Use of horseradish peroxidase for gene-directed enzyme prodrug therapy with paracetamol

Abstract

Gene therapy is a potential method of treating cancer with a greater degree of targeting than conventional therapies. In addition, therapy can be directed towards cells within the tumour population that are traditionally resistant to current treatment schedules. Horseradish peroxidase (HRP) can oxidise paracetamol to N-acetyl-p-benzoquinoneimine via a one-electron pathway. Incubation of human cells expressing HRP with 0.5 -10 mM paracetamol reduced clonogenic survival, but had little effect on control cells. A small increase in apoptosis was seen and a decrease in the number of cells undergoing mitosis, consistent with reports in hepatocytes using higher paracetamol concentrations. The cytotoxicity was also seen under conditions of severe hypoxia (catalyst induced anoxia), indicating that the HRP/paracetamol combination may be suitable for hypoxia-targeted gene therapy.

In vivo characterization of horseradish peroxidase with indole-3-acetic acid and 5-bromoindole-3-acetic acid for gene therapy of cancer

“…In vitro enzyme activity was lower in transiently transfected FaDu cells (0.008 ± 0.2 U mg -1 protein, unpublished data) than stable transfectants 18 (HRP8: 0.08±0.003 U mg -1 protein). Yet, in vitro effectiveness of the HRP/IAA system in stable transfectants 11,18 was less than in transient transfectants of the same cell line. 4 Enzyme activity per cell may be more important than enzyme activity per population of cells.…”

Recombinant horseradish peroxidase variants for targeted cancer treatment

“…Potential strategies to overcome this challenge are antibody‐directed enzyme prodrug therapy (ADEPT) and gene‐directed enzyme prodrug therapy (GDEPT) which allow the selective release of a cytotoxic agent from a non‐toxic prodrug at the site of the tumor (e.g., ). In this respect numerous studies investigated the cytotoxic effect of the prodrug indole‐3‐acetic acid (IAA) after oxidation with the heme‐containing enzyme horseradish peroxidase (HRP, EC 1.11.7.1; ). In 1998, Folkes et al.…”

Bystander or No Bystander for Gene Directed Enzyme Prodrug Therapy

“…To test our hypothesis, a series of established (HSV-TK/GCV, NfsB/CB1954) and novel GDEPT combinations (NfsB/SN26634 [ 64 ], NfsB/MTZ [ 57 ], CYPOR/SN26955 and SN28141 [ 88 ], horseradish peroxidase/paracetamol [ 90 ]) were compared in endothelial cells in culture (Dachs et al . [ 91 ] and unpublished data).…”