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Binding of superoxide-modified DNA by cancer antibodies

G Waris1, M A Khan, S Khan

  • 1Department of Biochemistry, Faculty of Medicine, A.M.U., Aligarh, India.

Journal of Experimental & Clinical Cancer Research : CR
|March 28, 2008
PubMed

Insights

Excess superoxide radicals damage DNA, leading to cancer. This study found cancer patients

Area of Science:

  • Biochemistry and Molecular Biology
  • Oxidative Stress and Disease Mechanisms
  • Immunology and Cancer Research

Background:

  • Elevated superoxide anion radical concentrations can damage vital biomolecules like DNA, proteins, and lipids.
  • Such damage can lead to cytotoxicity and the development of various diseases.
  • Understanding the role of oxidative stress in disease pathogenesis is crucial for developing new therapeutic strategies.

Purpose of the Study:

  • To generate superoxide anion radicals in vitro and investigate their effects on DNA.
  • To assess the presence of antibodies reactive to superoxide-modified DNA in cancer patients.
  • To explore the potential of autoantibodies as biomarkers for cancer detection.

Main Methods:

  • Superoxide anion radicals were generated in vitro using riboflavin and cool white fluorescent light.
  • Radical formation was confirmed by superoxide dismutase enzyme quenching and nitrobluetetrazolium dye reduction.
  • Double-stranded DNA was exposed to superoxide radicals, and its structural modifications were analyzed using various biochemical assays, including hyperchromicity, single-strand break detection, melting temperature determination, and base modification analysis.
  • An immunoassay (ELISA) was employed to detect modified-DNA reactive antibodies in sera from patients diagnosed with breast, lung, liver, urinary bladder, and gall bladder cancers.
  • Competition ELISA was used to compare the binding affinity of serum antibodies to superoxide-modified DNA versus control DNA.

Main Results:

  • Exposure of double-stranded DNA to superoxide anion radicals resulted in hyperchromicity, single-strand breaks, a decrease in melting temperature, and modifications to thymine, adenine, and guanine bases.
  • Serum antibodies from cancer patients demonstrated a higher reactivity towards superoxide-modified DNA compared to unmodified DNA in competition ELISA.
  • These findings suggest that the immune system generates autoantibodies that specifically recognize DNA damaged by superoxide radicals in cancer patients.

Conclusions:

  • Superoxide anion radicals induce significant structural and chemical modifications in DNA.
  • The presence of autoantibodies recognizing superoxide-modified DNA in cancer patients' sera indicates a role for humoral immunity in cancer.
  • These findings highlight the potential of modified-DNA reactive autoantibodies as novel biomarkers for cancer diagnosis and monitoring.

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