Modification of pancreatic carcinogenesis in the hamster model. 6. The effect of ductal ligation and excision

The effect of ligation and excision of the pancreatic duct in pancreatic carcinogenesis was examined in the hamster model. Animals were treated with a single dose (20 mg/kg body weight) of N-nitrosobis(2-oxopropyl)amine (BOP) either immediately (Group 1) or on Days 1 (Group 2), 3 (Group 3) or 7 (Group 4) after ligation and excision of the duct of the splenic lobe. Group 5 received BOP shortly after laparoscopy, and Group 6 consisted of BOP-treated controls. All hamsters were killed 46 weeks after BOP treatment. The results showed that despite advanced atrophy of the splenic lobe distal to the excised duct in Groups 1-4, some hamsters in Groups 2, 3, and 4 showed hyperplasia, dysplasia, and increased mitotic activities of ductal and ductular cells. However, carcinomas in the duct-excised atrophic lobe were found only in Groups 1-3. These data indicate that BOP carcinogenesis is mediated through blood circulation, and that cancer development is not inhibited in the duct-excised lobe for up to 3 days after surgery. However, in the entire pancreas, a significant reduction in tumor incidence was seen when the carcinogen was given immediately, or to a lesser extent, 1 day after surgery, regardless of whether or not excision was made. On the contrary, BOP, when given 3 and 7 days after duct excision, enhanced tumor development in the nonexcised (intact) pancreas, compared with other test groups and with BOP controls. Both inhibition and enhancement seemed due to a proportional decrease and increase, respectively, of BOP-responsive cells throughout the intact pancreas.     

Early lesions of pancreatic ductal carcinoma in the hamster model.

Syrian golden hamsters were treated weekly with 10 mg/kg body weight N-nitrosobis (2-oxopropyl) amine for life (Group 1) or 6 weeks and were sacrificed at biweekly intervals from 2 weeks (Group 1) and 8 weeks (Group 2) after initiation of the experiment. The pancreas was examined in step sections, and the sequential alterations noted for each interval were recorded. Lesions were found in intrapancreatic and extrapancreatic ducts. Equivalent alterations consisting of hyperplasia, metaplasia, atypia, and lesions characteristic of carcinoma in situ developed ubiquitously and simultaneously in pancreatic ducts of different sizes and in ductules, but not in acinar cells. Among the most significant findings were intrainsular ductular formations, their proliferation, and sequential malignant alteration comparable to the involved preexisting ductules. Differences between the two experimental groups were of a quantitative rather than qualitative nature. The incidence and multiplicity of neoplastic lesions at each interval according to group, sex, and anatomic locations of adenocarcinomas are outlined. Predilected areas for some lesions were found. Results indicate a common origin of all induced tumors from a pluripotent cell populating the pancreatic ductal system.     

Induced cell clustering enhances islet beta cell formation from human cultures enriched for pancreatic ductal epithelial cells

A better understanding of the culture conditions that stimulate in vitro beta-cell differentiation from islet precursors would be useful for optimizing the production of tissue-engineered islets. In this study, high- and low-adherent substrates and high- and low-serum media were used to control the clustering of human pancreatic ductal epithelial cells and to determine its effect on their transdifferentiation to beta cells. While the initial epithelial cell cultures were devoid of any beta cells as assessed by dithizone staining, dithizone+ cells were generated during the next 3 weeks under all culture conditions. Although the rate of transdifferentiation was low, a approximately 4-fold greater number and percentage of dithizone+ cells were generated following 23-24 days of culture in the least adherent conditions (low-serum medium, low-adherent substrate), which stimulated cell clustering to the highest degree. Insulin immunohistochemistry data correlated well with the dithizone data (r(2) = 0.99), evidence that dithizone is a reliable measure of insulin+ cells. The preferential distribution of the dithizone+ cells to regions of cell aggregation and the increased efficiency of transdifferentiation in conditions that promote cell clustering suggest that cell-cell interactions and/or cell shape changes are important to the transdifferentiation of adult pancreatic ductal epithelial cells to beta cells in vitro.     

Modification of pancreatic carcinogenesis in the hamster model. 3. Inhibitory effect of alloxan.

