In vivo efficacy and toxicity of 5-fluorocytosine/cytosine deaminase gene therapy for malignant gliomas mediated by adenovirus

Abstract

We evaluated the therapeutic efficacy and neurotoxicity of adenovirus-mediated transduction of the cytosine deaminase (CD) gene and 5-fluorocytosine (5-FC) for experimental malignant brain tumors. The 5-FC sensitivity in 9 L cells infected by an adenovirus vector expressing CD (AdexCACD) was increased 1700-fold compared with control cells. Rats bearing 9 L brain tumors were treated with an intratumoral injection of AdexCACD followed by intraperitoneal administration of 5-FC. The rats demonstrated remarkable inhibition of tumor growth by magnetic resonance imaging, and 7 of 10 rats survived for Ͼ90 days. To evaluate the potential side-effects of the 5-FC/CD gene therapy, rats were treated with an intracerebral injection of AdexCACD into the right basal ganglia and with 5-FC. The magnetic resonance imaging showed a highly enhanced area on the gadollinium-enhanced T1-weighted image at 18 days postinjection. Pathologically, this corresponded to an area of necrosis with surrounding apoptotic cells. In addition, there was demyelination and gliosis with enlargement of the lateral ventricles. These results suggest that the 5-FC/CD gene therapy may provide an anticancer effect for malignant brain tumors in humans, but also show that there are neurotoxic effects on normal brain tissue. Cancer Gene Therapy (2000) 7, 74 -82

Therapeutic effect of suicide gene-transferred mesenchymal stem cells in a rat model of glioma

“…The recombinant adenovirus vectors AdexCAEGFP and AdexCACD were prepared according to previously described methodology. 13 The viral stocks were produced by infecting 293 cells with recombinant adenoviruses, purifying using CsCl density-gradient centrifugation and dialysis against phosphate-buffered saline (PBS) containing 10% glycerol. The stocks were stored at --80 1C.…”

“…After 24 h of incubation, the supernatant was collected and its 5-FU concentration was measured by highperformance liquid chromatography. 13 5-FC chemosensitivity of 9L cell co-cultured with AdexCACDinfected MSCs…”

“…The 9L-DsR cells (5 Â 10 5 cells/5 ml) were slowly injected into the basal ganglia of the right cerebral hemisphere (3 mm lateral to the midline, 1 mm posterior to the coronal suture, 4 mm deep from the dura) with a Hamilton syringe (Hamilton, Reno, NV), according to previously published procedures. 13 Seven days after tumor inoculation, rats bearing brain tumors were re-anesthetized and received an intratumoral injection of MSC-EGFP (1 Â 10 6 cells/5 ml) or PBS only (control; 5 ml) according to the same stereotactic coordinates. At 14 days after tumor inoculation, the rats were perfused with PBS and 4% paraformaldehyde while under deep anesthesia.…”

“…12,13 Expression of the CD gene within the target cell produces an enzyme that converts the prodrug, 5-FC, to the toxic metabolite, 5-fluorouracil (5-FU). The use of 5-FC may be particularly suitable for brain tumors, because it can readily cross the blood--brain barrier.…”

“…Moreover, gene therapy with 5-FC/CD also possesses a strong bystander effect that does not require direct cell-to-cell contact. 13 In a recent study of mice bearing melanoma, it was reported that human MSCs expressing CD were associated with tumor regression. 14 Thus, in this study, we sought to evaluate the migratory ability of MSCs and the antitumor effects of 5-FC/CD gene therapy with MSC (5-FC/MSC-CD) as the targeting vehicle in vitro and in vivo models of glioma.…”