Taken together, these findings suggest that TCTP enabled the HeLa cells to acquire chemoresis tance in etoposide induced sellectchem apoptosis possibly through inhibition of initiator or effector caspase activity thereby preserving the key players for tumor cell function such as EGFR and PLC. TCTP inhibits mitochondrial membrane perturbation thereby reducing cytochrome c release from mitochondria to cytosol in etoposide induced cell death Following Bax translocation to mitochondria, release of intermembrane cytochrome c lead to the perturbation of the mitochondrial membrane potential by disturbing the electron transfer. We tested whether TCTP inhibits mitochondrial membrane polarization during etoposide induced cell death.

Flow cytometry, employing the dye, JC 1, an indicator for mitochondrial Inhibitors,Modulators,Libraries membrane potential, showed that the distribution of membrane potential is normal in untreated HeLa cells. In contrast, the distribution Inhibitors,Modulators,Libraries of membrane potential shifted from red to green fluorescence when carbonyl cyanide m chlorophenylhydrazone, a protonophore, was treated as a positive control, through its effects on mito chondrial uncoupling. Interestingly, hyperpo larized distribution of mitochondrial membrane potential in etoposide induced cell death was inhibited by TCTP overexpression. Next, we examined if TCTP also inhibits cytochrome c release under genotoxic stress. As shown in Figure 2B, the content of cytochrome c was higher in the cytosolic fraction of etoposide treated HeLa cells than in un treated cells.

In contrast, TCTP overexpression inhibited the cytochrome c release from mitochondria to cytosolic fraction in etoposide treated HeLa cells, Inhibitors,Modulators,Libraries as also confirmed by the fluorimetry analysis using fluorescence tagged anti cytochrome c antibody. There fore, TCTP appears to induce the chemoresistance of etoposide induced cell death by inhibiting the mitochon drial membrane damage and Inhibitors,Modulators,Libraries the resultant cyto chrome release into cytosolic fraction. TCTP inhibits caspase activation in etoposide induced cell death Release of cytochrome c from mitochondria, induces the formation of functional apoptosome that signals the acti vation of caspase Inhibitors,Modulators,Libraries cascade in the mitochondria dependent apoptotic pathway. Apoptosome cleaves apical caspase 9, which in turn induces the activation of caspases 3 and 7 to execute the dismantling of the cells through proteolysis of its target proteins such as poly ADP ribose polymerase.

In etoposide treated human melanoma cells, cytochrome c release was observed along with upregulation of caspases 9 and 3. Because TCTP inhibits cytochrome c release from the mitochondria, effects on caspase activity by TCTP were investigated by specifically detecting sellckchem the cleaved form of caspases. As presented in Figure 3A, etoposide treatment induced cleavage of caspase 9, 3, and 7 as well as fragmentation of its target PARP in HeLa cells.