C-Cbl mediates the degradation of tumorigenic nuclear ?-catenin contributing to the heterogeneity in Wnt activity in colorectal tumors.

ABSTRACT: Despite the loss of Adenomatous Polyposis Coli (APC) in a majority of colorectal cancers (CRC), not all CRCs bear hallmarks of Wnt activation, such as nuclear ?-catenin. This underscores the presence of other Wnt regulators that are important to define, given the pathogenic and prognostic roles of nuclear ?-catenin in human CRC. Herein, we investigated the effect of Casitas B-lineage lymphoma (c-Cbl) on nuclear ?-catenin, which is an oncoprotein upregulated in CRC due to loss-of-function APC or gain-of-function CTNNB1 mutations. Despite mechanistic rationale and recent discoveries of c-Cbl's mutations in solid tumors, little is known about its functional importance in CRC. Our study in a cohort of human CRC patients demonstrated an inverse correlation between nuclear ?-catenin and c-Cbl. Further investigation showed that the loss of c-Cbl activity significantly enhanced nuclear ?-catenin and CRC tumor growth in cell culture and a mouse xenograft model. c-Cbl interacted with and downregulated ?-catenin in a manner that was independent of CTNNB1 or APC mutation status. This study demonstrates a previously unrecognized function of c-Cbl as a negative regulator of CRC.

SUBMITTER: Shashar M 

PROVIDER: S-EPMC5342068 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature