Acceleration of spontaneous biliary carcinogenesis in hamsters by bilioenterostomy

Biliary carcinomas can occur as a delayed complication of bilioenterostomy. The aim of this study was to determine whether bilioenterostomy influences biliary carcinogenesis in hamsters. Syrian hamsters were subjected to three different surgical procedures: simple laparotomy (SL), choledochoduodenostomy (CD) and choledochojejunostomy (CJ). They were given no carcinogens, and five to six hamsters from each group were killed every 20 weeks up to 120 weeks after surgery. Thirty-seven, 32 and 38 hamsters were sampled from the SL, CD and CJ groups, respectively. Cholangiocarcinomas developed in 5.4, 15.6 and 23.7% of hamsters in the SL, CD and CJ groups, respectively. The incidence of biliary carcinoma was significantly higher in the bilioenterostomy groups, especially CJ (P < 0.05), than in SL. The tumor latency period after surgery was 20-40 weeks shorter in the bilioenterostomy groups than in SL. Persistent cholangitis and bile stasis were frequent in the bilioenterostomy groups, and a significant correlation between cholangitis and biliary carcinogenesis was noted in the CD group. The proliferative cell nuclear antigen (PCNA) labeling index was higher in the biliary epithelium of the bilioenterostomy groups. In conclusion, persistent cholangitis after bilioenterostomy accelerates biliary carcinogenesis through activation of biliary epithelial cell kinetics.     

Linkage of persistent cholangitis after bilioenterostomy with biliary carcinogenesis in hamsters

Biliary carcinoma occurring after bilioenterostomy has been reported as a late complication of this surgical procedure. The present study was designed to determine if bilioenterostomy promotes biliary carcinogenesis, and also to clarify the relationship between biliary inflammation and biliary carcinogenesis in hamsters. Syrian hamsters underwent a simple laparotomy (SL), choledochoduodenostomy (CD) or choledochojejunostomy (CJ). All hamsters received subcutaneous injections of the chemical carcinogen, N-nitrosobis (2-oxopropyl) amine (BOP), and were sacrificed 20 weeks after surgery. Neoplastic lesions in the biliary tree were histologically examined, and the presence and degree of cholangitis was also evaluated with special reference to biliary carcinogenesis. The incidence of bile duct carcinoma was not significantly different among the three groups. Numerous bile duct carcinomas, however, were recognized in the bilioenterostomized animals, especially in the CJ group. Moreover, significant correlations between biliary carcinogenesis and the presence of cholangitis were noted in both the CD and CJ groups, but not in the SL control group. Severe cholangitis was evident in the CJ group, and the number of biliary carcinomas was well correlated with the degree of cholangitis. In conclusion, the risk of carcinoma in the biliary tract may increase when persistent cholangitis is present after biliary reconstruction.     

Chemopreventative effect of a cyclooxygenase-2-specific inhibitor (etodolac) on chemically induced biliary carcinogenesis in hamsters

The present study was designed to evaluate whether etodolac, a cyclooxgenase-2 (COX-2)-specific inhibitor, could prevent chemically induced biliary carcinogenesis in bilioenterostomized hamsters. Syrian golden hamsters were subjected to choledochojejunostomy and then received subcutaneous injections of N-nitrosobis(2-oxopropyl)amine (BOP) every 2 weeks at a dose of 10 mg/kg body wt. BOP administration was started 4 weeks after surgery, and continued for 18 weeks. The animals were simultaneously orally administered etodolac three times per week at a dose of 10 mg/kg body wt in 0.5% methylcellose solution (etodolac group). The control hamsters were administered methylcellose solution alone. The hamsters were killed 22 weeks after surgery, and the biliary carcinomas were evaluated histologically. The presence and degree of cholangitis and the cell kinetic status of the biliary epithelium were also evaluated with special reference to biliary carcinogenesis. Intrahepatic bile duct carcinomas developed in 15 of 17 (88%) hamsters in the control group, and in only six of 18 (33%) hamsters in the etodolac group (P < 0.01). The incidence and number of developing biliary carcinomas were well correlated with the degree of cholangitis, and severe cholangitis was evident in the controls. The cell kinetic study demonstrated that the proliferating cell nuclear antigen-labeling index of the biliary epithelium was 9.67 and 5.14% in the control and etodolac groups, respectively (P < 0.05). The mean levels of prostaglandin E(2) (PGE(2)) products in the liver tissue were 14.14 +/- 3.31 pg/total protein (TP) mg in the control group, and 7.46 +/- 2.34 pg/TP mg in the etodolac group (P < 0.05). These findings indicated that etodolac reduced both the occurrence of severe cholangitis and the acceleration of biliary epithelial cell kinetics after bilioenterostomy, resulting in the prevention of BOP-induced biliary carcinogenesis in hamsters. In conclusion, COX-2-specific inhibitor (etodolac) may be a possible agent against not only reflux cholangitis, but also biliary carcinoma after bilioenterostomy.     