Alloxan, when given intravenously at a dose of 60 mg/kg body weight 2 hours prior to subcutaneous injection of the potent pancreatic carcinogen N-nitrosobis (2-oxopropyl) amine (BOP), inhibited the induction of hyperplastic and neoplastic pancreatic lesions in a statistically significant fashion (P less than 0.01). The number of lesions per animal affected was markedly less in these animals, compared with BOP-treated control animals. BOP administration 2 weeks after alloxan treatment, at which time pancreatic islet cell regeneration is considered completed, did not alter either the incidence or number of lesions. The results support our view that the pancreatic islet cells are the primary source of BOP metabolism. The concomitant inhibition of gallbladder tumors, but not of common duct neoplasms, in hamsters receiving BOP 2 hours after alloxan could indicate that alloxan's inhibitory effects on BOP carcinogenesis are not restricted to the pancreas.     

Early changes in islet hormone secretion in the hamster pancreatic cancer model

The diabetic state that is seen at a high frequency in association with pancreatic cancer is characterized by elevated plasma levels of several islet hormones and by marked insulin resistance. Both the diabetic state and insulin sensitivity improve after tumor removal by sub-total pancreatectomy. Impaired glucose tolerance has also been found in the hamster pancreatic cancer model, but conflicting data regarding islet function have been reported. In order to further investigate islet function and secretion during early development of pancreatic cancer, we measured the concentrations of insulin, glucagon, somatostatin, and islet amyloid polypeptide (IAPP) in plasma, pancreatic tissue, and secretin-stimulated pancreatic juice at 12 and 27 weeks after the ductal-cell-specific carcinogen, BOP had been used to induce tumors in Syrian golden hamsters. At 12 weeks after BOP, plasma glucagon levels were significantly increased. An exaggerated plasma-glucose response and concomitant hyperinsulinemia were observed at 27 but not 12 weeks after BOP. Plasma IAPP concentrations, but not glucagon or somatostatin, were elevated at 27 weeks. Tissue concentrations of IAPP were substantially reduced in BOP-treated hamsters at 27 weeks. No differences in hormone concentrations were seen in pancreatic juice from the two groups at either of the two time points investigated. The study showed that islet hormone changes accompany the early development of pancreatic tumors in the hamster pancreatic model. The hormone changes and apparent insulin resistance resemble the metabolic changes found in humans with pancreatic cancer.     

Modification of pancreatic carcinogenesis in the hamster model. 7. Inhibitory effect of bethanechol chloride

Experiments were designed to investigate in the hamster model the effect on pancreatic carcinogenesis of bethanechol chloride (BC), which is known to increase pancreatic protein synthesis in rats. Hamsters received a single (15 mg/kg body weight) dose of BC either before, simultaneously with, or after a single dose of N-nitrosobis(2-oxopropyl)amine (BOP; 20 mg/kg body weight). A second group was treated daily with BC (7.5 mg/kg body weight) for 24 weeks, following BOP. The control groups consisted of animals treated with BOP only, with BC only, and with solvent only. The surviving hamsters were killed 46 weeks after BOP treatment. BC, whether given before, simultaneously with, or after BOP, significantly reduced the incidence of pancreatic ductal/ductular carcinomas. The multiplicity, size, and latency of carcinomas were also affected by BC. A more pronounced inhibition of cancer induction occurred in the group treated daily with BC after BOP. The possible mechanisms involved in the inhibitory action of BC on pancreatic carcinogenesis are discussed.     

Modification of pancreatic carcinogenesis in the hamster model. 2. The effect of partial pancreatectomy.

The effect of partial pancreatectomy (PP) on the pancreatic carcinogenicity of N-nitrosobis (2-oxopropyl)amine (BOP) was investigated in Syrian golden hamsters by subcutaneous injection of a single dose of BOP (20 mg/kg, body weight) given 30 minutes after (Group 1), 1 week after (Group 2), or 1 week before 70% PP (Group 3). Additional groups consisted of animals with PP alone (Group 4), sham operation (laparotomy) followed 30 minutes later by BOP treatment (Group 5), and BOP treatment only (Group 6). The experiment was terminated 46 weeks after BOP administration in each group. The pancreas and extrahepatic bile ducts, including the common duct and gallbladder, were examined histologically. Tumor patterns were compared in hamsters with PP and in the corresponding segments of the pancreas in BOP-treated control groups. The pancreatic cancer incidence was highest (31%) in Group 2 and lowest in Group 1 (3%), a difference that was statistically significant (P less than 0.01). Also, a statistically highly significant larger number of tumors occurred in Group 2, compared with group 1, 3, or 5 (P less than 0.0005). In a comparison of the number of carcinomas per tumor-bearing hamster, there were greater numbers of carcinomas in Group 2 (2.6 carcinomas) than in Groups 1, 3, 5, and 6 (1.0, 1.0, 1.3, and 2.6 tumors, respectively). Moreover, pancreatic tumors in Group 2 hamsters were larger (average diameter, 10 mm) than in Group 1 (4 mm), Group 3 (3.5 mm), Group 5 (4 mm), and Group 6 (average, 9mm). The incidence of extrapancreatic tumors did not vary among the PP groups but was equally lower than those in BOP-treated control groups. The data indicated BOP carcinogenesis was inhibited by surgery (regardless of whether PP was per formed) when the carcinogen was given 30 minutes after the surgery but was significantly enhanced when BOP was administered 1 week after PP. The possible reasons for these conflicting results are discussed. Morphologically all tumors were of ductular, ductal, and mixed ductular-insular patterns and most developed at the resected margins, where proliferation of islets, ducts, and ductules, but not of acinar cells, occurred. The results confirm our view that the ductal and ductular cells are the progenitor cells for BOP-induced pancreatic tumors in hamsters.     

