Cancer gene therapy using a survivin mutant adenovirus

We have constructed a replication-deficient adenovirus encoding a nonphosph orylatable Thr(34) --> Ala mutant of the apoptosis inhibitor survivin (pAd- T34A) to target tumor cell viability in vitro and in vivo. Infection with p Ad-T34A caused spontaneous apoptasis in cell lines of breast, cervical, pro state, lung, and colorectal cancer. in contrast, pAd-T34A did not affect ce ll viability of proliferating normal human cells, including fibroblasts, en dothelium, or smooth muscle cells. Infection of tumor cells with pAd-T34A r esulted in cytochrome c release from mitochondria, cleavage of approximatel y 46-kDa upstream caspase-9, processing of caspase-3 to the active subunits of approximately 17 and 19 kDa, and increased caspase-3 catalytic activity . When compared with chemotherapeutic regimens, pAd-T34A was as effective a s taxol and considerably more effective than adriamycin in induction of tum or cell apoptosis and enhanced taxol-induced cell death. In three xenograft breast cancer models in immunodeficient mice, pAd-T34A suppressed de novo tumor formation, inhibited by approximately 40% the growth of established t umors, and reduced intraperitoneal tumor dissemination. Tumors injected wit h pAd-T34A exhibited loss of proliferating cells and massive apoptosis by i n situ internucleosomal DNA fragmentation. These data suggest that adenovir al targeting of the survivin pathway may provide a novel approach for selec tive cancer gene therapy.