The effect of streptozotocin and a high-fat diet on BOP-induced tumors in the pancreas and in the submandibular gland of hamsters bearing transplants of homologous islets

Comparatively analyzing the liver-specific transcriptomic profiles in Kunming mice afflicted with streptozotocin- and natural food-induced type 2 diabetes mellitus

BACKGROUND

Streptozotocin is a classic drug used to induce diabetes in animal models.

OBJECTIVE

The aim of this study is to investigate the liver transcriptome of Kunming mice with diabetes induced by either streptozotocin (STZ) or Non-STZ.

METHODS

Forty male mice were randomly assigned into four groups: Control (Ctr, standard diet), mHH (high fat and high carbohydrate diet), mHS (high fat and high carbohydrate diet for 4 weeks followed by 60 mg/kg STZ for 3 consecutive days) and mSH (60 mg/kg STZ for 3 consecutive days followed by a high fat and high carbohydrate diet for 12 weeks). All mice injected with STZ were identified as diabetic despite the sequential feeding of high fat and high carbohydrate diets.

RESULTS

Only 7 of 13 mice in the mHH group met the diagnostic criteria for diabetes. The asting blood glucose (FBG) of the mHH, mHS, mSH and Ctrl groups was 13.27 ± 1.14, 15.01 ± 2.59, 15.95 ± 4.38 and 6.28 ± 0.33 mmol/L at the 12th week, respectively. Compared with the mHH group, transcription was elevated in 85 genes in the livers of mHS mice, while 21 genes were downregulated and 97 genes were upregulated in the mSH group while 35 genes were decreased. A total of 43 co-expressed genes were identified in the mHS vs mHH and mSH vs mHH groups. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses showed that two corporate GO terms and two KEGG pathways were significantly annotated in the STZ-treated groups. Both the GO term and pathway were related to the metabolism mediated by p53.

CONCLUSION

A high fat and high carbohydrate diet combined with a low dose of STZ can effectively induce diabetes in Kunming mice despite the abnormal expressions of genes in the liver. The differentially expressed genes were related to metabolism mediated by p53.

Long-term in vitro culture of hamster pancreatic β-cells and induction of adenocarcinoma by treatment with N-nitrosobis(2-oxopropyl)amine

OBJECTIVES

Earlier studies indicated that hamster pancreatic ductal adenocarcinoma not only derives from ductal/ductular structures but also from cells within the islet. So far unidentified cells within the islet are responsive to the carcinogenic effect of N-nitrosobis (2-oxopropyl) amine (BOP) forming poorly differentiated ductal adenocarcinoma. However, studies indicated a major role of β-cells during carcinogenesis. To find out, if β-cells are the primary target cells of BOP and if they are capable to form ductal adenocarcinoma after malignant transformation, we established a long-term culture of undifferentiated cells deriving from isolated β-cells and treated them with BOP.

METHODS

Langerhans' islets from pancreata of Syrian golden hamsters were isolated and dispersed into single cells by dispase digestion. Cells were labeled with a highly specific β-cell surface antibody (K14D10) and these K14D10+ cells were extracted from the suspension by paramagnetic Dynabeads. Cells were cultured in vitro and treated with BOP. Untreated cells served as control.

RESULTS

K14D10+ cells formed a monolayer and produced insulin over a period of 28 days in culture. However, with time in culture they became undifferentiated with a higher proliferation rate and after about 60 days in culture BOP treated cells showed anchorage independent growth. These cells autotransplanted s.c. formed a well-differentiated ductal adenocarcinoma.

CONCLUSIONS

Pancreatic β-cells are the primary target of BOP without necessarily being embedded in the compound of the Langerhans' islet. With time in culture, they give rise to undifferentiated cells and after malignant transformation they are able to form ductal adenocarcinoma.

Promoting Effects of Sucrose-rich Diet on N-Nitrosobis (2-oxopropyl) amine-induced Pancreatic Carcinogenesis in Hamsters

It has been reported that there is an association between pancreatic cancer and obesity, impaired glucose metabolism and diabetes based on excess dietary fat and sugar intakes. A number of studies have suggested that a high-fat diet increases development of carcinomas in various organs and possible risk factors for pancreatic cancer. However, how an excess sugar intake promotes pancreatic carcinogenesis is still unknown. In the present study, we investigated the influence of an excess sugar intake on pancreatic carcinogenesis by administration of a sucrose-rich diet in which starch was replaced by sucrose in order to contain the same calories and other nutrients. Two similar experiments were performed. Six-week-old male Syrian golden hamsters were given N-nitrosobis (2-oxopropyl) amine (BOP) at a dose of 50 and 20 mg/kg body weight as a carcinogen in Week 0 and 1, respectively. In Week 2, the animals were divided into control and experimental groups. In experiment 1, 15 animals received a control diet or sucrose-rich diet in which 100% of the starch was replaced by sucrose, respectively. Since five animals fed on the sucrose-rich diet died by Week 12, the diet was changed to a sucrose-rich diet in which 50% of the starch was replaced by sucrose. In experiment 2, 15 animals received a control diet or sucrose-rich diet in which 50 or 20% of the starch was replaced by sucrose, respectively. All animals were sacrificed 25 weeks after the start of the experiment, and histological examination of the pancreas was performed. No significant difference was seen in the body weight at the end of the experiment. There were no significant differences in the glycosylated hemoglobin (HbA1c) and serum triglyceride, total cholesterol and HDL-cholesterol levels between the control and sucrose-rich diet groups in experiments 1 and 2. The incidence and number of carcinomas increased in hamsters fed the sucrose-rich diet compared with the control diet in experiments 1 and 2. These results suggest that an excess sucrose intake may promote the development of pancreatic cancer in hamsters.

