Inhibition of β-catenin signalling promotes DNA damage elicited by benzo[a]pyrene in a model of human colon cancer cells via CYP1 deregulation

Mutagenesis. 2015 Jul;30(4):565-76. doi: 10.1093/mutage/gev019. Epub 2015 Mar 24.


Deregulation of Wnt/β-catenin signalling plays an important role in the pathogenesis of colorectal cancer. Interestingly, this pathway has been recently implicated in transcriptional control of cytochrome P450 (CYP) family 1 enzymes, which are responsible for bioactivation of a number of dietary carcinogens. In the present study, we investigated the impact of inhibition of Wnt/β-catenin pathway on metabolism and genotoxicity of benzo[a]pyrene (BaP), a highly mutagenic polycyclic aromatic hydrocarbon and an efficient ligand of the aryl hydrocarbon receptor, which is known as a primary regulator of CYP1 expression, in cellular models derived from colorectal tumours. We observed that a synthetic inhibitor of β-catenin, JW74, significantly increased formation of BaP-induced DNA adducts in both colorectal adenoma and carcinoma-derived cell lines. Using the short interfering RNA (siRNA) targeting β-catenin, we then found that β-catenin knockdown in HCT116 colon carcinoma cells significantly enhanced formation of covalent DNA adducts by BaP and histone H2AX phosphorylation, as detected by (32)P-postlabelling technique and immunocytochemistry, respectively, and it also induced expression of DNA damage response genes, such as CDKN1A or DDB2. The increased formation of DNA adducts formed by BaP upon β-catenin knockdown corresponded with enhanced production of major BaP metabolites, as well as with an increased expression/activity of CYP1 enzymes. Finally, using siRNA-mediated knockdown of CYP1A1, we confirmed that this enzyme plays a major role in formation of BaP-induced DNA adducts in HCT116 cells. Taken together, the present results indicated that the siRNA-mediated inhibition of β-catenin signalling, which is aberrantly activated in a majority of colorectal cancers, modulated genotoxicity of dietary carcinogen BaP in colon cell model in vitro, via a mechanism involving up-regulation of CYP1 expression and activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Benzo(a)pyrene / adverse effects*
  • Blotting, Western
  • Carcinogens, Environmental / adverse effects
  • Cell Proliferation
  • Colonic Neoplasms / drug therapy
  • Colonic Neoplasms / etiology*
  • Colonic Neoplasms / pathology*
  • Cytochrome P-450 CYP1A1 / antagonists & inhibitors
  • Cytochrome P-450 CYP1A1 / genetics
  • Cytochrome P-450 CYP1A1 / metabolism*
  • DNA Adducts / adverse effects*
  • DNA Damage*
  • Gene Expression Regulation, Enzymologic / drug effects*
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Humans
  • Immunoenzyme Techniques
  • RNA, Messenger / genetics
  • RNA, Small Interfering / genetics
  • Real-Time Polymerase Chain Reaction
  • Receptors, Aryl Hydrocarbon / genetics
  • Receptors, Aryl Hydrocarbon / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Tumor Cells, Cultured
  • beta Catenin / antagonists & inhibitors*
  • beta Catenin / genetics
  • beta Catenin / metabolism


  • Carcinogens, Environmental
  • DNA Adducts
  • RNA, Messenger
  • RNA, Small Interfering
  • Receptors, Aryl Hydrocarbon
  • benzo(a)pyrene-DNA adduct
  • beta Catenin
  • Benzo(a)pyrene
  • CYP1A1 protein, human
  • Cytochrome P-450 CYP1A1