Der Effekt von volatilem Tabakrauch auf die Karzinogenese des Adenokarzinoms des Pankreas im P48+/Cre; LSL-KRASG12D-Mausmodell

Epidemiological studies show that regular consumption of tobacco is a major risk factor of pancreatic adenocarcinoma. However, there are only a few in vivo studies that investigate tumor development under the influence of this risk factor. Therefore, the aim of this study was to investigate carcinogenesis following exposure to tobacco smoke in a realistic in vivo mouse model. For this purpose, wild-type K-ras (WT) and P48+/cre; LSL-KRASG12D (K/C) mice were exposed to volatile tobacco smoke in a special experimental chamber for 3 or 6 months. In the WT group no histological effect on tumor induction was found. In all K/C mice carcinogenesis was induced by the mutation of ras before exposure to smoke: they showed development of the precursor lesions PanIN and ADM. In cooperation with an expert pathologist the expression of precursor lesions and other pathologies in the K/C mice were assessed. No significant differences between the groups of exposed and unexposed mice were seen after manual quanitification. A computer-assisted evaluation of the histology, however, found a singificantly higher number of PanIN-1a lesions in the pancreata of smokers. Furthermore, the effects of tobacco smoke such as DNA damage, cell proliferation, and angiogenesis were investigated immunohistochemically by marker proteins after volatile exposure. In vitro, an increased expression of the DNA-damage cascade (γ-H2AX and p-ATR) after exposure to a specially designed “smoke-exposed medium“ was detected in HPDE cells. However, in the immunohistochemical analysis of the smoke-exposed mice no significantly increased DNA damage (p-ATM) was detected. Furthermore, the exposure and control groups showed no difference in cell proliferation rate (Ki-67) and in angiogenesis (CD31). After automated quantification, an increased formation of precursor lesions and thus a progression of carcinogenesis after volatile smoke exposure was detected. To investigate whether volatile tobacco smoke exposure ultimately results in increased cancer in the K-ras mouse, a new series of experiments should be carried out in which the test animals are analyzed at a mature age.