HtrA1 resensitizes multidrug-resistant hepatocellular carcinoma cells by targeting XIAP

The study aims to clarify the relation between chemosensitivity and HtrA1 expression, and the possible way HtrA1 works. Drug-resistant cell line HepG2/ADM was induced by increasing adriamycin (ADM), and eukaryotic expression vector pEGFP-N1-HtrA1 was constructed using BamHI and EcoRI restriction enzymes, after which, HepG2/ADM was transfected with pEGFP-N1-HtrA1. Resistance index (RI) of the hepatoma cell lines to different anti-cancer drugs (ADM, 5-Fu, MMC, L-OHP and VCR) was determined by MTT assay before and after HtrA1 high expression. After an HtrA1 inhibitor, NVP-LEB748 was adopted in the HtrA1 overexpressing cells, expression of proteins P-gp, MRP and XIAP (X-linked inhibitor of apoptosis protein) in HepG2/ADM cells were analyzed by western blot, and the activities of caspases 3, 7 and 9 were respectively measured using activity assay kits. The results showed that RI was negatively correlated with the expression of HtrA1, upregulated XIAP expression was resulted from the HtrA1 inhibitor, and variance of activities of caspases 3, 7 and 9 were remarkably descended with its increasing concentration. It was concluded that high expression of HtrA1 could significantly reverse multidrug resistance of hepatoma cells by targeting XIAP. HtrA1 is therefore expected to be an effective tool in the therapy of hepatocellular carcinoma.