Experimental Gene Therapy for Brain Tumors Using Adenovirus-Mediated Transfer of Cytosine Deaminase Gene and Uracil Phosphoribosyltransferase Gene with 5-Fluorocytosine

Abstract

Transduction of the cytosine deaminase (CD) gene into tumor cells followed by administration of 5-fluorocytosine (5-FC), called 5-FC/CD gene therapy, was created as suicide gene therapy for various cancers. The uracil phosphoribosyltransferase (UPRT) gene, which is absent from mammalian cells, directly converts 5-fluorouracil (5-FU) to 5-fluorouridine 5'-monophosphate. We evaluated whether the coexpression of CD and UPRT genes could generate a synergistic antitumor effect on experimental brain tumors. In vitro study showed that 9L cells, transduced with the UPRT gene by an adenovirus, were 16 times more sensitive to 5-FU, and CD + UPRT-transduced cells were 6,000 times more sensitive to 5-FC than parent cells, indicating that the acquisition of CD and UPRT further increased the 5-FC sensitivity of 9L cells compared with cells transduced with CD alone. In a rat brain tumor model, decreased amounts of CD and UPRT vectors were inoculated into the tumors to detect any additional effect of UPRT. CD and UPRT coexpression followed by 5-FC administration showed an antitumor effect as detected by sequential magnetic resonance imaging. This therapy significantly prolonged animal survival. These results suggest that 5-FC/CD + UPRT gene therapy can enhance the antitumor effect of 5-FC/CD gene therapy. Consequently, this approach might be a more feasible modality for the treatment of malignant brain tumors.

Enhanced suicide gene effect by adenoviral transduction of a VP22-cytosine deaminase (CD) fusion gene

“…When combining UPRT with the CD gene, the deamination of 5-FC to 5-FU can be augmented by the subsequent enzymatic conversion into 5-fluoro-UMP. 43 Additionally, cytosine deaminase from bakers' yeast, Saccharomyces cerevisiae (yeast CD, yCD), is reported to toxify 5-FC more efficiently than bacterial CD. 44 Joining yeast CD (FCY-1) with yeast UPRT (FUR-1) as a fusion protein is described to be even more potent in killing tumour cells.…”

Antitumor effect of genetically engineered mesenchymal stem cells in a rat glioma model

“…3 Recent developments in molecular biology have made intracranial gene therapy a new option for the treatment of malignant glioma. Although successful treatment of experimental glioma by suicide gene therapy combining herpes simplex virus thymidine kinase with ganciclovir, 4,5 cytosine deaminase with 5-fluorocytosine, 6,7 or cytokine gene therapy has been reported, the results of clinical trials using this approach have been disappointing. 8,9 In these studies, adenoviral vectors were mainly employed as in many current gene therapy strategies because of their high infectivity for nondividing as well as proliferating tumor cells.…”

A novel fusion suicide gene yeast CDglyTK plays a role in radio-gene therapy of nasopharyngeal carcinoma

“…[23][24][25] In our study, we utilized a novel fusion gene yCDglyTK under the control of a synthetic promoter CE, the CMV enhancer increasing the regulation force of Egr-1 promoter proven by our previous study, 26 to kill NPC cells by combining with radiation. The suicide vector p11MsCEyCDglyTK was transferred onto CNE-2 cells A novel fusion gene yCDglyTK for cancer therapy K Xia et al and this suicide gene was successfully expressed at both mRNA and protein levels.…”