Cyclooxygenase expression in the gallbladder

A genetic model for gallbladder carcinogenesis and its dissemination

Gallbladder cancer, although regarded as the most common malignancy of the biliary tract, continues to be associated with a dismal overall survival even in the present day. While complete surgical removal of the tumour offers a good chance of cure, only a fraction of the patients are amenable to curative surgery owing to their delayed presentation. Moreover, the current contribution of adjuvant therapies towards prolonging survival is marginal, at best. Thus, understanding the biology of the disease will not only enable a better appreciation of the pathways of progression but also facilitate the development of an accurate genetic model for gallbladder carcinogenesis and dissemination. This review provides an updated, evidence-based model of the pathways of carcinogenesis in gallbladder cancer and its dissemination. The model proposed could serve as the scaffolding for elucidation of the molecular mechanisms involved in gallbladder carcinogenesis. A better understanding of the pathways involved in gallbladder tumorigenesis will serve to identify patients at risk for the cancer (and who thus could be offered prophylactic cholecystectomy) as well as aid oncologists in planning the most suitable treatment for a particular patient, thereby setting us on the vanguard of transforming the current treatment paradigm for gallbladder cancer.

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

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

Therapeutic effect of rapamycin on gallbladder cancer in a transgenic mouse model

The macrolide fungicide rapamycin has shown significant antiproliferative action toward a variety of tumor types. In this study, we used BK5.erbB2 transgenic mice as an animal model to examine the therapeutic effect of rapamycin as a potential treatment for gallbladder cancer. Homozygous BK5.erbB2 mice overexpressing the wild-type rat erbB2 gene in basal epithelial cells of the gallbladder have an approximately 70% incidence of gallbladder adenocarcinoma by 2 to 3 months of age. Groups of mice ( approximately 2-3 months of age) were treated with rapamycin by i.p. injection (once daily for 14 days) and then sacrificed 24 h after the last treatment. Rapamycin significantly reduced the incidence and severity of gallbladder carcinoma in BK5.erbB2 mice in a dose-dependent manner. Tumors responsive to treatment exhibited a higher number of apoptotic cells. Furthermore, rapamycin treatment led to decreased levels of phosphorylated p70 S6 kinase (Thr(389)) in gallbladder tissue as assessed by both Western blot and immunofluorescence analyses. Finally, immunofluorescence staining revealed elevated phosphorylated Akt (Ser(473)) and phosphorylated mammalian target of rapamycin (mTOR; Ser(2448)) in human gallbladder cancer compared with normal gallbladder tissue. Based on our results using a novel genetically engineered mouse model and the fact that the Akt/mTOR pathway is activated in human gallbladder cancer, rapamycin and related drugs may be effective therapeutic agents for the treatment of human gallbladder cancer.

Tea drinking and the risk of biliary tract cancers and biliary stones: a population-based case-control study in Shanghai, China

Biliary tract cancers, encompassing tumors of the gallbladder, extrahepatic bile ducts and ampulla of Vater, are rare but highly fatal malignancies. Apart from gallstones, etiologic factors for biliary tract cancer are not clearly defined. Several epidemiologic studies have suggested that consumption of tea, especially green tea, is protective against a variety of cancers, including gastrointestinal malignancies. As part of a large population-based case-control study of biliary tract disease in Shanghai, China, we evaluated the effects of tea consumption on the risk of biliary tract cancers and biliary stones. The study included 627 incident cases with biliary tract cancer, 1,037 cases with biliary stones and 959 randomly selected controls. Study subjects were interviewed to ascertain data on demographic, medical and dietary factors, including tea consumption. Forty-one percent of the controls were ever tea drinkers, defined as those who consumed at least 1 cup of tea per day for at least 6 months. After adjustment for age, education and body mass index, among women, ever tea drinkers had significantly reduced risks of biliary stones (OR = 0.73, 95% CI = 0.54-0.98) and gallbladder cancer (OR = 0.56, 95% CI = 0.38-0.83). The inverse relationship between tea consumption and gallbladder cancer risk was independent of gallstone disease. Among men, tea drinkers were more likely to be cigarette smokers, and the risk estimates were generally below 1.0, but were not statistically significant. Further studies are needed to confirm these results in other populations and clarify the hormonal and other mechanisms that may be involved.

