Research article

Prodrug converting enzyme gene delivery by L. monocytogenes

Jochen Stritzker^1,2*, Sabine Pilgrim^3,1, Aladar A Szalay^4,1,2 and Werner Goebel^1,5

• * Corresponding author: Jochen Stritzker jochen.stritzker@biozentrum.uni-wuerzburg.de

Author Affiliations

¹ Biocenter (Microbiology), University of Würzburg, Am Hubland, D-97074 Würzburg, Germany

² Genelux Corporation, San Diego Science Center, San Diego, USA; Institute for Biochemistry, Biocenter and Institute for Molecular Infectious Biology, University of Würzburg, Würzburg, Germany

³ Dade Berhing Marburg GmbH – A Siemens Company, Marburg, Germany

⁴ Virchow Center for Biomedical Research, School of Medicine, University of Würzburg, Würzburg, Germany

⁵ Max von Pettenkofer Institute for Hygiene and Medical Microbiology, Ludwig Maximillians University, Munich, Germany

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BMC Cancer 2008, 8:94 doi:10.1186/1471-2407-8-94

Published: 10 April 2008

Abstract

Background

Listeria monocytogenes is a highly versatile bacterial carrier system for introducing protein, DNA and RNA into mammalian cells. The delivery of tumor antigens with the help of this carrier into tumor-bearing animals has been successfully carried out previously and it was recently reported that L. monocytogenes is able to colonize and replicate within solid tumors after local or even systemic injection.

Methods

Here we report on the delivery of two prodrug converting enzymes, purine-deoxynucleoside phosphorylase (PNP) and a fusion protein consisting of yeast cytosine deaminase and uracil phosphoribosyl transferase (FCU1) into cancer cells in culture by L. monocytogenes. Transfer of the prodrug converting enzymes was achieved by bacterium mediated transfer of eukaryotic expression plasmids or by secretion of the proteins directly into the host cell cytosol by the infecting bacteria.

Results

The results indicate that conversion of appropriate prodrugs to toxic drugs in the cancer cells occured after both procedures although L. monocytogenes-mediated bactofection proved to be more efficient than enzyme secretion 4T1, B16 and COS-1 tumor cells. Exchanging the constitutively P_CMV-promoter with the melanoma specific P_4xTETP-promoter resulted in melanoma cell-specific expression of the prodrug converting enzymes but reduced the efficiencies.

Conclusion

These experiments open the way for bacterium mediated tumor specific activation of prodrugs in live animals with tumors.