Effective Gene Transfer to Human Melanomas via Integrin-Targeted Adenoviral Vectors

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Abstract
The utility of recombinant adenoviral vectors (Adv) for gene therapy is limited by their low transduction efficiency and lack of specificity for target cells. The low transduction efficiency is often recognized as due to deficiency of the primary adenoviral receptor, the coxsackievirus-adenovirus receptor (CAR). In this paper, studies of CAR levels on human melanoma cell lines confirmed that low transduction efficiency was closely related to deficiency of the adenoviral receptor. To achieve CAR-independent gene transfer via Adv, we modified viral tropism via genetic alteration of the adenovirus type 5 (Ad5) fiber protein. Insertion of an Arg-Gly-Asp (RGD)-containing peptide in the HI loop of the fiber knob domain allowed the virus to use an alternative receptor, the integrin receptor, during the cell entry process. With this modified vector (Adv-F/RGD) transduction was increased 5- to 96-fold relative to a vector containing wild-type fiber (Adv-F/wt) in five human melanoma cells expressing integrins of the αvβ3, αvβ5 class, which are recognized by the RGD peptide motif. In contrast, no significant difference in transduction efficiency between Adv-F/RGD and Adv-F/wt was observed in 293 cells, which show high-level expression of CAR. In this study, we attempted to apply Adv-F/RGD for gene therapy for malignant melanoma. At the same multiplicity of infection, melanoma cells infected with Adv-F/RGD carrying human interleukin 2 (AxCAhIL2-F/RGD) produced a higher level of cytokine than cells infected with AxCAhIL2-F/wt. Treatment by intratumoral injection of AxCAhIL2-F/RGD was more effective than intratumoral injection of AxCAhIL2-F/wt in regressing tumors in a melanoma xenograft model. These data suggest that integrin-targeted adenoviral vectors may be a powerful tool in gene therapy for CAR-deficient melanomas.

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