and a later developed intestinal-type of cholangiocarcinoma induced in the liver of furan-treated rats.

Effects of medium and substratum conditions on the rates of DNA synthesis in primary cultures of bile ductular epithelial cells

SummarySelect medium and substratum conditions were investigated for their effects on semiconservative DNA synthesis in essentially pure primary cultures of bile ductular epithelial cells that were initially isolated from cholestatic rat livers at 6 to 10 wk after bile duct ligation. DNA synthesis in these cultured cells was serum-dependent, being at its highest level when the concentration of fetal bovine serum present in the medium was maintained at 10%. This serum-dependent DNA synthesis was completely inhibited when 10 mM hydroxyurea was also included in the medium, and bile ductular cells cultured in the continued presence of 1.0% fetal bovine serum showed only marginal DNA synthesis during 8 to 10 d of primary culture when compared with no-serum controls. Maximum rates of serum-dependent DNA synthesis were obtained when the bile ductular cells were cultured for 7 to 14 d on tissue culture plastic coated with obtained when the bile ductular cells were cultured for 7 to 14 d on tissue culture plastic coated with either fibronectin from bovine plasma or type I rat-tail collagen. Cells cultured on plastic coated with basement membrane Matrigel exhibited the lowest levels of DNA synthesis, whereas those on plastic alone had intermediate amounts. Furthermore, the addition of epidermal growth factor (50 ng·ml−1·d−1) to medium supplemented with 1.0% fetal bovine serum greatly enhanced the rate of DNA synthesis in bile ductular cells after 6 d in primary culture on type I collagen-coated plastic over that measured in solvent control cultures. These findings indicate that our bile ductular epithelial cell culture model is potentially useful in the study of biliary cell growth regulation and carcinogenesis.

Characterization of rat hyperplastic bile ductular epithelial cells in culture and in vivo.

A novel intrahepatic biliary cell culture/in vivo transplantation system has been developed with an essentially pure population of bile ductular epithelial cells isolated from rat liver 6–12 weeks after bile duct ligation. In primary culture, these cells retain staining strongly for γ-glutamyltranspeptidase and glutathione S-transferase P. The cytoplasm of cultured bile ductular cells reacts with an anti-laminin antibody, but loses immunoreactivity with a monoclonal anti-cytokeratin 19 antibody. Semiconservative DNA synthesis in the cultured cells was dependent upon the continued presence of 10% fetal calf serum in the medium. Replicating bile ductular cells could be subcultured for a finite number of passages. In addition, freshly isolated bile ductular epithelial cells gave rise to well differentiated bile ductular structures when transplanted into the interscapular fat pads of syngeneic recipient rats.