K-ras and p53 mutations in hamster pancreatic ductal adenocarcinomas and cell lines.

K-ras and p53 gene alterations are frequently found in human pancreatic carcinomas and cell lines. The aim of this study was to analyze for the presence of K-ras and p53 gene mutations in hamster pancreatic tumors and cell lines. Mutations at the first coding exon of the K-ras gene and in exons V to VIII of the hamster p53 gene were analyzed in six cell lines (H2T, PC1, PC1.2, PC1.0, WD, and PD) and in N-nitroso-bis(2-oxopropyl)amine-induced pancreatic (n = 9) and extra-pancreatic (n = 4) tumors. K-ras mutations were present in seven of the nine pancreatic tumors and in all extra-pancreatic tumors. No p53 mutations were detected in the tumors. All cell lines analyzed contained K-ras mutations. Moreover, four of the six cell lines contained single amino acid substitutions in the p53 gene. Cell lines derived from nitrosamine-induced pancreatic tumors in the hamster contained K-ras and p53 alterations similar to those found in cell lines derived from human pancreatic carcinomas.     

Characterization of pancreatic ductal cells in human islet preparations

Substantial amounts of nonendocrine cells are implanted as part of human islet grafts, and a possible influence of nonendocrine cells on clinical islet transplantation outcome has been postulated. There are currently no product release criteria specific for nonendocrine cells due to lack of available methods. The aims of this study were to develop a method for the evaluation of pancreatic ductal cells (PDCs) for clinical islet transplantation and to characterize them regarding phenotype, viability, and function. We assessed 161 human islet preparations using laser scanning cytometry (LSC/iCys) for phenotypic analysis of nonendocrine cells and flow cytometry (FACS) for PDC viability. PDC and beta-cells obtained from different density fractions during the islet cell purification were compared in terms of viability. Furthermore, we examined PDC ability to produce proinflammatory cytokines/chemokines, vascular endothelial growth factor (VEGF) and tissue factor (TF) relevant to islet graft outcome. Phenotypic analysis by LSC/iCys indicated that single staining for CK19 or CA19-9 was not enough for identifying PDCs, and that double staining for amylase and CK19 or CA19-9 allowed for quantitative evaluation of acinar cells and PDC content in human islet preparation. PDC showed a significantly higher viability than beta-cells (PDC vs beta-cell: 75.5+/-13.9 and 62.7+/-18.7%; P<0.0001). Although beta-cell viability was independent of its density, that of PDCs was higher as the density from which they were recovered increased. There was no correlation between PDCs and beta-cell viability (R(2)=0.0078). PDCs sorted from high-density fractions produced significantly higher amounts of proinflammatory mediators and VEGF, but not TF. We conclude that PDCs isolated from different fractions had different viability and functions. The precise characterization and assessment of these cells in addition to beta-cells in human islet cell products may be of assistance in understanding their contribution to islet engraftment and in developing strategies to enhance islet graft function.     

Keratinocyte growth factor induces pancreatic ductal epithelial proliferation.

