c-Cbl Expression Correlates with Human Colorectal Cancer Survival and Its Wnt/ß-Catenin Suppressor Function Is Regulated by Tyr371 Phosphorylation.

The proto-oncogene ß-catenin drives colorectal cancer (CRC) tumorigenesis. Casitas B-lineage lymphoma (c-Cbl) inhibits CRC tumor growth through targeting nuclear ß-catenin by a poorly understood mechanism. In addition, the role of c-Cbl in human CRC remains largely underexplored. Using a novel quantitative histopathologic technique, we demonstrate that patients with high c-Cbl-expressing tumors had significantly better median survival (3.7 years) compared with low c-Cbl-expressing tumors (1.8 years; P = 0.0026) and were more than twice as likely to be alive at 3 years compared with low c-Cbl tumors (P = 0.0171). Our data further demonstrate that c-Cbl regulation of nuclear ß-catenin requires phosphorylation of c-Cbl Tyr371 because its mutation compromises its ability to target ß-catenin. The tyrosine 371 (Y371H) mutant interacted with but failed to ubiquitinate nuclear ß-catenin. The nuclear localization of the c-Cbl-Y371H mutant contributed to its dominant negative effect on nuclear ß-catenin. The biological importance of c-Cbl-Y371H was demonstrated in various systems, including a transgenic Wnt-8 zebrafish model. c-Cbl-Y371H mutant showed augmented Wnt/ß-catenin signaling, increased Wnt target genes, angiogenesis, and CRC tumor growth. This study demonstrates a strong link between c-Cbl and overall survival of patients with CRC and provides new insights into a possible role of Tyr371 phosphorylation in Wnt/ß-catenin regulation, which has important implications in tumor growth and angiogenesis in CRC.

MicroRNA-21 promotes Th17 differentiation and mediates experimental autoimmune encephalomyelitis.

Accumulation of IL-17-producing Th17 cells is associated with the development of multiple autoimmune diseases; however, the contribution of microRNA (miRNA) pathways to the intrinsic control of Th17 development remains unclear. Here, we demonstrated that miR-21 expression is elevated in Th17 cells and that mice lacking miR-21 have a defect in Th17 differentiation and are resistant to experimental autoimmune encephalomyelitis (EAE). Furthermore, we determined that miR-21 promotes Th17 differentiation by targeting and depleting SMAD-7, a negative regulator of TGF-ß signaling. Moreover, the decreases in Th17 differentiation in miR-21-deficient T cells were associated with defects in SMAD-2/3 activation and IL-2 suppression. Finally, we found that treatment of WT mice with an anti-miR-21 oligonucleotide reduced the clinical severity of EAE, which was associated with a decrease in Th17 cells. Thus, we have characterized a T cell-intrinsic miRNA pathway that enhances TGF-ß signaling, limits the autocrine inhibitory effects of IL-2, and thereby promotes Th17 differentiation and autoimmunity.