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Comparison of DNA Damage and Repair in Target Versus Non-Target Cells: Relevance to Diet and Colon Cancer

Institutions
University of Leicester
Start date
2000
End date
2004
Objective
This research project aims to assess the DNA adducts, and the repair activities which modulate these levels, in the target cells.

AIMS: To investigate this hypothesis by addressing the following objectives:

  1. Develop methods to measure DNA damage (caused by lipid oxidation products), which minimises the complications inherent in other methods of analysis.
  2. Establish a suitable model of target and non-target colon cells, using cells grown in the laboratory and to characterise these selected cells to show they represent a good model.
  3. Develop methods for measuring the ability of a specific cell type to protect against permanent DNA damage (i.e. prevent or repair).
  4. Examine the relative responses of target and non-target cells exposed to fat oxidation products.
  5. Examine target and non-target cells in colon samples removed from patients undergoing surgery for colorectal cancer.
APPROACHES
  1. Antibodies to DNA adducted to fat oxidation products were produced in rabbits, characterised and then used to measure DNA damage caused by fat oxidation products.
  2. Human colon-like cells have been grown in the laboratory, and chemically stimulated to develop into mature non-target cells. These changes were used to show that the cells had matured by analysis of their protein profiles and from their genetic characteristics.
  3. Three methods, including the use of anti-lipid DNA adduct antibodies were used to examine DNA repair as a measure of the cells' protective ability.
  4. Using these methods (see above) responses of target/non-target cells to a chemical exposure related to fat oxidation was carried out.
  5. Samples of colon obtained from patients undergoing surgery for colorectal cancer are being used to examine DNA damage and for genetic analysis of cellular protective abilities.
This main strength of this study is that it is considered to offer advantages over other approaches as the availability of antibodies and specialised instrumentation that makes it possible to select target and non-target cells specifically from within colon tissue so examine the proposed "target" and "non-target" cells in situ in genuine samples.
More information
High dietary lipid (fat) has a strong association with colorectal carcinoma, a common cancer in the European Union, thought to be derived from the effects of reactive and free radical species generated during lipid peroxidation.

Damage of DNA is frequently used as a marker of lipid peroxidation, an index of exposure to oxidising environments/agents and hence the risk of tumour formation.

However, DNA extracted from tissue will contain adducts derived from many different cell types, hampering attempts to correlate adduct levels with carcinogenicity and as a result, impeding the accumulation of meaningful cancer risk data. The risk of tumourigenic changes occurring following exposure to insult is likely to be greater in the tissue cells which are undifferentiated and proliferating (target cells), as these possess some similarities to tumour cells.

On this basis it would be more appropriate to assess DNA adduct levels and the repair activities that modulate these levels, in the target cells. Such an approach will provide (i) a better correlation between adduct levels and risk of tumourogenicity allowing enhancement of existing safety/risk assessment procedures and (ii) elucidation of the mechanisms linking lesion induction and tumourogenesis.

Find more about this project and other FSA food safety-related projects at the Food Standards Agency Research webpage.

Funding Source
Food Standards Agency
Project number
T01016
Categories
Risk Assessment, Management, and Communication
Commodities
Meat, Poultry, Game