Effects of high-fat diet and cholecystokinin receptor blockade on promotion of pancreatic ductal cell tumors in the hamster

Increased dietary fatty acids determine the fatty-acid profiles of human pancreatic cancer cells and their carrier's plasma, pancreas and liver

Primary contents of dietary fat are three or four types of fatty acids, namely saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), n6-polyunsaturated fatty acid (n6PUFA) and, to less extent, n3-polyunsaturated fatty acid (n3PUFA). Previous studies suggest that increased SFA, MUFA, and n6PUFA in high fat diets (HFDs) stimulate the origination, growth, and liver metastasis of pancreatic cancer cells, whereas increased n3PUFA has the opposite effects. It is unclear whether the fatty acid-induced effects are based on changed fatty-acid composition of involved cells. Here, we investigated whether increased SFA, MUFA, n6PUFA, and n3PUFA in different HFDs determine the FA profiles of pancreatic cancer cells and their carrier's plasma, pancreas, and liver. We transplanted MiaPaCa2 human pancreatic cancer cells in athymic mice and fed them normal diet or four HFDs enriched with SFA, MUFA, n6PUFA, and n3PUFA, respectively. After 7 weeks, fatty acids were profiled in tumor, plasma, pancreas, and liver, using gas chromatography. When tumor carriers were fed four HFDs, the fatty acids that were increased dietarily were also increased in the plasma. When tumor carriers were fed MUFA-, n6PUFA-, and n3PUFA-enriched HFDs, the dietarily increased fatty acids were also increased in tumor, pancreas, and liver. When tumor-carriers were fed the SFA-enriched HFD featuring lauric and myristic acids (C12:0 and C14:0), tumor, pancreas, and liver showed an increase not in the same SFAs but palmitic acid (C16:0) and/or stearic acid (C18:0). In conclusion, predominant fatty acids in HFDs determine the fatty-acid profiles of pancreatic cancer cells and their murine carriers.

Increased lipid metabolism and cell turnover of MiaPaCa2 cells induced by high-fat diet in an orthotopic system

In this study, we investigated whether increased dietary fat influences established pancreatic cancer cells. MiaPaCa2 human pancreatic cancer cells were grown orthotopically in athymic mice fed normal diet (ND) or high-fat diet (HF). In the resulting tumors, medium-chain acyl-coenzyme A dehydrogenase (MCAD, a regulator of fatty acid beta-oxidation) and Cu/Zn-superoxide dismutase (an antioxidant enzyme) were determined using Western blotting. The MCAD messenger RNA (mRNA) was determined by real-time polymerase chain reaction. Intracellular lipid droplets, proliferating cells (Ki67 positive), and apoptotic cells were stained in tumor sections. The HF tumors were heavier than the ND tumors (1.60 +/- 0.08 vs 1.13 +/- 0.10 g, P < .01, 6 tumors per group). The MCAD and Cu/Zn-superoxide dismutase proteins and the MCAD mRNA were increased in HF tumors compared with those seen in ND tumors. The HF tumors contained extensive central necrosis, which was surrounded with apoptotic and proliferating cells. The HF tumors also showed numerous lipid droplets. In the ND tumors, necrosis was uncommon, apoptotic cells were sporadic, and lipid droplets were few. In follow-up experiments, MiaPaCa2 cells were incubated in vitro in the presence or absence of fatty acids (oleic and linoleic acids). The fatty acid exposure increased lipid droplets, cell proliferation, and MCAD mRNA expression in MiaPaCa2 cells. In conclusion, increased dietary fat stimulates lipid metabolism and cell turnover in MiaPaCa2 human pancreatic cancer cells.

Gastrins, cholecystokinins and gastrointestinal cancer

The gastrointestinal peptide hormones gastrin and cholecystokinin (CCK) are well known for their ability to stimulate gastric acid secretion and pancreatic enzyme secretion, respectively. The suggestion that gastrin and CCK might also promote the development of cancers of the gastrointestinal tract has been controversial, but an increasing body of evidence now supports the view that the amidated and non-amidated forms of gastrin act as growth factors via different receptors in different regions of the gut. For example, animal experiments indicate that amidated gastrins are involved in cellular differentiation and repair in the gastric mucosa, and synergize with Helicobacter pylori infection in the development of gastric carcinoma. In contrast, non-amidated gastrins stimulate colonic mucosal growth, accelerate the early steps in colorectal carcinoma formation, and are elevated in the tumour and circulation of patients with colorectal cancer. Although human pancreatic carcinomas express CCK-1 and CCK-2 receptors, the role of gastrins and CCK in pancreatic carcinogenesis is yet to be established. Further investigation of the possible role of the CCK-2 receptor in gastric and pancreatic neoplasia, and of the hypothesis that gastrin precursors act as autocrine growth factors in colorectal carcinoma, is warranted. However, therapies aimed at the gastrins must be targeted to the relevant gastrin/gastrin receptor combination.

Short- and intermediate-term carcinogenicity testing--a review. Part 2: available experimental models

Numerous experimental protocols for short- and intermediate-term carcinogenicity assays have been available for many years. This paper surveys various of these test systems in rodents, fish species, non-vertebrates and avian embryos in ovo. The mouse skin tumour assay and the rat liver foci assay were used to introduce the basic concepts of short- and intermediate-term carcinogenicity testing in the previous part of the review. The focus of this second part of the review is on rodent assays for carcinogenicity testing in the lung, kidney, urinary bladder, pancreas, stomach, oral cavity, small intestine, colon, and on the possibility to combine several target organs in multi-organ models. The potential use of various fish species, non-vertebrates and hatching eggs for carcinogenicity testing is outlined and the advantages and limitations are discussed. This review also presents the problem of validation of any carcinogenicity test system and proposes a strategy for contemporary safety assessment of chemicals with regard to the detection and evaluation of carcinogenicity.