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Extracellular Bad fused to toxin transport domains induces apoptosis

Makoto Ichinose1, Xiu-Huai Liu, Naoshi Hagihara

  • 1Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.

Cancer Research
|March 13, 2002
PubMed

Insights

Extracellular Bad protein, fused to diphtheria toxin, can enter cancer cells to induce apoptosis. Mutating Bad to prevent inactivation significantly increased its cancer-killing potency.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Biology

Background:

  • Bad is a proapoptotic protein inactivated by phosphorylation.
  • This inactivation contributes to malignancies like glioblastoma and prostate cancer.

Purpose of the Study:

  • To investigate if extracellular Bad can be delivered into cells to induce apoptosis.
  • To develop a novel cancer therapy by targeting Bad delivery.

Main Methods:

  • Genetically fused mouse Bad gene to diphtheria toxin translocation and receptor-binding domains (DTTR).
  • Created mutated Bad proteins (S112A S136A and S112D S136A) to alter phosphorylation and activity.
  • Assessed cytotoxicity and subcellular distribution of Bad-DTTR fusion proteins in human glioma cells.

Main Results:

  • Bad-DTTR fusion protein demonstrated dose-dependent cytotoxicity to glioma cells.
  • Mutating Bad phosphorylation sites (S112A S136A) increased toxicity by over 5-fold.
  • The mutated Bad-DTTR entered cells, altered Bcl-X(L) distribution, and induced apoptosis.

Conclusions:

  • Extracellular Bad can be effectively delivered into cells using a bacterial toxin's transport domain.
  • Engineered Bad-DTTR fusion proteins show potential for inducing apoptosis in cancer cells.
  • Targeted delivery of apoptosis-inducing proteins offers a promising strategy for cancer treatment.

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