Comparative carcinogenesis by hydroxylated nitrosopropylamines in Syrian hamsters

The relationship between the chemical structure of nitrosamines and their carcinogenic activity has been examined in Syrian golden hamsters in parallel with similar studies in rats to aid in explaining the sharp interspecies differences in response to these compounds. The relationship between the beta-oxidized N-propyl-nitrosamine structure and the induction of tumors of the pancreatic duct in Syrian golden hamsters was investigated by administration of a number of asymmetric acyclic nitrosamines containing that structure to female hamsters for 29-50 weeks. N-Nitroso-2-oxopropyl-2-hydroxyethylamine (OPE), N-nitroso-2-hydroxypropyl-2-hydroxyethylamine (NIEA), and N-nitroso-2,3-dihydroxypropyl-2-oxopropylamine (DHPOP) induced pancreatic tumors. OPE also induced a high incidence of liver neoplasms, and a number of animals given NIEA and N-nitrosoallyl-2-oxopropylamine (NAOP) also had liver neoplasms. N-Nitroso-2,3-dihydroxypropyl-2-hydroxyethylamine was very weakly carcinogenic. N-Nitroso-2,3-dihydroxypropyl-2-hydroxypropylamine and DHPOP induced a high incidence of neoplasms of the forestomach (mainly papillomas). N-Nitrosoallyl-2,3-dihydroxypropylamine, N-nitrosoallyl-2-hydroxypropylamine, and NAOP induced primarily neoplasms of the nasal mucosa but no neoplasms of the pancreatic ducts in hamsters.     

Differential susceptibility to bronchial carcinogenesis in syngeneic hamsters

Previous studies of chemical carcinogenesis in the lung of Syrian golden hamsters have utilized outbred (nonsyngeneic) animals. Using the endobronchial sustained release implant technique, which causes focally originating cancers in outbred hamsters, we studied the course of bronchial carcinogenesis in two varieties of syngeneic Syrian golden hamsters, the LSH and the F1D strains (BIO 15.16 male X BIO 87.20 female). With either 10% benzo(a)pyrene or 10% methylcholanthrene sustained release implants the time course of epithelial transition from normal to neoplastic was the same for F1D hamsters as previously described for outbred hamsters. Using 10% benzo(a)pyrene sustained release implants the incidence of cancers as a function of time was significantly lower (P less than 0.001) in LSH hamsters as compared to outbred and F1D animals. Of 19 tumors transplanted into syngeneic F1D hamsters, 16 have been successfully propagated by serial transplantation. We conclude that (a) F1D hamsters are comparable to outbred animals in the response of their bronchial epithelium to endobronchial benzo(a)pyrene and methylcholanthrene, (b) there are significant differences in susceptibility to bronchial chemical carcinogenesis among hamster strains, thereby giving opportunity to study potential genetic control mechanisms during bronchial carcinogenesis, and (c) F1D hamsters are suitable for studies of lung cancer biology using tumor transplantation methods.     