Prostaglandin-endoperoxide synthase 2 (PTGS2) gene polymorphisms and risk of biliary tract cancer and gallstones: a population-based study in Shanghai, China

There is evidence that chronic inflammation predisposes to biliary tract cancer and that use of non-steroidal anti-inflammatory drugs (NSAIDs) is protective. Although the mechanisms by which NSAIDs lower cancer risk remain unclear, NSAIDs reduce prostaglandin production by blocking prostaglandin-endoperoxide synthase 2 (PTGS2, commonly known as COX-2), an enzyme induced by proinflammatory stimuli that is often overexpressed in malignant tissue. Since variants in the PTGS2 gene may modify the expression or function of its encoded enzyme to modulate the inflammatory response in the biliary tract, we examined the associations of eight PTGS2 polymorphisms (-645C-->T; Ex3 -8G-->C; IVS5 -275T-->G; IVS7 +111T-->C; Ex10 +127T-->C; Ex10 +686 --->ATTAT-->TTATA; Ex10 +837T-->C; Ex10 -90C-->T) with biliary tract cancer and stones in a population-based case-control study conducted in Shanghai, China. Genotyping was performed for 411 patients with biliary tract cancer (237 gallbladder, 127 extrahepatic bile duct and 47 ampulla of Vater), 895 patients with biliary stones (673 gallbladder, 222 bile duct), and 786 healthy individuals randomly selected from the population. Significant associations were seen only between the Ex10 +837T-->C marker and bile duct cancer risk. Relative to individuals with the TT genotype, those carrying the C allele (TC or CC genotype) had a 1.8-fold (95% confidence interval: 1.2-2.7) risk of bile duct cancer. Inferred haplotypes including this risk-conferring allele were also associated with increased bile duct cancer risk of similar magnitude. Our results suggest that a common PTGS2 variant increases bile duct cancer risk. Further investigation is needed to confirm and extend our findings in studies of biliary tract cancer that more comprehensively examine PTGS2 and other inflammation-related genes.

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.

Aspirin use and risk of biliary tract cancer: a population-based study in Shanghai, China

The association of gallbladder and bile duct cancers with gallstones, cholecystitis, and cholangitis suggest that chronic inflammation contributes to the carcinogenic process. However, the effect of nonsteroidal anti-inflammatory drugs, such as aspirin, on biliary tract cancer has not been well studied. In a population-based case-control study conducted in Shanghai, China, we examined the relationship between aspirin use and the risk of biliary disease. A total of 627 patients with biliary tract cancer, including cancers of the gallbladder (n = 368), extrahepatic bile duct (n = 191), and ampulla of Vater (n = 68); 1,037 patients with biliary stones; and 958 healthy adults were included in the study. Self-reported data on aspirin use was collected from study participants by in-person interview. The prevalence of aspirin use was low, with 5.7% of the population controls being regular users. After controlling for age, sex, education, and biliary stone status, aspirin use was associated with a reduced risk of gallbladder cancer [odds ratio (OR), 0.37; 95% confidence interval (CI), 0.17-0.88]. An inverse relationship was also observed for frequency and duration of use and with younger age when starting use. In addition, there was a nonsignificant reduction in the risk of bile duct (OR, 0.48; 95% CI, 0.19-1.19) and ampullary cancers (OR, 0.22; 95% CI, 0.03-1.65) associated with aspirin use, whereas no clear association was seen with biliary stones (OR, 0.92; 95% CI, 0.59-1.44). Further studies of biliary tract cancer in other populations are needed to confirm these results and to elucidate the mechanisms that underlie the reduced risk associated with use of aspirin and possibly other nonsteroidal anti-inflammatory drugs.