01. Gene therapy Boulikas.pdf - Gene therapy & Molecular Biology

Gene Therapy and Molecular Biology Vol 1, page 75
Figure 25. Eradication of peritoneal carcinomatosis with HSV-tk plus GCV. Intraperitoneal injection to rats of DHD/K12 colon
carcinoma cells stably expressing the HSV-tk gene caused peritoneal carcinomatosis at day 21 (A). The animal whose intraperitoneal
cavity is shown in (B) was treated with HBSS buffer alone and the animal shown in (C) was treated with GCV for 5 days at 150mg/Kg.
The letter “T” indicates the peritoneal tumor nodes. From Lechanteur C, Princen F, Bue SL, Detroz B, Fillet G, Gielen J, Bours V, and
Merville M-P (1997) HSV-1 thymidine kinase gene therapy for colorectal adenocarcinoma-derived peritoneal carcinomatosis. Gene
Ther 4, 1189-1194. Reproduced with the kind permission of the authors (Vincent Bours, University of Liège, Belgium) and of Stockton
Press.
Infection of the human breast cancer cell line, MDA-
MB-231, with a recombinant adenovirus expressing the
Escherichia coli CD resulted in high levels of cytosine
deaminase enzyme activity and infected cells became
1000-fold more sensitive to 5-FC than cells infected with a
control adenovirus; only 10% of infected cells in a
population were needed to induce complete cytotoxicity of
noninfectious cells exposed to 5-FC via bystander effects.
Direct injection of the CD-adenovirus into human breast
tumor xenografts in nude mice, followed by daily
intraperitoneal injection of 5-FC was sufficient to inhibit
tumor growth (Li et al, 1997).
F. Bacterial purine nucleoside
phosphorylase (PNP) gene
Another suicide gene/prodrug couple is the E. coli
DeoD gene which encodes the purine nucleoside
phosphorylase (PNP). The E. coli PNP, unlike the
mammalian endogenous PNP, can utilize certain
adenosine analogs as substrates including nontoxic purine
nucleosides converting them to very toxic adenine
analogs; these substrates include 6-methylpurine-2’-
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deoxyriboside (MeP-dR) and arabinofuranosyl-2fluoroadenine
monopho-sphate (F-araAMP) commercially
known as fludarabine. This enzyme converts the 6methylpurine
deoxyribose (MeP-dR) prodrug into the
diffusible, toxic 6-methylpurine and can become a
powerful suicide gene under these conditions (Sorscher et
al, 1994).
The significant advantages in eradicating experimentally-induced
human tumors in nude mice with this
system were: (i) the bystander effect was 2-3 orders of
magnitude higher than with HSV-tk/GCV and tumor
eradication could be seen only after 3 doses of PNP/MePdR
treatment, (ii) the MeP-dR and F-araAMP crossed
readily the cell membrane unlike GCV, and (iii)
PNP/MeP-dR could kill both proliferating and
nonproliferating tumor cells as has been demonstrated by
eradication of the slowly-growing D54MG glioma tumors
expressing the bacterial PNP gene in nude mice after
treatment with MeP-dR (Figure 26; Parker et al, 1997).