We additionally found that the level of survivin increased slightly as the normal cell lines were passed in vitro for many passages. A low level of survivin expression in normal cell lines may be necessary for the cells to survive in culture.We detected a high level of survivin in of breast cancer tissues but not in any normal breast tissues.Using an antibody specific for cleaved active L-α-Phosphatidylcholine caspase fragments, we also found that breast cancer tissues that were positive for survivin had a high level of active caspase as well.However, active caspase fragments were not detected in any normal tissues. Four breast cancer tissues that did not have a detectable level of active caspase fragments also lacked expression of survivin. We additionally examined caspase activity in the tissue lysates using a fluorometric assay with a caspase substrate. We also analyzed caspase activity from breast cancer and normal tissue lysates in vitro. This Captopril increase was greater in SW cells with a very high level of caspase activity. On the other hand, few apoptotic cells were observed in normal cell lines such as HDF and MCFA after overexpression of survivinTA or XAF gene alone or a combination of both genes. We also found a high basal level of XAF in MCFA cells but not MDAMB cells, which further suggested that the level of XAF was downregulated in human breast cancer cells. It has been shown that XIAP inhibits the caspase activation and blocks activity of active caspase and caspase. We have examined caspase and caspase activities in tumor and normal cell lines after transduction of the cells with the adenoviral vectors for days.We observed increases in caspase and caspase activity after blocking XIAP function by XAF in several tumor cell lines. However, inhibition of survivin function by survivinTA increased caspase activity but did not significantly increase the caspase activity in the tumor cell lines. Expression of survivinTA or XAF in normal cell lines also slightly increased caspase or caspase activity in those cells. However, the levels of capase and capase activity in normal cells after the adenoviral vector transduction were still very low as compared with the tumor cells.A promising approach to induce apoptotic cell death or to enhance the effectiveness of chemotherapy drugs is to target the apoptotic pathway directly.A high level of survivin was detected in all breast, pancreatic, and colon cancer cell lines examined.Expression of survivin was very low in normal cell lines such as MCFA and HDF.Expression of XIAP was found in both normal and tumor cell lines.However, the level of XIAP was upregulated in all tumor cell lines.The level of cleaved caspase fragments in the cell lysates was examined using antibodies specific for active caspase or PARP.A positive control sample was obtained from treating the herpes simplex virus thymidine kinase genemodified BXPC cells with gml ganciclovir. We found that expression of procaspase and procaspase induced apoptotic cell death in both tumor and normal cell lines.Expression of procaspase gene only induced a low level of apoptotic cells in the cell lines.