[7][“Agonist K”

Human tumor and normal cell lines were transduced with adenoviral vectors containing survivinTA or XAF gene.An adenoviral XY1 vector expressing only a GFP gene was used as a control vector.Consistent with the hypothesis, our results showed that expression of survivinTA or XAF gene by adenoviral vectors induced apoptosis preferentially in tumor cell lines but not in normal cell lines. B, levels of survivin and active caspase fragments in breast cancer tissues and normal breast tissues obtained from breast reduction surgery.C, comparison of average caspase activity detected by a fluorometric assay in cell lysates obtained from normal and breast cancer tissues.N, normal tissue; C, cancer tissue; LN, draining lymph node.The same lysate samples were also examined for the caspase activity using a fluorometric assay.C, average caspase activity from normal and cancer tissue samples were compared.The caspase activity was fold higher in the tumor tissues than that of the normal tissues.However, the question regarding which molecular targets in the apoptotic pathway have the greatest potential for tumor specific therapy has yet to be answered.To address this question, we have examined the regulatory factors in the apoptotic pathways in human tumor and normal cells.We found that in comparison with normal cell lines and tissues, many tumor cell lines and tissues had activated apoptotic signaling such as high levels of caspase and caspase activities in the absence of apoptotic stimuli.Experimental results from our study additionally revealed that these human tumor cell lines and tissues also had high levels of survivin and XIAP.Cellular apoptosis or survival results from a balance between apoptotic and survival factors.One of the logical therapeutic approaches for induction of apoptosis in tumor cells is to activate caspases.Several studies have shown that overexpression of initiator caspase and caspase or executioner caspase and caspase genes induced apoptotic cell death in human tumor cell lines induced apoptosis in the absence of upstream stimuli in and MCF cells. The tumor and normal cell lines were cultured in well plates for hand then transduced with the adenoviral vector at a MOI of pfu.The percentage of viable cells at days after transduction was determined by staining the cells with crystal violet followed by extraction of the dye for measuring absorbance at nm.Each value in the bar figure represents a mean value of three to four repeat samples.Similar results were found in three repeat experiments.Thus, our results suggest that activation or expression of caspases alone is not a powerful strategy for induction of apoptosis in cancer cells and does not have specificity for tumor cells.Recently, studies have revealed that tumor cells have acquired various resistant mechanisms to apoptosis.At present, the role and mechanism of increases in IAP proteins during the process of tumorigenesis are still unknown.In particular, it is not known how survivin is upregulated in tumors because this protein is not expressed in most normal adult tissues.Our results that human tumor cells have both activated apoptotic signaling and elevated antiapoptotic factors are in agreement with those of several recent studies that detected a high level of caspase expression or active caspase in various human tumor tissues.

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