Adenovirus-mediated human endostatin gene delivery demonstrates strain-specific antitumor activity and acute dose-dependent toxicity in mice

Purified recombinant mouse endostatin protein has been reported to regress established murine solid tumors by inhibiting the proliferation of endothel ial cells. To develop a clinical gene therapy strategy with endostatin, we cloned the cDNA of human endostatin by RT-PCR from human placenta. A 150-bp sequence encoding the IgG leader peptide was fused in frame to the 5' end of the endostatin cDNA and recombinant adenoviruses, AdENDO-YFP and AdENDO, carrying endostatin gene expression cassettes were rescued. AdENDO-YFP inf ects cultured mammalian cells at high efficiency and expresses a biological ly active human endostatin in secreted form at high levels both in vitro an d in vivo. When delivered in vivo, a strain-specific expression pattern was observed, with the highest and longest endostatin expression in 129/J mice . After systemic delivery of 2 x 10(9) PFU of AdENDO-YFP into 129/J mice, h uman endostatin expression was achieved at a mean value of 1.34 +/- 0.42 mu g/ml of serum (n = 6) and inhibition of lung metastasis was observed in an EOMA tumor model. However, high dose intravenous delivery of AdENDO-YFP and AdENDO was associated with severe acute toxicity in recipient mice that in cluded loss of weight, bleeding, and death of animals. These events were no t observed with the injection of identical doses of a control adenovirus th at did not contain the endostatin gene. Because the endostatin adenovirus-a ssociated acute toxicity was also observed in immunodeficient NCRNU-M nude mice, the toxicity does not appear to be the result of the immunogenicity a gainst human endostatin or the EYFP protein.