Dual targeting of Bromodomain and Extraterminal Domain Proteins, and WNT or MAPK Signaling, Inhibits c-MYC Expression and Proliferation of Colorectal Cancer Cells

Togel, L., Nightingale, R.-, Chueh, A.. C., Jayachandran, A., Tran, Huynh, Phesse, Toby ORCID: https://orcid.org/0000-0001-9568-4916, Wu, R., Sieber, O. M., Arango, D., Dhillon, A. S., Dawson, M. A., Diez-Dacal, B., Gahman, T. C., Filippakopoulos, P., Shiau, A. K. and Mariadason, J. M. 2016. Dual targeting of Bromodomain and Extraterminal Domain Proteins, and WNT or MAPK Signaling, Inhibits c-MYC Expression and Proliferation of Colorectal Cancer Cells. Molecular Cancer Therapeutics 15 (6) , pp. 1217-1226. 10.1158/1535-7163.MCT-15-0724

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Abstract

Inhibitors of the bromodomain and extraterminal domain (BET) protein family attenuate the proliferation of several tumor cell lines. These effects are mediated, at least in part, through repression of c-MYC. In colorectal cancer, overexpression of c-MYC due to hyperactive WNT/β-catenin/TCF signaling is a key driver of tumor progression; however, effective strategies to target this oncogene remain elusive. Here, we investigated the effect of BET inhibitors (BETi) on colorectal cancer cell proliferation and c-MYC expression. Treatment of 20 colorectal cancer cell lines with the BETi JQ1 identified a subset of highly sensitive lines. JQ1 sensitivity was higher in cell lines with microsatellite instability but was not associated with the CpG island methylator phenotype, c-MYC expression or amplification status, BET protein expression, or mutation status of TP53, KRAS/BRAF, or PIK3CA/PTEN. Conversely, JQ1 sensitivity correlated significantly with the magnitude of c-MYC mRNA and protein repression. JQ1-mediated c-MYC repression was not due to generalized attenuation of β-catenin/TCF-mediated transcription, as JQ1 had minimal effects on other β-catenin/TCF target genes or β-catenin/TCF reporter activity. BETi preferentially target super-enhancer–regulated genes, and a super-enhancer in c-MYC was recently identified in HCT116 cells to which BRD4 and effector transcription factors of the WNT/β−catenin/TCF and MEK/ERK pathways are recruited. Combined targeting of c-MYC with JQ1 and inhibitors of these pathways additively repressed c-MYC and proliferation of HCT116 cells. These findings demonstrate that BETi downregulate c-MYC expression and inhibit colorectal cancer cell proliferation and identify strategies for enhancing the effects of BETi on c-MYC repression by combinatorial targeting the c-MYC super-enhancer.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Biosciences European Cancer Stem Cell Research Institute (ECSCRI)
Publisher:	American Association for Cancer Research
ISSN:	1535-7163
Date of Acceptance:	6 March 2016
Last Modified:	01 Nov 2022 10:38
URI:	https://orca.cardiff.ac.uk/id/eprint/92358

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