Browsing by Subject "Pancreatic cancer"

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Influence of selenium on pancreatic carcinogenesis and the role of the selenoproteins cytosolic and mitochondrial thioredoxin reductase in the pancreas
(2007) Aichler, Michaela; Graeve, Lutz
Pancreatic ductal adenocarcinoma (PDA) is one of the most aggressive cancers in humans. It is the fourth leading cause of cancer related deaths in Germany and in the United States. Most PDA occurs sporadically, but there are also approximately 5-10% of patients with a family history of pancreatic cancer. The high mortality of PDA is attributed to a lack of early detection methods and poor efficacy in therapies for advanced disease. As an alternative, preventive strategies in individuals with familial pancreatic carcinoma should be considered. Several epidemiological studies showed an inverse correlation between selenium-intake and mortality of certain types of cancer and particularly in gastrointestinal cancers. To this end, in the first part of this study, the influence of selenium as a preventive nutritional additive was investigated in a genetically defined pancreatic cancer mouse model, the EL-TGFatg/+;p53+/- mouse strain. As a major finding, the differentiation grade of the pancreatic carcinomas was heavily influenced by the selenium status. In the selenium-deficient group there were more non-differentiated pancreatic carcinomas than in the selenium-adequate group, which highlighted the implication of selenium or selenoproteins in tumour differentiation. Unexpectedly, however, there was no protective effect of selenium on total or pancreatic tumour latency. Within the selenoproteins, the thioredoxin reductases are strong candidates which may influence cell death and differentiation in pancreatic carcinogenesis. Their function is generally associated with tumour proliferation and also linked to the activation of the tumour suppressor p53. Consequently, the role of the thioredoxin reductases in the pancreas was studied in the second part of this thesis. The enzymatic activity of cytosolic (TXNRD1) and mitochondrial (TXNRD2) thioredoxin reductase in the pancreas and other organs was determined in relation to the selenium-status. TXNRD1 activity in the pancreas was moderate and decreased under selenium deficiency. TXNRD2, instead, showed very high pancreatic activity in relation to other organs and its activity was even increased under selenium-deficiency emphasising its special role in this organ. To further investigate the function of Txnrd1 and Txnrd2 in the pancreas, tissue-specific knockout mice were created and characterized. The Txnrd1 knockout mice did not show an overt phenotype. Interestingly although, pancreatic acinus cells in one year old mice showed a disturbed rough endoplasmic reticulum and alterations in serum amylase and lipase. These mice also had an impaired glucose tolerance. The pancreas of Txnrd2 knockout mice showed severe chronic pancreatitis and pancreatic atrophy at the end of an observation period of one year. The progressive pathogenic process started with mild pancreatitis, developing spontaneously at an age of four weeks. The chronic stage was characterized by the formation of different types of acinar-to-ductal metaplastic lesions, which could be classified in part as early precursor lesions of pancreatic carcinomas. The endocrine pancreas was not affected. The pancreas-specific Txnrd2 knockout mouse strain is the first genetically modified mouse model spontaneously developing acute and chronic pancreatitis. This strain constitutes a unique and powerful tool to model pancreatic pathogenesis, especially the yet unresolved process of transformation from inflammatory to malignant disease.
The therapeutic potential of vitamins A, C, and D in pancreatic cancer
(2025) Piotrowsky, Alban; Burkard, Markus; Schmieder, Hendrik; Venturelli, Sascha; Renner, Olga; Marongiu, Luigi
The pancreatic ductal adenocarcinoma (PDAC) is among the deadliest tumor diseases worldwide. While treatment options have generally become more diverse, little progress has been made in the treatment of PDAC and the median survival time for patients with locally advanced PDAC is between 8.7 and 13.7 months despite treatment. The aim of this review was to explore the therapeutic potential of complementing standard therapy with natural or synthetic forms of vitamins A, C, and D. The therapeutic use of vitamins A, C, and D could be a promising addition to the treatment of PDAC. For all three vitamins and their derivatives, tumor cell-specific cytotoxicity and growth inhibition against PDAC cells has been demonstrated in vitro and in preclinical animal models. While the antitumor effect of vitamin C is probably mainly due to its pro-oxidative effect in supraphysiological concentrations, vitamin A and vitamin D exert their effect by activating nuclear receptors and influencing gene transcription. In addition, there is increasing evidence that vitamin A and vitamin D influence the tumor stroma, making the tumor tissue more accessible to other therapeutic agents. Based on these promising findings, there is a high urgency to investigate vitamins A, C, and D in a clinical context as a supplement to standard therapy in PDAC. Further studies are needed to better understand the exact mechanism of action of the individual compounds and to develop the best possible treatment regimen. This could contribute to the long-awaited progress in the treatment of this highly lethal tumor entity.