Email updates

Keep up to date with the latest news and content from BMC Molecular Biology and BioMed Central.

Open Access Highly Accessed Open Badges Research article

A protein knockdown strategy to study the function of β-catenin in tumorigenesis

Feng Cong1*, Jianxuan Zhang2, William Pao1, Pengbo Zhou2* and Harold Varmus1

Author Affiliations

1 Program in Cell Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA

2 Department of Pathology, Weill Medical College and Graduate School of Medical Sciences, Cornell University, New York, New York 10021, USA

For all author emails, please log on.

BMC Molecular Biology 2003, 4:10  doi:10.1186/1471-2199-4-10

Published: 29 September 2003



The Wnt signaling pathway plays critical roles in cell proliferation and cell fate determination at many stages of development. A critical downstream target of Wnt signaling is the cytosolic β-catenin, which is stabilized upon Wnt activation and promotes transcription of a variety of target genes including c-myc and cyclin D. Aberrant Wnt signaling, which results from mutations of either β-catenin or adenomatous polyposis coli (APC), renders β-catenin resistant to degradation, and has been associated with multiple types of human cancers.


A protein knockdown strategy was designed to reduce the cytosolic β-catenin levels through accelerating its turnover rate. By engineering a chimeric protein with the β-catenin binding domain of E-cadherin fused to βTrCP ubiquitin-protein ligase, the stable β-catenin mutant was recruited to the cellular SCF (

ullin 1, and
-box-containing substrate receptor) ubiquitination machinery for ubiquitination and degradation. The DLD1 colon cancer cells express wild type β-catenin at abnormally high levels due to loss of APC. Remarkably, conditional expression of βTrCP-E-cadherin under the control of a tetracycline-repressive promoter in DLD1 cells selectively knocked down the cytosolic, but not membrane-associated subpopulation of β-catenin. As a result, DLD1 cells were impaired in their growth and clonogenic ability in vitro, and lost their tumorigenic potential in nude mice.


We have designed a novel approach to induce degradation of stabilized/mutated β-catenin. Our results suggest that a high concentration of cytoplasmic β-catenin is critical for the growth of colorectal tumor cells. The protein knockdown strategy can be utilized not only as a novel method to dissect the role of oncoproteins in tumorigenesis, but also as a unique tool to delineate the function of a subpopulation of proteins localized to a specific subcellular compartment.