Duodenal reflux leads to down regulation of DNA mismatch repair pathway in an animal model of esophageal cancer

Ann Thorac Surg. 2007 Feb;83(2):433-40; discussion 440. doi: 10.1016/j.athoracsur.2006.06.090.

Abstract

Background: Gastroduodenal reflux is implicated in esophageal carcinogenesis. This effect is mediated by reactive oxygen species. We hypothesized that this is mediated by DNA mismatch lesion 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxoG), which is repaired by the Mut Y homologue (MYH). We tested the effect of reflux, either alone or in combination with the human dietary mutagen methyl-n-amyl nitrosamine (MNAN), on DNA damage in adenocarcinoma and squamous cell cancer of the esophagus in a rat model.

Methods: Reflux was promoted in male Sprague-Dawley rats by duodenoesophageal anastomosis (8 weeks) without gastric bypass. MNAN treatment (25 mg/kg per week intraperitoneally for four doses) commenced at 10 weeks age. Ten animals served as controls. Quantification of 8-oxoG was performed by using immunohistochemistry, and MYH was analyzed by Western blot. Apoptosis was assessed by terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling (TUNEL), cytochrome C, and caspase.

Results: Tumors (adenocarcinoma) developed in 15 (50%) of 30 animals with reflux alone; this increased to 26 (86.6%) of 30 when reflux was combined with MNAN treatment, with tumor histology consistent with adenosquamous and squamous cell cancer. DNA damage, as reflected by positive 8-oxoG staining in reflux groups, was significantly increased compared with control (p < 0.01), and this was maximal in tissues with malignant transformation. Protein levels of the DNA repair enzyme MYH were significantly less in tissues subjected to reflux compared with controls (p < 0.05). TUNEL, cytochrome C, and caspase positivity confirmed increased apoptosis in cancer lesions.

Conclusions: Gastroduodenal reflux leads to increased DNA damage and downregulation of the DNA mismatch repair pathway. This pathway has an important role in esophageal carcinogenesis in rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / etiology*
  • Adenocarcinoma / pathology
  • Adenocarcinoma / physiopathology
  • Animals
  • Apoptosis
  • Carcinogens
  • Carcinoma, Squamous Cell / chemically induced
  • Carcinoma, Squamous Cell / etiology*
  • Carcinoma, Squamous Cell / pathology
  • Carcinoma, Squamous Cell / physiopathology
  • Caspases / metabolism
  • Cytochromes c / metabolism
  • DNA Damage
  • DNA Mismatch Repair*
  • DNA Repair Enzymes / metabolism
  • Down-Regulation*
  • Duodenogastric Reflux / complications*
  • Duodenogastric Reflux / genetics*
  • Duodenogastric Reflux / metabolism
  • Esophageal Neoplasms / chemically induced
  • Esophageal Neoplasms / etiology*
  • Esophageal Neoplasms / pathology
  • Esophageal Neoplasms / physiopathology
  • Guanosine / analogs & derivatives
  • Guanosine / metabolism
  • In Situ Nick-End Labeling
  • Male
  • Nitrosamines
  • Rats
  • Rats, Sprague-Dawley
  • Staining and Labeling

Substances

  • Carcinogens
  • Nitrosamines
  • Guanosine
  • N-amyl-N-methylnitrosamine
  • 8-hydroxyguanosine
  • Cytochromes c
  • Caspases
  • DNA Repair Enzymes