Adenoviral Transduction Efficiency of Ovarian Cancer Cells Can Be Limited by Loss of Integrin β3Subunit Expression and Increased by Reconstitution of Integrin αvβ3

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Abstract
Recombinant adenoviruses expressing a therapeutic gene are currently used in clinical studies for treatment of advanced ovarian cancer. We therefore tested whether the expression level of primary (CAR) and secondary adenovirus receptors (integrins) was predictive of the efficacy of adenoviral gene transfer in ovarian cancer cells. Adenoviral transduction efficiency (ATE) was determined with an E1-deleted adenovirus type 5 expressing β-galactosidase under a CMV promoter (AdGal). ATE was studied in relationship to the expression level of both CAR (coxsackie and adenovirus receptor) and integrins. A representative sample of 25 permanent human cell lines established from advanced ovarian cancer in our laboratory and the OV-2774 cell line were tested. Overall, ATE increased with increasing titers of AdGal. At a given titer of 50 infectious units per cell, transduction efficiency varied from 6 to 94% among the individual cell lines. All cell lines expressed CAR and integrin αvβ5, but no relation between ATE and expression level of CAR or αvβ5 integrin was observed. In contrast, cell lines with poor ATE, despite expressing high levels of CAR, lacked expression of integrins αvβ3 and α5β1. Reconstitution of αvβ3 integrin by reexpressing the β3 subunit significantly enhanced ATE of ovarian cancer cells. In ovarian cancer, neither integrins nor CAR alone appear to be potentially useful predictive markers for ATE by serotype 5 adenovirus in clinical gene therapy. A minimum level of CAR necessary for binding of adenoviruses was observed in all tested ovarian cancer cell lines. Loss of αvβ3 integrin is frequently associated with advanced stages of ovarian cancer and can significantly reduce ATE.