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E. coli NfsA: an alternative nitroreductase for prodrug activation gene therapy in combination with CB1954

S O Vass1, D Jarrom, W R Wilson

  • 1Cancer Research UK Institute for Cancer Studies, University of Birmingham, Birmingham, UK.

British Journal of Cancer
|May 21, 2009
PubMed

Insights

The nitroreductase NfsA enzyme shows superior activation of the cancer prodrug CB1954 compared to NfsB, leading to enhanced cell killing and bystander effects. This finding improves prodrug activation gene therapy strategies.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cancer Therapy

Background:

  • Prodrug activation gene therapy utilizes tumor-expressed enzymes to convert non-toxic prodrugs into cytotoxic agents.
  • The Escherichia coli nitroreductase NfsB is currently used with prodrug CB1954 in clinical trials.
  • NfsA, another E. coli nitroreductase, has known activity with nitrofuran antibiotics but its efficacy with CB1954 was uncharacterized.

Purpose of the Study:

  • To compare the efficacy of nitroreductase NfsA and NfsB in activating the prodrug CB1954.
  • To evaluate the resulting cell sensitivity and bystander effects mediated by NfsA and NfsB.
  • To assess NfsA's effectiveness with alternative prodrugs.

Main Methods:

  • In vitro kinetic analysis of CB1954 activation by NfsA and NfsB using NADPH cofactor.
  • Expression of NfsA and NfsB in bacterial and human cells to determine drug sensitivity.
  • Analysis of CB1954 reduction sites by NfsA and NfsB.
  • Assessment of cell sensitization to nitrofurans and dinitrobenzamide mustard (DNBM) prodrugs.

Main Results:

  • NfsA demonstrated superior in vitro kinetics for CB1954 activation compared to NfsB.
  • Cells expressing NfsA showed 3.5- to 8-fold greater sensitivity to CB1954 than those expressing NfsB.
  • NfsA preferentially reduced the 2-NO(2) group of CB1954, enhancing the bystander effect.
  • NfsA was more effective than NfsB in sensitizing cells to nitrofurans and DNBM prodrugs.

Conclusions:

  • NfsA is a more potent enzyme than NfsB for CB1954 activation in prodrug gene therapy.
  • NfsA enhances both direct tumor cell killing and the bystander effect, improving therapeutic potential.
  • NfsA offers broader applicability for sensitizing cancer cells to various prodrugs.

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