Precancerous conditions for pancreatic cancer

Pathogenesis of multiple pancreatic cancers involves multicentric carcinogenesis and intrapancreatic metastasis

There are increased opportunities in oncology clinics to identify multiple pancreatic ductal adenocarcinomas (PDAC) that co-occur simultaneously or arise metachronously in the pancreatic parenchyma, yet their pathogenesis remains elusive. We hypothesized that two potential pathways, multicentric carcinogenesis and intrapancreatic metastasis, might contribute to forming multiple PDAC. Among 241 resected cases, we identified 20 cancer nodules from nine patients with multiple PDAC (six with synchronous PDAC, one with metachronous PDAC, and two with both synchronous and metachronous PDAC). Integrated clinical, pathological, and mutational analyses, using TP53 and SMAD4 immunostaining and targeted next-generation sequencing of 50 cancer-related genes, were conducted to examine the intertumor relationships. Four of the nine patients were assessed as having undergone multicentric carcinogenesis because of heterogeneity of immunohistochemical and/or mutation characteristics. In contrast, tumors in the other five patients showed intertumor molecular relatedness. Two of these five patients, available for matched sequencing data, showed two or more shared mutations. Moreover, all the smaller nodules in these five patients showed identical TP53 and SMAD4 expression patterns to the corresponding main tumors. Consequently, these five patients were considered to have undergone intrapancreatic metastasis. None of the five smaller nodules arising from intrapancreatic metastasis was accompanied by pancreatic intraepithelial neoplasia, and three of them were tiny (≤1mm). Patients whose tumors resulted from intrapancreatic metastasis appeared to have higher disease stages and worse outcome than those with tumors from multicentric carcinogenesis. Our results provide insight into pancreatic carcinogenesis, showing that the development of multiple PDAC involves distinct evolutionary paths that potentially affect patient prognosis.

Mature acinar cells are refractory to carcinoma development by targeted activation of Ras oncogene in adult rats

Pancreatic ductal adenocarcinoma (PDA) is one of the most debilitating malignancies in humans. A thorough understanding of the cytogenesis of this disease will aid in establishing successful treatments. We have developed an animal model which uses adult Hras(G12V) and Kras(G12V) transgenic rats in which oncogene expression is regulated by the Cre/loxP system and neoplastic lesions are induced by injection of adenovirus-expressing Cre recombinase. When adenovirus with Cre recombinase under the control of the CMV enhancer/chicken beta-actin (CAG) promoter (Ad-CAG-Cre) is injected into the pancreatic duct of these animals, pancreatic neoplasias develop. Pathologically, the origin of these lesions is duct, intercalated duct, and centroacinar cells, but not acinar cells. The present study was undertaken to test the effect of acinar cell-specific oncogenic ras expression. Adult transgenic rats were injected with adenovirus with Cre recombinase under the control of the acinar cell-specific promoters amylase (Ad-Amy-Cre) and elastase-1 (Ad-Ela-Cre) or under the control of the non-specific CAG promoter. Injection of either Ad-Amy-Cre or Ad-Ela-Cre into the pancreatic ducts of transgenic animals in which oncogenic Kras is tagged with hemagglutinin (HA), HA-Kras(G12V) rats resulted in expression of oncogenic ras in acinar cells but not in duct, intercalated duct, or centroacinar cells. Notably, injected animals did not develop any observable proliferative or neoplastic lesions. In marked contrast, injection of Ad-CAG-Cre resulted in pancreatic cancer development within 4 weeks. These results indicate that adult acinar cells are refractory to Ras oncogene activation and do not develop neoplasia in this model.

Invasive ductal adenocarcinoma of the pancreas may originate from the larger pancreatic duct: a study of 13 tumors less than 2 cm in diameter

BACKGROUND/PURPOSE

We aimed to elucidate the origin/primary site of invasive ductal adenocarcinoma of the pancreas, based on the distribution of intraductal carcinoma components. These components were identified by a mural elastic fiber cuff.

METHODS

Thirteen specimens from patients with invasive ductal adenocarcinoma (microscopically, less than 2 cm in diameter) of the pancreas were studied histopathologically. Variants of invasive ductal adenocarcinoma and intraductal papillary-mucinous carcinoma were excluded.

