A p75 tumor necrosis factor receptor-specific mutant of murine tumor necrosis factor alpha expressed from an adenovirus vector induces an antitumor response with reduced toxicity

The toxic effects of tumor necrosis factor alpha (TNF alpha) have greatly l imited its use in tumor therapy. Recently, clear evidence has been obtained linking the p55 TNF receptor (TNFR) to the induction of systemic toxicity. We have generated a p75 murine TNFR (mTNFR)-specific mutant of mTNF alpha (D142 N-A144R), cloned this gene into a recombinant adenovirus vector (Ad-7 5), and studied its efficacy for tumor immunotherapy of a murine transgenic breast cancer model. Cell culture supernatants from Ad-75-transduced cells showed no cytotoxic activity on L929 cells, but retained the ability to in duce proliferation of a murine T-cell line (CT6); this activity was not blo cked by soluble p55 mTNFR. Furthermore, it was shown that the mutant form o f mTNF alpha was able to coimmunoprecipitate only with the p75 mTNFR and no t with the p55 mTNFR. Tumors injected with Ad-75 became necrotic, and mice injected with less than or equal to 1 x 10(9) plaque-forming units showed n o mortality, whereas both wild-type murine and human TNF vectors induced le thality at doses of 1 and 5 x 10(8) plaque-forming units. All Ad-TNF vector s induced partial or permanent tumor regressions, with cured mice showing i mmune memory against the tumor. These results demonstrate that a p75 mTNFR agonist expressed from a recombinant adenovirus vector does not induce mort ality at doses that cause tumor regression.