Nitrosamine-induced pancreatic carcinogenesis in outbred and inbred Syrian hamsters

Pancreatic carcinogenesis was investigated in outbred and infive strains of inbred Syrian golden hamsters utilizing thenitrosamines N-nitrosobis(2-hydroxypropyl)amine (BHP) and N-nitrosobis(2-oxopropyl)amine(BOP). Thirty eight outbred hamsters were treated for an averageof 15 weeks with weekly s.c. inoculations of BHP at doses of250, 500, or 1000 mg/kg. Pancreatic carcinomas developed in19%. Eighty nine inbred hamsters of strains CB, LHC, and PD4were given BHP at 250 mg/kg weekly for an average of 25 weeks.Pancreatic carcinomas developed in 61%. Pancreatic inflammation,fibrosis, and ductal hyperplasia were prominent. Toxic changesin the liver, biliary hyperplasia, and pulmonary interstitialinflammation were also prominent features of BHP-treated hamsters,along with occasional carcinomas of the liver and respiratorytract. One hundred and sixteen inbred hamsters of strains CB,LHC, LSH, MHA, and PD4 were treated with BOP at a dose of 5mg/kg weekly for 15 weeks. The incidence of pancreatic carcinomawas 51%. BHP-treated hamsters exhibited pancreatic fibrosisand ductal hyperplasia. Livers of BHP-treated animals showedbiliary hyperplasia, and lungs exhibited chronic inflammation.Occasional carcinomas of the liver and lung developed. From243 hamsters treated with nitroso carcinogens, eight pancreaticductal adenocarcinoma lines were derived that can be transplantedand propagated in inbred hamsters.     

Pancreatobiliary diversion enhances experimental pancreatic carcinogenesis

Since compensatory hyperplasia promotes experimental carcinogenesis in the gut, we tested the ability of two surgical models of pancreatic growth to promote pancreatic carcinogenesis. Male Wistar rats (n = 60) weighing 250-300 g underwent pancreatobiliary diversion (PBD), 90% small bowel resection (PSBR) or triple transection and reanastomosis of the small intestine (controls). Postoperatively, each group received azaserine (20 mg kg-1 wk-1 i.p.) for 6 weeks. Surviving rats were killed at 6 months, pancreatic wet weight was measured and histological sections were examined for atypical acinar cell foci (AACF), the putative precursor of carcinoma. Median relative pancreatic weight (mg pancreas/g body weight) was 2.20 for controls (n = 18), 4.08 for PSBR (n = 11) (P less than 0.001) and 6.86 for PBD (n = 16) (P less than 0.001). PSBR did not affect the development of acidophilic AACF, but PBD produced an enormous increase in their number per cm3 (median 96 vs. 0; P less than 0.001) and a 7-fold increase in their volume (P less than 0.001). Both operations cause pancreatic growth, but only PBD promotes carcinogenesis, possibly because of its unique hormonal effect.     

Inhibition of N-nitrosodiethylamine-induced respiratory tract carcinogenesis by piperonylbutoxide in hamsters

The influence of pretreatment with piperonylbutoxide (PIP) on the biological effects of N-nitrosodiethylamine (DEN) in vivo in Syrian golden hamsters was investigated. PIP pretreatment significantly reduced covalent binding of N-[ethyl-1-14C]DEN to tissue macromolecules in trachea, lung, and liver, while it did not change the tissue distribution of the parent compound. In a chronic experiment, hamsters treated with PIP before each DEN injection did not develop any tumors or precancerous changes in the lungs, while 60% of the animals given DEN alone developed lung tumors with the morphology of Clara cells and endocrine cells. Tumor incidence in the trachea was also significantly reduced by PIP, but to a lesser extent than in the lungs.     

Failure of two retinoids to inhibit tracheal carcinogenesis in hamsters

The effect of 2 retinoids, 13-cis-retinoic acid and 4-methoxy-2,3,6-trimethylphenylanalog of retinoic acid ethyl amide (designated Roll-1430),on tracheal tumor development in hamsters exposed to N-nitro-so-N-methylureawas tested. Hamsters were in-tratracheally exposed either 18,20, or 23 times to 1% N-nitroso-N-methylurea before the retinoidswere administered in the diet. Evidence was presented whichindicates that the great majority of the animals are free ofinvasive neoplasia at the start of retinoid feeding. In noneof the 6 retinoid-treated groups could a statistically significantinhibition of tumor development be demonstrated. Hamsters treatedwith 13-cis-retinoic acid (128 or 172 mg/kg of diet) tendedto have an elevated cancer risk; this effect was at a statisticallysignificant level in the group treated with 172 mg/kg of diet.The distribution of histologic tumor types seemed to be shiftedin favor of adeno and mixed adeno-epidermoid tumors in the groupreceiving a low carcinogen dose and Roll-1430. Similar to earlierstudies with retinyl acetate tested in hamsters and rats, 13-cisretinoic acid and the retinoic acid ethyl amide analog Roll-1430,failed to inhibit development of respiratory tract neoplasms.We suspect that the reason for this is the absence of significantpromoting influences in the current lung cancer models and thatretinoids act mostly as anti-promoters.     

