IN-VIVO MARKING OF SPONTANEOUS OR VACCINE-INDUCED FIBROSARCOMAS IN THE DOMESTIC HOUSE CAT, USING AN ADENOVIRAL VECTOR CONTAINING A BIFUNCTIONAL FUSION PROTEIN, GAL-TEK

We evaluated the ability of a replication-deficient, recombinant adeno viral vector to transfer the bifunctional gene GAL-TEK, which expresse s a marking/therapeutic gene product, to naturally occurring cat fibro sarcomas in situ. GAL-TEK contains an in-frame fusion of the bacterial LacZ gene for histochemical marking of tumors with beta-galactosidase (beta-Gal) and the HSV tk gene for enzyme-prodrug activation of the p rodrug ganciclovir (GCV) to induce selective tumor cell killing. GAL-T EK bifunctional marking and cell killing activities were tested in vit ro after adenoviral vector infection of HT1080 human fibrosarcoma cell s. The tk activity of GAL-TEK is shown to be almost as potent as HSV t k to catalyze conversion of GCV to GCV nucleotides and promote selecti ve cell killing. Using 8 cats with recurring 2.5-cm(2) fibrosarcomas t hat either arose spontaneously or were induced by vaccine, we determin ed experimentally the administration routes and times required for opt imum GAL-TEK gene transfer by beta-Gal histological staining and rever se transcriptase polymerase chain reaction to the multiple compartment s of the growing fibrosarcomas consonant with minimizing collateral in fection of neighboring tissues and other unwanted side effects.