C-Cbl Expression Correlates with Human Colorectal Cancer Survival and its Wnt/ ?-catenin Suppressor Function is Regulated by Tyr371 Phosphorylation
*Nkiruka Arinze1, *Sowmiya Kumaradevan1, *Shin Y. Lee1, *Sean Richards1, *Vijay Kolachalama1, *Chimera Lyle1, *Qing Zhao1, *Umit Tapan1, *Yilan Jiangliu1, *Shmyle Ghumman1, *Joshua Walker1, *Mostafa Belghasem1, *Angela Kuhnen1, *Janice Weinberg2, *Jean Francis1, *Kevan Hartshorn1, *Daniel Cifuentes1, *Nader Rahimi1, *Vipul Chitalia1
1Boston University School of Medicine, Boston, MA; 2Boston University School of Public Health, Boston, MA
Objective: The proto-oncogene beta-catenin is linked to colorectal carcinogenesis. Recent work demonstrates that the Casitas B-lineage lymphoma (c-Cbl) protein inhibits colorectal cancer (CRC) growth by ubiquitinating and degrading nuclear beta-catenin. However, the effect of c-Cbl on human CRC survival and the mechanism by which it regulates nuclear beta-catenin remains largely unknown.The objective of this study was to analyze the relationship between c-Cbl expression and CRC survival.
Design: Retrospective single center clinico-pathological association study, in vitro cellular model and in vitro tumor formation assay, transgenic Wnt-8 zebrafish model
Setting: Large academic, safety net hospital
Patients: Evaluated the tumors of 72 patients who presented with stage IV Colorectal cancer between 2004-2014
Interventions: For tumor samples, β-catenin and c-Cbl expression was measured using quantitative histology and color based image segmentation analysis followed by Kaplan Meier analysis. For zebrafish experiments, transient overexpression of different c-Cbl constructs were done.
Main Outcome Measures: All-cause mortality
Results: Patients with high c-Cbl expressing tumors had significantly better median survival compared to those with low c-Cbl expressing tumors (3.7 vs.1.8 years; p=.0026). c-Cbl Tyr371 lacked the ability to regulate nuclear β-catenin and served as a dominant negative in transgenic zebrafish model. Compared to wild-type c-Cbl, c-Cbl Tyr371 mutant augmented Wnt activity, induced Wnt target genes, and enhanced angiogenesis and in vitro tumor growth.
Conclusions: This study demonstrates a link between c-Cbl expression in tumors and overall survival of CRC patients. Our study also illustrates the role of ubiquitin ligase activity modulated by a single Tyr residue of c-Cbl in Wnt/β-catenin regulation, which has important implications in CRC tumorigenesis.