Spatiotemporal analysis of tumour-infiltrating immune cells in biliary carcinogenesis

Background Intraductal papillary neoplasms (IPN) and biliary epithelial neoplasia (BilIN) are well‐defined precursor lesions of biliary tract carcinoma (BTC). The aim of this study was to provide a comprehensive characterisation of the inflammatory microenvironment in BTC precursor lesions.Methods Immunohistochemistry was employed to assess tumour-infiltrating immune cells in tissue samples from patients, for whom precursor lesions were identified alongside invasive BTC. The spatiotemporal evolution of the immune microenvironment during IPN-associated carcinogenesis was comprehensively analysed using triplet sample sets of non-neoplastic epithelium, precursor lesion and invasive BTC. Immune-cell dynamics during IPN- and BilIN-associated carcinogenesis were subsequently compared.Results Stromal CD3⁺ (P = 0.002), CD4⁺ (P = 0.007) and CD8⁺ (P < 0.001) T cells, CD20⁺ B cells (P = 0.008), MUM1⁺ plasma cells (P = 0.012) and CD163⁺ M2-like macrophages (P = 0.008) significantly decreased in IPN compared to non-tumorous biliary epithelium. Upon transition from IPN to invasive BTC, stromal CD68⁺ (P = 0.001) and CD163⁺ (P < 0.001) macrophages significantly increased. In contrast, BilIN-driven carcinogenesis was characterised by significant reduction of intraepithelial CD8⁺ T-lymphocytic infiltration from non-tumorous epithelium via BilIN (P = 0.008) to BTC (P = 0.004).Conclusion IPN and BilIN are immunologically distinct entities that undergo different immune-cell variations during biliary carcinogenesis. Intraepithelial CD8⁺ T-lymphocytic infiltration of biliary tissue decreased already at the IPN-precursor stage, whereas BilIN-associated carcinogenesis showed a slowly progressing reduction towards invasive carcinoma.Subject terms: Cancer microenvironment, Immunoediting, Biliary tract cancer     

Inhibitory effect of meloxicam, a cyclooxygenase-2 inhibitor, on N-nitrosobis (2-oxopropyl) amine induced biliary carcinogenesis in Syrian hamsters

Pancreaticobiliary maljunction (PBM) is a high risk factor in biliary tract carcinoma. The chemopreventive action of a cyclooxygenase (COX)-2 inhibitor (meloxicam) on N-nitrosobis (2-oxopropyl) amine (BOP)-induced gallbladder cancer in hamster PBM models was investigated. In 7-week-old female Syrian golden hamsters, the extrahepatic bile duct at the distal end of the common duct was ligated and cholecystoduodenostomy was performed (group I). In group II, the same surgery was performed and from week 4 after surgery, 10 mg/kg of BOP was injected subcutaneously once a week with a 1-week interval. In group III, in addition to the measures employed in group II, 5 mg/kg/day of meloxicam was administered once a day, every weekday. Pathological findings in the gallbladder in week 20 after surgery were as follows. In group I, proper epithelium (PE) was predominant and there was no cancer. In group II, PE was predominant, but there was also hyperplasia and atypical epithelium (AE) recognized in 8 of 11 cases (72.7%); the area of AE was more extensive than that in group I. Carcinoma in situ (CIS) was recognized in 4 of 11 cases (36.4%) in group II. Group III showed the same pathological findings as group I. However, compared with group II, the incidence of AE decreased to 27.3% and no cancerous lesion was observed. In week 20 after surgery, the proliferative cell nuclear antigen labeling index in group III was statistically significantly lower than in group II (P = 0.045). No statistically significant differences were noted among the groups in terms of apoptosis labeling index in week 20 after surgery. In conclusion, it was confirmed that meloxicam suppresses carcinogenesis in hamster PBM models and its mechanism may be based on the suppression of cell growth.     

