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Cancer Metastasis Rev. 2004 Jan-Jun;23(1-2):41-52.

Lymphoid enhancer factor/T cell factor expression in colorectal cancer.

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1
Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, USA. mlwaterm@uci.edu

Abstract

Genetic inactivation of key components of the Wnt signal transduction system is a frequent event in colorectal cancer. These genetic mutations lead to stabilization of beta-catenin, a cytoplasmic-nuclear shuttling protein with a potent transcription activation domain. Stabilization and subsequent nuclear localization of beta-catenin produces aberrant, Wnt-independent signals to target genes, an activity tightly linked to the genesis of colon cancers. In the nucleus, the transcription factor family of LEF/TCF proteins transmits Wnt signals by binding to beta-catenin and recruiting it to target genes for activation. Such activities are carried out by full-length LEF/TCFs that are thought to be mostly interchangeable and redundant. However, truncated forms of LEF-1 and TCF-1 that do not bind to beta-catenin function as dominant negatives and an alternatively spliced TCF isoform with a unique activation function has recently been discovered. The dominant negative forms block Wnt signals because they occupy Wnt target genes and limit beta-catenin access; the alternatively spliced TCF isoform activates certain Wnt target promoters whereas other TCF isoforms and LEF-1 do not. A study of LEF/TCF expression and activity in normal intestine and colon carcinomas suggests that the relative amounts of LEF/TCF isoforms may change as tumors progress and this may influence the strength and specificity of Wnt signals in the nucleus. While the underlying mechanism for a change in the LEF/TCF isoform expression is not yet known, recent evidence implicates the Wnt signaling pathway itself as a potential modulator.

PMID:
15000148
[Indexed for MEDLINE]
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