Abstract A65: Characterization of CBP/p300-mediated butyrate-induced Wnt activity in colonic microadenoma cells.

Abstract

Abstract Objectives of the study: We wished to (a) compare gene expression profiles between a colonic microadenoma cell line (LT97) and a metastatic colorectal cancer (CRC) cell line (SW620) in the presence and absence of butyrate, (b) determine whether the sensitivity of LT97 cells to the growth suppressive effects of butyrate correlates to a high-fold upregulation of Wnt signaling in these cells, and (c) evaluate how modulation of CBP/p300-mediated Wnt signaling influences the ability of butyrate to upregulate Wnt activity in LT97 cells. Methods: RNA was isolated from mock treated or butyrate treated LT97 microadenoma cells or SW620 metastatic CRC cells, followed by full human genome microarray analysis (Genus Biosystems). Colonic cells were transfected with Wnt reporter plasmids and treated with ICG-001 (which inhibits CBP-mediated Wnt activity) or co-transfected with a p300 expression vector or with an expression vector for KLF4, which inhibits CBP/p300 association with beta-catenin. Reporter assays, western blotting, and caspase assays were performed. Results: We demonstrate that LT97 colonic microadenoma cells differ substantially in gene expression profiles compared to a metastatic CRC cell line (SW620), both in the presence and absence of butyrate. Further, we demonstrate that the high degree of sensitivity to the growth repressive effects of butyrate of LT97 cells correlates to a marked butyrate-induced hyperactivation of Wnt activity in that cell line. Further, the induction of Wnt activity by butyrate in LT97 cells is sensitive to treatment with ICG-001, overexpression of CBP or p300, or blockade of CBP/p300-mediated Wnt activity by the transcription factor KLF4. Conclusions: Microadenoma cells, reflecting very early stage colonic neoplasia, are highly sensitive to the effects of butyrate on Wnt signaling, in a manner dependent upon CBP/p300. The findings generated from this study may lead to approaches to modulate the action of CBP/p300-mediated Wnt signaling transcriptional programs for therapeutic or chemopreventive effect. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A65. Citation Format: Darina L. Lazarova, Christopher Chiaro, Terrence Wong, Michael Bordonaro. Characterization of CBP/p300-mediated butyrate-induced Wnt activity in colonic microadenoma cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A65.