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  • Title: Transactivation of the multidrug resistance 1 gene by T-cell factor 4/beta-catenin complex in early colorectal carcinogenesis.
    Author: Yamada T, Takaoka AS, Naishiro Y, Hayashi R, Maruyama K, Maesawa C, Ochiai A, Hirohashi S.
    Journal: Cancer Res; 2000 Sep 01; 60(17):4761-6. PubMed ID: 10987283.
    Abstract:
    The mutational inactivation of a tumor suppressor gene, adenomatous polyposis coli (APC), results in the accumulation of cytoplasmic beta-catenin protein and the activation of T-cell factor (TCF)/lymphoid enhancer factor transcriptional factors. A colorectal carcinoma cell line, DLD-1, was engineered to suppress transactivation by the TCF4/beta-catenin complex in a dominant-negative manner under the strict control of the tetracycline regulatory system. A large-scale comparison of the expression profiles, using two-color fluorescence hybridization of cDNA microarray, led to the identification of MDR1 as a target gene of the TCF4/beta-catenin complex. Luciferase reporter and gel retardation assays revealed the TCF4/beta-catenin responsive elements in the promoter of the human MDR1 gene. Corresponding to the accumulation of beta-catenin, expression of the MDR1 gene product was steadily up-regulated in adenomas and adenocarcinomas of 10 patients with familial adenomatous polyposis. In combination with cell proliferative activities of c-myc and cyclin D1, MDR1 may initiate colorectal tumorigenesis by suppressing cell death pathways programmed in intestinal epithelial cells.
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