Figure 4
Inhibition of the mitochondrial function of p53 with pifithrin-μ diminishes the cytolytic activity of sorafenib/MI-319. (A). Effect of pifithrin-μ(10 μM) on the apoptotic effects of 10 μM sorafenib (S) and 20 μM MI-319 (M) in A375 cells. Cell death data are presented as the percentage of total cells staining positive for propidium iodide. (B). Effect of pifithrin-μ on the nuclear translocation of AIF induced by the sorafenib/MI-319 combination (but not sorafenib alone). c-myc and COX4 were used as markers for the nuclear and mitochondrial subcellular fractions used in these assays. (C). GSK-3β activity determines whether pifithrin-μ inhibits the cell death induced in melanoma cells by sorafenib and MI-319. (Left Panel). A375 cells expressing the tetracycline-regulable GSK-3β shRNA with and without doxycycline pretreatment were treated with sorafenib and MI-319 in the presence or absence of pifithrin-μ. Cell death data are presented as the percentage of total cells staining positive for propidium iodide. (Right Panel). SKMEL5 and SKMEL5-GSK-3βS9A cells were treated with sorafenib and MI-319 in the presence or absence of pifithrin-μ. Cell death data are presented as the percentage of total cells staining positive for propidium iodide. (D). Effect of MI-319 and sorafenib on PARP cleavage in A375 cells.