Dro1/Ccdc80 inactivation promotes AOM/DSS-induced colorectal carcinogenesis and aggravates colitis by DSS in mice.

Colorectal carcinogenesis is a progressive multistep process involving the sequential accumulation of genetic alterations in tumor suppressor genes and oncogenes. Downregulated by oncogenes 1 (Dro1/Ccdc80) has been shown to be a potent tumor suppressor of colorectal carcinogenesis in the genetic ApcMin/+ mouse model. In ApcMin/+ mice, loss of DRO1 strongly increases colonic tumor multiplicity and leads to the regular formation of adenocarcinoma in the colon. To investigate DRO1's role in chemically induced as well as inflammation-associated colorectal carcinogenesis, the effect of Dro1 inactivation was studied in mice subjected to the carcinogen azoxymethane (AOM) and upon combined treatment with AOM and the proinflammatory agent dextran sodium sulfate (DSS), respectively. Loss of DRO1 increases multiplicity of preneoplastic aberrant crypt foci and colonic tumors upon administration of AOM. Combined treatment with AOM and DSS leads to increased colonic tumor number and promotes formation of adenocarcinoma in the colon. Moreover, Dro1 inactivation aggravates histological signs of acute and chronic DSS-induced colitis, strongly enlarges the size of ulcerative lesions in the intestinal lining, and exacerbates clinical signs and morbidity by DSS. Our results demonstrate DRO1 to be a strong tumor suppressor in the chemically induced colon carcinogenic mouse model. Additionally, we demonstrate DRO1 to inhibit colitis-associated colon cancer formation and uncover a novel putative role for DRO1 in inflammatory bowel disease.

Inactivation of Itf2 promotes intestinal tumorigenesis in Apc(Min/+) mice.

Deregulation of Wnt/ß-catenin signaling following inactivation of the adenomatous polyposis coli (APC) tumor suppressor gene is frequently found in colorectal cancer. We have previously shown that levels of ITF-2B, encoded by the ß-catenin target gene ITF2 that is located on the tumor suppressor gene locus 18q21, are increased in colonic adenomas with deregulated ß-catenin activity. However, during tumor progression ITF-2B levels are reduced, suggesting that ITF-2B interferes with tumor development. To investigate the role of ITF2 in intestinal tumorigenesis, we specifically inactivated Itf2 in the intestinal epithelium of Apc(Min/+) mice. We found that genetic disruption of Itf2 on the Apc(Min/+) background results in earlier death and a significant increase in tumor number and size in the small intestine. Based on these data Itf2 acts as a tumor suppressor gene of the intestinal tract that inhibits tumor initiation and growth.

Intestinal E-cadherin Deficiency Aggravates Dextran Sodium Sulfate-Induced Colitis.

BACKGROUND: E-cadherin is a cell adhesion protein with crucial roles in development, tissue homeostasis, and disease. Loss of E-cadherin in the adult intestinal epithelium disrupts tissue architecture and is associated with impaired localization and function of goblet and Paneth cells, reduced expression of antibacterial factors, and deficiency in clearing enteropathogenic bacteria. Several studies have suggested a role of E-cadherin in human inflammatory bowel disease. AIM: To investigate the role of E-cadherin deficiency in the pathogenesis of inflammatory bowel disease in a mouse model of experimentally induced colitis. METHODS: To induce E-cadherin deficiency, Villin-Cre-ER (T2) ;Cdh1 (fl/fl) mice received intraperitoneal injections of tamoxifen at days 1, 2, 5, and 8. Experimental colitis was induced by oral administration of dextran sodium sulfate (DSS, 3.5 % in the drinking water) for 3 days, starting at the third day after the first tamoxifen injection. RESULTS: E-cadherin deficiency in the adult mouse intestinal epithelium aggravates the clinical and histological features of DSS-induced colitis. Upon DSS treatment, mice deficient in E-cadherin lost more weight, were more severely dehydrated, and showed more frequently blood in the feces. Histologically, intestinal E-cadherin deficiency was associated with exacerbated acute and chronic inflammation and increased regenerative epithelial changes. Finally, the changes in the epithelium were distributed more diffusely in E-cadherin-deficient mice, while the mucosal damage was more focally localized in control animals. CONCLUSIONS: Our findings suggest that E-cadherin may play an important role in the pathogenesis of ulcerative colitis, one of the major clinical forms of inflammatory bowel disease.

Loss of DRO1/CCDC80 results in obesity and promotes adipocyte differentiation.

To investigate the role of DRO1 in obesity and adipogenesis in vivo, we generated a constitutive Dro1 knockout mouse model and analyzed the effect of DRO1 loss on body growth under standard and high fat diet feeding conditions. Loss of DRO1 resulted in a significant increase in body weight which was accompanied by a substantial expansion of white adipose tissue depots. The obese phenotype could be further enhanced by a high fat dietary challenge which also resulted in impaired glucose metabolism and the development of hepatosteatosis in Dro1 knockout mice. To study the role of DRO1 in adipocyte differentiation, primary stromal-vascular (SV) cells were isolated from inguinal white fat pads of knockout and control mice. In primary SV cells, depletion of DRO1 significantly promoted adipogenesis with upregulation of markers for adipogenesis (Cebpa, Pparg, Adipoq) and lipid metabolism (Dgat1, Dgat2). Our results demonstrate that DRO1 is a crucial regulator of energy homeostasis in vivo and functions as an inhibitor of adipogenesis in primary cells.

DRO1 inactivation drives colorectal carcinogenesis in ApcMin/+ mice.

UNLABELLED: Colorectal cancer develops from adenomatous precursor lesions by a multistep process that involves several independent mutational events in oncogenes and tumor suppressor genes. Inactivation of the adenomatous polyposis coli (APC) tumor suppressor gene is an early event and a prerequisite for the development of human colorectal adenoma. Previous in vitro studies identified DRO1 (CCDC80) to be a putative tumor suppressor gene that is negatively regulated in colorectal cancers and downregulated upon neoplastic transformation of epithelial cells. To investigate the in vivo role of DRO1 in colorectal carcinogenesis, a constitutive DRO1 knockout mouse model was generated. Disruption of DRO1 did not result in spontaneous intestinal tumor formation, consistent with the notion that DRO1 might have a role in suppressing the development of colon tumors in Apc(Min) (/+) mice, a widely used model for studying the role of APC in intestinal tumorigenesis that is hampered by the fact that mice predominantly develop adenomas in the small intestine and not in the colon. Here, deletion of DRO1 in Apc(Min) (/+) mice results in earlier death, a dramatically increased colonic tumor burden, and frequent development of colorectal carcinoma. Furthermore, enhanced phosphorylation of ERK1/2 is observed in colon epithelium and tumors from DRO1 knockout mice. Thus, this study reveals that inactivation of DRO1 is required for colorectal carcinogenesis in the Apc(Min) (/+) mouse and establishes a new mouse model for the study of colorectal cancer. IMPLICATIONS: This report characterizes a new mouse model for the study of colorectal cancer and establishes DRO1 (CCDC80) as a tumor suppressor via a mechanism involving ERK phosphorylation.