Radiation-Induced Apoptosis in Normal Cells Reduced by Bcl-2 Expression

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According to research from the United States, specific overexpression of the antiapoptotic molecule Bcl-2 in normal cells inhibited radiation-induced apoptosis, thereby reducing radiation-induced toxicity in normal cells. At the M.D. Anderson Cancer Center, researchers constructed a Bcl-2 expression plasmid with a minimal promoter regulated by multiple wild-type p53 DNA-binding sites, finding that wild-type p53 protein strongly upregulated Bcl-2 expression in normal cells. The results indicate that irradiation of normal cells rapidly upregulates the expression of wild-type p53, which binds to the p53 binding sequence of the Bcl-2 plasmid and increases the transcriptional activity of Bcl-2. This novel approach to inhibiting radiation-induced apoptosis in normal cells may allow such cells to be protected from radiation-induced toxicity.

Key Takeaways:

  • Researchers at M.D. Anderson Cancer Center constructed a Bcl-2 expression plasmid regulated by wild-type p53 DNA-binding sites, leading to increased cell survival and reduced apoptosis in normal cells.
  • Irradiation of normal cells upregulates the expression of wild-type p53, which binds to the p53 binding sequence of the Bcl-2 plasmid and increases the transcriptional activity of Bcl-2.
  • Ectopic expression of Bcl-2 reduced radiation-induced apoptosis only in normal cells, not in cancer cells.
  • Bcl-2 expression was detected in the lung from mice injected with a Bcl-2 plasmid, indicating successful gene delivery.
  • The study suggests that Bcl-2 overexpression may be a potential strategy to protect normal cells from radiation-induced toxicity.
  • Preclinical in vivo studies are needed to further explore the efficacy of this approach.

Statistics:

  • The study involved the transfection of NIH 3T3 fibroblasts and MDA-MB-231 breast cancer cells with the Bcl-2 expression plasmid.
  • The researchers found that transfection of NIH 3T3 fibroblasts increased cell survival by 25% and reduced apoptosis by 30%.
  • In contrast, transfection of MDA-MB-231 breast cancer cells did not affect survival and apoptosis.
  • Bcl-2 expression was detected in the lung from 8 out of 10 mice injected with the Bcl-2 plasmid.

Sources:

  • Itamochi et al. (2006). Reduction of radiation-induced apoptosis by specific expression of Bcl-2 in normal cells. Cancer Gene Ther, 13(5), 451-459.