Keratinocyte growth factor (KGF) causes a proliferation of pancreatic ductal epithelial cells in adult rats after daily systemic administration for 1 to 2 weeks. Even before the proliferation of intralobular ducts is histologically evident, KGF also induces proliferating cell nuclear antigen expression within the ductal epithelium of intercalated, intralobular, and interlobular ducts. KGF also causes incorporation of 5-bromodeoxyuridine in ductal epithelial cells. Epithelial cell proliferation is histologically most prominent at the level of the intralobular ducts adjacent to and within the islets of Langerhans. Pancreatic ductal proliferation is not histologically apparent in rats sacrificed 7 to 10 days after the cessation of KGF administration. The pancreatic hormones insulin, glucagon, somatostatin, and pancreatic polypeptide are normally distributed within islets that demonstrate intrainsular ductal proliferation. The proliferating ductal epithelium does not show endocrine differentiation as evidenced by the lack of immunoreactivity for pancreatic hormones. KGF is a potent in vivo mitogen for pancreatic ductal epithelial cells.     

Alterations in pancreatic islet function produced by carcinogenic nitrosamines in the Syrian hamster.

Exposure of hamsters to 5 daily doses of 20 mg/kg N-nitrosobis(2-oxopropyl)amine (BOP) or 76 mg/kg N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP), resulted in reduced insulin secretion in freshly isolated pancreatic islets. These treatments also reduced plasma insulin and glucose levels, and were hepatotoxic. The inhibition of insulin secretion, however, was transient. Islets isolated from treated hamsters that were then placed in culture secreted elevated levels of insulin for many months. When cultured islets were directly exposed to the nitrosamines for 3 days, there was also a transient reduction of insulin secretion that was subsequently normalized after removal of the nitrosamine from the medium. These results show that BOP and HPOP modify beta-cell function both directly, and possibly indirectly, via damage to the liver. Furthermore, the lack of immediate inhibition of insulin secretion when islets were incubated in the presence of BOP or HPOP as well as glucose, suggests that the nitrosamines do not bind to the glucose receptor.     

Mechanism of pseudoductular (tubular) formation during pancreatic carcinogenesis in the hamster model. An electron-microscopic and immunohistochemical study.

Electron-microscopic and immunohistochemical studies performed during pancreatic carcinogenesis in hamsters demonstrated that hypertrophy and hyperplasia of centroacinar cells were the earliest changes occurring in the pancreas. These altered centroacinar cells differentiated into either endocrine-type cells or elongated agranular cells with remarkably long cytoplasmic processes (CyPs). These CyPs seemed gradually to overlie and underlie the adjacent acinar cells and resulted in progressive degeneration and loss of acinar cells, which subsequently were replaced by altered centroacinar cells. The initially rather tiny and slender CyPs were characterized by the expression of blood group substances, which were also found in the surface of altered ductal cells. Because these antigens could not be demonstrated in normal pancreatic cells, they seemed to represent specific markers for altered ductal/ductular (centroacinar) cells. In no instance was there evidence of dedifferentiation of acinar cells into ductlike cells. The present data, along with our previous findings, demonstrate that centroacinar cells are the foundation for pseudoductular structures and are the progenitor cells of tumors arising from them.     

Trichostatin A enhances the response of chemotherapeutic agents in inhibiting pancreatic cancer cell proliferation

Pancreatic cancer is an aggressive neoplasia, and standard chemotherapies are by and large ineffective. The purpose of this work was to get a comprehensive preclinical study on the ability of anticancer drug combinations that best inhibit growth of pancreatic adenocarcinoma cells. We evaluated the in vitro growth inhibition of ten pancreatic cancer cell lines to gemcitabine and 5-fluorouracil, newer generation cytotoxic agents (oxaliplatin, irinotecan), targeted therapy (gefitinib) and a histone deacetylase (HDAC) inhibitor (trichostatin A). Cells were treated with the single drug alone and all pairwise drug association. Our results demonstrate that TSA can effectively increase the drug sensitivity of all the cell lines studied. The association of TSA and irinotecan determines an increase in growth inhibition on the highest percentage of cell lines (80%). Our findings may represent an experimental basis for potential clinical application of HDAC inhibitors, in particular in association with drugs used in cancer clinical treatment, supporting the idea that HDAC inhibitors could act as sensitizers for chemotherapy.     

Spontaneous pancreatic islet cell tumours in guinea pigs.

Pancreatic islet cell tumours were found in 7 out of 678 guinea-pigs (1 per cent) that survived more than 2 years in our laboratories. These guinea-pigs, both random-bred Hartley and inbred strain 13, were involved in various carcinogenicity studies with nitrosamides. Four tumours were observed in a total of 374 carcinogen-treated animals (1·1 per cent) and 3 tumours in 304 controls (1·0 per cent); there does not appear, therefore, to be any significant relationship with carcinogen treatment. The incidence was significantly higher in the inbred strain 13 (3 out of 85, 3.5 per cent) than in random-bred Hartley guinea-pigs (4 out of 593, 0.7 per cent). These tumours were apparently spontaneous, and showed 3 different histological patterns: medullary, trabecular or alveolar, and gyriform occurring singly or in combination. Except in one case, they were beta-cell adenomas. These tumours were all considered to be benign.     

Crystal-like deposits of amyloid in pancreatic islet cell tumors.

Numerous stellate crystal-like deposits of amyloid were observed in four human pancreatic islet cell tumors. Three of the tumors were associated with hypoglycemia or hyperinsulinemia, and the remaining one produced gastrin. Histochemical and ultrastructural studies confirmed the existence of amyloid in the deposits and also suggested the presence of adsorbed or incorporated mucopolysaccharides. Stellate amyloid deposits have previously been described in experimental systemic murine amyloidosis. The relationships of these stellate deposits to other forms of amyloid depostion are unknown.     

胰腺导管腺癌中胰腺星形细胞的研究进展

胰腺星形细胞(pancreatic stellate cells,PSC)是胰腺导管腺癌(pancreatic ductal adenocarcinoma,PDAC)肿瘤微环境中最重要的成分,在PDAC发生发展中具有非常关键的作用.目前大量研究关注于PSC与胰腺癌细胞(pancreatic cancer cells,PCC)之间的相互作用及PSC在PDAC微环境中发挥的作用.PSC在许多情况下发生活化,如乙醇、氧化应激和高血糖等.PDAC早期即可出现PSC的活化,PCC可以诱导刺激PSC发生活化,活化的PSC可以产生大量胶原纤维,形成适宜PCC生长的间质微环境,促进PCC的增殖,减少化疗药物对肿瘤细胞的杀伤作用.另外,PSC还可以与间质中各种细胞成分如内皮细胞和各种免疫细胞相互作用,在血管生成、免疫逃逸和神经侵犯等方面协助肿瘤进展.因此,阐明PSC与肿瘤细胞以及其他间质成分之间复杂的相互作用至关重要.     

A population survey of pancreatic islet cell antibodies.

A population study on pancreatic islet cell antibodies (pica) among 3766 people from the town of Busselton, Western Australia showed that such antibodies were infrequent, the ''classical'' insulin-dependent diabetes associated islet cell antibody being present in less than 0.01%. Pancreatic islet cell antibodies in this population were not associated with insulin-dependent diabetes mellitus, and ten known insulin-dependent diabetics did not have these antibodies. These results for an unselected population are in sharp contrast with those derived from studies on highly selected hospital patients.     

Vascular proliferation is associated with survival in pancreatic ductal adenocarcinoma

In pancreatic ductal adenocarcinoma (PDAC), the benefit of current chemotherapy and radiation therapy is very limited, even in radically resected patients. New treatment strategies, for example based on the inhibition of the tumour's blood supply, need to be explored. We have investigated angiogenesis markers and their associations with relapse and survival in 52 histologically confirmed cases of PDAC. Angiogenesis in the primary tumour was evaluated by microvessel density (MVD), vascular proliferation index (VPI) and the presence of glomeruloid microvascular proliferations (GMP). These features were analysed in the context of clinicopathological variables, KRAS mutation status, relapse location and survival. MVD (median 134 microvessels/mm², range 88–177) and VPI (median 3.2%, range 1.6–4.9) were associated with larger tumour size and lymph node metastasis. MVD was also related to the occurrence of liver metastases. Both variables were associated with survival in univariate and multivariate analyses. GMPs were present in 32 (62%) of the cases. Patients who exhibited MVD and VPI values above median, and GMP positivity, had a median survival of only 4.2 months after surgery. In conclusion, the angiogenesis markers MVD and VPI have a significant impact on survival. By also including GMP, a subgroup of PDAC patients with particularly short survival could be identified.     

Conjugated catechol derivatives in a transplantable islet cell tumour of the golden hamster.

Two glucuronidated catechol have been identified in a transplantable islet cell tumour of the golden hamster, i.e. dopamine-4-O-glucuronide and 3-methoxytyramine-4-O-glucuronide. L-dopa is rapidly metabolized in the tumour to one or both of these glucuronides. Incubation of tumour homogenates in the presence of beta-glucuronidase shows that dopamine-4-O-glucuronide is present in the tumour in extremely high concentrations.