DEVELOPMENT OF AN ADENOVIRUS VECTOR WITH TETRACYCLINE-REGULATABLE HUMAN TUMOR-NECROSIS-FACTOR-ALPHA GENE-EXPRESSION

Tumor necrosis factor alpha (TNF-alpha) is a multifunctional cytokine with direct antitumor activity. However, clinical trials using TNF-alp ha for cancer treatment have been disappointing due in part to its sev ere side effects, and it has been estimated that TNF-alpha therapy wou ld be effective only at 5-25 times the maximum tolerated dose, We have recently modified a tetracycline (Tc) repressor/operator-based mammal ian gene expression system and have generated a Tc-responsive recombin ant adenovirus vector, AdVtTA.TNF-alpha. A variety of human tumor cell s and T lymphocytes transduced by AdVtTA.TNF-alpha secreted high-titer (5,000-100,000 pg/10(6) cells/24 h) and biologically active TNF-alpha in the absence of Tc. Expression of TNF-alpha in the transduced cells was nondetectable when the culture medium contained as little as 0.1 mu g/ml of Tc. At least a fraction of the clonogenic cells from human peripheral blood stem cell concentrates were also transducible by AdVt TA.TNF-alpha. The availability of this type of adenovirus vector opens a door to tumor- or organ-specific delivery of high-dose TNF-alpha an d other therapeutic gene products for systemic cancer gene therapy.