An investigation of adverse effects caused by the injection of high-dose TNFα-expressing adenovirus vector into established murine melanoma

We previously reported that RGD fiber-mutant adenovirus vector carrying human TNFalpha cDNA (AdRGD-TNFalpha) could more effectively induce mouse B16 BL6 melanoma regression than conventional Ad-TNFalpha on intratumoral injection at less than 10(9) vector particles (VP). Although mice treated with either Ad type at 10(10) VP showed remarkable tumor regression due to hemolytic necrosis, severe adverse effects including extreme reduction in body weight were also induced by Ad treatment. Here, we attempted to elucidate the cause of the adverse effects to optimize the application of AdRGD-TNFalpha. More than 99% of systemically administered Ad accumulated in the liver, and the rate of Ad leakage into systemic circulation from the B16 BL6 tumors injected with AdRGD or conventional Ad at 10(10) VP was about 1% of the administered VP. Although the leaked Ad did not directly induce hepatotoxicity or body weight reduction, excessive TNFalpha produced in the tumors leaked into the blood at high concentrations and caused systemic inflammation, tissue denaturation, and body weight reduction in mice injected intratumorally with AdRGD-TNFalpha or Ad-TNFalpha at 10(10) VP. Our results demonstrated that an exact AdRGD-TNFalpha dosage must be determined to prevent TNFalpha leakage from tumors into systemic circulation, thereby enabling safe application of AdRGD-TNFalpha to clinical melanoma gene therapy in the future.