Survivin inhibition by si-RNA induces apoptosis and increases sensitivity to adriamycin in human lung cancer cells with p53 mutation

2933 Survivin is a novel member of the inhibitor of apoptosis protein (IAP) family that is specifically overexpressed in cancer tissues/cells but not in normal adult tissues/cells. Survivin gene expression is downregulated in G1 and upregulated in G2/M phase in a cell cycle-dependent manner. Overexpression of Survivin has been found in many human cancers, including lung, colon, pancreas, prostate and breast, and correlates with poor prognosis. p53 is one of the tumor suppressor genes, frequently mutates in cancer tissues/cells. p53 induction and check points control in response to DNA damage induce apoptosis and correlates with drug sensitivity. Generally, cancer tissues/cells with mutated p53 have a tendency to be resistant to anti-cancer drug. Recent report suggests that wild type (wt) p53 downregulates Survivin expression in ALL cell lines. To investigate the possible regulation of Survivin by p53, we examined the Survivin expression level in lung cancer cell lines in response to DNA-damaging stimulus by adriamycin. mRNA and protein expression level of Survivin in 3 cell lines with (wt) p53, were dramatically decreased following p53 inductions. In contrast, in other 3 cell lines with mutated or null p53, no induction of p53 and no reduction of survivin (both mRNA and protein level) were observed after the treatment of adriamycin. To evaluate the direct downregulation of Survivin by (wt) p53, we have inhibited the (wt) p53 in A549 by short interfering (si) RNA technique. Administration of siRNA targeting p53 has significantly reduced p53 protein expression and comparatively increased Survivin protein expression. To investigate differences of sensitivity to adriamycin in cancer cells by inhibition of Survivin, we have inhibited Survivin by siRNA in PC9 which has mutated p53. After 48h siRNA administration to PC9 which has significantly inhibited the Survivin expression, we replaced the medium and added to IC 50 dose of adriamycin. Additional 48h incubation with adriamycin, the cell proliferation was significant repressed in the cell treated by siRNA targeting survivin, in comparison with in the cell treated by anti-scramble. Furthermore, we observed a significant increase of apoptosis after the treatment of adriamycin and siRNA targeting survivin in comparison with adriamycin and anti-scramble, by pro-caspase3 expression assay and TUNEL assay. Our results demonstrate that Survivin is transcriptionally downregulated by p53, and the siRNA targeting survivin increase a sensitivity to adriamycin and promotes apoptosis. The siRNA targeting survivin could be a potential approach to increase sensitivity to anti-cancer drug especially in the drug resistant cells which has mutated p53.