Transcription Factor ZBP-89 Drives a Feedforward Loop of β-Catenin Expression in Colorectal Cancer

Cancer Res. 2016 Dec 1;76(23):6877-6887. doi: 10.1158/0008-5472.CAN-15-3150. Epub 2016 Oct 10.

Abstract

In colorectal cancer, APC-mediated induction of unregulated cell growth involves posttranslational mechanisms that prevent proteasomal degradation of proto-oncogene β-catenin (CTNNB1) and its eventual translocation to the nucleus. However, about 10% of colorectal tumors also exhibit increased CTNNB1 mRNA. Here, we show in colorectal cancer that increased expression of ZNF148, the gene coding for transcription factor ZBP-89, correlated with reduced patient survival. Tissue arrays showed that ZBP-89 protein was overexpressed in the early stages of colorectal cancer. Conditional deletion of Zfp148 in a mouse model of Apc-mediated intestinal polyps demonstrated that ZBP-89 was required for polyp formation due to induction of Ctnnb1 gene expression. Chromatin immunoprecipitation (ChIP) and EMSA identified a ZBP-89-binding site in the proximal promoter of CTNNB1 Reciprocally, siRNA-mediated reduction of CTNNB1 expression also decreased ZBP-89 protein. ChIP identified TCF DNA binding sites in the ZNF148 promoter through which Wnt signaling regulates ZNF148 gene expression. Suppression of either ZNF148 or CTNNB1 reduced colony formation in WNT-dependent, but not WNT-independent cell lines. Therefore, the increase in intracellular β-catenin protein initiated by APC mutations is sustained by ZBP-89-mediated feedforward induction of CTNNB1 mRNA. Cancer Res; 76(23); 6877-87. ©2016 AACR.

MeSH terms

  • Animals
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Humans
  • Mice
  • Proto-Oncogene Mas
  • Signal Transduction
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transfection
  • beta Catenin / metabolism*

Substances

  • DNA-Binding Proteins
  • MAS1 protein, human
  • Proto-Oncogene Mas
  • Transcription Factors
  • Zfp148 protein, mouse
  • beta Catenin