Transkriptionelle Regulation mitogener "Immediate early"- Gene im Pankreaskarzinom

Adenocarcinoma of the pancreas is known primarily because of its aggressive growth pattern. Patients with an inoperable state of this disease have a cumulative survival rate of only four to six months (Greer et al. 2007). This prognosis becomes even more evident when taken into consideration that the possibility for curative operative therapy approaches in locally restricted tumor statement only 10- 20 % at the time of the diagnosis (Rosewicz und Wiedenmann 1997, Yeo et al. 2002). For a better understanding of the biomolecular background of this growth phenomenon, this thesis attempted to create a differentiated explanation of “the transcriptional regulation of mitogenic ‚Immediate early‘- genes of pancreatic cancer“ with the functional consequence of growth induction. The question was which signaling cascade and associated transcriptional mechanisms are of particular relevance for increased G1-/ S- phase cell cycle transition. As an established stimulant serum caused the induction of cell- growth and resulted in an increased cell proliferation. It could be shown that serum is an inductor of “Immediate early“- genes c- myc and Egr- 1. It seems that c- myc, representative for “Immediate early“- genes, has a central importance for the functional qualities of cell growth, because after suppression of its gene product a massive decrease of proliferation could be observed. In this context two primary mitogenic signaling cascades have been verified in detail, the Ras- dependent Ras- Raf- MEK- ERK- signaling cascade and the Ras- independent Calcineurin- signaling pathway. In cooperation with the pharmacological and toxicological institute of the University of Marburg, among others, the importance of the Ras- independent Calcium-/ Calcineurin- signaling pathway for the induction of c- myc in context with the growth regulation could be demonstrated by using pharmacological inhibitors as well as other established methods. Further analyses on transcriptional levels were able to integrate NFAT, “nuclear factor of activated T- cells“, as an established mitogenic transcription factor. Finally, it was possible to show activation and nuclear translocation of NFAT in response to serum treatment and also an increase of DNA- binding affinity followed by an augmentation of the promoter activity. These results have been demonstrated at first by using a NFAT responsive reporter construct (cis- NFAT) and in the following it has been assigned on specific promoter analyses of c- myc. Using detailing c- myc- promotor analyses it was possible to show that the so- called TIE-domain, „TGFβ inhibitory element“, is responsible for NFAT- dependent induction of c- myc for growth regulation. In summary, this thesis provided a better understanding of the growth regulation of pancreatic cancer. As a result, a model can be postulated that Calcineurin-/ NFAT- signaling pathway plays an important part in cell- cycle progression which is selected by transcriptional induction of the „Immediate early“- gene c- myc. It was possible to demonstrate the central part of NFAT in the initial phase of cell- cycle induction of pancreatic cancer for the first time.