Adenovirus-mediated gene transfer in the treatment of pancreatic cancer.

Abstract

Suicide gene therapy is a new experimental form of cancer chemotherapy that is currently being evaluated in human trials. To evaluate the killing effects of the cytosine deaminase (CD) gene mediated by an adenovirus vector on human pancreatic carcinoma in vitro and in vivo. The CD gene was cloned into pAdTrack-CMV-CD, pAdTrack-CMV-CD, and pAdEasy-1, which underwent recombination in bacteria BJ5183. The newly recombinant Ad-CD containing green fluorescent protein was propagated in 293 cells and purified by cesium chloride gradient centrifugation. The human pancreatic carcinoma cell line PaTu8988/SW1990 was infected with this virus, and then 5-fluorocytosine (5-FC) was added; XTT assay was used to estimate relative numbers of viable cells. An in vivo model of pancreatic cancer was established by injecting 1.0 x 10(7) PaTu8988/SW1990 cells subcutaneously in Balb/c nude mice. When tumors were palpable, Ad-CD was injected into each tumor, and 5-FC was administered. The positive clones were selected by endonuclease digestion of the combinations, and the concentration of viral liquids containing the CD gene was 2 x 10(11) pfu/mL. It was found that significant cytotoxic activities were possessed by 5-FC for CD gene-transduced PaTu8988/SW1990 cells, but there was little effect on the nontransduced pancreatic carcinoma cells. The antitumor effect was observed in PaTu8988/SW1990 xenografts from nude mice with in situ CD gene transduction. These results indicate that the CD gene mediated by adenovirus has a high level of infectivity and is efficient for gene therapy for pancreatic carcinoma.