Generation of Fiber-Mutant Recombinant Adenoviruses for Gene Therapy of Malignant Glioma

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Abstract
Recombinant adenovirus (Adv)-mediated gene transduction is a powerful technology for cancer gene therapy. In this article, we report the generation of a fiber-mutant Adv vector, using the Adv genomic DNA–terminal protein complex (DNA–TPC) cotransfection method. First, a fiber-mutant construct in a plasmid carrying the right-side two-thirds of the human adenovirus type 5 (Ad5) genome (pTR) was cotransfected with Ad5 DNA–TPC, yielding the recombinant Adv with the desired fiber mutation. The DNA–TPC from the mutant Adv was then utilized to produce a second-step recombinant Adv with an expression cassette in the place of E1. By this procedure, we generated a fiber mutant, F/K20, that has a linker and a stretch of 20 lysine residues added at the C terminus of the fiber. By using Adv carrying a reporter lacZ gene (AxCAZ2) with either F/K20 or wild-type fiber (F/wt), we examined the transduction efficiency of F/K20-Adv. No significant difference in the transduction efficiency between F/K20 and F/wt-Adv was observed for a human fibroblast line, WI-38, or various tumor cell lines, including melanoma, prostate, esophageal, and pancreatic cancer lines. In clear contrast, F/K20-Adv showed a remarkably enhanced efficiency in genetic transduction of human glioma cells. In all four human glioma lines tested, the multiplicities of infection (MOIs) for transduction of 50% of the population (ED50) were decreased with F/K20-Adv compared with F/wt-Adv: 7-fold for T98G, 14-fold for U251, 9-fold for U373, and 42-fold for U87 cells. Therefore, we attempted to apply F/K20-Adv for gene therapy of malignant glioma. Glioma cells infected with F/K20-Adv carrying genes for interleukin 2 or interleukin 12 produced a high level of each cytokine at a much lower MOI than did cells infected with F/wt-Adv. Infection with F/K20-Adv carrying the wild-type p53 tumor suppressor gene resulted in an enhanced level of p53 protein expression and an increased incidence of F/K20-Adv in transduction efficiency for malignant glioma, providing promising tools for gene therapy. Yoshida et al. report the construction and analysis of mutant adenoviral vectors with a stretch of 20 lysine residues added at the C terminus of the fiber (F/K20). The mutation greatly enhanced the transduction efficiency of human glioma cells. F/K20-Adv vectors designed for the overexpression of cytokine genes (i.e., IL-2 and IL-12), or of the tumor suppressor p53 gene described here, will be promising tools for gene therapy of malignant glioma.