A DNA vaccine against ERBB2 impairs chemical carcinogenesis in random-bred hamsters

Vaccines against oncoantigens halt early neoplastic lesions in several cancer-prone, genetically engineered mouse models, whereas their ability to prevent chemical carcinogenesis has not been explored. This is a significant issue, as exposure to chemical mutagens is responsible for a substantial percentage of cancers worldwide. Here, we show that the archetypal oncoantigen ERBB2 is transiently overexpressed in Syrian hamsters during the early stages of 7,12-dimethylbenz[α]anthracene (DMBA)-induced oral carcinogenesis. Repeated DNA vaccinations against ERBB2 significantly reduce the number, size, and severity of oral lesions in a manner directly proportional to the anti-ERBB2 antibody response. These results support the prospects of vaccines as a fresh strategy in the management of individuals at risk for exposure to defined carcinogenic agents.     

Effect of castration and testosterone replacement on pancreatic carcinogenesis in Syrian hamsters.

Hormonal manipulation has been proposed as a possible new approach to the treatment of pancreatic cancer. We studied the effect of orchiectomy and testosterone replacement on early stage pancreatic carcinogenesis induced by diisopropanolnitrosamine (DIPIN) in Syrian golden hamsters. Eighty-five hamsters (mean body weight, 100 g) were divided into the following treatment groups: 1) DIPN (n = 20); 2) DIPN plus orchiectomy (n = 17); 3) DIPN plus orchiectomy plus testosterone (n = 18); 4) orchiectomy (n = 10); 5) sham operation (n = 10); 6) DIPN plus testosterone (n = 10). DIPN (125 mg/kg/body wt.) was administered s.c. every week and testosterone propionate (10 micrograms/g) was administered s.c. every 3 weeks. Bilateral orchiectomy was performed 1 week after the first injection of DIPN. All animals were killed 15 weeks after starting the treatment. The whole pancreas was removed, weighted and histologically examined. There was no difference in the incidence of preneoplastic lesions among groups 1, 2, 3 and 6 (respectively 87%, 83%, 77% and 80%); 3 animals in each group developed invasive carcinoma. In control groups (4 and 5), no precancerous lesions were recorded. In this experimental model, orchiectomy and testosterone replacement had no effect on nitrosamine-induced pancreatic carcinogenesis.     

Chemoprevention of biliary carcinogenesis in syrian hamsters by the novel carboxamide derivative IS-741 after initiation with N-nitrosobis(2-oxopropyl)amine (BOP)

To elucidate the possible inhibitory effect of a novel carboxamide derivative (IS-741) on biliary carcinogenesis, Syrian hamsters were subjected to cholecystoduodenostomy and ligation of the distal end of the common duct, and then given a regular diet (group I) or a diet containing 200 p.p.m. of IS-741 (group II). All hamsters were subcutaneously injected with N-nitrosobis(2-oxopropyl)amine until 10 weeks after surgery, and continued to feed on their respective dietary regimen until termination of the experiment at 16 weeks after surgery. Biliary adenocarcinomas were evaluated histologically. Non-cancerous and cancerous hepatobiliary tract tissues were analyzed for phospholipase A(2) (PLA(2)) activity, myeloperoxidase (MPO) activity, and the concentrations of prostaglandin (PG), i.e., prostaglandin E(2), 6-ketoprostaglandin F(1)alpha and thromboxane B(2). IS-741 significantly inhibited the development and multiplicity of hepatobiliary adenocarcinomas and reduced the proliferating cell nuclear antigen labeling indices in non-cancerous hepatobiliary tissues, compared with group I. The anti-cancerous effect of IS-741 was associated with a significant inhibition of PLA(2) and MPO levels in non-cancerous tissues of the extrahepatic biliary tract and the liver, and in cancerous tissue of the liver. Furthermore, IS-741 reduced the production of PGs in non-cancerous hepatobiliary tissues, compared with group I. Although the precise mechanism of action of IS-741 in preventing biliary tumorigenesis remains to be elucidated, it is likely to be related to modulation of arachidonic acid metabolism and/or suppression of neutrophil accumulation.     

