14-3-3 and ß-catenin are secreted on extracellular vesicles to activate the oncogenic Wnt pathway.

Aberrant activation of the canonical Wnt signal transduction pathway is involved in a large number of human diseases. ß-catenin, the key effector protein of the canonical Wnt pathway, functions in the nucleus with T-cell factor/lymphoid enhancer factor (TCF/LEF) to activate expression of Wnt target genes. Here we show that members of the 14-3-3 protein family bind disheveled-2 (Dvl-2) and glycogen synthase-3ß (GSK-3ß) to attenuate the interaction between GSK-3ß and ß-catenin. Importantly, 14-3-3 and ß-catenin form "bleb-like" structures and are secreted via extracellular vesicles to induce Wnt signaling activity in target cells. Our data suggest a novel way of transducing the oncogenic Wnt signal in which ß-catenin is regulated by 14-3-3ζ through the formation of "oncosomes" that contain both the 14-3-3 and ß-catenin proteins.

Restoration of APC gene function in colorectal cancer cells by aminoglycoside- and macrolide-induced read-through of premature termination codons.

Adenomatous polyposis coli (APC) is a multifunctional tumour suppressor protein that negatively regulates the Wnt signalling pathway. The APC gene is ubiquitously expressed in tissues and organs, including the large intestine and central nervous system. The majority of patients with sporadic and hereditary colorectal cancer have mutations in the gene encoding APC. Approximately 30% of these mutations are single nucleotide changes that result in premature stop codons (nonsense mutations). A potential therapeutic approach for treatment of this subset of patients is the use of aminoglycosides and macrolides that induce nonsense mutation read-through and restore levels of full-length protein. We have used reporter plasmids and colorectal cancer cell lines to demonstrate that several aminoglycosides and tylosin, a member of the macrolide family, induced read-through of nonsense mutations in the APC gene. In xenograft experiments and in the Apc(Min/+) mouse model, these compounds ameliorated the tumorigenic clinical symptoms caused by nonsense mutations in the APC gene.