RESULTS

Intraductal carcinoma components of invasive ductal adenocarcinoma were found in 12 of the specimens 13 (92%), and were observed within the tumor mass and/or on its boundary, or outside the tumor mass. Intraductal components were characterized by low papillary projections lacking a fibrovascular core, with/without surrounding tubular structures, or by irregular stratification and pleomorphism of the epithelial cells. Invasive components mostly showed a tubular pattern with desmoplasia. The distribution of the intraductal components in the 12 specimens was as follows: in 9 (75%), they were in both the main pancreatic duct and large branch ducts; and in 3, they were in the smaller branch ducts only.

CONCLUSIONS

Invasive ductal adenocarcinomas of the pancreas may originate most frequently from the main pancreatic duct or larger branch ducts, while the smaller ducts are less often the site of cancer origin.

Bile-reflux into the pancreatic ducts is associated with the development of intraductal papillary carcinoma in hamsters

BACKGROUND

Reflux of pancreatic juice into the biliary tract is a well-known risk factor for the development of biliary carcinoma. In this study, we investigated the significance of bile-reflux into the pancreatic ducts in pancreatic carcinogenesis, especially in the development of carcinoma in the main pancreatic duct in hamsters.

MATERIALS AND METHODS

Syrian hamsters were subjected to three different surgical procedures: cholecystoduodenostomy with dissection of the extrahepatic bile duct on the distal end of the common duct (Model A); cholecystoduodenostomy along with a dissection of the common bile duct (Model B); or simple laparotomy (Model C). The animals then received weekly subcutaneous injections of N-nitrosobis(2-oxopropyl)amine (BOP), for 9 weeks, and were killed for pathological investigation at 16 weeks after the initial BOP administration.

RESULTS

Pancreas carcinomas developed in 95, 88, and 90% of the Model A hamsters (n = 22), B (n = 24), and C (n = 21), respectively. The induced pancreatic tumors were histologically classified into four types: papillary; tubular; cystic adenocarcinoma; or intraductal carcinoma of the main pancreatic duct consisting of intraductal papillary carcinoma (IPC) and intraductal tubular carcinoma (ITC). The number and the incidence of IPCs induced in Model A hamsters were 24 lesions and 77% and were statistically higher than those in Model B (7 lesions and 29%) and C hamsters (7 lesions and 33%) (P < 0.01). Bile-reflux into the pancreatic ducts was clearly demonstrated in only hamsters of Model A by means of Indocyanine green injection via the portal vein. Proliferative cell nuclear antigen labeling indices of the epithelial cells in the main pancreatic duct in hamsters, with no BOP treatment, were 3.8, 0.8, and 1.1% in Models A (n = 10), B (n = 10), and C (n = 10), respectively, and the difference was statistically significant (P < 0.01).

CONCLUSIONS

Our findings suggest that bile-reflux into the pancreatic ducts is a significant factor predisposing to the development of IPC of the pancreas through an acceleration of epithelial cell kinetics of the main pancreatic duct.

Characterization of pancreatic lesions from MT-tgf alpha, Ela-myc and MT-tgf alpha/Ela-myc single and double transgenic mice

In order to identify good animal models for investigating therapeutic and preventive strategies for pancreatic cancer, we analyzed pancreatic lesions from several transgenic models and made a series of novel findings. Female MT-tgfα mice of the MT100 line developed pancreatic proliferation, acinar-ductal metaplasia, multilocular cystic neoplasms, ductal adenocarcinomas and prominent fibrosis, while the lesions in males were less severe. MT-tgfα-ES transgenic lines of both sexes developed slowly progressing lesions that were similar to what was seen in MT100 males. In both MT100 and MT-tgfα-ES lines, TGFα transgene was expressed mainly in proliferating ductal cells. Ela-myc transgenic mice with a mixed C57BL/6, SJL and FVB genetic background developed pancreatic tumors at 2–7 months of age, and half of the tumors were ductal adenocarcinomas, similar to what was reported originally by Sandgren et al [1]. However, in 20% of the mice, the tumors metastasized to the liver. MT100/Ela-myc and MT-tgfα-ES/Ela-myc double transgenic mice developed not only acinar carcinomas and mixed carcinomas as previously reported but also various ductal-originated lesions, including multilocular cystic neoplasms and ductal adenocarcinomas. The double transgenic tumors were more malignant and metastasized to the liver at a higher frequency (33%) compared with the Ela-myc tumors. Sequencing of the coding region of p16ink4, k-ras and Rb cDNA in small numbers of pancreatic tumors did not identify mutations. The short latency for tumor development, the variety of tumor morphology and the liver metastases seen in Ela-myc and MT-tgfα/Ela-myc mice make these animals good models for investigating new therapeutic and preventive strategies for pancreatic cancer.