To investigate our hypothesis, we examined the effect of uPA deficiency on the outcome of transient episodes of dextran sodium sulfate (DSS)–induced colitis in BALB/c mice. The DSS administration protocol we used leads neither to overt chronic colitis nor to colon cancer when applied to genetically intact BALB/c mice. However, it does lead to the induction of preneoplastic epithelial changes [31]. Using this experimental setting, we

found that the mice lacking uPA, in contrast to their wild-type ALK inhibitor (WT) counterparts, were predisposed to adenomatous polyp formation. The colonic epithelial preneoplasia in these mice evolved into adenomatous polyps on the basis of a significantly altered mucosal inflammatory milieu, which was characterized by more neutrophils and macrophages, less regulatory T cells (Treg), significantly upregulated cytokines, including interleukin-6 (IL-6), IL-17, tumor necrosis factor-α (ΤΝF-α), and IL-10, and lower levels of active TGF-β1. Our results challenge the dogma according to which uPA is viewed solely as a tumor promoter. Specific pathogen-free certified C.129S2-Plau/J

uPA-deficient (uPA−/−) mice and background strain-matched control BALB/cJ WT mice were purchased this website from Jackson Laboratories (Bar Harbor, ME) and bred in-house to provide animals for the experiments. Mice were kept in bio-containment facilities in static micro-isolator cages, fed with sterilized regular

mouse chow, and given sterilized water. Helicobacter-free status of the mice was confirmed by polymerase chain reaction (PCR) using Helicobacter genus–specific primers in fecal and gut mucosa samples as previously described [32]. All experimental procedures were approved by the Faculty of Veterinary Medicine, Aristotle University of Thessaloniki and licensed by the competent National Veterinary Dichloromethane dehalogenase Administration authorities (License No. 13/11197/11.09.08). A total of 130 (66 uPA−/− and 64 WT) male mice were used. Experiments were performed in three replications to achieve a total number of 11 to 24 mice per experimental group. For the induction of chronic colitis, 3.5% DSS (molecular weight: 36-50 kDa; MP Biomedicals Inc, Cleveland, OH) was given in the drinking water of 8- to 10-week-old mice for 1 week followed by 1 week of regular water. This cycle was repeated three times. uPA−/− and WT mice were either treated with DSS or remained untreated. Mice were killed either at 7 months (first experiment—long term) or at 1 week (second experiment—short term) after DSS treatment. Numbers of mice per experimental group for each experiment were as follows: first experiment: uPA−/− (n = 11), WT (n = 11), uPA−/− + DSS (n = 11), WT + DSS (n = 11); second experiment: uPA−/− (n = 20), WT (n = 19), uPA−/− + DSS (n = 24), WT + DSS (n = 23). Mice were killed with an overdose of isoflurane, weighted, and necropsied.