Efficacy and safety of SAGA in the treatment of breast cancer

2257 Survivin , a member of the inhibitor of apoptosis (IAP) family of proteins, is widely expressed in transformed cell lines and in different primary cancer cells. It is not expressed in many non-malignant adult tissues, but is essential for fetal development, as demonstrated by conventional gene-deletion experiments in mice that show embryonic lethality at day 4-6 of development. In adult cancers, including lymphoma and many epithelial carcinomas (colon, breast, gastric) the expression level of survivin, as assayed by immunohistochemical analysis and RT-PCR, correlates with overall survival. We designed a suicide gene therapy approach driven by the survivin promoter to express the active form of the cytolytic gene granzyme B, emulating in part the mode of action of cytotoxic T-lymphocytes (CTL) and natural killer (NK) cells, and designated this SAGA. We performed in vitro studies to test the efficacy of this system on model breast cell lines in a panel encompassing neoplastic and non-transformed cells. SAGA induced apoptosis exclusively in the malignant cancer cell lines. Following SAGA treatment multiple granzyme B inducible pathways were activated. These included caspase 3, mitochondrial potential changes, and activation of ICAD, as evidenced by DNA fragmentation. The failure of SAGA to induce apoptosis in a non-transformed cell line created from healthy breast tissue (MCF10A) suggests that SAGA will not adversely affect surrounding healthy mammary tissue in a breast tumor undergoing SAGA-treatment. We also evaluated of the safety of SAGA treatment in vivo . To this end, we injected SAGA hydrodynamically into the tail vein of immunocompetent mice (FVB). We confirmed the presence of the plasmid in a range of different tissues by PCR. SAGA-treated mice were healthy with no weight loss, no signs of anemia or alopecia, and no increased apoptosis observed in select tissues including thymus, spleen and bone marrow. Additionally, SAGA-treated mice had no behavioral changes, and fed ad libitum as prior to injection with no detectable diarrhea. No adverse symptoms were detected during the study period of 60 days. Overall our data suggests that SAGA is a highly efficient and safe therapeutic alternative at inhibiting tumor cell growth and decreasing tumor cell number, in a tumor-specific fashion. Testing in subcutaneous and orthotopic breast cancer mouse xenograft models is currently under way. Taken together, our data suggests a promising future for SAGA in the treatment of breast cancer.