Role of Notch signaling pathway in urothelial cancer

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. two biological replicates from normal and tumor urothelial tissue were hybridized on Affymetrix mm 430 2.0 chips