Wnt signaling is one of the most common pathways linked to carcinogenesis in the intestine. The transcription factors that mediate Wnt signals are members of the Lymphoid Enhancer Factor/T Cell Factor (LEF/TCF) family. This four-member family is complex in that there are full-length activating forms, truncated dominant negative forms, and alternatively spliced isoforms that modify Wnt target gene recognition. TCF-1 and TCF-4 are the two family members expressed in the epithelial crypt compartment of the intestine. Normally, TCF-1 is expressed as a dominant negative isoform and it counteracts the action of TCF-4 which is expressed as a Wnt-mediating, active isoform. This pattern changes in cancer because TCF-1 expression switches to a full-length, Wnt mediating form. We have discovered a second DNA binding domain in TCF-1 and TCF-4 isoforms called the C-clamp. We have shown that the C-clamp is important for regulating cell proliferation of colon cancer cells. We have also identified Wnts that trigger TCF-1 export in colon cancer cells. Export of TCF-1 leaves the C-clamp form of TCF-4 in the nucleus to mediate aberrant Wnt signaling.
Three aims are proposed for this project. First, the extracellular Wnts and intracellular components that direct TCF-1 nuclear export will be defined (Aim1). Second, the biological impact of export will be defined in colon cancer cells and colon cancer initiating 3D cultures (Aim2). Third, the DNA binding specificities and target gene selection of C-clamp forms of TCF-1 and TCF-4 will be defined through genome-wide binding assays (ChIP-Seq), high-throughput protein binding microarrays, and in vitro biochemical analysis (Aim3). The overall goal is to define the mechanisms behind changes in TCF expression in colon carcinogenesis, and to define how extracellular Wnts and DNA binding specificities of TCFs influence aberrant signaling in colon cancer cells with stabilized ?-catenin.

Public Health Relevance

In colon cancer, Wnt signaling is an overactive and strong signal for tumor initiation and progression. Wnt signaling is mediated by the TCF transcription factors and we have discovered their activities and expression to be different in colon cancer versus normal colon tissue. This project investigates basic mechanisms of TCF localization and gene targeting and asks how differences in these attributes contribute to the cancer cell phenotype.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Molecular Oncogenesis Study Section (MONC)
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Mietz, Judy
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University of California Irvine
Schools of Medicine
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Pate, Kira T; Stringari, Chiara; Sprowl-Tanio, Stephanie et al. (2014) Wnt signaling directs a metabolic program of glycolysis and angiogenesis in colon cancer. EMBO J 33:1454-73
Chodaparambil, Jayanth V; Pate, Kira T; Hepler, Margretta R D et al. (2014) Molecular functions of the TLE tetramerization domain in Wnt target gene repression. EMBO J 33:719-31
Wu, Beibei; Piloto, Sarah; Zeng, Weihua et al. (2013) Ring Finger Protein 14 is a new regulator of TCF/ýý-catenin-mediated transcription and colon cancer cell survival. EMBO Rep 14:347-55
Wang, Yuli; Dhopeshwarkar, Rahul; Najdi, Rani et al. (2010) Microdevice to capture colon crypts for in vitro studies. Lab Chip 10:1596-603
Sikandar, Shaheen S; Pate, Kira T; Anderson, Scott et al. (2010) NOTCH signaling is required for formation and self-renewal of tumor-initiating cells and for repression of secretory cell differentiation in colon cancer. Cancer Res 70:1469-78
Yokoyama, Noriko N; Pate, Kira T; Sprowl, Stephanie et al. (2010) A role for YY1 in repression of dominant negative LEF-1 expression in colon cancer. Nucleic Acids Res 38:6375-88
Crampton, Steve P; Wu, Beibei; Park, Edward J et al. (2009) Integration of the beta-catenin-dependent Wnt pathway with integrin signaling through the adaptor molecule Grb2. PLoS One 4:e7841
Najdi, R; Syed, A; Arce, L et al. (2009) A Wnt kinase network alters nuclear localization of TCF-1 in colon cancer. Oncogene 28:4133-46
Semler, Bert L; Waterman, Marian L (2008) IRES-mediated pathways to polysomes: nuclear versus cytoplasmic routes. Trends Microbiol 16:1-5
Atcha, Fawzia A; Syed, Adeela; Wu, Beibei et al. (2007) A unique DNA binding domain converts T-cell factors into strong Wnt effectors. Mol Cell Biol 27:8352-63

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