Effects of sandostatin and castration on pancreatic carcinogenesis in rats and hamsters.

The effects of treatment with the somatostatin analogue Sandostatin, separately and in combination with surgical castration, on the development of azaserine-induced lesions in rat pancreas and N-nitrosobis(2-oxopropyl)amine (BOP)-induced lesions in hamster pancreas were investigated. The animals were divided in 4 groups and treated as follows: (a) controls, injected s.c. with saline solution (0.9% NaCl); (b) orchiectomy directly after the last treatment with carcinogen; (c) Sandostatin (SMS 201-995) subcutaneously; (d) orchiectomy followed by treatment with Sandostatin. No significant suppressive effects on plasma EGF or IGF-I concentrations were noted after Sandostatin treatment, but plasma gastrin levels decreased slightly in the rats, not in the hamsters. In rats, Sandostatin treatment enhanced rather than inhibited growth of acidophilic atypical acinar cell nodules. In hamster pancreas, by contrast, Sandostatin inhibited the development of putative pre-neoplastic ductular lesions. There was no interaction between treatment with Sandostatin and surgical castration. It was concluded that Sandostatin, when administered prophylactically, has an inhibitory effect on the growth of putative pre-neoplastic ductular, but not acinar, lesions.     

Interaction of dietary fat and protein on pancreatic carcinogenesis in Syrian golden hamsters

The role of interactions between dietary fat and protein in experimental pancreatic cancer was determined in Syrian golden hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Two levels of corn oil [4.5 and 18 g/385 kilocalorie (kcal)] were fed with each of two levels of casein (9 g/385 kcal and 36 g/385 kcal), either before or after a single sc injection of BOP (10 mg/kg body wt) at 8 weeks of age. Control diet was fed at other times (9 g corn oil and 18 g casein/385 kcal). The pancreatic ductular carcinoma incidence and multiplicity (average No. of tumors/tumor-bearing animals) increased as dietary fat and protein levels rose in hamsters fed the four diets after carcinogen treatment. Enhanced carcinogenesis by high-fat (HF) diets occurred only in hamsters fed the high-protein (HP) level, and protein effects were seen only with the HF diets. The low-fat-low-protein (LF-LP) diet inhibited pancreatic carcinogenesis among the hamsters given the four diets before BOP treatment. Pancreatic adenoma yields were elevated in hamsters given either HF or HP diets following BOP treatment, by comparison with the low levels. However, when diets were fed before BOP treatment, an increased yield occurred with the rise in protein, but the yield was reduced in males with the increase in fat. Acinar cell nodules were observed primarily in hamsters fed LP levels after BOP, and their multiplicity was highest in those given the HF diet. The interaction between dietary fat and protein demonstrated the interdependence of the effects of these two nutrients on pancreatic carcinogenesis in hamsters.     

Bombesin enhances experimental carcinogenesis induced in rat colon by 1,2-dimethylhydrazine

The effects of bombesin on the colonic mucosa and on the incidence,number, size and histology of colon cancers induced by 1,2-dimethylhydrazine(DMH) were studied in Fischer 344 rats. In experiment 1, ratswere randomized into three groups to receive either saline orbombesin (10 or 30 µg/kg body wt) to determine the labelingindex of normal colonic mucosa. In experiment 2, rats were given20 weekly injections of DMH (20 µg/kg body wt) and receivedeither saline or bombesin (10 or 30 µg/kg body wt) everyother day for 24 weeks. Administration of bombesin significantlyincreased the labeling indices of colonic mucosa in a dose-dependentmanner. Chronic administration of bombesin at both dosages withDMH caused significant increases in the incidence, number anddepth of involvement of colon cancers; however, it did not affectthe size and histological type of colon cancers. In addition,bombesin at the dose of 30 µg/kg significantly increasedthe labeling index of colon cancer. These results suggest thatbombesin stimulates the cell proliferation of colonic mucosaand colon cancer and enhances colon carcinogenesis in rats.