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Role of Notch signaling pathway in urothelial cancer

ABSTRACT: The Notch signaling pathway controls cell fates through interactions between neighboring cells by positively or negatively affecting, in a context-dependent manner, processes of proliferation, differentiation, and apoptosis1. It has been implicated in human cancer both as an oncogene and a tumor suppressor2. Here we report, for the first time, novel inactivating mutations in the Notch pathway components in over forty percent of the human bladder cancers examined. Bladder cancer is the fourth most commonly diagnosed malignancy in the US male population3. Thus far, driver mutations in the FGFR3 and less commonly RAS proteins have been identified4,5. We show that Notch activation in bladder cancer cells suppresses proliferation both in vitro and in vivo by directly upregulating dual specificity phosphatases (DUSPs), thus reducing ERK1/2 phosphorylation. In mouse models, genetic inactivation of Notch signaling leads to ERK1/2 phosphorylation resulting in tumorigenesis in the urinary tract. In recent years, the tumor suppressor role of Notch has been recognized by loss-of-function mutations identified in myeloid cancers6 as well as squamous cell carcinomas of the skin, lung7, and the head and neck8,9. Of the 4 Notch receptors (N1-4), only N1 and 2 have been implicated in human cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE54589 | GEO | 2014/07/01

SECONDARY ACCESSION(S): PRJNA237097

REPOSITORIES: GEO

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Project description:Background & Aims: Ursodeoxycholic acid (UDCA) attenuates chemical and colitis-induced colon carcinogenesis in animal models. We investigated its mechanism of action on normal intestinal cells, in which carcinogenesis- or inflammation-related alterations do not interfere with the result. Methods: Alterations of gene expression were identified in Affymetrix arrays in isolated colon epithelium of mice fed with a diet containing 0.4% UDCA and were confirmed in the normal rat intestinal cell line IEC-6 by RT-PCR. The effect of the insulin receptor substrate 1 (Irs-1) expression and of ERK phosphorylation on proliferation was investigated in vitro by flow cytometry, western blotting, siRNA-mediated gene suppression or by pharmacological inhibition of the kinase activity. The ERK1-effect on Irs-1 transcription was tested in a reporter system. Results: UDCA-treatment in vivo suppressed potential pro-proliferatory genes including Irs-1 and reduced cell proliferation by more than 30%. In vitro it neutralised the proliferatory signals of IGF-1 and EGF and slowed down the cell cycle. Irs-1 transcription was suppressed due to high ERK1 activation. Both Irs-1 suppression and the persistent high ERK activation inhibited proliferation. Conversely, the decrease of phosphorylation of ERK1 (but not ERK2) or of its expression partially abrogated the inhibitory effects of UDCA. Conclusions: UDCA inhibits proliferation of intestinal epithelial cells by acting upon IGF-1 and EGF pathways and targeting ERK1 and, consequently, Irs-1. The inhibition of these pathways adds a new dimension to the physiological and therapeutic action of UDCA and, since both pathways are activated in inflammation and cancer, suggests new applications of UDCA in chemoprevention and chemotherapy. Six normal mice were used for isolation of control RNA and six mice were used for isolation of RNA after UDCA treatment. RNAs of two animals were pooled i.e. there were six treated samples, named T1+2;T3+4,T5+6 and six nontreated samples named N1+2;N3+4 and N5+6.

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Role of Notch signaling pathway in urothelial cancer

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