Pancreatic cancer microenvironment

Pancreatic ductal adenocarcinoma remains an extremely aggressive malignancy that is virtually therapy-resistant and has therefore one of the worst prognoses of all human cancers. The focus of research, which had been placed mostly on genetic and epigenetic alterations of the cancer cells themselves, has shifted gradually towards the microenvironment. The cancer microenvironment consists of various components, including fibroblasts, endothelial cells, immune cells, and endocrine cells, that interact with each other and the cancer cells in a complex fashion. This interplay has implications for pancreatic cancer cell growth, migration and invasion, angiogenesis, and immunological recognition of cancer cells. Evidence is accumulating that the cancer microenvironment plays an active role in disease progression, and efforts are being made to target this interplay between cancer cells and host cells to improve the outcome of this deadly disease.

Potential involvement of the cyclooxygenase-2 pathway in the regulation of tumor-associated angiogenesis and growth in pancreatic cancer

Background

Gleevec (aka STI571, Imatinib) is a recently FDA approved anti-tumor drug for chronic myelogenous leukemia. Gleevec binds specifically to BCR-ABL tyrosine kinase and inhibit the tyrosine kinase activity. It cross-reacts with another two important membrane tyrosine kinase receptors, c-kit and PDGF receptors. We sought to investigate if Gleevec has a potential role in treatment of non-small cell lung cancer.

Results

We have shown that Gleevec alone can inhibit the A549 lung cancer cell growth in dose-dependent manner, and the optimal concentration of Gleevec inhibition of A549 cell growth is at the range of 2–3 μM (IC50). We have also shown that A549 cells are resistant to cisplatin treatment (IC50 64 μM). Addition of Gleevec to the A549 cells treated with cisplatin resulted in a synergistic cell killing effect, suggesting that Gleevec can potentiate the effect of cisplatin on A549 cells. We also showed that the A549 lung cancer cells expresses the platelet derived growth factor receptor α, and the inhibitory effects of Gleevec on A549 cells is likely mediated through inhibition of PDGFR α phosphorylation. We further tested 33 lung cancer patients' tumor specimens to see the frequency of PDGFR-α expression by tissue micro-arrays and immunohistochemistry. We found that 16 of the 18 squamous carcinomas (89%), 11 of the 11 adenocarcinomas (100%), and 4 of the 4 small cell lung cancers (100%) expressed PDGFR-α.

Conclusion

These results suggest a potential role of Gleevec as adjuvant therapeutic agent for treatment of non-small cell lung cancer.

Are islet cells the gatekeepers of the pancreas?

The pancreas is one of the body's most complex tissues composed of a mixture of endocrine and exocrine cell components. Although, islets comprise 1-2% of the pancreatic volume, there is some evidence that they control the function and the integrity of the pancreas and play the role of a gatekeeper. This review intends to highlight the importance of islet cells, not only for glucose metabolism, but also for their significant role in drug metabolism and diseases, especially in pancreatic cancer.

What is the origin of pancreatic adenocarcinoma?

The concept of pancreatic cancer origin is controversial. Acinar, ductal or islet cells have been hypothesized as the cell of origin. The pros and cons of each of these hypotheses are discussed. Based on the world literature and recent observations, pancreatic cells seem to have potential for phenotypical transdifferentiation, i.e ductal-islet, ductal-acinar, acinar-ductal, acinar-islet, islet-acinar and islet-ductal cells. Although the possibility is discussed that cancer may arise from either islet, ductal or acinar cells, the circumstances favoring the islet cells as the tumor cell origin include their greater transdifferentiation potency into both pancreatic and extrapancreatic cells, the presence of a variety of carcinogen-metabolizing enzymes, some of which are present exclusively in islet cells and the growth factor-rich environment of islets.

The relationship between diabetes and pancreatic cancer

About 80% of pancreatic cancer patients have glucose intolerance or frank diabetes. This observation has led to the following two hypotheses: i. pancreatic cancer causes the associated diabetes and ii. the conditions associated with diabetes promote the development of pancreatic cancer. Evidence supporting both hypotheses has been accumulated in previous studies. This article reviews these studies, especially those that have been conducted recently.