Expression of TRAIL and its receptors in primary hepatic carcinoma and apoptosis-inducing effect of HrsTRAIL on hepatoma cell line HepG2

摘要

Objective: To investigate the expression of tumor necrosis factor-related apoptosis-inducing ligand(TRAIL) and its receptors in primary hepatic carcinoma (PHC) and the apoptosis-inducing effect on hepatoma cell line HepG2. Methods: TRAIL and its receptors were detected by semiquantitive RT-PCR in 30 PHC and para-carcinoma tissues and two hepatoma cell lines of HepG2 and SMMC-7721. HepG2 cells were treated with human recombinant soluble TRAIL protein (HrsTRAIL) and then the viability of HepG2 cells was measured by microculture tetrazolium dye(MTT) assay and apoptosis index was demonstrated by fluorescence-activated cell sorting (FACS). Results: TRAIL and its receptors were detectable in all PHC and para-carcinoma tissues and hepatoma cell line HepG2. TRAIL, death receptor 4 (DR4), DR5, and decoy receptor 2 (DcR2) but not DcR1 were detectable in hepatoma cell line SMMC-7721. The expression patterns of TRAIL receptors in HepG2 were quite similar to PHC specimens. The semiquantitive results showed that the expression level of TRAIL and DcR were lower but DR was higher in hepatoma tissues than in para-carcinoma tissues. In PHC tissues, the expressions of DR were higher than DcR, while there was no difference in para-carcinoma tissues. HrsTRAIL had potent antitumor activity in a time- and dose-dependent manner. After co-incubations of the HepG2 cells in the presence of HrsTRAIL at concentration 1 000 ng/ml for 24 hours, the viability of HepG2 cells decreased to 45% and the apoptosis index reached 51%. Conclusion: TRAIL and its receptors were expressed in both PHC tissues and para-carcinoma tissues but the expression levels were different. The lower expression of TRAIL in PHC tissues suggested that insufficient apoptosis occured in the development of PHC. High expression of DR in PHC tissues may be a self-defense mechanism and may afford a theory of HrsTRAIL therapy for PHC. HrsTRAIL may be a potential cytotoxic drug for PHC, and it can kill majority of HepG2 cells, but minority of HepG2 were resistant to TRAIL-inducing apoptosis.