The tumor-promoting activity of 2-acetylaminofluorene is associated with disruption of the p53 signaling pathway and the balance between apoptosis and cell proliferation

Toxicol Appl Pharmacol. 2009 Mar 15;235(3):305-11. doi: 10.1016/j.taap.2008.12.021. Epub 2009 Jan 6.

Abstract

The aromatic amine 2-acetylaminofluore (2-AAF) is a powerful complete genotoxic rat liver carcinogen that induces tumors without any additional interventions. While the tumor-initiating genotoxic activity of 2-AAF is well established, its tumor-promotion activity is far less understood. It is believed that the tumor-promoting property of 2-AAF is associated with selective enhancement of cell replication and sustained suppression of apoptosis in initiated cells. In the present study, we investigated the underlying mechanisms of tumor-promoting events induced by 2-AAF-exposure. Male Sprague-Dawley rats were fed NIH-31 diet containing 0.02% of 2-AAF for 12 and 24 weeks, and the expression pattern of genes associated with the p53-signaling pathway and microRNA genes was determined in the livers of control and 2-AAF-fed rats. The results indicate that the tumor-promoting property of 2-AAF during hepatocarcinogenesis is associated predominantly with the up-regulation of anti-apoptotic growth-related genes and down-regulation of expression of pro-apoptotic genes. This disrupts the balance between cell proliferation and apoptosis, which leads to consequential unrestricted cell proliferation, especially of initiated cells. Also, the long-term-administration of 2-AAF resulted in disruption of regulatory miR-34a-p53 feed-back loop that mediates apoptosis. This was evidenced by an increased expression of miR-34a in response to genotoxic effects of 2-AAF in the absence of p53 up-regulation, and loss of regulatory control of mir-34a on SIRT1 function. Additionally, the livers of 2-AAF-exposed rats were characterized by the substantial deregulation of expression of miR-18, miR-21, miR-182, and miR-200 family, microRNAs involved in control of apoptosis/cell proliferation and cell-cell contact pathways, two major pathways disrupted during the promotion stage of hepatocarcinogenesis.

Publication types

  • Comparative Study

MeSH terms

  • 2-Acetylaminofluorene / administration & dosage
  • 2-Acetylaminofluorene / toxicity*
  • Animals
  • Apoptosis / drug effects*
  • Apoptosis / physiology
  • Carcinogens / administration & dosage
  • Carcinogens / toxicity*
  • Cell Proliferation / drug effects*
  • Liver Neoplasms, Experimental / chemically induced
  • Liver Neoplasms, Experimental / metabolism
  • Liver Neoplasms, Experimental / pathology
  • Male
  • MicroRNAs / genetics
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / drug effects*
  • Signal Transduction / physiology
  • Tumor Suppressor Protein p53 / antagonists & inhibitors*
  • Tumor Suppressor Protein p53 / metabolism

Substances

  • Carcinogens
  • MIRN182 microRNA, rat
  • MicroRNAs
  • Tumor Suppressor Protein p53
  • 2-Acetylaminofluorene