Self-synthesized second mitochondria-derived activator of caspase (SMAC) mimetic TP-WY-1345 enhances the radiosensitivity of NSCLC cells H1299 by targeting anti-apoptotic protein cIAP1

Objective

To explore the toxicity and cellular uptake of the self-synthesized second mitochondria-derived activator of caspase (SMAC) mimetic TP-WY-1345 polypeptide and its radiosensitizing effect on non-small cell lung cancer (NSCLC).

Methods

A fluorescence microscope was used to observe the uptake efficiency of TP-WY-1345 by human NSCLC cells H1299. Toxicity of the TP-WY-1345 peptide in normal cells was examined in human embryonic lung fibroblasts MRC5. CCK-8 and clone formation experiments were performed to detect the radiosensitizing effect of TP-WY-1345 in the H1299 ​cells. The AutoDock Vina simulation software was employed to predict the binding efficiency of TP-WY-1345 to the inhibitor of apoptosis proteins (IAPs). Moreover, Western blot and qPCR experiments were carried out to determine the protein and gene expressions, and the flow cytometry (FCM) technique was used to detect the apoptosis level under different conditions.

Results

TP-WY-1345 can be self-synthesized, and significant green fluorescence was observed in H1299 2 ​h and 6 ​h after incubation with TP-WY-1345. The cell counting and CCK-8 results showed that 10 ​μmol/L and 20 ​μmol/L TP-WY-1345 did not produce a significant toxic effect on the MRC5 cells (P ​> ​0.05). Compared with the single ionizing radiation group, the cell viability and clone formation of H1299 ​cells were significantly inhibited after treatment with TP-WY-1345 at a concentration of 50 ​μmol/L (P ​< 0.05). The sensitivity enhancement ratio (SER) was calculated to be 1.14. Moreover, the binding efficiency of TP-WY-1345 to cIAP1 protein was predicted to be −7.3, and this strong binding force was demonstrated by Western blot. TP-WY-1345 inhibited the protein and mRNA expressions of cIAP1 and further increased the apoptosis level of the H1299 ​cells at 24 ​h ​(P ​< ​0.01) and 48 ​h after radiation (P ​< ​0.05).

Conclusion

SMAC mimetic TP-WY-1345 can enter the H1299 ​cells and produce a radiosensitizing effect by increasing the level of radiation-induced apoptosis of the cells. There, TP-WY-1345 is expected to become a new generation of radiosensitizing drugs.