Transgene expression of α tumor necrosis factor with mutations D142N and A144R under control of human telomerase reverse transcriptase promoter eradicates well-established tumors and induces long-term antitumor immunity

Recombinant adenoviral vectors (AdVTNF-α) expressing α tumor necrosis factor (TNF-α) under control of cytomegalovirus (CMV) promoter have been used in cancer gene therapy. To reduce its cytotoxicity, we constructed a recombinant AdV TERT mTNF-α expressing a mutant TNF-α (mTNF-α) with mutations at D142N and A144R under control of human telomerase reverse transcriptase (hTERT) promoter for treatment of well-established ovalbumin (OVA)-expressing murine B16 melanoma (BL6-10 OVA) (6 mm in diameter). We demonstrated that the mTNF-α with mutations at D142N and A144R has less in vitro cytotoxicity, but maintains its functional effect in the stimulation of T-cell proliferation. The in vitro and in vivo transgene expressions under control of hTERT promoter are highly restricted in tumor cells compared with those under the control of the CMV promoter. AdV TERT mTNF-α gene therapy by intratumoral injection of AdV TERT mTNF-α vector (2 × 10⁹ PFU) expressing the mutant mTNF-α under control of hTERT promoter reduces its in vivo toxicity, eradicates well-established BL6-10 OVA tumors in 4/10 tumor-bearing mice, and induces OVA-specific CD8⁺ T-cell-mediated long-term antitumor immunity. Therefore, AdV TERT mTNF-α gene therapy may be very useful in the immunotherapy of cancer.